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  • richardmitnick 12:59 pm on January 13, 2017 Permalink | Reply
    Tags: , , Nuclear physics, Physics,   

    From BNL: “sPHENIX Gets CD0 for Upgrade to Experiment Tracking the Building Blocks of Matter” 

    Brookhaven Lab

    January 13, 2017
    Karen McNulty Walsh
    kmcnulty@bnl.gov

    First step on a path toward a detector with unprecedented capabilities for deciphering how the properties of the hottest matter in the universe emerge from the interactions of its fundamental particles.

    [SEE? THE USA CAN STILL GET IT DONE IN HEP IF WE JUST MAKE THE RIGHT DECISIONS.]

    1
    The solenoid magnet that will form the core of the sPHENIX detector. No image credit.

    The U.S. Department of Energy (DOE) has granted “Critical Decision-Zero” (CD-0) status to the sPHENIX project, a transformation of one of the particle detectors at the Relativistic Heavy Ion Collider (RHIC)—a DOE Office of Science User Facility at Brookhaven National Laboratory—into a research tool with unprecedented precision for tracking subatomic interactions.

    BNL RHIC Campus
    BNL/RHIC
    RHIC a BNL, with map.

    This decision is an important first step in the DOE process for starting new projects, stating that there is a “mission need” for the capabilities described by the proposal.

    “We are very excited that the Department of Energy has recognized the importance of the sPHENIX project,” said Berndt Mueller, Associate Laboratory Director for Nuclear and Particle Physics at Brookhaven. “This upgrade will offer new insight into how the interactions of the smallest building blocks of matter give rise to the remarkable properties of ‘quark-gluon plasma’—a four-trillion-degree soup of fundamental particles that existed in the universe a microsecond after its birth and recreated regularly in particle collisions at RHIC.”

    As Brookhaven Lab physicist Dave Morrison, a co-spokesperson for the sPHENIX collaboration, explained, “sPHENIX will be an essential tool for exploring the quark-gluon plasma, including its ability to flow like a nearly ‘perfect’ liquid. The capabilities we develop and scientific insight we gain will also help us to prepare for the coming research directions in nuclear physics,” he said.

    2
    A schematic of the sPHENIX experiment at BNL. No image credit.

    The sPHENIX project is an upgrade of RHIC’s former PHENIX detector, which completed its data-taking mission in June 2016.

    “We’ll be leveraging scientific and financial investments already made when building RHIC,” said Gunther Roland, a physicist at the Massachusetts Institute of Technology and the other co-spokesperson for sPHENIX. “But at the same time, the transformation will introduce new, state-of-the-art detector systems.”

    With a superconducting solenoid magnet recycled from a physics experiment at DOE’s SLAC National Laboratory at its core, state-of-the-art particle-tracking detectors, and an array of novel high-acceptance calorimeters, sPHENIX will have the speed and precision needed to track and study the details of particle jets, heavy quarks, and rare, high-momentum particles produced in RHIC’s most energetic collisions. These capabilities will allow nuclear physicists to probe properties of the quark-gluon plasma at varying length scales to make connections between the interactions among individual quarks and gluons and the collective behavior of the liquid-like primordial plasma.

    Conceptual studies and R&D are already underway for key components, including the solenoid, calorimeters, and tracking detectors. The CD0 decision—the go-ahead that enables conceptual design and R&D to proceed—will enable these efforts and set sPHENIX on the path toward an exciting physics program starting in 2022.

    Research at RHIC and the sPHENIX project are supported primarily by the DOE Office of Science.

    See the full article here .

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 11:38 am on January 13, 2017 Permalink | Reply
    Tags: , , , , Physicist Peter Graham, Physics,   

    From Stanford: “Stanford physicist suggests looking for dark matter in unusual places” 

    Stanford University Name
    Stanford University

    January 12, 2017
    Amy Adams

    Most experiments searching for mysterious dark matter require massive colliders, but Stanford physicist Peter Graham advocates a different, less costly approach.

    1
    Physicist Peter Graham recently received a Breakthrough New Horizons Prize for his novel approach to particle physics. (Image credit: L.A. Cicero)

    For decades, particle physics has been the domain of massive colliders that whip particles around at high speeds and smash them into one another while teams of thousands observe the results. These kinds of experiments have produced great insights into forces and particles that make up the physical world.

    But Stanford physicist Peter Graham is advocating a much different approach – one that could be faster and cheaper than massive colliders, and that may be able to detect previously elusive forms of physics like dark matter.

    Graham pointed out that colliders cost tens of billions of dollars and come along so rarely that there might only be one new collider built in his lifetime. His approach evokes a time when physics could be carried out on a tabletop by one or two people and produce results in just a few years.

    “It’s going back to that in some ways, but using very different types of technologies and different approaches,” said Graham, who is an assistant professor of physics. “It’s a new direction for looking for the most basic laws of nature.”

    Graham, who is also a collaborator with the elementary particle physics division at SLAC National Accelerator Laboratory, recently received a Breakthrough New Horizons in Physics Prize for his novel direction, which he hopes more people will join. He spoke with Stanford Report about why physics needs new types of experiments, what dark matter might be and how he hopes to detect it.

    You’ve said that your experiments explore new physics. What does that mean?

    The standard model of particle physics is everything we’ve discovered. It explains almost every experiment ever done over gigantic scales, from nuclei to galaxies.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    There’s really just a very few things it doesn’t explain, which we call new physics. We know there is stuff out there beyond what we’ve seen, like dark matter, and new fundamental laws. Those are the things we are trying to discover.

    Dark matter is one form of new physics you might be able to detect. Can you explain what dark matter is and why physicists believe it exists?

    Initially, people realized that there’s much more gravity pulling in on galaxies than they could account for. Either the laws of gravity were wrong, which was possible, or there was something else that we don’t know about pulling on the galaxies. Either way, you can’t explain it with what we know.

    There’s now a lot of evidence that our understanding of gravity isn’t wrong, and instead there’s some new kind of stuff that physicists have named dark matter. It’s been a major goal in physics to understand dark matter and come up with new types of experiments to try to detect it. But you have to have some guesses about what it might be if you are going to find it. It’s a universal point in science that you have to have some idea what you are looking for in order to know how to go about looking for it.

    What are some of the theories about what dark matter might be?

    There is a lot of evidence for two candidates, called WIMPs and axions. You can look for WIMPs [weakly interacting massive particles] with more traditional techniques, like the giant colliders, and that attracted a lot of attention.

    There was just one experiment looking for axions and it only looked at part of the possible axion spectrum. It was a scary scenario that axions might be the dark matter and there might be no way to detect them. Axions are very difficult to search for because they don’t interact much with our experiments.

    Dark matter could also be some crazy new kind of particle, or a combination of WIMPs and axions, or even collections of black holes. We don’t know.

    What motivated you to think about alternate ways of exploring new physics?

    Part of the motivation is that the big colliders are important but they are also getting expensive to build. In addition, we are realizing that some new theories about dark matter really couldn’t be discovered at colliders.

    My work has been to take techniques from other fields of physics and use them in particle physics. The Breakthrough Prize is really nice because it brings a stamp of approval and could really help us get this new experimental direction going.

    Can you give me an example of one type of experiment you’ve designed?

    People had thought about one approach to detect axion dark matter and it did a good job for higher mass axions, but could not possibly see lower mass axions. We came up with a new technique to detect low mass axions. It involved combining NMR [nuclear magnetic resonance], which is commonly used in medical applications, and magnetometry, which is a very precise tool for measuring magnetic fields. We use NMR to amplify the axion signal so that the magnetometer can pick it up.

    We’ve already started building this experiment, and it could generate results in a few years. It’s very exciting because these kinds of experiments can produce results on short time scales.

    Why is it important to explore these new frontiers in physics?

    Humanity has always stared up at the stars and wondered why we are here. These kinds of questions, like the nature of dark matter, tell us about the birth of the universe, why the whole universe is here.

    But a part of it for me is also that I want to be making some contribution. One example of how basic physics helps people came from quantum mechanics. I’m sure at the time they thought it was a pure physics exercise and had no relation to human health. Well, we learned quantum mechanics and now we have MRI machines and PET scans. I would say that’s a really important lesson. Humans are creative and we do find ways to use new information.

    See the full article here .

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    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

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  • richardmitnick 3:52 pm on January 11, 2017 Permalink | Reply
    Tags: , , , , , , Physics,   

    From PI via Motherboard: “Dark Matter Hunters Are Hoping 2017 is Their Year” 

    Perimeter Institute
    Perimeter Institute

    Motherboard

    January 3, 2017
    Kate Lunau

    It can be unsettling to realize that only five percent of the universe is made of the kind of matter we know and understand—everything from the planets and stars, to trees and animals and your dining room table.

    Roughly one-quarter is dark matter. This is thought to knit the galaxies together, and has been called the “scaffolding” of the universe, but we’ve never detected it directly. Scientists believe they can see dark matter’s traces in the way that galaxies rotate, but they still have no idea what it is. (Most of the universe, about 70 percent, is dark energy, a mysterious force that permeates space and time. It’s even less well-understood than dark matter.)

    Confirming dark matter’s existence would change humankind’s perspective on the universe. 2016 was a year of dark matter disappointments, as big searches came up empty. Most are looking for WIMPs—weakly interacting massive particles, the leading contender for a dark matter particle.

    2017 might just be the year we finally catch one. And if we don’t, well, it may be that our best theories about dark matter are wrong—that we’re looking in the wrong places, with the wrong instruments. Maybe dark matter, whatever it is, will turn out to be even weirder and more surprising than anyone has so far predicted. Maybe it’s not a WIMP, but some other bizarre kind of particle.

    Then there’s the outside possibility that dark matter doesn’t exist, that it’s an illusion. If that’s the case, we’ll have to consider whether we’ve been fundamentally misreading the universe’s clues.

    Buried deep in a mine near Sudbury in northern Ontario is SNOLAB, a vast underground laboratory where scientists are performing a range of experiments, including looking for dark matter. Often compared to the lair of a Bond villain, it’s an ultra-clean, high-tech facility. Two kilometers of solid rock overhead shield its detectors from cosmic radiation, allowing them to sift for bits of matter from dying stars and the Sun: science done here won the Nobel Prize in Physics, in 2015.

    2
    A scientist works on the deck of DEAP-3600, a dark matter search at SNOLAB. Image: SNOLAB

    I recently travelled to SNOLAB. To get there, I had to don full mining gear (including a hardhat and headlamp), drop down underground in a rattling dark cage, and hike a kilometre or so to reach the gleaming white facility, which is cleaner inside than an operating room—a startling contrast to the dirty nickel mine that surrounds it.

    After the long hike through the mine, anyone who wants to enter SNOLAB has to undress, shower (with soap and shampoo), and put on lint-free clothing and a hairnet. Any bit of dust from the mine, which is naturally radioactive, can mess up the experiments.

    There, I met research scientist Ken Clark, a congenial physicist with a sandy-coloured beard. Like me, he was wearing safety goggles and a hardhat. Clark has worked on high-profile dark matter searches like CDMS and LUX, and collaborates on the IceCube detector at the South Pole in Antarctica.

    LBL SuperCDMS
    LBL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)
    LBL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    LUX Xenon experiment at SURF
    LUX Xenon experiment at SURF, Lead, SD, USA

    U Wisconsin ICECUBE neutrino detector at the South Pole
    IceCube neutrino detector interior
    U Wisconsin ICECUBE neutrino detector at the South Pole

    Now he’s with PICO, a dark matter search that targets the WIMP particle.

    5

    It was launched in 2013 when two other collaborations, called PICASSO and COUPP, merged.

    6
    A multi-bubble image of a neutron scattering in the PICO detector. Image: PICO Collaboration

    PICO is a bubble detector: a tank of superheated fluid kept higher than its natural boiling point. If dark matter bumps into the nucleus of another particle in the detector, it should cause a tiny bubble to form. Dark matter courses through the Earth and right through our bodies, so it will reach the detector underground, even through all that rock overhead. But that’s also part of the challenge—dark matter is thought to only rarely interact with normal matter, if at all, so it’s really tricky to catch.

    Clark believes we might just find dark matter in the next year or two. “It’s exciting times,” he said.

    Other searches are due to turn on soon, he explained, and those that are already up-and-working are getting increasingly sensitive. In 2017, Clark said it’s possible we’ll see new results from PICO, DEAP (a different detector, also at SNOLAB), as well as China’s ambitious PandaX project, and another in Italy called XENON1T. Even more searches will turn on in 2018.

    “Provided the models are correct, we should see something soon,” Clark told me.

    7
    A scientist works on the steel vessel of DEAP-3600. Image: DEAP Collaboration

    Still, there’s no guarantee, and WIMP searches keep turning up empty-handed. For example, in the summer, the highly sensitive LUX—which uses liquid xenon in a South Dakota mine as its detector—announced it had seen zero WIMPs, after looking for more than a year.

    I phoned Lisa Randall, a prominent theoretical physicist and professor at Harvard University, to ask whether she thinks there’s a chance we’ll find dark matter in the next year or two.

    “I would say kind of the opposite,” said Randall, author of Dark Matter and the Dinosaurs. While she agrees that if dark matter is indeed a WIMP, these searches could find it soon, “that’s just one possibility,” she said.

    The WIMP is “lowest-hanging fruit,” Randall continued: this theoretical particle fits snugly within what’s already known about the Standard Model of physics, which explains how the building blocks of the universe interact. And scientists can imagine ways to actually look for WIMPs, unlike some of the more far-out theories, which are much harder to test in experiments.

    “What if it’s not a WIMP?” Randall said. “Could we still learn something about what dark matter is?”

    Other scientists have different strategies for solving the dark matter puzzle.

    Leslie Rosenberg, a professor of physics at the University of Washington in Seattle, is project scientist on the Axion Dark Matter Experiment, or ADMX, which is looking for a theoretical particle called the axion, which is thought to be much lighter than a WIMP.

    ADMX Axion Dark Matter Experiment
    U Washington ADMX
    U Washington ADMX

    It’s being targeted by other searches under development around the world, Rosenberg told me. ADMX, though, is “the only high-sensitivity axion search now,” he said.

    Maybe we’re being fooled into thinking that dark matter is there.

    ADMX, which uses a resonant microwave cavity nested inside a huge superconducting magnet, started out of a collaboration that began in the mid-nineties. It’s been at full sensitivity for about a year now, Rosenberg told me, and will only get better as the team continues to tweak it. He’s hoping they turn up something soon: their next update should come in the summer of 2017.

    “Axions are bound up in our galaxy,” Rosenberg said. “There [should be] an awful lot of them, and we depend on that as the source of our signal.”

    Axions are a mainstream dark matter candidate. Other ideas get weirder.

    “Personally, I’m interested in the idea that dark matter might have nothing to do with the Standard Model,” Randall told me. “One of the possibilities is that it could be some other type of particle. Maybe it interacts [with itself] via its own light, a dark photon.”

    7
    ESA/Gaia’s first sky map of the Milky Way, based on data collected from July 2014 to Sept. 2015. Image: ESA/Gaia/DPAC

    Randall thinks that one of the best ways to learn about dark matter may be to study the structure of galaxies, and watching the universe at work, to understand how it interacts with itself. The European Space Agency’s Gaia mission, which is making a three-dimensional map of over a thousand million stars, could give insight into some of this, Randall said.

    Asimina Arvanitaki, a theoretical physicist at the Perimeter Institute for Theoretical Physics, suggested to me in a Skype call that dark matter might be detectable through resonant-mass detectors, which are used to hunt for gravitational waves. These ripples in spacetime were detected for the first time in 2016, a hundred years after Albert Einstein predicted their existence.

    Dark matter could also be behaving like a wave, “trapped by gravity and oscillat[ing] at a frequency set by the mass,” she said.

    “The funny thing is you could perhaps even hear dark matter,” Arvanitaki said, “depending on the frequency.”

    Over millions of years, humans have come up with ingenious ways to probe the world around us, from Copernicus and Kepler, through the thousands of scientists involved in the search for the Higgs boson particle at the Large Hadron Collider, and those who are now shaking out the endless diversity of exoplanets that populate our galaxy.

    Because of them, our perspective has changed. When we look up at the night sky today, we understand that just about every star we see hosts at least one planet. The first confirmed exoplanet was announced just over two decades ago.

    Nature can still surprise us.

    7
    The Bullet cluster, formed by the collision of two large galaxy clusters, provides some of the best evidence yet for dark matter. Image: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

    “There’s a chance that dark matter isn’t necessarily a particle at all,” Clark told me. “Some [theorists] say there’s no dark matter. It’s just that we don’t understand how gravity works at large scales,” he continued. “If that’s the case, we’re being fooled into thinking that dark matter is there.”

    Clark and the other dark matter hunters continue their search. If it’s real, “we’re not even made of what most of the universe is made of,” Rosenberg told me. In the grand scheme of things, then, it isn’t dark matter that’s really so exotic and strange—it’s us.

    See the full article here .

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    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 10:13 am on January 11, 2017 Permalink | Reply
    Tags: , Here’s how to build a whirligig, Inspired by a whirligig toy Stanford bioengineers develop a 20-cent hand-powered blood centrifuge, , Physics,   

    From Stanford: “Inspired by a whirligig toy, Stanford bioengineers develop a 20-cent, hand-powered blood centrifuge” 

    Stanford University Name
    Stanford University

    January 10, 2017
    Kris Newby

    Stanford bioengineers have developed an ultra-low-cost, human-powered blood centrifuge. With rotational speeds of up to 125,000 revolutions per minute, the device separates blood plasma from red cells in 1.5 minutes, no electricity required.


    Access mp4 video here .
    Inspired by a toy, Stanford bioengineers have developed an inexpensive, human-powered blood centrifuge that will enable precise diagnosis and treatment of diseases like malaria, African sleeping sickness and tuberculosis in the poor, off-the-grid regions where these diseases are most prevalent. Video by Kurt Hickman

    Here’s how to build a whirligig: Thread a loop of twine through two holes in a button. Grab the loop ends, then rhythmically pull. As the twine coils and uncoils, the button spins at a dizzying speed.

    Now, using the same mechanical principles, Stanford bioengineers have created an ultra-low-cost, human-powered centrifuge that separates blood into its individual components in only 1.5 minutes. Built from 20 cents of paper, twine and plastic, a “paperfuge” can spin at speeds of 125,000 rpm and exert centrifugal forces of 30,000 Gs.

    “To the best of my knowledge, it’s the fastest spinning object driven by human power,” said Manu Prakash, an assistant professor of bioengineering at Stanford.

    A centrifuge is critical for detecting diseases such as malaria, African sleeping sickness, HIV and tuberculosis. This low-cost version will enable precise diagnosis and treatment in the poor, off-the-grid regions where these diseases are most prevalent.

    The physics and test results of this device are published in the Jan. 10 issue of Nature Biomedical Engineering.

    No electricity required

    When used for disease testing, a centrifuge separates blood components and makes pathogens easier to detect. A typical centrifuge spins fluid samples inside an electric-powered, rotating drum. As the drum spins, centrifugal forces separate fluids by density into layers within a sample tube. In the case of blood, heavy red cells collect at the bottom of the tube, watery plasma floats to the top, and parasites, like those that cause malaria, settle in the middle.

    Prakash, who specializes in low-cost diagnostic tools for underserved regions, recognized the need for a new type of centrifuge after he saw an expensive centrifuge being used as a doorstop in a rural clinic in Uganda because there was no electricity to run it.

    “There are more than a billion people around the world who have no infrastructure, no roads, no electricity. I realized that if we wanted to solve a critical problem like malaria diagnosis, we needed to design a human-powered centrifuge that costs less than a cup of coffee,” said Prakash, who was senior author on the study.

    Inspired by spinning toys, Prakash began brainstorming design ideas with Saad Bhamla, a postdoctoral research fellow in his lab and first author on the paper. After weeks of exploring ways to convert human energy into spinning forces, they began focusing on toys invented before the industrial age – yo-yos, tops and whirligigs.

    “One night I was playing with a button and string, and out of curiosity, I set up a high-speed camera to see how fast a button whirligig would spin. I couldn’t believe my eyes,” said Bhamla, when he discovered that the whirring button was rotating at 10,000 to 15,000 rpms.

    After two weeks of prototyping, he mounted a capillary of blood on a paper-disc whirligig and was able to centrifuge blood into layers. It was a definitive proof-of-concept, but before he went to the next step in the design process, he and Prakash decided to tackle a scientific question no one else had: How does a whirligig actually work?

    The other string theory

    Bhamla recruited three undergraduate engineering students from MIT and Stanford to build a mathematical model of how the devices work. The team created a computer simulation to capture design variables like disc size, string elasticity and pulling force. They also borrowed equations from the physics of supercoiling DNA strands to understand how hand-forces move from the coiling strings to power the spinning disc.

    “There are some beautiful mathematics hidden inside this object,” Prakash said.

    Once the engineers validated their models against real-world prototype performance, they were able to create a prototype with rotational speeds of up to 125,000 rpm, a magnitude significantly higher than their first prototypes.

    “From a technical spec point of view, we can match centrifuges that cost from $1,000 to $5,000,” said Prakash.

    In parallel, they improved the device’s safety and began testing configurations that could be used to test live parasites in the field. From lab-based trials, they found that malaria parasites could be separated from red blood cells in 15 minutes. And by spinning the sample in a capillary precoated with acridine orange dye, glowing malaria parasites could be identified by simply placing the capillary under a microscope.

    Bhamla and Prakash, who recently returned from fieldwork in Madagascar, are currently conducting a paperfuge field validation trial for malaria diagnostics with PIVOT and Institut Pasteur, community-health collaborators based in Madagascar.

    A frugal science toolbox

    Paperfuge is the third invention from the Prakash lab driven by a frugal design philosophy, where engineers rethink traditional medical tools to lower costs and bring scientific capabilities out of the lab and into hands of health care workers in resource-poor areas.

    The first was the foldscope, a fully functional, under-a-dollar paper microscope that can be used for diagnosing blood-borne diseases such as malaria, African sleeping sickness and Chagas. To date there are 50,000 foldscopes in the hands of people around the world, and a spinoff company recently launched a Kickstarter campaign to ship 1 million more.

    The second was a $5 programmable kid’s chemistry set, inspired by hand-crank music boxes, which enables the execution of precise chemical assays in the field.

    Prakash’s dream is that these tools will enable health workers, field ecologists and children in the most remote areas of the world to carry a complete laboratory in a backpack.

    “Frugal science is about democratizing scientific tools to get them out to people around the world,” said Prakash.

    Prakash is also a member of Stanford Bio-X and Stanford ChEM-H, a senior fellow at the Stanford Center for Innovation in Global Health and an affiliate of the Stanford Woods Institute for the Environment.

    Other co-authors on the paper are Brandon Benson, Chew Chai, Georgios Katsikis and Aanchal Johri.

    This work was supported by the Stanford-Spectrum Clinical and Translational Science Award from the National Center for Advancing Translational Sciences (NCATS), a Stanford School of Medicine Dean’s Postdoctoral Fellowship, the Pew Foundation, the Moore Foundation, a National Science Foundation Career Award and the National Institutes of Health (NIH) New Innovator Award.

    See the full article here .

    Please help promote STEM in your local schools.
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    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

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  • richardmitnick 3:41 pm on January 10, 2017 Permalink | Reply
    Tags: , , , , Physics,   

    From astrobites: “A Too-Hot Pulsar Speeding Through the Galaxy” 

    Astrobites bloc

    Astrobites

    Jan 10, 2017
    Thankful Cromartie

    Title: Hubble Space Telescope detection of the millisecond pulsar J2124-3358 and its far-ultraviolet bow shock nebula
    Authors: B. Rangelov, G. G. Pavlov, O. Kargaltsev, A. Reisenegger, S. Guillot, M. van Kerkwijk & C. Reyes
    First Author’s Institution: Department of Physics, The George Washington University, Washington, DC
    1
    Status: Accepted to ApJ [open access]

    1
    Pulsars Are Spinning Neutron Stars
    CREDIT: Bill Saxton, NRAO/AUI/NSF

    Pulsars – the rapidly rotating, highly magnetized neutron stars that beam radiation from their magnetic axes — are as mysterious as they are exotic. They’re most often observed at radio frequencies using single-dish telescopes, and are sometimes glimpsed in X-ray and gamma-ray bands. Far rarer are pulsar observations at “in-between” frequencies, such as ultraviolet (UV), optical, and infrared (IR) (collectively, UVOIR); in fact, only about a dozen pulsars have been detected this way. However, their study in this frequency range has proved enlightening, as we will see in today’s post.
    A pulsar too hot to handle

    While one would expect a neutron star to cool with age if an internal heating mechanism does not operate throughout its lifetime, observations of the millisecond pulsar J0437–4715 (an interesting object in its own right) yielded surprising results. In a 2016 study, far-UV observations revealed the 7-billion-year-old pulsar to have a surface temperature of about 2 × 105 K — about 35 times the temperature of the Sun’s photosphere. This finding inspired Rangelov et al. to observe another millisecond pulsar, J2124-3358 (a 3.8-billion-year-old pulsar with a spin period of 4.93 ms), in the far-UV and optical bands using the Hubble Space Telescope (HST).

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    Because so few pulsars have been studied in these frequency ranges, their spectral energy distributions (SEDs) in this regime are poorly understood. Generally speaking, the spectra of normal, rotation-powered pulsars reveal a nonthermal (not dependent on temperature) component in optical and X-rays caused by electrons and positrons in the pulsar magnetosphere. In the far-UV, some pulsars show a thermal (blackbody) component in their spectra, thought to come from the surface of the cooling object. Analysis of the team’s HST images revealed an SED that is best modeled by a combined nonthermal and thermal spectral fit, with nonthermal emission dominating at optical wavelengths and thermal emission appearing in the far-UV (see Figure 1). If their interpretation is correct, this implies a surface temperature for J2124-3358 that is between 0.5 × 105 and 2.1 × 105 K, which is very much in line with the temperature of J0437-4715. If this proves to be the case, these two measurements will strongly suggest the presence of a heating mechanism in millisecond pulsars. However, various fits using only nonthermal components in the far-UV are still valid, so it is impossible to make an absolute determination of the correct fit.

    There are quite a few heating mechanisms that could be invoked to explain these objects’ high temperatures, ranging from the release of stored strain energy from the pulsar’s crust to dark matter annihilation in the pulsar’s interior. More spectral coverage of J2124-3358 is necessary to both check the validity of the nonthermal and thermal combined fit and to get closer to determining more specifically the heating mechanism in play.

    2
    Figure 1: Thermal (red dashed) and nonthermal (blue dashed) combined spectral fit to HST far-UV/optical data for J2124-3358. The black line signifies the sum of both components. Because there is uncertainty about the nature of the nonthermal component, two possible spectral slopes are shown. Figure 7 in the paper.

    A (bow) shocking find in the far-UV

    Images of J2124-3358 also show the presence of a bow shock, which is an arc-shaped shock that occurs when an object is moving faster than the interstellar medium (ISM) sound speed. J2124-3358 was known before this study to be accompanied by such a shock in H-alpha (Hydrogen transition from n=3 to n=2) filters, for which plenty of neutral hydrogen is required. As a result of the HST observations, J2124-3358 was found to have an (albeit fainter) far-UV shock coincident with the H-alpha shock (see Figure 2). This is only the second such object (after J0437-4715) to show a far-UV bow shock. It is absolutely possible that many pulsars cause bow shocks that don’t emit in H-alpha, but do in other wavelength regimes. Studying these more carefully will yield information about the nature of the ISM.

    In order to learn more about the heating mechanisms operating in these objects as well as the bow shocks that sometimes accompany them, many more pulsars will need to be studied using various optical, UV, and IR filters. Studies in the far-UV are only possible with Hubble, so it will be a long time before a sufficient number of objects will be studied at these frequencies in order to make solid conclusions about the nature of such interesting phenomena.

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    Figure 2: New observations of J2124-3358 from this study using the HST at three different wavelengths are shown in the top (left and right) and bottom left images. The shock is clearly visible in the far-UV using the F125LP filter. The bottom right image shows a previous H-alpha observation of the same pulsar. Figure 1 in the paper.

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    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 2:34 pm on January 5, 2017 Permalink | Reply
    Tags: , , Physics, ,   

    From U Chicago: “Research reinforces role of supernovae in clocking the universe” 

    U Chicago bloc

    University of Chicago

    January 3, 2017
    Greg Borzo

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    New research confirms the role Type Ia supernovae, like G299 pictured above, play in measuring universe expansion. Courtesy of NASA.

    How much light does a supernova shed on the history of universe?

    New research by cosmologists at the University of Chicago and Wayne State University confirms the accuracy of Type Ia supernovae in measuring the pace at which the universe expands. The findings support a widely held theory that the expansion of the universe is accelerating and such acceleration is attributable to a mysterious force known as dark energy. The findings counter recent headlines that Type Ia supernova cannot be relied upon to measure the expansion of the universe.

    Using light from an exploding star as bright as entire galaxies to determine cosmic distances led to the 2011 Nobel Prize in physics. The method relies on the assumption that, like lightbulbs of a known wattage, all Type Ia supernovae are thought to have nearly the same maximum brightness when they explode. Such consistency allows them to be used as beacons to measure the heavens. The weaker the light, the farther away the star. But the method has been challenged in recent years because of findings the light given off by Type Ia supernovae appears more inconsistent than expected.

    “The data that we examined are indeed holding up against these claims of the demise of Type Ia supernovae as a tool for measuring the universe,” said Daniel Scolnic, a postdoctoral scholar at UChicago’s Kavli Institute for Cosmological Physics and co-author of the new research published in Monthly Notices of the Royal Astronomical Society. “We should not be persuaded by these other claims just because they got a lot of attention, though it is important to continue to question and strengthen our fundamental assumptions.”

    One of the latest criticisms of Type Ia supernovae for measurement concluded the brightness of these supernovae seems to be in two different subclasses, which could lead to problems when trying to measure distances. In the new research led by David Cinabro, a professor at Wayne State, Scolnic, Rick Kessler, a senior researcher at the Kavli Institute, and others, they did not find evidence of two subclasses of Type Ia supernovae in data examined from the Sloan Digital Sky Survey Supernovae Search and Supernova Legacy Survey.

    SDSS Telescope at Apache Point, NM, USA
    SDSS Telescope at Apache Point, NM, USA

    The recent papers challenging the effectiveness of Type Ia supernovae for measurement used different data sets.

    A secondary criticism has focused on the way Type Ia supernovae are analyzed. When scientists found that distant Type Ia supernovae were fainter than expected, they concluded the universe is expanding at an accelerating rate. That acceleration is explained through dark energy, which scientists estimate makes up 70 percent of the universe. The enigmatic force pulls matter apart, keeping gravity from slowing down the expansion of the universe.

    Yet a substance that makes up 70 percent of the universe but remains unknown is frustrating to a number of cosmologists. The result was a reevaluation of the mathematical tools used to analyze supernovae that gained attention in 2015 by arguing that Type Ia supernovae don’t even show dark energy exists in the first place.

    Scolnic and colleague Adam Riess, who won the 2011 Nobel Prices for the discovery of the accelerating universe, wrote an article for Scientific American Oct. 26, 2016, refuting the claims. They showed that even if the mathematical tools to analyze Type Ia supernovae are used “incorrectly,” there is still a 99.7 percent chance the universe is accelerating.

    The new findings are reassuring for researchers who use Type Ia supernovae to gain an increasingly precise understanding of dark energy, said Joshua A. Frieman, senior staff member at the Fermi National Accelerator Laboratory [FNAL] who was not involved in the research.

    “The impact of this work will be to strengthen our confidence in using Type Ia supernovae as cosmological probes,” he said.

    Citation: “Search for Type Ia Supernova NUV-Optical Subclasses,” by David Cinabro and Jake Miller (Wayne State University); and Daniel Scolnic and Ashley Li (Kavli Institute for Cosmological Physics at the University of Chicago); and Richard Kessler (Kavli Institute for Cosmological Physics at University of Chicago and the Department of Astronomy and Astrophysics at the University of Chicago). Monthly Notices of the Royal Astronomical Society, November 2016. DOI: 10.1093/mnras/stw3109

    Funding: Kavli Institute for Cosmological Physics at the University of Chicago, Kavli Foundation, Fred Kavli, Space Telescope Science Institute, and National Aeronautics and Space Administration.

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  • richardmitnick 1:52 pm on January 5, 2017 Permalink | Reply
    Tags: , , Physics, , Semiconductor discs could boost night vision   

    From physicsworld.com: “Semiconductor discs could boost night vision” 

    physicsworld
    physicsworld.com.com

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    Frequency double: Maria del Rocio Camacho-Morales studies the new optical material.

    A new method of fabricating nanoscale optical crystals capable of converting infrared to visible light has been developed by researchers in Australia, China and Italy. The new technique allows the crystals to be placed onto glass and could lead to improvements in holographic imaging – and even the development of improved night-vision goggles.

    Second-harmonic generation, or frequency doubling, is an optical process whereby two photons with the same frequency are combined within a nonlinear material to form a single photon with twice the frequency (and half the wavelength) of the original photons. The process is commonly used by the laser industry, in which green 532 nm laser light is produced from a 1064 nm infrared source. Recent developments in nanotechnology have opened up the potential for efficient frequency doubling using nanoscale crystals – potentially enabling a variety of novel applications.

    Materials with second-order nonlinear susceptibilities – such as gallium arsenide (GaAs) and aluminium gallium arsenide (AlGaAs) – are of particular interest for these applications because their low-order nonlinearity makes them efficient at conversion.

    Substrate mismatch

    To be able to exploit second-harmonic generation in a practical device, these nanostructures must be fabricated on a substrate with a relatively low refractive index (such as glass), so that light may pass through the optical device. This is challenging, however, because the growth of GaAs-based crystals in a thin film – and type III-V semiconductors in general – requires a crystalline substrate.

    “This is why growing a layer of AlGaAs on top of a low-refractive-index substrate, like glass, leads to unmatched lattice parameters, which causes crystalline defects,” explains Dragomir Neshev, a physicist at the Australian National University (ANU). These defects, he adds, result in unwanted changes in the electronic, mechanical, optical and thermal properties of the films.

    Previous attempts to overcome this issue have led to poor results. One approach, for example, relies on placing a buffer layer under the AlGaAs films, which is then oxidized. However, these buffer layers tend to have higher refractive indices than regular glass substrates. Alternatively, AlGaAs films can be transferred to a glass surface prior to the fabrication of the nanostructures. In this case the result is poor-quality nanocrystals.

    Best of both

    The new study was done by Neshev and colleagues at ANU, Nankai University and the University of Brescia, who combined the advantages of the two different approaches to develop a new fabrication method. First, high-quality disc-shaped nanocrystals about 500 nm in diameter are fabricated using electron-beam lithography on a GaAs wafer, with a layer of AlAs acting as a buffer between the two. The buffer is then dissolved, and the discs are coated in a transparent layer of benzocyclobutene. This can then be attached to the glass substrate, and the GaAs wafer peeled off with minimal damage to the nanostructures.

    The development could have various applications. “The nanocrystals are so small they could be fitted as an ultrathin film to normal eye glasses to enable night vision,” says Neshev, explaining that, by combining frequency doubling with other nonlinear interactions, the film might be used to convert invisible, infrared light to the visible spectrum.

    If they could be made, such modified glasses would be an improvement on conventional night-vision binoculars, which tend to be large and cumbersome. To this end, the team is working to scale up the size of the nanocrystal films to cover the area of typical spectacle lenses, and expects to have a prototype device completed within the next five years.

    Security holograms

    Alongside frequency doubling, the team was also able to tune the nanodiscs to control the direction and polarization of the emitted light, which makes the film more efficient. “Next, maybe we can even engineer the light and make complex shapes such as nonlinear holograms for security markers,” says Neshev, adding: “Engineering of the exact polarization of the emission is also important for other applications such as microscopy, which allows light to be focused to a smaller volume.”

    “Vector beams with spatially arranged polarization distributions have attracted great interest for their applications in a variety of technical areas,” says Qiwen Zhan, an engineer at the University of Dayton in Ohio, who was not involved in this study. The novel fabrication technique, he adds, “opens a new avenue for generating vector fields at different frequencies through nonlinear optical processes”.

    With their initial study complete, Neshev and colleagues are now looking to refine their nanoantennas, both to increase the efficiency of the wavelength conversion process but also to extend the effects to other nonlinear interactions such as down-conversion.

    The research is described in the journal Nano Letters.

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  • richardmitnick 3:00 pm on January 2, 2017 Permalink | Reply
    Tags: , Deep Within a Mountain Physicists Race to Unearth Dark Matter, Physics, , , Xenon Collaboration   

    From WIRED: Women in STEM- “Deep Within a Mountain, Physicists Race to Unearth Dark Matter” Elena Aprile 

    Wired logo

    WIRED

    01.01.17
    Joshua Sokol

    1
    Elena Aprile in her lab at Columbia University.Ben Sklar for Quanta Magazine

    In a lab buried under the Apennine Mountains of Italy, Elena Aprile, a professor of physics at Columbia University, is racing to unearth what would be one of the biggest discoveries in physics.

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    There is five times more dark matter in the Universe than “normal” matter, the atoms and molecules that make up all we know. Yet, it is still unknown what this dominant dark component actually is.

    Today, an international collaboration of scientists inaugurated the new XENON1T instrument designed to search for dark matter with unprecedented sensitivity, at the Gran Sasso Underground Laboratory of INFN in Italy.

    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO
    Gran Sasso LABORATORI NAZIONALI del GRAN SASSO,located in the Abruzzo region of central Italy

    She has not yet succeeded, even after more than a decade of work. Then again, nobody else has, either.

    Aprile leads the XENON dark matter experiment, one of several competing efforts to detect a particle responsible for the astrophysical peculiarities that are collectively attributed to dark matter.

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    These include stars that rotate around the cores of galaxies as if pulled by invisible mass, excessive warping of space around large galaxy clusters, and the leopard-print pattern of hot and cold spots in the early universe.

    For decades, the most popular explanation for such phenomena was that dark matter is made of as-yet undiscovered weakly interacting massive particles, known as WIMPs. These WIMPs would only rarely leave an imprint on the more familiar everyday matter.

    That paradigm has recently been under fire. The Large Hadron Collider located at the CERN laboratory near Geneva has not yet found anything to support the existence of WIMPs. Other particles, less studied, could also do the trick. Dark matter’s astrophysical effects might even be caused by modifications of gravity, with no need for the missing stuff at all.

    The most stringent WIMP searches have been done using Aprile’s strategy: Pour plenty of liquid xenon—a noble element like helium or neon, but heavier—into a vat. Shield it from cosmic rays, which would inundate the detector with spurious signals. Then wait for a passing WIMP to bang into a xenon atom’s nucleus. Once it does, capture out the tiny flash of light that should result.

    These experiments use progressively larger tanks of liquid xenon that the researchers believe should be able to catch the occasional passing WIMP. Each successive search without a discovery shows that WIMPs, if they exist, must be lighter or less prone to leave a mark on normal matter than had been assumed.

    In recent years, Aprile’s team has vied with two close competitors for the title of Most-thorough WIMP Search: LUX, the Large Underground Xenon experiment, a U.S.-based group that split from her team in 2007, and PandaX, the Particle and Astrophysical Xenon experiment, a Chinese group that broke away in 2009. Both collaborators-turned-rivals also use liquid-xenon detectors and similar technology. Soon, though, Aprile expects her team to be firmly on top: The third-generation XENON experiment—larger than before, with three and a half metric tons of xenon to catch passing WIMPs—has been running since the spring, and is now taking data. A final upgrade is planned for the early 2020s.

    The game can’t go on forever, though. The scientists will eventually hit astrophysical bedrock: The experiments will become sensitive enough to pick up neutrinos from space, flooding the particle detectors with noise. If WIMPs haven’t been detected by that point, Aprile plans to stop and rethink where else to look.

    Aprile splits her time between her native Italy and New York City, where in 1986 she became the first female professor of physics at Columbia University. Quanta caught up with her on a Saturday morning in her Brooklyn high-rise apartment that faces toward the Statue of Liberty. An edited and condensed version of the interview follows.

    QUANTA MAGAZINE: How closely do you follow the theoretical back and forth about the nature of dark matter?

    ELENA APRILE: For me, driving the technology, driving the detector, making it the best detector is what makes it exciting. The point right now is that in a couple of years, maybe four or five in total, we will definitely say there is no WIMP or we will discover something.

    I don’t care much about what the theorists say. I go on with my experiment. The idea of the WIMP is clearly today still quite ideal. Nobody could tell you “No, you’re crazy looking for a WIMP.”

    What do you imagine will happen over the next few years in this search?

    If we find a signal, we have to go even faster and build a larger scale detector which we are planning already—in order to have a chance to see more of them, and have a chance to build up the statistics. If we see nothing after a year or two, the same story.

    The plan for the collaboration, for me and how I drive these 130 people, is very clear for the next four or five years. But beyond that, we will go almost to the level that we start really to see neutrinos. If we end up being lucky—if a supernova goes off next to us and we see neutrinos—we will not have found dark matter, but still detect something very exciting.

    How did you get started with this xenon detector technology?

    I started my career as a summer student at CERN. Carlo Rubbia was a professor at Harvard and also a physicist at CERN. He proposed a liquid-argon TPC—time projection chamber. This was hugely exciting as a detector because you can measure precisely the energy of a particle, and you can measure the location of the interaction, and you can do tracking. So, that was my first experience, to build the first liquid-argon ‘baby’ detector—1977, yes, that’s when it started. And then I went to Harvard, and I did my early work with Rubbia on liquid argon. That was the seed that led eventually to the monstrous, huge liquid-argon detector called ICARUS.

    Later, I left Rubbia and I accepted the position of assistant professor here at Columbia. I got interested in continuing with liquid-argon detectors, but for neutrino detection from submarines. I got my first grant from DARPA [the Defense Advanced Research Projects Agency]. They didn’t give a damn about supernova neutrinos, but they wanted to see neutrinos from the [nuclear] Russian submarines. And then we had Supernova 1987A, and I made a proposal to fly a liquid-argon telescope on a high-altitude balloon to detect the gamma rays from this supernova.

    I studied a lot—the properties of argon, krypton, xenon—and then it became clear that xenon is a much more promising material for gamma-ray detection. So I turned my attention to liquid xenon for gamma-ray astrophysics.

    How did that swerve into a search for dark matter?

    I had this idea that this detector I built for gamma-ray astrophysics could have been, in another version, ideal to look for dark matter. I said to myself: “Maybe it’s worth going into this field. The question is hot, and maybe we have the right tool to finally make some progress.”

    It’s atypical that the NSF [National Science Foundation], for someone new like me, will fund the proposal right away. It was the strength of what I had done all those years with the a liquid-xenon TPC for gamma-ray astrophysics. They realized that this woman can do it. Not because I’m very bold and I proposed a very aggressive program—which of course is typical of me—but I think it was the work that we did for another purpose which gave the strength to the XENON program, which I proposed in 2001 to the NSF.

    What was it like to go from launching high-altitude balloons to working underground?

    We had quite a few balloon campaigns. It’s something that I would do again, and I didn’t appreciate it then. You get your detector ready, you sit it on this gondola. At some point you are ready, but you can’t do anything because every morning you go and you wait for the weather guy to tell you if it’s the right moment to fly. In that scenario you are a slave to something bigger than you, which you can’t do anything about. You go on the launch pad, you look at the guy measuring, checking everything, and he says “No.”

    Underground, I guess, there is no such major thing holding you from operating your detector. But there are still, in the back of your mind, thoughts about the seismic resilience of what you designed and what you built.

    In a 2011 interview with The New York Times about women at the top of their scientific fields, you described the life of a scientist as tough, competitive and constantly exposed. You suggested that if one of your daughters aspired to be a scientist you would want her to be made of titanium. What did you mean by that?

    Maybe I shouldn’t demand this of every woman in science or physics. It’s true that it might not be fair to ask that everyone is made of titanium. But we must face it—in building or running this new experiment—there is going to be a lot of pressure sometimes. It’s on every student, every postdoc, every one of us: Try to go fast and get the results, and work day and night if you want to get there. You can go on medical leave or disability, but the WIMP is not waiting for you. Somebody else is going to get it, right? This is what I mean when I say you have to be strong.

    Going after something like this, it’s not a 9-to-5 job. I wouldn’t discourage anyone at the beginning to try. But then once you start, you cannot just pretend that this is just a normal job. This is not a normal job. It’s not a job. It’s a quest.

    In another interview, with the Italian newspaper La Repubblica, you discussed having a brilliant but demanding mentor in Carlo Rubbia, who won the Nobel Prize for Physics in 1984. What was that relationship like?

    It made me of titanium, probably. You have to imagine this 23-year-old young woman from Italy ending up at CERN as a summer student in the group of this guy. Even today, I would still be scared if I were that person. Carlo exudes confidence. I was just intimidated.

    He would keep pushing you beyond the state that is even possible: “It’s all about the science; it’s all about the goal. How the hell you get there I don’t care: If you’re not sleeping, if you’re not eating, if you don’t have time to sleep with your husband for a month, who cares? You have a baby to feed? Find some way.” Since I survived that period I knew that I was made a bit of titanium, let’s put it that way. I did learn to contain my tears. This is a person you don’t want to show weakness to.

    Now, 30 years after going off to start your own lab, how does the experience of having worked with him inform the scientist you are today, the leader of XENON?

    For a long time, he was still involved in his liquid-argon effort. He would still tell me, “What are you doing with xenon; you have to turn to argon.” It has taken me many years to get over this Rubbia fear, for many reasons, probably—even if I don’t admit it. But now I feel very strong. I can face him and say: “Hey, your liquid-argon detector isn’t working. Mine is working.”

    I decided I want to be a more practical person. Most guys are naive. All these guys are naive. A lot of things he did and does are exceptional, yes, but building a successful experiment is not something you do alone. This is a team effort and you must be able to work well with your team. Alone, I wouldn’t get anywhere. Everybody counts. It doesn’t matter that we build a beautiful machine: I don’t believe in machines. We are going to get this damn thing out of it. We’re going to get the most out of the thing that we built with our brains, with the brains of our students and postdocs who really look at this data. We want to respect each one of them.

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  • richardmitnick 7:50 am on December 31, 2016 Permalink | Reply
    Tags: , , , , GANIL, , , Physics, SPIRAL2   

    From CNRS: “At the Heart of Nuclear Matter with SPIRAL2” 

    CNRS bloc

    The National Center for Scientific Research

    11.14.2016
    Yaroslav Pigenet

    1
    View of part of the high energy transmission line of Spiral2 which makes it possible to focus the ion beams inside the tubes kept under high vacuum. 2. STROPPA/CEA/CNRS

    A new heavy-ion accelerator was inaugurated at the GANIL facility in Caen (northwestern France). The first phase in the SPIRAL2 project, this new instrument will enable scientists to delve further into the mysteries of the atom and even create new elements.

    3
    3

    In days of old, alchemists pursued a goal long believed illusory, that of transmuting a base metal into another—preferably noble. Today, at facilities like the French Large Heavy-ion Accelerator (GANIL) in Caen, the alchemists’ dream has become scientific reality. For the last 35 years, GANIL’s physicists have been smashing accelerated ions in order to produce new atoms and find the secrets of matter on atomic scales. Once the facilities of GANIL’s SPIRAL2 project (2nd generation Production System of Online Accelerated Radioactive Ions) are up and running, scientists will be able to perform transmutation on an unprecedented scale, opening the way to the discovery of as yet unknown elements and atomic structures.

    One of the world’s largest ion accelerators

    GANIL was jointly set up in 1976 by the French Alternative Energies and Atomic Energy Commission (CEA) and the CNRS National Institute of Nuclear and Particle Physics (IN2P3).1 In the years that followed, the facility continued to expand, establishing international collaborations and acquiring new equipment. This constant evolution, in which SPIRAL2 is a milestone, made it one of the world’s four leading laboratories in the field of ion beam research. Its operating principle has nonetheless remained the same: the production of electrically charged ions by stripping electrons from neutral atoms. When they enter the accelerator’s magnetic fields, the nuclei of these atoms near a third of the speed of light before smashing into the atomic nuclei in the target.

    These extremely high-energy collisions result in nuclear reactions that give rise to new nuclei with unusual neutron-proton ratios, structures or shapes. Observing and analyzing these short-lived radioactive nuclei helps scientists to gain a better grasp of the properties of nuclear matter. Thanks to the work of its 250 permanent staff (physicists, engineers, technicians, administrative staff, etc) and with the contribution of 700 visiting researchers from across the world, GANIL has witnessed a host of discoveries about the structure of atomic nuclei, their thermal and mechanical properties, and their decay modes.

    3
    The chart of nuclides. Each square represents a nucleus positioned according to its number of neutrons (on the horizontal x-axis) and protons (on the vertical y-axis). The white squares correspond to the 291 nuclei found in the natural state on Earth, while the orange and light grey areas show the 2 800 nuclei synthesized so far in the laboratory. Beyond feature the nuclei predicted by theory to exist in the Universe.

    The search for exotic nuclei

    The laboratory is at the cutting edge of research into exotic nuclei, so-called because they are not among the 291 stable isotopes found in the natural state on Earth. Over a hundred such nuclei have already been discovered, synthesized and studied. Once SPIRAL2 begins operation, it will become possible to produce and study new exotic nuclei at GANIL, enabling the facility to compete in the global race to produce super-heavy nuclei (nuclei with an atomic number, in other words number of protons, exceeding 110). For instance, GANIL will be able to produce new elements surpassing Oganesson (Og) the heaviest to date with 118 protons, and whose synthesis by a Russian laboratory was verified in December 2015.

    Buried nine meters underground, the various instruments making up the first phase of SPIRAL2 will begin operation progressively. They will not replace but rather extend GANIL’s existing facilities, whose area will increase from 11,000 m² to around 20,000 m². The project was divided into several phases so as to take budgetary constraints and safety clearance procedures into account.

    On November 3rd, 2016, the first phase, which is set to continue until 2019, will be marked by the inauguration of the brand new linear accelerator LINAC, and the two ion sources and injector that will feed into it.
    The first source will produce beams of heavy ions from elements ranging from carbon to uranium. “The heavy ion beams produced by this source will be ten to a hundred times more powerful than those currently available at GANIL,” explains Jean-Charles Thomas, a CNRS researcher at the site. “The beams will be used mainly to produce (exotic) radioactive nuclei by fusion reactions.”

    The second source will produce beams of lighter particles: protons, deuterons (nuclei made up of a proton and a neutron) and alpha particles (helium-4 nuclei, comprising two protons and two neutrons). “Beams of lightweight particles such as these are not currently available at GANIL,” Thomas points out. “They will be used principally to generate powerful beams of neutrons.” The beams of heavy ions or lightweight particles will then enter the radio-frequency quadrupole (RFQ), whose role is to accelerate the ions up to 4% of light speed, while separating them into packets suitable for injection into the accelerator.

    4
    The new LINAC accelerator comprises 19 cryomodules, each containing one or two acceleration cavities.
    2 P. STROPPA/CEA/CNRS

    From pure research to social applications

    At the heart of the SPIRAL2 facilities, the LINAC linear accelerator is made up of a sequence of 19 cryomodules containing superconducting cavities that operate at 4.5 K (-270 °C). The whole assembly will accelerate the particles to energies of up to 25% of the speed of light, while heavy ions will reach 18% of light speed. Depending on their nature, the high-energy beams will be sent to two new experimental areas, NFS (Neutrons For Science) and S3 (Super Separator Spectrometer), which are due to begin operation shortly.

    NFS, which will get underway in 2017, will be used to study the reactions brought about by fast neutrons in next-generation nuclear reactors, as well as the effects of neutron irradiation in the fields of healthcare and materials. The S3 area, due to become operational in 2019, will use beams of heavy ions to generate and study the exotic nuclei produced in nuclear fusion reactions.

    “In fundamental terms, SPIRAL2 let us elucidate the structure and behavior of atomic nuclei produced under extreme conditions,” says Julien Piot, a CNRS physicist involved with S3 at GANIL.”It should also confirm the existence of certain ‘magic numbers’ of protons/neutrons, as well as that of a possible island of stability for super-heavy nuclei.”

    However, SPIRAL2 will also have applications including the treatment of radioactive waste, the production of isotopes for nuclear medicine, and the study of the impact of neutrons on materials and living organisms.

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    Astroparticles: from particles to the Universe

     
  • richardmitnick 5:35 am on December 31, 2016 Permalink | Reply
    Tags: , , , , , How Many Fundamental Constants Does It Take To Define Our Universe?, Physics   

    From Ethan Siegel: “How Many Fundamental Constants Does It Take To Define Our Universe?” 

    Ethan Siegel
    Dec 30, 2016

    1
    Our Universe, from the hot Big Bang until the present day, must still be explicable. Image credit: NASA / CXC / M.Weiss.

    Inflationary Universe. NASA/WMAP
    Inflationary Universe. NASA/WMAP

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    When we think about our Universe at a fundamental level, we think about all the particles in it and all the forces and interactions that occur between them. If you can describe those forces, interactions and particle properties, you have everything you need to reproduce our Universe, or at least a Universe virtually indistinguishable from our own, in its entirety. Because if you know the laws of physics — gravitation, quantum mechanics, electromagnetism, the nuclear forces, etc. — all you need are the relationships that tell you “by how much,” and so long as you start with the same initial conditions, you’ll wind up with a Universe with the same structures from atoms to galaxy clusters, the same processes from electron transitions to stellar explosions, the same periodic table of elements, and the same chemical combinations from hydrogen gas to proteins and hydrocarbon chains, among a great number of other similarities.

    2
    From the largest cosmic scales down to the smallest subatomic ones, the same laws of physics define the entire Universe. Image credit: NASA / Jenny Mottar.

    When you encounter the question of “how much,” you probably think of the force of gravity being determined by a universal gravitational constant, G, and of the “energy of a particle” being determined by its rest mass, such as the mass of an electron, me. You think of the speed of light, c, and for quantum mechanics, Planck’s constant, ħ. But physicists don’t like to use these constants when we describe the Universe, because these constants have arbitrary dimensions and units to them.

    But there’s no inherent importance to a unit like a meter, a kilogram or a second; in fact there’s no reason at all to force ourselves to define things like “mass” or “time” or “distance” when it comes to the Universe. If we give the right dimensionless constants (without meters, kilograms, seconds or any other “dimensions” in them) that describe the Universe, we should naturally get out our Universe itself. This includes things like the masses of the particles, the strengths of their interactions, the speed limit of the Universe and even the fundamental properties of spacetime itself!

    3
    The fundamental constants of physics, as reported by the Particle Data Group in 1986. With very few exceptions, very little has changed. Image credit: Particle Data Group / LBL / DOE / NSF.

    As it turns out, it takes 26 dimensionless constants to describe the Universe as simply and completely as possible, which is quite a small number. Even at that, they don’t give us everything, because there are some important things that are fundamentally still unknown about our Universe. Here’s what the constants we need are.

    1.) The fine-structure constant, or the strength of the electromagnetic interaction. In terms of some of the physical constants we’re more familiar with, this is a ratio of the elementary charge (of, say, an electron) squared to Planck’s constant and the speed of light. But if you put these constants together, you get a dimensionless number! At the energies currently present in our Universe, this number comes out to ≈ 1/137.036, although the strength of this interaction increases as the energy of the interacting particles rise.

    2.) The strong coupling constant, which defines the strength of the force that holds protons and neutrons together. Although the way the strong force works is very different from the electromagnetic force or gravity, the strength of this interaction can still be parametrized by a single coupling constant. This constant of our Universe, too, like the electromagnetic one, changes strength with energy.

    4
    The particles and antiparticles of the Standard Model. Image credit: E. Siegel.

    Standard model of Supersymmetry DESY
    Standard model of Supersymmetry DESY, includes the non super-symmetry standard model

    3–17.) This one is a bit of a disappointment. We have fifteen particles in the Standard Model: the six quarks, six leptons, the W, Z, and the Higgs boson, that all have a rest mass. While it’s true that their antiparticles all have identical rest masses, we were hoping that there would’ve been some relationship, pattern, or more fundamental theory that gave rise to these masses with fewer parameters than the fifteen we need: one for each non-zero rest mass. Alas, it takes fifteen constants to describe these masses, with the lone good news that we can scale these parameters to be relative to the gravitational constant, G, to wind up with 15 dimensionless parameters that have no need for a separate descriptor of the gravitational force’s strength.

    18–21.) The quark mixing parameters. We have six different types of quarks, and because there are two subsets of three that all have the same quantum numbers as one another, they can mix together. If you’ve ever heard of the weak nuclear force, radioactive decay or CP-violation, these four parameters — all of which must be (and have been) measured — are required to describe them.

    4
    Vacuum oscillation probabilities for electron (black), muon (blue) and tau (red) neutrinos, for specific parameter values. Image credit: English Wikipedia user Strait under a cc-by-1.0.

    22–25.) The neutrino mixing parameters. Similar to the quark sector, there are four parameters that detail how neutrinos mix with one another, given that the three types of neutrino species all have the same quantum number. The solar neutrino problem — where the neutrinos emitted by the Sun weren’t arriving here on Earth — was one of the 20th century’s biggest conundrums, finally solved when we realized that neutrinos had very small but non-zero masses, mixed together, and oscillated from one type into another. The quark mixing is described by three angles and one CP-violating complex phase, and the neutrino mixing is described in the same way. While all four parameters have already been determined for the quarks, the CP-violating phase for the neutrinos is not yet measured.

    5
    The four possible fates of the Universe, with the bottom example fitting the data best: a Universe with dark energy. Image credit: E. Siegel.

    26.) The cosmological constant. You may have heard that the Universe’s expansion is accelerating due to dark energy, and this requires yet one more parameter — a cosmological constant — to describe the amount of that acceleration. Dark energy could yet turn out to be more complex than being a constant, in which case it may need more parameters as well, and hence the number may be greater than 26.

    If you give me the laws of physics and these 26 constants, I can throw these into a computer and tell it to simulate my Universe. And quite remarkably, what I get out looks pretty much indistinguishable from the Universe we have today, from the smallest, subatomic scales all the way up to the largest, cosmic ones.

    But even with this, there are still four puzzles that will likely require at least some additional constants to resolve. These are:

    The problem of the matter-antimatter asymmetry. The entirety of our observable Universe is made up dominantly of matter and not antimatter, yet we do not fully understand why this is so, or why our Universe has the amount of matter it does. This problem — the problem of baryogenesis — is one of the great unsolved problems in theoretical physics, and may require one (or more) new fundamental constants to describe its solution.
    The problem of cosmic inflation. This is the phase of the Universe that preceded and set up the Big Bang has made many new predictions that have been verified observationally, but isn’t included in this description. Very likely, when we more fully understand what this is, additional parameters will have to be added to this set of constants.
    The problem of dark matter. Given that it almost definitely consists of at least one (and maybe more) new type of massive particle, it stands to reason that more new parameters — potentially even more than one for each new particle type — will need to be added.
    The problem of strong CP-violation. We see CP-violation in the weak nuclear interactions and expect it in the neutrino sector, but we have yet to find it in the strong interactions, even though it is not forbidden. If it exists, there should be more parameters; if it doesn’t, there is likely an additional parameter related to the process that restricts it.

    Our Universe is an intricate, amazing place, and yet our greatest hopes of a unified theory — a theory of everything — ought to decrease the number of fundamental constants we need. But the more we learn about the Universe, the more parameters we’re learning it takes to fully describe it. While it’s important to recognize where we are and what it takes, today, to describe the entirety of what’s known, it’s also important to keep searching for a more complete paradigm that not only gives us everything the Universe has to give us, but makes it as simple as possible.

    Right now, unfortunately, anything simpler than what we’ve put forth here is too simple to work. Our Universe may not be as elegant as we hoped for after all.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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