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  • richardmitnick 7:54 pm on August 31, 2021 Permalink | Reply
    Tags: "Tiny diamond mirrors could smooth out already revolutionary x-ray lasers", , , , , SLAC LCLS, ,   

    From Science Magazine: “Tiny diamond mirrors could smooth out already revolutionary x-ray lasers” 

    From Science Magazine

    27 Aug 2021
    Adrian Cho

    Ambitious recycling scheme would make giant accelerator-driven machines work more like ordinary lasers.

    Twelve years ago, physicists turned on the first x-ray laser, and since then it and several others around the world have proved themselves revolutionary probes of materials and molecules. But the devices, called x-ray free-electron lasers (XFELs), are only partially laserlike. In contrast to the pure, single-wavelength light emitted by conventional lasers, they produce noisy, chaotic beams. Now, physicists are developing a scheme that would enlist perfect diamond mirrors to make the x-ray pulses much more like ordinary laser beams and even more useful.

    With two facilities now racing to stage proof-of-principle experiments as early as 2023, would-be users are taking notice. “I’m excited about the potential of this,” says Serena DeBeer, a chemist at the MGP Institute for Chemical Energy Conversion [MPG Institut für chemische Energieumwandlung (DE), who says the beams could be used to study the inner workings of enzymes as they catalyze reactions. But realizing such sophisticated XFELs may take 10 years and won’t be easy, warns Harald Sinn, an x-ray physicist at the European XFEL: “There are nightmares ahead.”

    A conventional laser consists of a light-emitting material sitting between two mirrors. The carefully spaced mirrors form a cavity that resonates with light of the desired wavelength, just as an organ pipe rings with sound of a specific pitch. As the light passes back and forth through the material, it stimulates the stuff to produce more photons of the same wavelength, amplifying the light until a wave of identical photons marching in quantum mechanical lockstep—a laser beam—shines through one mirror, which is purposefully made imperfectly reflective.

    This scheme won’t work for x-rays. Physicists lack both an obvious radiating material and, until recently, mirrors that will reflect x-rays at large enough angles to form a resonating cavity. So they use a particle accelerator to fire a bunch of electrons down a vacuum pipe and through long trains of magnets called undulators, which shake the electrons side to side so they radiate x-ray photons. The light then travels along with the electrons and pushes them into microbunches, which wiggle in unison and radiate far more strongly, producing a burst of x-rays just femtoseconds long.

    The first free-electrion laser flicked on in the 1970s, producing much longer wavelength microwaves. It was not until 2009 that physicists at DOE’s SLAC National Accelerator Laboratory (US) achieved the feat for “hard” x-rays, when they used the lab’s 3-kilometer-long linear accelerator to fire up the world’s first XFEL, the Linac Coherent Light Source (LCLS).

    Other countries have since built a half-dozen XFELS.

    As with ordinary laser beams, x-rays from an XFEL arrive in smooth fronts, like ocean waves across a beach. A single XFEL pulse can scatter off a nanometer-size crystal and reveal its atomic structure, even as it blows the crystal to bits. Biologists have used XFELs to determine the structures of myriad proteins and other molecules that won’t form crystals big enough to be studied at less intense x-ray sources. But because an XFEL uses fluctuations in the density of the electron beam to begin to generate x-rays, one pulse varies from another in intensity, and each pulse has a wide and randomly distributed spectrum of wavelengths.

    To squelch such noise, physicists have turned to an idea kicked around for decades, says Kwang-Je Kim, an accelerator physicist at DOE’s Argonne National Laboratory (US). “People talked about it from time to time over drinks, but it was party conversation,” he says. “Nobody did any serious calculations” until the late 2000s, when Kim and others tackled the issue.

    A gem of an idea to smooth out x-rays

    In an x-ray free-electron laser (XFEL), an undulator magnet shakes a bunch of energetic electrons sideways so they emit x-rays. The x-rays push the electrons into subbunches that, radiating in concert, then generate a noisy tsunami of x-rays. A twist on the concept could produce more consistent, smoother x-ray pulses.

    The idea is to extract part of the x-ray pulse generated by one bunch of electrons and feed it back to the entrance of the undulators just in time to overlap with the next bunch of electrons. The recirculated x-rays would serve as a seed that causes the electrons to radiate more predictably. In repeated cycles, the x-ray pulses should become very pure and smooth, with a spread of wavelengths only 1/1000th as wide as ordinary XFEL pulses.

    The plan requires very special mirrors, however. X-rays blast through most material, but for 100 years, physicists have known that a perfect crystal should reflect x-rays at certain angles, depending on the x-rays’ energy and the crystal’s structure and orientation, as the x-rays diffract off parallel planes of atoms in the crystal. The crystal also acts as a filter, as it reflects x-rays in a narrow range of wavelengths. Such crystal mirrors remained an aspiration until 2010, when Yuri Shvyd’ko, an x-ray physicist at Argonne, and colleagues showed small synthetic diamonds can reflect x-rays with 99% efficiency. Fortunately, an XFEL’s beam is less than 100 micrometers wide. “You don’t need a large crystal,” Shvyd’ko says. “You need a perfect crystal of small size.”

    The scheme also requires a linear accelerator with a high repetition rate, to ensure the x-ray beam encounters a fresh bunch of electrons each time it rounds its circuit of mirrors. SLAC’s original accelerator is way too slow, firing 120 times a second. The European XFEL runs at 2.2 million cycles a second, so a cavity just 136 meters long would synchronize the x-rays with the electron bunches. SLAC is installing an accelerator that will run at 1 million cycles per second starting in 2022.

    To test the essential elements for a cavity-based XFEL, physicists from Argonne, SLAC, and the Japanese lab Spring-8 plan to use four crystal mirrors to build a 66-meter-long cavity around seven LCLS undulators. By fiddling with SLAC’s current accelerator, they will shoot two bunches of electrons separated by 220 nanoseconds through the undulators and hope to show that recirculating x-rays from the first bunch make the second bunch radiate more efficiently. The system should be up and running in 2023, says Gabriel Marcus, an accelerator physicist at SLAC. Researchers at the European XFEL plan to implement a slightly different design by 2024. They hope to send up to 2700 electron bunches through the undulators and watch the laser beam grow stronger and smoother with each pass.

    Patrick Rauer, an x-ray physicist at The University of Hamburg [Universität Hamburg](DE) who has modeled the European XFEL project on a computer, cautions that the scheme will require extraordinary precision, with the millimeter-size diamonds aligned to a few millionths of a degree. “It’s a major problem,” Rauer says. “This is going to very difficult.” Ilya Agapov, an accelerator physicist at the DESY Electron Synchrotron[ Deütsches Elektronen-Synchrotron](DE), says that even harder will be maintaining the alignment as circulating x-rays heat the mirrors.

    Still, potential users foresee major benefits. For example, Christian Gutt of The University of Siegen [Universität Siegen](DE) has used the European XFEL to study how proteins in solution diffuse and cluster on time scales as short as nanoseconds by studying correlations in the patterns of x-rays diffracted by the proteins. Those patterns would be far sharper with a cavity-based XFEL, he says. “That would be a game changer for us.”

    With its extremely narrow spectrum, a cavity-based XFEL might even serve to control the quantum states of atomic nuclei much as atomic physicists now control the states of atoms with visible light, says Linda Young, an atomic physicist at Argonne. “It’s very wild,” she says. All it will take is a few mirrors—and a lot of hard work.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 11:06 am on August 2, 2021 Permalink | Reply
    Tags: "AI learns physics to optimize particle accelerator performance", , , Before going to work on a given task machine learning algorithms typically need to be trained on pre-existing data., , , Machine learning-a form of artificial intelligence-vastly speeds up computational tasks and enables new technology., , , , SLAC LCLS, SLAC/Stanford Synchrotron Radiation Lightsource (SSRL)., Teaching machine learning the basics of accelerator physics is particularly useful in situations where actual data don’t exist.,   

    From DOE’s SLAC National Accelerator Laboratory (US) : “AI learns physics to optimize particle accelerator performance” 

    From DOE’s SLAC National Accelerator Laboratory (US)

    July 29, 2021
    Manuel Gnida

    Teaching machine learning the basics of accelerator physics is particularly useful in situations where actual data don’t exist.

    1
    SLAC researchers have paired machine learning with physics knowledge to optimize the performance of the SPEAR3 accelerator, which is the backbone of the lab’s Stanford Synchrotron Radiation Lightsource (SSRL), shown in this photo. Credit: Brad Plummer/SLAC National Accelerator Laboratory.

    Machine learning-a form of artificial intelligence-vastly speeds up computational tasks and enables new technology in areas as broad as speech and image recognition, self-driving cars, stock market trading and medical diagnosis.

    Before going to work on a given task machine learning algorithms typically need to be trained on pre-existing data so they can learn to make fast and accurate predictions about future scenarios on their own. But what if the job is a completely new one, with no data available for training?

    Now, researchers at the Department of Energy’s SLAC National Accelerator Laboratory have demonstrated that they can use machine learning to optimize the performance of particle accelerators by teaching the algorithms the basic physics principles behind accelerator operations – no prior data needed.

    “Injecting physics into machine learning is a really hot topic in many research areas – in materials science, environmental science, battery research, particle physics and more,” said Adi Hanuka, a former SLAC research associate who led a study published in Physical Review Accelerator and Beams. This is one of the first examples of using physics-informed machine learning in the accelerator physics community.

    Educating AI with physics

    Accelerators are powerful machines that energize beams of electrons or other particles for use in a wide range of applications, including fundamental physics experiments, molecular imaging and radiation therapy for cancer. To obtain the best beam for a given application, operators need to tune the accelerator for peak performance.

    When it comes to large particle accelerators this can be very challenging because there are so many components that need to be adjusted. What further complicates things is that not all components are independent, meaning that if you adjust one, it can affect the settings for another.

    Recent studies at SLAC have shown that machine learning can greatly support human operators by speeding up the optimization process and finding useful accelerator settings that nobody has thought of before. Machine learning can also help diagnose the quality of particle beams without interfering with them, as other techniques usually do.

    For these procedures to work, researchers first had to train the machine learning algorithms with data from previous accelerator operations, computer simulations that make assumptions about the accelerator’s performance, or both. However, they also found that using information from physics models combined with available experimental data could dramatically decrease the amount of new data required.

    The new study demonstrates that prior data are, in fact, not needed if you know enough about the physics that describes how an accelerator works.

    The team used this approach to tune SLAC’s SPEAR3 accelerator, which powers the lab’s Stanford Synchrotron Radiation Lightsource (SSRL). By using information obtained directly from physics-based models, they got results that were just as good, if not better, as those achieved by training the algorithm with actual archival data, the researchers said.

    “Our results are the latest highlight of a progressive push at SLAC to develop machine learning tools for tuning accelerators,” said SLAC staff scientist Joe Duris, the study’s principal investigator.

    Predicting the unknown

    That’s not to say that pre-existing data are not helpful. They still come in handy even if you have your physics down. In the SPEAR3 case, the researchers were able to further improve the physics-informed machine learning model by pairing it with actual data from the accelerator. The team is also applying the method to improve tuning of SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, one of the most powerful X-ray sources on the planet, for which archival data are available from previous experimental runs.

    The full potential of the new method will probably become apparent when SLAC crews turn on LCLS-II next year.

    This superconducting upgrade to LCLS has a brand-new accelerator, and its best settings need to be determined from scratch. Its operators may find it convenient to have AI by their side that has already learned some basics of accelerator physics.

    Funding came from a DOE Laboratory Directed Research and Development (LDRD) program at SLAC and DOE’s Office of Science (SC). LDRD and SC funded separate projects that both contributed to these results. Additional research contributions came from the University of Cambridge (UK). SSRL and LCLS are Office of Science user facilities.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC National Accelerator Laboratory (US) originally named Stanford Linear Accelerator Center, is a United States Department of Energy National Laboratory operated by Stanford University under the programmatic direction of the U.S. Department of Energy Office of Science and located in Menlo Park, California. It is the site of the Stanford Linear Accelerator, a 3.2 kilometer (2-mile) linear accelerator constructed in 1966 and shut down in the 2000s, which could accelerate electrons to energies of 50 GeV.

    Today SLAC research centers on a broad program in atomic and solid-state physics, chemistry, biology, and medicine using X-rays from synchrotron radiation and a free-electron laser as well as experimental and theoretical research in elementary particle physics, astroparticle physics, and cosmology.

    Founded in 1962 as the Stanford Linear Accelerator Center, the facility is located on 172 hectares (426 acres) of Stanford University-owned land on Sand Hill Road in Menlo Park, California—just west of the University’s main campus. The main accelerator is 3.2 kilometers (2 mi) long—the longest linear accelerator in the world—and has been operational since 1966.

    Research at SLAC has produced three Nobel Prizes in Physics

    1976: The charm quark—see J/ψ meson
    1990: Quark structure inside protons and neutrons
    1995: The tau lepton

    SLAC’s meeting facilities also provided a venue for the Homebrew Computer Club and other pioneers of the home computer revolution of the late 1970s and early 1980s.

    In 1984 the laboratory was named an ASME National Historic Engineering Landmark and an IEEE Milestone.

    SLAC developed and, in December 1991, began hosting the first World Wide Web server outside of Europe.

    In the early-to-mid 1990s, the Stanford Linear Collider (SLC) investigated the properties of the Z boson using the Stanford Large Detector.

    As of 2005, SLAC employed over 1,000 people, some 150 of whom were physicists with doctorate degrees, and served over 3,000 visiting researchers yearly, operating particle accelerators for high-energy physics and the Stanford Synchrotron Radiation Laboratory (SSRL) for synchrotron light radiation research, which was “indispensable” in the research leading to the 2006 Nobel Prize in Chemistry awarded to Stanford Professor Roger D. Kornberg.

    In October 2008, the Department of Energy announced that the center’s name would be changed to SLAC National Accelerator Laboratory. The reasons given include a better representation of the new direction of the lab and the ability to trademark the laboratory’s name. Stanford University had legally opposed the Department of Energy’s attempt to trademark “Stanford Linear Accelerator Center”.

    In March 2009, it was announced that the SLAC National Accelerator Laboratory was to receive $68.3 million in Recovery Act Funding to be disbursed by Department of Energy’s Office of Science.

    In October 2016, Bits and Watts launched as a collaboration between SLAC and Stanford University to design “better, greener electric grids”. SLAC later pulled out over concerns about an industry partner, the state-owned Chinese electric utility.

    Accelerator

    The main accelerator was an RF linear accelerator that accelerated electrons and positrons up to 50 GeV. At 3.2 km (2.0 mi) long, the accelerator was the longest linear accelerator in the world, and was claimed to be “the world’s most straight object.” until 2017 when the European x-ray free electron laser opened. The main accelerator is buried 9 m (30 ft) below ground and passes underneath Interstate Highway 280. The above-ground klystron gallery atop the beamline, was the longest building in the United States until the LIGO project’s twin interferometers were completed in 1999. It is easily distinguishable from the air and is marked as a visual waypoint on aeronautical charts.

    A portion of the original linear accelerator is now part of the Linac Coherent Light Source [below].

    Stanford Linear Collider

    The Stanford Linear Collider was a linear accelerator that collided electrons and positrons at SLAC. The center of mass energy was about 90 GeV, equal to the mass of the Z boson, which the accelerator was designed to study. Grad student Barrett D. Milliken discovered the first Z event on 12 April 1989 while poring over the previous day’s computer data from the Mark II detector. The bulk of the data was collected by the SLAC Large Detector, which came online in 1991. Although largely overshadowed by the Large Electron–Positron Collider at CERN, which began running in 1989, the highly polarized electron beam at SLC (close to 80%) made certain unique measurements possible, such as parity violation in Z Boson-b quark coupling.

    Presently no beam enters the south and north arcs in the machine, which leads to the Final Focus, therefore this section is mothballed to run beam into the PEP2 section from the beam switchyard.

    The SLAC Large Detector (SLD) was the main detector for the Stanford Linear Collider. It was designed primarily to detect Z bosons produced by the accelerator’s electron-positron collisions. Built in 1991, the SLD operated from 1992 to 1998.

    SLAC National Accelerator Laboratory(US)Large Detector

    PEP

    PEP (Positron-Electron Project) began operation in 1980, with center-of-mass energies up to 29 GeV. At its apex, PEP had five large particle detectors in operation, as well as a sixth smaller detector. About 300 researchers made used of PEP. PEP stopped operating in 1990, and PEP-II began construction in 1994.

    PEP-II

    From 1999 to 2008, the main purpose of the linear accelerator was to inject electrons and positrons into the PEP-II accelerator, an electron-positron collider with a pair of storage rings 2.2 km (1.4 mi) in circumference. PEP-II was host to the BaBar experiment, one of the so-called B-Factory experiments studying charge-parity symmetry.

    SLAC National Accelerator Laboratory(US) BaBar

    Fermi Gamma-ray Space Telescope

    SLAC plays a primary role in the mission and operation of the Fermi Gamma-ray Space Telescope, launched in August 2008. The principal scientific objectives of this mission are:

    To understand the mechanisms of particle acceleration in AGNs, pulsars, and SNRs.
    To resolve the gamma-ray sky: unidentified sources and diffuse emission.
    To determine the high-energy behavior of gamma-ray bursts and transients.
    To probe dark matter and fundamental physics.


    KIPAC

    The Stanford PULSE Institute (PULSE) is a Stanford Independent Laboratory located in the Central Laboratory at SLAC. PULSE was created by Stanford in 2005 to help Stanford faculty and SLAC scientists develop ultrafast x-ray research at LCLS.

    The Linac Coherent Light Source (LCLS)[below] is a free electron laser facility located at SLAC. The LCLS is partially a reconstruction of the last 1/3 of the original linear accelerator at SLAC, and can deliver extremely intense x-ray radiation for research in a number of areas. It achieved first lasing in April 2009.

    The laser produces hard X-rays, 10^9 times the relative brightness of traditional synchrotron sources and is the most powerful x-ray source in the world. LCLS enables a variety of new experiments and provides enhancements for existing experimental methods. Often, x-rays are used to take “snapshots” of objects at the atomic level before obliterating samples. The laser’s wavelength, ranging from 6.2 to 0.13 nm (200 to 9500 electron volts (eV)) is similar to the width of an atom, providing extremely detailed information that was previously unattainable. Additionally, the laser is capable of capturing images with a “shutter speed” measured in femtoseconds, or million-billionths of a second, necessary because the intensity of the beam is often high enough so that the sample explodes on the femtosecond timescale.

    The LCLS-II [below] project is to provide a major upgrade to LCLS by adding two new X-ray laser beams. The new system will utilize the 500 m (1,600 ft) of existing tunnel to add a new superconducting accelerator at 4 GeV and two new sets of undulators that will increase the available energy range of LCLS. The advancement from the discoveries using this new capabilities may include new drugs, next-generation computers, and new materials.

    FACET

    In 2012, the first two-thirds (~2 km) of the original SLAC LINAC were recommissioned for a new user facility, the Facility for Advanced Accelerator Experimental Tests (FACET). This facility was capable of delivering 20 GeV, 3 nC electron (and positron) beams with short bunch lengths and small spot sizes, ideal for beam-driven plasma acceleration studies. The facility ended operations in 2016 for the constructions of LCLS-II which will occupy the first third of the SLAC LINAC. The FACET-II project will re-establish electron and positron beams in the middle third of the LINAC for the continuation of beam-driven plasma acceleration studies in 2019.

    The Next Linear Collider Test Accelerator (NLCTA) is a 60-120 MeV high-brightness electron beam linear accelerator used for experiments on advanced beam manipulation and acceleration techniques. It is located at SLAC’s end station B

    SSRL and LCLS are DOE Office of Science user facilities.

    Stanford University (US)

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members.

    Stanford University, officially Leland Stanford Junior University, is a private research university located in Stanford, California. Stanford was founded in 1885 by Leland and Jane Stanford in memory of their only child, Leland Stanford Jr., who had died of typhoid fever at age 15 the previous year. Stanford is consistently ranked as among the most prestigious and top universities in the world by major education publications. It is also one of the top fundraising institutions in the country, becoming the first school to raise more than a billion dollars in a year.

    Leland Stanford was a U.S. senator and former governor of California who made his fortune as a railroad tycoon. The school admitted its first students on October 1, 1891, as a coeducational and non-denominational institution. Stanford University struggled financially after the death of Leland Stanford in 1893 and again after much of the campus was damaged by the 1906 San Francisco earthquake. Following World War II, provost Frederick Terman supported faculty and graduates’ entrepreneurialism to build self-sufficient local industry in what would later be known as Silicon Valley.

    The university is organized around seven schools: three schools consisting of 40 academic departments at the undergraduate level as well as four professional schools that focus on graduate programs in law, medicine, education, and business. All schools are on the same campus. Students compete in 36 varsity sports, and the university is one of two private institutions in the Division I FBS Pac-12 Conference. It has gained 126 NCAA team championships, and Stanford has won the NACDA Directors’ Cup for 24 consecutive years, beginning in 1994–1995. In addition, Stanford students and alumni have won 270 Olympic medals including 139 gold medals.

    As of October 2020, 84 Nobel laureates, 28 Turing Award laureates, and eight Fields Medalists have been affiliated with Stanford as students, alumni, faculty, or staff. In addition, Stanford is particularly noted for its entrepreneurship and is one of the most successful universities in attracting funding for start-ups. Stanford alumni have founded numerous companies, which combined produce more than $2.7 trillion in annual revenue, roughly equivalent to the 7th largest economy in the world (as of 2020). Stanford is the alma mater of one president of the United States (Herbert Hoover), 74 living billionaires, and 17 astronauts. It is also one of the leading producers of Fulbright Scholars, Marshall Scholars, Rhodes Scholars, and members of the United States Congress.

    Stanford University was founded in 1885 by Leland and Jane Stanford, dedicated to Leland Stanford Jr, their only child. The institution opened in 1891 on Stanford’s previous Palo Alto farm.

    Jane and Leland Stanford modeled their university after the great eastern universities, most specifically Cornell University. Stanford opened being called the “Cornell of the West” in 1891 due to faculty being former Cornell affiliates (either professors, alumni, or both) including its first president, David Starr Jordan, and second president, John Casper Branner. Both Cornell and Stanford were among the first to have higher education be accessible, nonsectarian, and open to women as well as to men. Cornell is credited as one of the first American universities to adopt this radical departure from traditional education, and Stanford became an early adopter as well.

    Despite being impacted by earthquakes in both 1906 and 1989, the campus was rebuilt each time. In 1919, The Hoover Institution on War, Revolution and Peace was started by Herbert Hoover to preserve artifacts related to World War I. The Stanford Medical Center, completed in 1959, is a teaching hospital with over 800 beds. The DOE’s SLAC National Accelerator Laboratory(US)(originally named the Stanford Linear Accelerator Center), established in 1962, performs research in particle physics.

    Land

    Most of Stanford is on an 8,180-acre (12.8 sq mi; 33.1 km^2) campus, one of the largest in the United States. It is located on the San Francisco Peninsula, in the northwest part of the Santa Clara Valley (Silicon Valley) approximately 37 miles (60 km) southeast of San Francisco and approximately 20 miles (30 km) northwest of San Jose. In 2008, 60% of this land remained undeveloped.

    Stanford’s main campus includes a census-designated place within unincorporated Santa Clara County, although some of the university land (such as the Stanford Shopping Center and the Stanford Research Park) is within the city limits of Palo Alto. The campus also includes much land in unincorporated San Mateo County (including the SLAC National Accelerator Laboratory and the Jasper Ridge Biological Preserve), as well as in the city limits of Menlo Park (Stanford Hills neighborhood), Woodside, and Portola Valley.

    Non-central campus

    Stanford currently operates in various locations outside of its central campus.

    On the founding grant:

    Jasper Ridge Biological Preserve is a 1,200-acre (490 ha) natural reserve south of the central campus owned by the university and used by wildlife biologists for research.
    SLAC National Accelerator Laboratory is a facility west of the central campus operated by the university for the Department of Energy. It contains the longest linear particle accelerator in the world, 2 miles (3.2 km) on 426 acres (172 ha) of land.
    Golf course and a seasonal lake: The university also has its own golf course and a seasonal lake (Lake Lagunita, actually an irrigation reservoir), both home to the vulnerable California tiger salamander. As of 2012 Lake Lagunita was often dry and the university had no plans to artificially fill it.

    Off the founding grant:

    Hopkins Marine Station, in Pacific Grove, California, is a marine biology research center owned by the university since 1892.
    Study abroad locations: unlike typical study abroad programs, Stanford itself operates in several locations around the world; thus, each location has Stanford faculty-in-residence and staff in addition to students, creating a “mini-Stanford”.

    Redwood City campus for many of the university’s administrative offices located in Redwood City, California, a few miles north of the main campus. In 2005, the university purchased a small, 35-acre (14 ha) campus in Midpoint Technology Park intended for staff offices; development was delayed by The Great Recession. In 2015 the university announced a development plan and the Redwood City campus opened in March 2019.

    The Bass Center in Washington, DC provides a base, including housing, for the Stanford in Washington program for undergraduates. It includes a small art gallery open to the public.

    China: Stanford Center at Peking University, housed in the Lee Jung Sen Building, is a small center for researchers and students in collaboration with Beijing University [北京大学](CN) (Kavli Institute for Astronomy and Astrophysics at Peking University(CN) (KIAA-PKU).

    Administration and organization

    Stanford is a private, non-profit university that is administered as a corporate trust governed by a privately appointed board of trustees with a maximum membership of 38. Trustees serve five-year terms (not more than two consecutive terms) and meet five times annually.[83] A new trustee is chosen by the current trustees by ballot. The Stanford trustees also oversee the Stanford Research Park, the Stanford Shopping Center, the Cantor Center for Visual Arts, Stanford University Medical Center, and many associated medical facilities (including the Lucile Packard Children’s Hospital).

    The board appoints a president to serve as the chief executive officer of the university, to prescribe the duties of professors and course of study, to manage financial and business affairs, and to appoint nine vice presidents. The provost is the chief academic and budget officer, to whom the deans of each of the seven schools report. Persis Drell became the 13th provost in February 2017.

    As of 2018, the university was organized into seven academic schools. The schools of Humanities and Sciences (27 departments), Engineering (nine departments), and Earth, Energy & Environmental Sciences (four departments) have both graduate and undergraduate programs while the Schools of Law, Medicine, Education and Business have graduate programs only. The powers and authority of the faculty are vested in the Academic Council, which is made up of tenure and non-tenure line faculty, research faculty, senior fellows in some policy centers and institutes, the president of the university, and some other academic administrators, but most matters are handled by the Faculty Senate, made up of 55 elected representatives of the faculty.

    The Associated Students of Stanford University (ASSU) is the student government for Stanford and all registered students are members. Its elected leadership consists of the Undergraduate Senate elected by the undergraduate students, the Graduate Student Council elected by the graduate students, and the President and Vice President elected as a ticket by the entire student body.

    Stanford is the beneficiary of a special clause in the California Constitution, which explicitly exempts Stanford property from taxation so long as the property is used for educational purposes.

    Endowment and donations

    The university’s endowment, managed by the Stanford Management Company, was valued at $27.7 billion as of August 31, 2019. Payouts from the Stanford endowment covered approximately 21.8% of university expenses in the 2019 fiscal year. In the 2018 NACUBO-TIAA survey of colleges and universities in the United States and Canada, only Harvard University(US), the University of Texas System(US), and Yale University(US) had larger endowments than Stanford.

    In 2006, President John L. Hennessy launched a five-year campaign called the Stanford Challenge, which reached its $4.3 billion fundraising goal in 2009, two years ahead of time, but continued fundraising for the duration of the campaign. It concluded on December 31, 2011, having raised a total of $6.23 billion and breaking the previous campaign fundraising record of $3.88 billion held by Yale. Specifically, the campaign raised $253.7 million for undergraduate financial aid, as well as $2.33 billion for its initiative in “Seeking Solutions” to global problems, $1.61 billion for “Educating Leaders” by improving K-12 education, and $2.11 billion for “Foundation of Excellence” aimed at providing academic support for Stanford students and faculty. Funds supported 366 new fellowships for graduate students, 139 new endowed chairs for faculty, and 38 new or renovated buildings. The new funding also enabled the construction of a facility for stem cell research; a new campus for the business school; an expansion of the law school; a new Engineering Quad; a new art and art history building; an on-campus concert hall; a new art museum; and a planned expansion of the medical school, among other things. In 2012, the university raised $1.035 billion, becoming the first school to raise more than a billion dollars in a year.

    Research centers and institutes

    DOE’s SLAC National Accelerator Laboratory(US)
    Stanford Research Institute, a center of innovation to support economic development in the region.
    Hoover Institution, a conservative American public policy institution and research institution that promotes personal and economic liberty, free enterprise, and limited government.
    Hasso Plattner Institute of Design, a multidisciplinary design school in cooperation with the Hasso Plattner Institute of University of Potsdam [Universität Potsdam](DE) that integrates product design, engineering, and business management education).
    Martin Luther King Jr. Research and Education Institute, which grew out of and still contains the Martin Luther King Jr. Papers Project.
    John S. Knight Fellowship for Professional Journalists
    Center for Ocean Solutions
    Together with UC Berkeley(US) and UC San Francisco(US), Stanford is part of the Biohub, a new medical science research center founded in 2016 by a $600 million commitment from Facebook CEO and founder Mark Zuckerberg and pediatrician Priscilla Chan.

    Discoveries and innovation

    Natural sciences

    Biological synthesis of deoxyribonucleic acid (DNA) – Arthur Kornberg synthesized DNA material and won the Nobel Prize in Physiology or Medicine 1959 for his work at Stanford.
    First Transgenic organism – Stanley Cohen and Herbert Boyer were the first scientists to transplant genes from one living organism to another, a fundamental discovery for genetic engineering. Thousands of products have been developed on the basis of their work, including human growth hormone and hepatitis B vaccine.
    Laser – Arthur Leonard Schawlow shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Kai Siegbahn for his work on lasers.
    Nuclear magnetic resonance – Felix Bloch developed new methods for nuclear magnetic precision measurements, which are the underlying principles of the MRI.

    Computer and applied sciences

    ARPANETStanford Research Institute, formerly part of Stanford but on a separate campus, was the site of one of the four original ARPANET nodes.

    Internet—Stanford was the site where the original design of the Internet was undertaken. Vint Cerf led a research group to elaborate the design of the Transmission Control Protocol (TCP/IP) that he originally co-created with Robert E. Kahn (Bob Kahn) in 1973 and which formed the basis for the architecture of the Internet.

    Frequency modulation synthesis – John Chowning of the Music department invented the FM music synthesis algorithm in 1967, and Stanford later licensed it to Yamaha Corporation.

    Google – Google began in January 1996 as a research project by Larry Page and Sergey Brin when they were both PhD students at Stanford. They were working on the Stanford Digital Library Project (SDLP). The SDLP’s goal was “to develop the enabling technologies for a single, integrated and universal digital library” and it was funded through the National Science Foundation, among other federal agencies.

    Klystron tube – invented by the brothers Russell and Sigurd Varian at Stanford. Their prototype was completed and demonstrated successfully on August 30, 1937. Upon publication in 1939, news of the klystron immediately influenced the work of U.S. and UK researchers working on radar equipment.

    RISCARPA funded VLSI project of microprocessor design. Stanford and UC Berkeley are most associated with the popularization of this concept. The Stanford MIPS would go on to be commercialized as the successful MIPS architecture, while Berkeley RISC gave its name to the entire concept, commercialized as the SPARC. Another success from this era were IBM’s efforts that eventually led to the IBM POWER instruction set architecture, PowerPC, and Power ISA. As these projects matured, a wide variety of similar designs flourished in the late 1980s and especially the early 1990s, representing a major force in the Unix workstation market as well as embedded processors in laser printers, routers and similar products.
    SUN workstation – Andy Bechtolsheim designed the SUN workstation for the Stanford University Network communications project as a personal CAD workstation, which led to Sun Microsystems.

    Businesses and entrepreneurship

    Stanford is one of the most successful universities in creating companies and licensing its inventions to existing companies; it is often held up as a model for technology transfer. Stanford’s Office of Technology Licensing is responsible for commercializing university research, intellectual property, and university-developed projects.

    The university is described as having a strong venture culture in which students are encouraged, and often funded, to launch their own companies.

    Companies founded by Stanford alumni generate more than $2.7 trillion in annual revenue, equivalent to the 10th-largest economy in the world.

    Some companies closely associated with Stanford and their connections include:

    Hewlett-Packard, 1939, co-founders William R. Hewlett (B.S, PhD) and David Packard (M.S).
    Silicon Graphics, 1981, co-founders James H. Clark (Associate Professor) and several of his grad students.
    Sun Microsystems, 1982, co-founders Vinod Khosla (M.B.A), Andy Bechtolsheim (PhD) and Scott McNealy (M.B.A).
    Cisco, 1984, founders Leonard Bosack (M.S) and Sandy Lerner (M.S) who were in charge of Stanford Computer Science and Graduate School of Business computer operations groups respectively when the hardware was developed.[163]
    Yahoo!, 1994, co-founders Jerry Yang (B.S, M.S) and David Filo (M.S).
    Google, 1998, co-founders Larry Page (M.S) and Sergey Brin (M.S).
    LinkedIn, 2002, co-founders Reid Hoffman (B.S), Konstantin Guericke (B.S, M.S), Eric Lee (B.S), and Alan Liu (B.S).
    Instagram, 2010, co-founders Kevin Systrom (B.S) and Mike Krieger (B.S).
    Snapchat, 2011, co-founders Evan Spiegel and Bobby Murphy (B.S).
    Coursera, 2012, co-founders Andrew Ng (Associate Professor) and Daphne Koller (Professor, PhD).

    Student body

    Stanford enrolled 6,996 undergraduate and 10,253 graduate students as of the 2019–2020 school year. Women comprised 50.4% of undergraduates and 41.5% of graduate students. In the same academic year, the freshman retention rate was 99%.

    Stanford awarded 1,819 undergraduate degrees, 2,393 master’s degrees, 770 doctoral degrees, and 3270 professional degrees in the 2018–2019 school year. The four-year graduation rate for the class of 2017 cohort was 72.9%, and the six-year rate was 94.4%. The relatively low four-year graduation rate is a function of the university’s coterminal degree (or “coterm”) program, which allows students to earn a master’s degree as a 1-to-2-year extension of their undergraduate program.

    As of 2010, fifteen percent of undergraduates were first-generation students.

    Athletics

    As of 2016 Stanford had 16 male varsity sports and 20 female varsity sports, 19 club sports and about 27 intramural sports. In 1930, following a unanimous vote by the Executive Committee for the Associated Students, the athletic department adopted the mascot “Indian.” The Indian symbol and name were dropped by President Richard Lyman in 1972, after objections from Native American students and a vote by the student senate. The sports teams are now officially referred to as the “Stanford Cardinal,” referring to the deep red color, not the cardinal bird. Stanford is a member of the Pac-12 Conference in most sports, the Mountain Pacific Sports Federation in several other sports, and the America East Conference in field hockey with the participation in the inter-collegiate NCAA’s Division I FBS.

    Its traditional sports rival is the University of California, Berkeley, the neighbor to the north in the East Bay. The winner of the annual “Big Game” between the Cal and Cardinal football teams gains custody of the Stanford Axe.

    Stanford has had at least one NCAA team champion every year since the 1976–77 school year and has earned 126 NCAA national team titles since its establishment, the most among universities, and Stanford has won 522 individual national championships, the most by any university. Stanford has won the award for the top-ranked Division 1 athletic program—the NACDA Directors’ Cup, formerly known as the Sears Cup—annually for the past twenty-four straight years. Stanford athletes have won medals in every Olympic Games since 1912, winning 270 Olympic medals total, 139 of them gold. In the 2008 Summer Olympics, and 2016 Summer Olympics, Stanford won more Olympic medals than any other university in the United States. Stanford athletes won 16 medals at the 2012 Summer Olympics (12 gold, two silver and two bronze), and 27 medals at the 2016 Summer Olympics.

    Traditions

    The unofficial motto of Stanford, selected by President Jordan, is Die Luft der Freiheit weht. Translated from the German language, this quotation from Ulrich von Hutten means, “The wind of freedom blows.” The motto was controversial during World War I, when anything in German was suspect; at that time the university disavowed that this motto was official.
    Hail, Stanford, Hail! is the Stanford Hymn sometimes sung at ceremonies or adapted by the various University singing groups. It was written in 1892 by mechanical engineering professor Albert W. Smith and his wife, Mary Roberts Smith (in 1896 she earned the first Stanford doctorate in Economics and later became associate professor of Sociology), but was not officially adopted until after a performance on campus in March 1902 by the Mormon Tabernacle Choir.
    “Uncommon Man/Uncommon Woman”: Stanford does not award honorary degrees, but in 1953 the degree of “Uncommon Man/Uncommon Woman” was created to recognize individuals who give rare and extraordinary service to the University. Technically, this degree is awarded by the Stanford Associates, a voluntary group that is part of the university’s alumni association. As Stanford’s highest honor, it is not conferred at prescribed intervals, but only when appropriate to recognize extraordinary service. Recipients include Herbert Hoover, Bill Hewlett, Dave Packard, Lucile Packard, and John Gardner.
    Big Game events: The events in the week leading up to the Big Game vs. UC Berkeley, including Gaieties (a musical written, composed, produced, and performed by the students of Ram’s Head Theatrical Society).
    “Viennese Ball”: a formal ball with waltzes that was initially started in the 1970s by students returning from the now-closed Stanford in Vienna overseas program. It is now open to all students.
    “Full Moon on the Quad”: An annual event at Main Quad, where students gather to kiss one another starting at midnight. Typically organized by the Junior class cabinet, the festivities include live entertainment, such as music and dance performances.
    “Band Run”: An annual festivity at the beginning of the school year, where the band picks up freshmen from dorms across campus while stopping to perform at each location, culminating in a finale performance at Main Quad.
    “Mausoleum Party”: An annual Halloween Party at the Stanford Mausoleum, the final resting place of Leland Stanford Jr. and his parents. A 20-year tradition, the “Mausoleum Party” was on hiatus from 2002 to 2005 due to a lack of funding, but was revived in 2006. In 2008, it was hosted in Old Union rather than at the actual Mausoleum, because rain prohibited generators from being rented. In 2009, after fundraising efforts by the Junior Class Presidents and the ASSU Executive, the event was able to return to the Mausoleum despite facing budget cuts earlier in the year.
    Former campus traditions include the “Big Game bonfire” on Lake Lagunita (a seasonal lake usually dry in the fall), which was formally ended in 1997 because of the presence of endangered salamanders in the lake bed.

    Award laureates and scholars

    Stanford’s current community of scholars includes:

    19 Nobel Prize laureates (as of October 2020, 85 affiliates in total)
    171 members of the National Academy of Sciences
    109 members of National Academy of Engineering
    76 members of National Academy of Medicine
    288 members of the American Academy of Arts and Sciences
    19 recipients of the National Medal of Science
    1 recipient of the National Medal of Technology
    4 recipients of the National Humanities Medal
    49 members of American Philosophical Society
    56 fellows of the American Physics Society (since 1995)
    4 Pulitzer Prize winners
    31 MacArthur Fellows
    4 Wolf Foundation Prize winners
    2 ACL Lifetime Achievement Award winners
    14 AAAI fellows
    2 Presidential Medal of Freedom winners

    Stanford University Seal

     
  • richardmitnick 10:42 am on June 15, 2019 Permalink | Reply
    Tags: A tale of two liquids, , , , , , SLAC LCLS, When stable becomes unstable,   

    From SLAC National Accelerator Lab: “A quick liquid flip helps explain how morphing materials store information” 

    From SLAC National Accelerator Lab

    June 14, 2019

    Experiments at SLAC’s X-ray laser reveal in atomic detail how two distinct liquid phases in these materials enable fast switching between glassy and crystalline states that represent 0s and 1s in memory devices.

    1
    In phase-change memory devices, a material switches between glassy and crystalline phases that represent the 0s and 1s used to store information. One pulse of electricity or light heats the material to high temperature, causing it to crystallize, and another pulse melts it into a disordered, glassy state. Experiments at SLAC’s X-ray laser revealed a key part of this switch – a quick transition from one liquid-like state to another – that enables fast and reliable data storage. (Peter Zalden/European XFEL)

    Instead of flash drives, the latest generation of smart phones uses materials that change physical states, or phases, to store and retrieve data faster, in less space and with more energy efficiency. When hit with a pulse of electricity or optical light, these materials switch between glassy and crystalline states that represent the 0s and 1s of the binary code used to store information.

    Now scientists have discovered how those phase changes occur on an atomic level.

    Researchers from European XFEL and the University of Duisburg-Essen in Germany, working in collaboration with researchers at the Department of Energy’s SLAC National Accelerator Laboratory, led X-ray laser experiments at SLAC that collected more than 10,000 snapshots of phase-change materials transforming from a glassy to a crystalline state in real time.

    They discovered that just before the material crystallizes, it changes from one liquid-like state to another, a process that could not be clearly seen in prior studies because it was blurred by the rapid motions of the atoms. And they showed that this transition is responsible for the material’s unique ability to store information for long periods of time while also quickly switching between states.

    The results, published in Science today, offer a new strategy for designing improved phase-change materials for specialized memory storage.

    “Current data storage technology has reached a scaling limit, so that new concepts are required to store the amounts of data that we will produce in the future,” said Peter Zalden, a scientist at European XFEL and lead author of the study. “Our study explains how the switching process in a promising new technology can be fast and reliable at the same time.”

    When stable becomes unstable

    The experiments took place at SLAC’s Linac Coherent Light Source (LCLS) which produces X-ray laser pulses that are short enough and intense enough to capture snapshots of atomic changes occurring in femtoseconds – millionths of a billionths of a second.

    To store information with phase-change materials, they must be cooled quickly to enter a glassy state without crystallizing, and remain in this glassy state as long as the information needs to stay there. This means the crystallization process must be very slow to the point of being almost absent, such as is the case in ordinary glass. But when it comes time to erase the information, which is done by applying high temperatures, the same material has to crystallize very quickly. The fact that a material can form a stable glass but then become very unstable at elevated temperatures has puzzled researchers for decades.

    At LCLS, the scientists used an optical laser to rapidly heat amorphous films of phase-change materials, just 50 nanometers thick, atop an equally thin support. The films cooled into a crystalline state as the heat from the laser blast dissipated into the surrounding support structure over billionths of a second.

    They used X-ray laser pulses to make images of the material’s structural evolution, collecting each snapshot in the instant before a sample deteriorated.

    A tale of two liquids

    The researchers found that when the liquid cools far enough below the material’s melting temperature, it undergoes a structural change to form another, lower-temperature liquid that exists for just billionths of a second.

    The two liquids not only have very different atomic structures, but they also behave differently: The one at higher temperature has highly mobile atoms that can quickly arrange themselves into the well-ordered structure of a crystal. But in the lower-temperature liquid, some chemical bonds become stronger and more rigid and can hold the disordered atomic structure of the glass in place. It is only the rigid nature of these chemical bonds that keeps the glass from crystallizing and – in the case of phase-change memory devices – secures information in place. The results also help scientists understand how other classes of materials form a glass.

    2
    The research team after performing experiments at SLAC’s Linac Coherent Light Source X-ray laser. (Klaus Sokolowski-Tinten/University of Duisburg-Essen)

    See the full article here.
    See the XFEL press release here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 9:11 am on April 25, 2019 Permalink | Reply
    Tags: "Researchers create the first maps of two melatonin receptors essential for sleep", , , Melatonin receptors belong to a group of membrane receptors called G protein-coupled receptors (GPCRs) which regulate almost all the physiological and sensory processes in the human body., MT1 and MT2 receptors, SLAC LCLS, These receptors oversee our clock genes- the timekeepers of the body’s internal clock or circadian rhythm., , When our circadian rhythms are disrupted it can lead to a number of downstream symptoms increasing the risk of cancer Type 2 diabetes and mood disorders., When there’s light the production of melatonin is inhibited; but when darkness comes that's the signal for our brains to go to sleep.,   

    From SLAC National Accelerator Lab: “Researchers create the first maps of two melatonin receptors essential for sleep” 

    From SLAC National Accelerator Lab

    April 24, 2019

    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282

    Written by Ali Sundermier

    1
    The behavior of humans and all animals is governed by a variety of natural cycles. The shift of seasons, tides, and day and night influences animal breeding and mating, predator-prey relationships, migration and foraging. Melatonin, depicted as a constellation in the night sky, is the key molecule that allows one of the most stable of these external cycles, a 24-hour day-night rhythm, to be correlated to an internal cycle, with responses at the level of individual cells and the whole animal. High melatonin levels during night time induce sleep-promoting properties by acting through melatonin receptors, depicted in the central reference point of the image composition. (Yekaterina Kadyshevskaya/Bridge Institute of the University of Southern California)

    A better understanding of how these receptors work could enable scientists to design better therapeutics for sleep disorders, cancer and Type 2 diabetes.

    An international team of researchers used an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to create the first detailed maps of two melatonin receptors that tell our bodies when to go to sleep or wake up, and guide other biological processes. A better understanding of how they work could enable researchers to design better drugs to combat sleep disorders, cancer and Type 2 diabetes. Their findings were published in two papers today in Nature: Structural basis of ligand recognition at the human MT1 melatonin receptor; XFEL structures of the human MT2 melatonin receptor reveal the basis of subtype selectivity.

    The team, led by the University of Southern California, used X-rays from SLAC’s Linac Coherent Light Source (LCLS) to map the receptors, MT1 and MT2, bound to four different compounds that activate them: an insomnia drug, a drug that mixes melatonin with the antidepressant serotonin, and two melatonin analogs.

    SLAC/LCLS

    They discovered that both melatonin receptors contain narrow channels embedded in the fatty membranes of the cells in our bodies. These channels only allow melatonin – which can exist in both water and fat – to pass through and bind to the receptors, blocking serotonin, which has a similar structure but is only happy in watery environments. They also uncovered how some much larger compounds may only target MT1 and not MT2, despite the structural similarities between the two receptors. This should inform the design of drugs that selectively target MT1, which so far has been challenging.

    “These receptors perform immensely important functions in the human body and are major drug targets of high interest to the pharmaceutical industry,” said Linda Johansson, a postdoctoral scholar at USC who led the structural work on MT2. “Through this work we were able to obtain a highly detailed understanding of how melatonin is able to bind to these receptors.”

    Time for bed

    People do it, birds do it, fish do it. Almost all living beings in the animal kingdom sleep, and for good reason.

    “It’s critical for the brain to take rest and process and store memories that we have accumulated during the day,” said co-author Alex Batyuk, a scientist at SLAC. “Melatonin is the hormone that regulates our sleep-wake cycles. When there’s light, the production of melatonin is inhibited, but when darkness comes that’s the signal for our brains to go to sleep.”

    Melatonin receptors belong to a group of membrane receptors called G protein-coupled receptors (GPCRs) which regulate almost all the physiological and sensory processes in the human body. MT1 and MT2 are found in many places throughout the body, including the brain, retina, cardiovascular system, liver, kidney, spleen and intestine.

    These receptors oversee our clock genes, the timekeepers of the body’s internal clock, or circadian rhythm. In a perfect world, our internal clocks would sync up with the rising and setting of the sun. But when people travel across time zones, work overnight shifts or spend too much time in front of screens or other artificial sources of blue light, these timekeepers are thrown out of whack.

    Controlling the rhythm

    When our circadian rhythms are disrupted, it can lead to a number of downstream symptoms, increasing the risk of cancer, Type 2 diabetes and mood disorders. MT1 in particular plays an important role in controlling these rhythms but designing drugs that can selectively target this receptor has proven difficult. Many people take over-the-counter melatonin supplements to combat sleep issues or shift their circadian rhythms, but these drugs often wear off within hours and can produce unwanted side effects.

    By cracking the blueprints of these receptors and mapping how ligands bind to and activate them, the researchers lit the way for others to design drugs that are safer, more effective and capable of selectively targeting each receptor.

    “Since the discovery of melatonin 60 years ago, there have been many landmark discoveries that led to this moment,” said Margarita L. Dubocovich, a State University of New York Distinguished Professor of pharmacology and toxicology at the University at Buffalo who pioneered the identification of functional melatonin receptors in the early 80s and provided an outside perspective on this research. “Despite remarkable progress, discovery of selective MT1 drugs has remained elusive for my team and researchers around the world. The elucidation of the crystal structures for the MT1 and MT2 receptors opens up an exciting new chapter for the development of drugs to treat sleep or circadian rhythm disorders known to cause psychiatric, metabolic, oncological and many other conditions.”

    Harvesting crystals

    To map biomolecules like proteins, researchers often use a method called X-ray crystallography, scattering X-rays off of crystallized versions of these proteins and using the patterns this creates to obtain a three-dimensional structure. Until now, the challenge with mapping MT1, MT2 and similar receptors was how difficult it was to grow large enough crystals to obtain high-resolution structures.

    “With these melatonin receptors, we really had to go the extra mile,” said Benjamin Stauch, a scientist at USC who led the structural work on MT1. “Many people had tried to crystallize them without success, so we had to be a little bit inventive.”

    A key piece of this research was the unique method the researchers used to grow their crystals and to collect X-ray diffraction data from them. For this research, the team expressed these receptors in insect cells and extracted them by using detergent. They mutated these receptors to stabilize them, enabling crystallization. After purifying the receptors, they placed them in a membrane-like gel, which supports crystal growth directly from the membrane environment. After obtaining microcrystals suspended in this gel, they used a special injector to create a narrow stream of crystals that they zapped with X-rays from LCLS.

    “Because of the tiny crystal size, this work could only be done at LCLS,” said Vadim Cherezov, a USC professor who supervised both studies. “Such small crystals do not diffract well at synchrotron sources as they quickly suffer from radiation damage. X-ray lasers can overcome the radiation damage problem through the ‘diffraction-before-destruction’ principle.”

    The researchers collected hundreds of thousands of images of the scattered X-rays to figure out the three-dimensional structure of these receptors. They also tested the effects of dozens of mutations to deepen their understanding of how the receptors work.

    3
    The researchers showed that both melatonin receptors contain narrow channels embedded in the cell’s fatty membranes. These channels only allow melatonin, which can exist happily in both water and fat, to pass through, preventing serotonin, which has a similar structure but is only happy in watery environments, from binding to the receptor. They also uncovered how some much larger compounds only target MT1 despite the structural similarities between the two receptors. (Greg Stewart/SLAC National Accelerator Laboratory)

    In addition to discovering tiny, gatekeeping melatonin channels in the receptors, the researchers were able to map Type 2 diabetes-associated mutations onto the MT2 receptor, for the first time seeing the exact location of these mutations in the receptor.

    Laying the groundwork

    In these experiments, the researchers only looked at compounds that activate the receptors, known as agonists. To follow up, they hope to map the receptors bound to antagonists, which block the receptors. They also hope to use their techniques to investigate other GPCR receptors in the body.

    “As a structural biologist, it was exciting to see the structure of these receptors for the first time and analyze them to understand how these receptors selectively recognize their signaling molecules,” Cherezov said. “We’ve known about them for decades but until now no one could say how they actually look. Now we can analyze them to understand how they recognize specific molecules, which we hope lays the groundwork for better, more effective drugs.”

    The team also included researchers from the University of North Carolina at Chapel Hill; Stanford University; Arizona State University; the University of Lille in France; and the University at Buffalo. LCLS is a DOE Office of Science user facility. This research was largely supported by the National Institutes of Health and the National Science Foundation BioXFEL Science and Technology Center.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 8:29 am on April 23, 2019 Permalink | Reply
    Tags: "A day in the life of a midnight beam master", , , Ben Ripman- operations engineer at the SLAC accelerator control room, , SLAC LCLS, SLAC SPEAR3, ,   

    From SLAC National Accelerator Lab: “A day in the life of a midnight beam master” 

    From SLAC National Accelerator Lab

    April 16, 2019 [Just today 4.23.19 in social media]
    Angela Anderson

    In SLAC’s accelerator control room, shift lead Ben Ripman and a team of operators fine-tune X-ray beams for science experiments around the clock.

    When is a day not a day? When you work in the central nervous system of the world’s longest linear accelerator, open 24-7.

    “There’s a constant cycle of people coming and going,” says Ben Ripman, an operations engineer at the Department of Energy’s SLAC National Accelerator Laboratory.

    1
    Ben Ripman, operations engineer at the SLAC accelerator control room (Angela Anderson/SLAC National Accelerator Laboratory)

    He might start at 8 a.m., at 4 p.m. or at midnight. But the shift rotations are no barrier to his passion for the job – leading a team of control room operators who deliver brilliant X-ray beams for scientific experiments.

    Control room operators spend most of their workdays (or nights) in a room filled with monitors, three deep and crowded with numbers, charts and graphs. Those displays track the status of thousands of devices and systems in the linear accelerator that runs through a tunnel below Highway 280 and feeds SLAC’s X-ray laser, the Linac Coherent Light Source (LCLS).

    SLAC/LCLS

    The accelerator boosts electrons to almost the speed of light and then wiggles them between magnets to generate X-rays. That X-ray light is formed into pulses and optimized for materials science, biology, chemistry, and physics experiments.

    The entire operation is monitored in the control room, which also serves SPEAR3, the accelerator that produces X-rays for the Stanford Synchrotron Radiation Lightsource (SSRL).

    2
    SLAC SPEAR3

    SLAC/SSRL

    Another set of monitors, staffed by SLAC Facilities, tracks water, compressed air and electricity systems that serve the lab campus.

    Ripman and his fellow operators are experts in reading these digital vital signs. But they are also some of the most knowledgeable people at the lab when it comes to the entire physical machine.

    “We know the accelerator from beginning to end,” he says. “When an operator adjusts something from the control room, they can picture that machine part and what it is doing.”

    For LCLS, they measure the amount of energy in individual X-ray pulses being fed to experimental hutches and often spend hours improving the pulses: tweaking magnets, adjusting the undulators, tuning the shape and length of the electron bunches.

    Some days the control room is quiet, and the operators focus on training and individual projects. On other, more challenging days when the machine is running in exotic modes, they work elbow to elbow with physicists.

    “We love this machine, but the accelerator was built decades ago and can be cantankerous,” Ripman explains. “When things do go wrong, it’s like a game of pickup sticks – one problem triggers another and you need to know how it all fits together.”

    An important part of the job is knowing who to call for help. “We wake up a lot of people in the middle of the night,” Ripman says with a smile.

    Control room operators also make sure everyone who goes into the accelerator tunnel stays safe.

    There are two ways to get into the accelerator. For minor repairs and inspections, people take keys from special key banks that block the accelerator from turning on until all the keys have been returned. On official maintenance days, the doors are thrown open.

    “On those days, maintenance crews, engineers and physicists descend into the tunnel and swarm the machine to resolve as many issues as possible before we have to summon them out again,” Ripman says. “We search the machine to make sure everyone is out before it’s turned back on.”

    Almost all of the displays in the control room were designed by the operators, he says. “We are known to hide ‘Easter eggs’ in them, but you have to get in our good graces to find out about them.”

    New operators take more than a year to get trained and proficient, Ripman says. “People come with a physics degree, but there is not a lot of formal coursework you can take on accelerator operations – it’s a lot of on-the-job training.”

    It was that hands-on learning that drew him to the job in 2010.

    “I was a nerd in high school,” Ripman admits proudly, “Stephen Hawking was my hero.” After studying physics and astronomy in college, Ripman worked as a contractor for NASA before joining SLAC. On his off hours, he plays board games and travels several times a year for card tournaments. He also loves hiking, skiing and snowboarding, and is a member of the Stanford University Singers.

    His favorite thing about the job? “My coworkers,” he says. “I have the privilege of working with smart, fun, quirky people. We all get along quite well, and there’s a great camaraderie.”

    Operators leave sticky notes with jokes or short messages for the next shift and share stories about their days and nights in the accelerator’s brain.

    Like the one about a ghost calling from an abandoned tunnel. But that’s a tale for another night…

    LCLS and SSRL are DOE Office of Science user facilities.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 11:18 am on April 15, 2019 Permalink | Reply
    Tags: "SLAC’s high-speed ‘electron camera’ films molecular movie in HD", , , , , How a bond in the ring breaks and atoms jiggle around for extended periods of time., , Researchers have made the first high-definition “movie” of ring-shaped molecules breaking open in response to light, SLAC LCLS, , The results demonstrate how our unique instruments for studying ultrafast processes complement each other, This allows us to ask new questions about fundamental processes stimulated by light., UED-ultrafast electron diffraction instrument   

    From SLAC National Accelerator Lab: “SLAC’s high-speed ‘electron camera’ films molecular movie in HD” 

    From SLAC National Accelerator Lab

    April 15, 2019

    Manuel Gnida
    mgnida@slac.stanford.edu
    (650) 926-2632

    1
    This illustration shows snapshots of the light-triggered transition of the ring-shaped 1,3-cyclohexadiene (CHD) molecule (background) to its stretched-out 1,3,5-hexatriene (HT) form (foreground). The snapshots were taken with SLAC’s high-speed “electron camera” – an instrument for ultrafast electron diffraction (UED). (Greg Stewart/SLAC National Accelerator Laboratory)

    With an extremely fast “electron camera” at the Department of Energy’s SLAC National Accelerator Laboratory, researchers have made the first high-definition “movie” of ring-shaped molecules breaking open in response to light. The results could further our understanding of similar reactions with vital roles in chemistry, such as the production of vitamin D in our bodies.


    Visualization of a molecular movie made with SLAC’s electron camera, in which researchers have captured in atomic detail how a ring-shaped molecule opens up in the first 800 millionths of a billionth of a second after being hit by a laser flash. Ring-opening reactions like this one play important roles in chemistry, such as the light-driven synthesis of vitamin D in our bodies. (Thomas Wolf/PULSE Institute)

    A previous molecular movie of the same reaction, produced with SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, for the first time recorded the large structural changes during the reaction.


    This video describes how the Linac Coherent Light Source, an X-ray free-electron laser at SLAC National Accelerator Laboratory, provided the first direct measurements of how a ring-shaped gas molecule unravels in the millionths of a billionth of a second after it is split open by light. The measurements were compiled in sequence to form the basis for computer animations showing molecular motion. (SLAC National Accelerator Laboratory)

    Now, making use of the lab’s ultrafast electron diffraction (UED) instrument, these new results provide high-resolution details – showing, for instance, how a bond in the ring breaks and atoms jiggle around for extended periods of time.

    3
    August 5, 2015- With SLAC’s new apparatus for ultrafast electron diffraction – one of the world’s fastest “electron cameras” – researchers can study motions in materials that take place in less than 100 quadrillionths of a second. A pulsed electron beam is created by shining laser pulses on a metal photocathode. The beam gets accelerated by a radiofrequency field and focused by a magnetic lens. Then it travels through a sample and scatters off the sample’s atomic nuclei and electrons, creating a diffraction image on a detector. Changes in these diffraction images over time are used to reconstruct ultrafast motions of the sample’s interior structure. (SLAC National Accelerator Laboratory)

    “The details of this ring-opening reaction have now been settled,” said Thomas Wolf, a scientist at the Stanford Pulse Institute of SLAC and Stanford University and leader of the research team. “The fact that we can now directly measure changes in bond distances during chemical reactions allows us to ask new questions about fundamental processes stimulated by light.”

    SLAC scientist Mike Minitti, who was involved in both studies, said, “The results demonstrate how our unique instruments for studying ultrafast processes complement each other. Where LCLS excels in capturing snapshots with extremely fast shutter speeds of only a few femtoseconds, or millionths of a billionth of a second, UED cranks up the spatial resolution of these snapshots. This is a great result, and the studies validate one another’s findings, which is important when making use of entirely new measurement tools.”

    LCLS Director Mike Dunne said, “We’re now making SLAC’s UED instrument available to the broad scientific community, in addition to enhancing the extraordinary capabilities of LCLS by doubling its energy reach and transforming its repetition rate. The combination of both tools uniquely positions us to enable the best possible studies of fundamental processes on ultrasmall and ultrafast scales.”

    The team reported their results today in Nature Chemistry.

    Molecular movie in HD

    This particular reaction has been studied many times before: When a ring-shaped molecule called 1,3-cyclohexadiene (CHD) absorbs light, a bond breaks and the molecule unfolds to form the almost linear molecule known as 1,3,5-hexatriene (HT). The process is a textbook example of ring-opening reactions and serves as a simplified model for studying light-driven processes during vitamin D synthesis.

    In 2015, researchers studied the reaction with LCLS, which resulted in the first detailed molecular movie of its kind and revealed how the molecule changed from a ring to a cigar-like shape after it was struck by a laser flash. The snapshots, which initially had limited spatial resolution, were brought further into focus through computer simulations.

    4
    Researchers created the first atomic-resolution movie of the ring-opening reaction of 1,3-cyclohexadiene (CHD) with an “electron camera” called UED. Bottom: The UED electron beam accurately measures the distances between pairs of atoms in the CHD molecule as the reaction proceeds. The distance between each pair is represented by a colored line in the graph. Variations in the distances as the molecule changes shape represent the molecular movie. Top: Visualization of the molecular structure corresponding to the distance distribution measured at about 380 femtoseconds into the reaction (dashed line at bottom). (David Sanchez/Stanford University)

    The new study used UED – a technique in which researchers send an electron beam with high energy, measured in millions of electronvolts (MeV), through a sample – to precisely measure distances between pairs of atoms.


    Taking snapshots of these distances at different intervals after an initial laser flash and tracking how they change allows scientists to create a stop-motion movie of the light-induced structural changes in the sample.

    The electron beam also produces strong signals for very dilute samples, such as the CHD gas used in the study, said SLAC scientist Xijie Wang, director of the MeV-UED instrument.

    3
    SLAC Megaelectronvolt Ultrasfast Electron Diffraction Instrument: MeV-UED

    “This allowed us to follow the ring-opening reaction over much longer periods of time than before.”

    Surprising details

    The new data revealed several surprising details about the reaction.

    They showed that the movements of the atoms accelerated as the CHD ring broke, helping the molecules rid themselves of excess energy and accelerating their transition to the stretched-out HT form.

    The movie also captured how the two ends of the HT molecule jiggled around as the molecules became more and more linear. These rotational motions went on for at least a picosecond, or a trillionth of a second.

    “I would have never thought these motions would last that long,” Wolf said. “It demonstrates that the reaction doesn’t end with the ring opening itself and that there is much more long-lasting motion in light-induced processes than previously thought.”

    A method with potential

    The scientists also used their experimental data to validate a newly developed computational approach for including the motions of atomic nuclei in simulations of chemical processes.

    “UED provided us with data that have the high spatial resolution needed to test these methods,” said Stanford chemistry professor and PULSE researcher Todd Martinez, whose group led the computational analysis. “This paper is the most direct test of our methods, and our results are in excellent agreement with the experiment.”

    In addition to advancing the predictive power of computer simulations, the results will help deepen our understanding of life’s fundamental chemical reactions, Wolf said: “We’re very hopeful our method will pave the way for studies of more complex molecules that are even closer to the ones used in life processes.”

    Other research institutions involved in this study were the University of York, UK; University of Nebraska-Lincoln; University of Potsdam, Germany; University of Edinburgh, UK; and Brown University. Large parts of this work were financially supported by the DOE Office of Science. SLAC’s MeV-UED instrument is part of LCLS, a DOE Office of Science user facility.

    See the full article here .


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    Please help promote STEM in your local schools.

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    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 10:05 am on April 4, 2019 Permalink | Reply
    Tags: A new method could turn random fluctuations in the intensity of laser pulses from a nuisance into an advantage facilitating studies of these fundamental interactions., In a computational process that borrows ideas from machine learning researchers can then turn these data into a visualization of the X-ray pulse’s effects on the sample., In addition we need to control the time delay between them very well., Pump-probe experiments therefore typically require that we first prepare well-defined short pulses that are less random, SLAC LCLS, , Taking advantage of X-ray spikes-by repeating the experiment with varying time delays between the pulses researchers can make a stop-motion movie of the tiny fast motions., Taking ghostly snapshots-Daniel Ratner and his coworkers want to apply the technique of ghost imaging., The secret is applying a method known as “ghost imaging” which reconstructs what objects look like without ever directly recording their images.,   

    From SLAC National Accelerator Lab: “Ghostly X-ray images could provide key info for analyzing X-ray laser experiments” 

    From SLAC National Accelerator Lab

    April 3, 2019
    Manuel Gnida

    1
    SLAC researchers suggest using the randomness of subsequent X-ray pulses from an X-ray laser to study the pulses’ interactions with matter, a method they call pump-probe ghost imaging. (Greg Stewart/SLAC National Accelerator Laboratory)

    X-ray free-electron lasers (XFELs) produce incredibly powerful beams of light that enable unprecedented studies of the ultrafast motions of atoms in matter. To interpret data taken with these extraordinary light sources, researchers need a solid understanding of how the X-ray pulses interact with matter and how those interactions affect measurements.

    Now, computer simulations by scientists from the Department of Energy’s SLAC National Accelerator Laboratory suggest that a new method could turn random fluctuations in the intensity of laser pulses from a nuisance into an advantage, facilitating studies of these fundamental interactions. The secret is applying a method known as “ghost imaging,” which reconstructs what objects look like without ever directly recording their images.

    “Instead of trying to make XFEL pulses less random, which is the approach we most often pursue for our experiments, we actually want to use randomness in this case,” said James Cryan from the Stanford PULSE Institute, a joint institute of Stanford University and SLAC. “Our results show that by doing so, we can get around some of the technical challenges associated with the current method for studying X-ray interactions with matter.”

    The research team published their results in Physical Review X.

    Taking advantage of X-ray spikes

    Scientists commonly look at these interactions through pump-probe experiments, in which they send pairs of X-ray pulses through a sample. The first pulse, called the pump pulse, rearranges how electrons are distributed in the sample. The second pulse, called the probe pulse, investigates the effects these rearrangements have on the motions of the sample’s electrons and atomic nuclei. By repeating the experiment with varying time delays between the pulses, researchers can make a stop-motion movie of the tiny, fast motions.

    One of the challenges is that X-ray lasers generate light pulses in a random process, so that each pulse is actually a train of narrow X-ray spikes whose intensities vary randomly between pulses.

    “Pump-probe experiments therefore typically require that we first prepare well-defined, short pulses that are less random,” said SLAC’s Daniel Ratner, the study’s lead author. “In addition we need to control the time delay between them very well.”

    In the new approach, he said, “We wouldn’t have to worry about any of that. We would use X-ray pulses as they come out of the XFEL without further modifications.”

    In fact, in this new way of thinking each pair of spikes within a single X-ray pulse can be considered a pair of pump and probe pulses, so researchers could do many pump-probe measurements with a single shot of the XFEL.

    2
    Simulated profile of an X-ray pulse from an X-ray free-electron laser. It consists of a train of narrow spikes whose intensity (power) fluctuates randomly. SLAC researchers suggest using pairs of these spikes for pump-probe experiments that trigger and measure structural changes in a sample, turning a former nuisance into an advantage. This example highlights three pairs of spikes with different time delays between them. (DOI: 10.1103/PhysRevX.9.01104 [N/A])

    Taking ghostly snapshots

    To produce snapshots of a sample’s molecular motions with this method, Ratner and his coworkers want to apply the technique of ghost imaging.

    In conventional imaging, light falling on an object produces a two-dimensional image on a detector – whether the back of your eye, the megapixel sensor in your cell phone or an advanced X-ray detector. Ghost imaging, on the other hand, constructs an image by analyzing how random patterns of light shining onto the object affect the total amount of light coming off the object.

    “In our method, the random patterns are the fluctuating spike structures of individual XFEL pulses,” said co-author Siqi Li, a graduate student at SLAC and Stanford and lead author of a previous study that demonstrated ghost imaging using electrons [Physical Review Letters]. “To do the image reconstruction, we need to repeat the experiment many times – about 100,000 times in our simulations. Each time, we measure the pulse profile with a diagnostic tool and analyze the signal emitted by the sample.”

    In a computational process that borrows ideas from machine learning, researchers can then turn these data into a visualization of the X-ray pulse’s effects on the sample.

    3
    In conventional imaging (left), light falling on an object produces a two-dimensional image on a detector. Ghost imaging (right) constructs an image by analyzing how random patterns of light shining onto the object affect the total amount of light coming off the object. (Greg Stewart/SLAC National Accelerator Laboratory)

    A complementary tool

    So far, the new idea has been tested only in simulations and awaits experimental validation, for instance at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, a DOE Office of Science user facility.

    SLAC LCLS

    Yet, the researchers are already convinced their method could complement conventional pump-probe experiments.

    “If future tests are successful, the method could strengthen our ability to look at very fundamental processes in XFEL experiments,” Ratner said. “It would also offer a few advantages that we would like to explore.” These include more stability, faster image reconstruction, less sample damage and the prospect of doing experiments at faster and faster timescales.

    Other co-authors of the paper are SLAC’s TJ Lane and Gennady Stupakov. The project was financially supported by the DOE Office of Science.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 7:29 am on March 14, 2019 Permalink | Reply
    Tags: "A new lens on materials under extreme conditions allows researchers to watch shock waves travel through silicon", , Elasticity in silicon shock wave, SLAC LCLS,   

    From SLAC National Accelerator Lab: “A new lens on materials under extreme conditions allows researchers to watch shock waves travel through silicon” 

    From SLAC National Accelerator Lab

    March 13, 2019
    Ali Sundermier

    1
    After blasting silicon with intense laser pulses at SLAC’s Linac Coherent Light Source, researchers saw an unexpected shock wave appear in the material before its structure was irreversibly changed. (Gregory Stewart/SLAC National Accelerator Laboratory)

    Elasticity, the ability of an object to bounce back to its original shape, is a universal property in solid materials. But when pushed too far, materials change in unrecoverable ways: Rubber bands snap in half, metal frames bend or melt and phone screens shatter.

    For instance, when silicon, an element abundant in the Earth’s crust, is subjected to extreme heat and pressure, an initial “elastic” shock wave travels through the material, leaving it unchanged, followed by an “inelastic” shock wave that irreversibly transforms the structure of the material.

    Using a new technique, researchers were able to directly watch and image this process. To their surprise, they discovered that it included an extra step that had not been seen before: After the first elastic shock wave traveled through the silicon, a second elastic wave appeared before the final inelastic wave changed the material’s properties.

    Their results were published in Science Advances last week.

    “We discovered that this transformation is more nuanced than previously thought,” says Shaughnessy Brennan Brown, a postdoctoral candidate at Stanford University and graduate research associate at the Department of Energy’s SLAC National Accelerator Laboratory who led the analysis. “We illuminated an entirely new feature potentially observable in other materials.”

    Seeing through a new lens

    In addition to contributing to a deeper understanding of silicon, a material that is important in fields like engineering, geophysics and plasma physics, this new technique lights the path for solving problems in other fields.

    “The platform Shaughnessy developed is also useful in areas like meteoritics,” says co-author Arianna Gleason-Holbrook, a staff scientist at the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC. “Let’s say a large metal impactor, like the remnant core of some planet, hits a terrestrial planet. This technique will allow us to zoom in and spatially walk through the history of that type of shock to answer a number of important questions, like how life gets delivered to a new planet or what happens during asteroid collisions.”

    “It’s almost like you’ve had blurry vision for a while,” she said, “but then you put on glasses and the world opens up. What we’ve done in this paper is provide a new lens on materials properties.”

    Catching the wave

    At SLAC, researchers can see what’s happening deep in the belly of samples by hitting them with ultrafast X-ray laser pulses from the Linac Coherent Light Source (LCLS), and then using the patterns formed by the scattered X-rays to reconstruct images.

    At the Matter in Extreme Conditions (MEC) instrument, researchers blast the samples with intense pulses from a second high-power laser before hitting them with X-rays to watch how materials respond to extreme heat and pressure. In many experiments, researchers position these two lasers nearly parallel to each other. This helps them understand how the material is changing over time but doesn’t give them a clear picture of what these structural transformations actually look like.

    A key feature of the technique used in this paper is that the researchers took advantage of a new laser placement that had been used in previous papers, shooting the pulses from the second laser perpendicular to the X-ray pulses from LCLS. This different vantage point allowed them to watch elusive structural changes to the silicon as they occurred, which is how they imaged the second wave moving through the silicon.

    Wide range of scales

    This new experimental setup also allowed the researchers to magnify what they saw, boosting the resolution of their images and allowing them to get a holistic picture of what was happening to the silicon on a wide range of scales, from the microscopic to the macroscopic.

    To follow up, the researchers will repeat the experiment in much more extreme conditions and apply it to a much broader class of materials to find out if they still see this extra step, which will lead to a better understanding of how materials transform.

    “We’ve been attempting to understand fundamental processes of material transformation without always seeing the whole picture,” Brennan Brown says. “Many scientists use clever techniques to approach the problem from different angles. The beauty of this new platform is its clarity, directness and scope.”

    The team also included researchers from the University of York in England; the University of California, Berkeley; the Deutsches Elektronen-Synchrotron and the University of Hamburg, both in Germany.

    LCLS is a DOE Office of Science user facility. Funding was provided by the DOE Office of Science.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 8:30 pm on February 21, 2019 Permalink | Reply
    Tags: , , , , Molecular ensemble, , , , PtPOP, , SLAC LCLS, ,   

    From SLAC National Accelerator Lab: “Researchers watch molecules in a light-triggered catalyst ring ‘like an ensemble of bells’’ 

    From SLAC National Accelerator Lab

    February 21, 2019
    Ali Sundermier

    1
    Synchronized molecules
    When photocatalyst molecules absorb light, they start vibrating in a coordinated way, like an ensemble of bells. Capturing this response is a critical step towards understanding how to design molecules for the efficient transformation of light energy to high-value chemicals. (Gregory Stewart/SLAC National Accelerator Laboratory)

    A better understanding of these systems will aid in developing next-generation energy technologies.

    Photocatalysts ­– materials that trigger chemical reactions when hit by light – are important in a number of natural and industrial processes, from producing hydrogen for fuel to enabling photosynthesis.

    Now an international team has used an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to get an incredibly detailed look at what happens to the structure of a model photocatalyst when it absorbs light.

    The researchers used extremely fast laser pulses to watch the structure change and see the molecules vibrating, ringing “like an ensemble of bells,” says lead author Kristoffer Haldrup, a senior scientist at Technical University of Denmark (DTU). This study paves the way for deeper investigation into these processes, which could help in the design of better catalysts for splitting water into hydrogen and oxygen for next-generation energy technologies.

    “If we can understand such processes, then we can apply that understanding to developing molecular systems that do tricks like that with very high efficiency,” Haldrup says.

    The results published last week in Physical Review Letters.

    Molecular ensemble

    The platinum-based photocatalyst they studied, called PtPOP, is one of a class of molecules that scissors hydrogen atoms off various hydrocarbon molecules when hit by light, Haldrup says: “It’s a testbed – a playground, if you will – for studying photocatalysis as it happens.”

    At SLAC’S X-ray laser, the Linac Coherent Light Source (LCLS), the researchers used an optical laser to excite the platinum-containing molecules and then used X-rays to see how these molecules changed their structure after absorbing the visible photons.

    SLAC/LCLS

    The extremely short X-ray laser pulses allowed them to watch the structure change, Haldrup says.

    The researchers used a trick to selectively “freeze” some of the molecules in their vibrational motion, and then used the ultrashort X-ray pulses to capture how the entire ensemble of molecules evolved in time after being hit with light. By taking these images at different times they can stitch together the individual frames like a stop-motion movie. This provided them with detailed information about molecules that were not hit by the laser light, offering insight into the ultrafast changes occurring in the molecules when they are at their lowest energy.

    Swimming in harmony

    Even before the light hits the molecules, they are all vibrating but out of sync with one another. Kelly Gaffney, co-author on this paper and director of SLAC’s Stanford Synchrotron Radiation Lightsource, likens this motion to swimmers in a pool, furiously treading water.

    SLAC SSRL Campus


    SLAC/SSRL


    SLAC/SSRL

    When the optical laser hits them, some of the molecules affected by the light begin moving in unison and with greater intensity, switching from that discordant tread to synchronized strokes. Although this phenomenon has been seen before, until now it was difficult to quantify.

    “This research clearly demonstrates the ability of X-rays to quantify how excitation changes the molecules,” Gaffney says. “We can not only say that it’s excited vibrationally, but we can also quantify it and say which atoms are moving and by how much.”

    Predictive chemistry

    To follow up on this study, the researchers are investigating how the structures of PtPOP molecules change when they take part in chemical reactions. They also hope to use the information they gained in this study to directly study how chemical bonds are made and broken in similar molecular systems.

    “We get to investigate the very basics of photochemistry, namely how exciting the electrons in the system leads to some very specific changes in the overall molecular structure,” says Tim Brandt van Driel, a co-author from DTU who is now a scientist at LCLS. “This allows us to study how energy is being stored and released, which is important for understanding processes that are also at the heart of photosynthesis and the visual system.”

    A better understanding of these processes could be key to designing better materials and systems with useful functions.

    “A lot of chemical understanding is rationalized after the fact. It’s not predictive at all,” Gaffney says. “You see it and then you explain why it happened. We’re trying to move the design of useful chemical materials into a more predictive space, and that requires accurate detailed knowledge of what happens in the materials that already work.”

    LCLS and SSRL are DOE Office of Science user facilities. This research was supported by DANSCATT; the Independent Research Fund Denmark; the Icelandic Research Fund; the Villum Foundation; and the AMOS program within the Chemical Sciences, Geosciences and Biosciences Division of the DOE Office of Basic Energy Sciences.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 11:19 am on January 15, 2019 Permalink | Reply
    Tags: An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon, , , , , SLAC LCLS,   

    From SLAC National Accelerator Lab: “An effect that Einstein helped discover 100 years ago offers new insight into a puzzling magnetic phenomenon” 

    From SLAC National Accelerator Lab

    January 14, 2019
    Ali Sundermier

    1
    At SLAC’s Linac Coherent Light Source, the researchers blasted an iron sample with laser pulses to demagnetize it, then grazed the sample with X-rays, using the patterns formed when the X-rays scattered to uncover details of the process. (Gregory Stewart/SLAC National Accelerator Laboratory)

    2
    Researchers from ETH Zürich in Switzerland used LCLS to show a link between ultrafast demagnetization and an effect that Einstein helped discover 100 years ago. (Dawn Harmer/SLAC National Accelerator Laboratory)

    Using an X-ray laser, researchers watched atoms rotate on the surface of a material that was demagnetized in millionths of a billionth of a second.

    More than 100 years ago, Albert Einstein and Wander Johannes de Haas discovered that when they used a magnetic field to flip the magnetic state of an iron bar dangling from a thread, the bar began to rotate.

    Now experiments at the Department of Energy’s SLAC National Accelerator Laboratory have seen for the first time what happens when magnetic materials are demagnetized at ultrafast speeds of millionths of a billionth of a second: The atoms on the surface of the material move, much like the iron bar did. The work, done at SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, was published in Nature earlier this month.

    SLAC/LCLS

    Christian Dornes, a scientist at ETH Zürich in Switzerland and one of the lead authors of the report, says this experiment shows how ultrafast demagnetization goes hand in hand with what’s known as the Einstein-de Haas effect, solving a longstanding mystery in the field.

    “I learned about these phenomena in my classes, but to actually see firsthand that the transfer of angular momentum actually makes something move mechanically is really cool,” Dornes says. “Being able to work on the atomic scale like this and see relatively directly what happens would have been a total dream for the great physicists of a hundred years ago.”

    Spinning sea of skaters

    At the atomic scale, a material owes its magnetism to its electrons. In strong magnets, the magnetism comes from a quantum property of electrons called spin. Although electron spin does not involve a literal rotation of the electron, the electron acts in some ways like a tiny spinning ball of charge. When most of the spins point in the same direction, like a sea of ice skaters pirouetting in unison, the material becomes magnetic.

    When the magnetization of the material is reversed with an external magnetic field, the synchronized dance of the skaters turns into a hectic frenzy, with dancers spinning in every direction. Their net angular momentum, which is a measure of their rotational motion, falls to zero as their spins cancel each other out. Since the material’s angular momentum must be conserved, it’s converted into mechanical rotation, as the Einstein-de Haas experiment demonstrated.

    Twist and shout

    In 1996, researchers discovered that zapping a magnetic material with an intense, super-fast laser pulse demagnetizes it nearly instantaneously, on a femtosecond time scale. It has been a challenge to understand what happens to angular momentum when this occurs.

    In this paper, the researchers used a new technique at LCLS combined with measurements done at ETH Zürich to link these two phenomena. They demonstrated that when a laser pulse initiates ultrafast demagnetization in a thin iron film, the change in angular momentum is quickly converted into an initial kick that leads to mechanical rotation of the atoms on the surface of the sample.

    3
    At SLAC’s Linac Coherent Light Source, the researchers blasted an iron sample with laser pulses to demagnetize it, then grazed the sample with X-rays, using the patterns formed when the X-rays scattered to uncover details of the process. (Gregory Stewart/SLAC National Accelerator Laboratory)

    According to Dornes, one important takeaway from this experiment is that even though the effect is only apparent on the surface, it happens throughout the whole sample. As angular momentum is transferred through the material, the atoms in the bulk of the material try to twist but cancel each other out. It’s as if a crowd of people packed onto a train all tried to turn at the same time. Just as only the people on the fringe would have the freedom to move, only the atoms at the surface of the material are able to rotate.

    Scraping the surface

    In their experiment, the researchers blasted the iron film with laser pulses to initiate ultrafast demagnetization, then grazed it with intense X-rays at an angle so shallow that it was nearly parallel to the surface. They used the patterns formed when the X-rays scattered off the film to learn more about where angular momentum goes during this process.

    “Due to the shallow angle of the X-rays, our experiment was incredibly sensitive to movements along the surface of the material,” says Sanghoon Song, one of three SLAC scientists who were involved with the research. “This was key to seeing the mechanical motion.”

    To follow up on these results, the researchers will do further experiments at LCLS with more complicated samples to find out more precisely how quickly and directly the angular momentum escapes into the structure. What they learn will lead to better models of ultrafast demagnetization, which could help in the development of optically controlled devices for data storage.

    Steven Johnson, a scientist and professor at ETH Zürich and the Paul Scherrer Institute in Switzerland who co-led the study, says the group’s expertise in areas outside of magnetism allowed them to approach the problem from a different angle, better positioning them for success.

    “There have been numerous previous attempts by other groups to understand this, but they failed because they didn’t optimize their experiments to look for these tiny effects,” Johnson says. “They were swamped by other much larger effects, such as atomic movement due to laser heat. Our experiment was much more sensitive to the kind of motion that results from the angular momentum transfer.”

    LCLS is a DOE Office of Science user facility. This work was supported by NCCR Molecular Ultrafast Science and Technology, a research instrument of the Swiss National Science Foundation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
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