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  • richardmitnick 2:10 pm on April 14, 2021 Permalink | Reply
    Tags: "New method measures super-fast free electron laser pulses", , DOE's Los Alamos National Laboratory, Femtosecond optical shutter, Free electron lasers (FELs), ,   

    From DOE’s Los Alamos National Laboratory via phys.org : “New method measures super-fast free electron laser pulses” 

    LANL bloc

    From DOE’s Los Alamos National Laboratory

    via

    phys.org

    April 14, 2021

    1
    An optical shutter created by ionization allows an ordinary camera to measure a femtosecond pulse from a free electron laser. Credit: Los Alamos National Laboratory.

    New research shows how to measure the super-short bursts of high-frequency light emitted from free electron lasers (FELs). By using the light-induced ionization itself to create a femtosecond optical shutter, the technique encodes the electric field of the FEL pulse in a visible light pulse so that it can be measured with a standard, slow, visible-light camera.

    “This work has the potential to lead to a new online diagnostic for FELs, where the exact pulse shape of each light pulse can be determined. That information can help both the end-user and the accelerator scientists,” said Pamela Bowlan, Los Alamos National Laboratory’s lead researcher on the project. The paper was published April 12, 2021 in Optica. “This work also paves the way for measuring X-ray pulses or femtosecond time-resolved X-ray images.”

    Free electron lasers, which are driven by kilometer-long linear accelerators, emit bursts of short-wavelength light lasting one quadrillionth of a second. As a result, they can act as strobe lights for viewing the fastest events in nature—atomic or molecular motion—and therefore promise to revolutionize our understanding of almost any kind of matter.

    Measuring such a vanishingly rapid burst of ionizing radiation has previously proved challenging. But while electronics are too slow to measure these light pulses, optical effects can be essentially instantaneous. Squeezing all of the energy of a continuous laser into short pulses means that femtosecond laser pulses are extremely bright and have the ability to modify a material’s absorption or refraction, creating effectively instantaneous “optical shutters.”

    This idea has been widely used for measuring visible-light femtosecond laser pulses. But the higher-frequency extreme ultraviolet light from FELs interacts with matter differently; this light is ionizing, meaning that it pulls electrons out of their atoms. The researchers showed that ionization itself can be used as a “femtosecond optical shutter” for measuring extreme ultraviolet laser pulses at 31 nanometers.

    “Ionization typically changes the optical properties of a material for nanoseconds, which is 10,000 times slower than the FEL pulse duration,” Bowlan said. “But the duration of the rising edge of ionization, determined by how long it takes the electron to leave the atom, is significantly faster. This resulting change in the optical properties can act as the fast shutter needed to measure the FEL pulses.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Los Alamos National Laboratory mission is to solve national security challenges through scientific excellence.

    LANL campus
    Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and URS for the Department of Energy’s National Nuclear Security Administration.
    Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

    Operated by Los Alamos National Security, LLC for the U.S. Dept. of Energy’s NNSA

     
  • richardmitnick 12:28 pm on February 24, 2021 Permalink | Reply
    Tags: "Lack of symmetry in qubits can’t fix errors in quantum computing but might explain matter/antimatter imbalance", A new way to separate isotopes, DOE's Los Alamos National Laboratory, Hobbled by decoherence, Kibble-Zurek theory, , Quantum annealing computers, , The adiabatic theorem   

    From DOE’s Los Alamos National Laboratory(US): “Lack of symmetry in qubits can’t fix errors in quantum computing but might explain matter/antimatter imbalance” 

    LANL bloc

    From DOE’s Los Alamos National Laboratory(US)

    February 22, 2021

    1
    A new paper seeking to cure a time restriction in quantum annealing computers instead opened up a class of new physics problems that can now be studied with quantum annealers without requiring they be too slow.

    A team of quantum theorists seeking to cure a basic problem with quantum annealing computers—they have to run at a relatively slow pace to operate properly—found something intriguing instead. While probing how quantum annealers perform when operated faster than desired, the team unexpectedly discovered a new effect that may account for the imbalanced distribution of matter and antimatter in the universe and a novel approach to separating isotopes.

    “Although our discovery did not cure the annealing time restriction, it brought a class of new physics problems that can now be studied with quantum annealers without requiring they be too slow,” said Nikolai Sinitsyn, a theoretical physicist at Los Alamos National Laboratory. Sinitsyn is author of the paper published Feb. 19 in Physical Review Letters, with coauthors Bin Yan and Wojciech Zurek, both also of Los Alamos, and Vladimir Chernyak of Wayne State University(US).

    Significantly, this finding hints at how at least two famous scientific problems may be resolved in the future. The first one is the apparent asymmetry between matter and antimatter in the universe.

    “We believe that small modifications to recent experiments with quantum annealing of interacting qubits made of ultracold atoms across phase transitions will be sufficient to demonstrate our effect,” Sinitsyn said.

    Explaining the matter/antimatter discrepancy

    Both matter and antimatter resulted from the energy excitations that were produced at the birth of the universe. The symmetry between how matter and antimatter interact was broken but very weakly. It is still not completely clear how this subtle difference could lead to the large observed domination of matter compared to antimatter at the cosmological scale.

    The newly discovered effect demonstrates that such an asymmetry is physically possible. It happens when a large quantum system passes through a phase transition, that is, a very sharp rearrangement of quantum state. In such circumstances, strong but symmetric interactions roughly compensate each other. Then subtle, lingering differences can play the decisive role.

    Making quantum annealers slow enough

    Quantum annealing computers are built to solve complex optimization problems by associating variables with quantum states or qubits. Unlike a classical computer’s binary bits, which can only be in a state, or value, of 0 or 1, qubits can be in a quantum superposition of in-between values. That’s where all quantum computers derive their awesome, if still largely unexploited, powers.

    In a quantum annealing computer, the qubits are initially prepared in a simple lowest energy state by applying a strong external magnetic field. This field is then slowly switched off, while the interactions between the qubits are slowly switched on.

    “Ideally an annealer runs slow enough to run with minimal errors, but because of decoherence, one has to run the annealer faster,” Yan explained. The team studied the emerging effect when the annealers are operated at a faster speed, which limits them to a finite operation time.)

    “According to the adiabatic theorem in quantum mechanics, if all changes are very slow, so-called adiabatically slow, then the qubits must always remain in their lowest energy state,” Sinitsyn said. “Hence, when we finally measure them, we find the desired configuration of 0s and 1s that minimizes the function of interest, which would be impossible to get with a modern classical computer.”

    Hobbled by decoherence

    However, currently available quantum annealers, like all quantum computers so far, are hobbled by their qubits’ interactions with the surrounding environment, which causes decoherence. Those interactions restrict the purely quantum behavior of qubits to about one millionth of a second. In that timeframe, computations have to be fast—nonadiabatic—and unwanted energy excitations alter the quantum state, introducing inevitable computational mistakes.

    The Kibble-Zurek theory, co-developed by Wojciech Zurek, predicts that the most errors occur when the qubits encounter a phase transition, that is, a very sharp rearrangement of their collective quantum state.

    For this paper, the team studied a known solvable model where identical qubits interact only with their neighbors along a chain; the model verifies the Kibble-Zurek theory analytically. In the theorists’ quest to cure limited operation time in quantum annealing computers, they increased the complexity of that model by assuming that the qubits could be partitioned into two groups with identical interactions within each group but slightly different interactions for qubits from the different groups.

    In such a mixture, they discovered an unusual effect: One group still produced a large amount of energy excitations during the passage through a phase transition, but the other group remained in the energy minimum as if the system did not experience a phase transition at all.

    “The model we used is highly symmetric in order to be solvable, and we found a way to extend the model, breaking this symmetry and still solving it,” Sinitsyn explained. “Then we found that the Kibble-Zurek theory survived but with a twist—half of the qubits did not dissipate energy and behaved ‘nicely.’ In other words, they maintained their ground states.”

    Unfortunately, the other half of the qubits did produce many computational errors—thus, no cure so far for a passage through a phase transition in quantum annealing computers.

    A new way to separate isotopes

    Another long-standing problem that can benefit from this effect is isotope separation. For instance, natural uranium often must be separated into the enriched and depleted isotopes, so the enriched uranium can be used for nuclear power or national security purposes. The current separation process is costly and energy intensive. The discovered effect means that by making a mixture of interacting ultra-cold atoms pass dynamically through a quantum phase transition, different isotopes can be selectively excited or not and then separated using available magnetic deflection technique.

    The funding: This work was carried out under the support of the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, Condensed Matter Theory Program. Bin Yan also acknowledges support from the Center for Nonlinear Studies at LANL.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    DOE’s Los Alamos National Laboratory(US) mission is to solve national security challenges through scientific excellence.

    LANL campus

    DOE’sLos Alamos National Laboratory(US), a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and URS for the Department of Energy’s National Nuclear Security Administration.
    Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

    Operated by Los Alamos National Security, LLC for the U.S. Dept. of Energy’s NNSA

     
  • richardmitnick 3:12 pm on January 21, 2021 Permalink | Reply
    Tags: "Scientists use diamonds to generate better accelerator beams", , , Argonne Cathode Test-stand (ACT) beamline at the Argonne Wakefield Accelerator facility, , DOE's Los Alamos National Laboratory, Field emission, , ,   

    From DOE’s Argonne National Laboratory and From DOE’s Los Alamos National Laboratory: “Scientists use diamonds to generate better accelerator beams” 

    Argonne Lab
    News from From DOE’s Argonne National Laboratory

    and

    LANL bloc

    From DOE’s Los Alamos National Laboratory

    January 20, 2021
    Jared Sagoff

    More efficient beams thanks to nanoscale diamonds.

    1
    Electron beamlets as observed on YAG screens at varying distances from a cathode source. Credit: Argonne National Laboratory.)

    Beam-driven wakefield acceleration approaches are promising candidates for future large-scale machines, including X-ray free electron lasers and linear colliders, as they have the potential to improve efficiency and reduce operation cost.

    One of the key factors that drives this efficiency improvement involves manipulating the temporal distribution of beams of electrons. Over the past few decades, researchers have investigated a number of different mechanisms that successfully produce temporally shaped electron beams of varied quality with different limitations.

    In a new study from the U.S. Department of Energy’s (DOE) Argonne and Los Alamos national laboratories, scientists used a phenomenon called field emission to explore the use of arrays of tiny diamond tips to produce what they hoped would be a transversely shaped electron beam. The beam will then be sent into an emittance exchange beamline to convert the transverse distribution into the temporal one.

    Field emission works by decreasing the quantum barriers that electrons can, according to the laws of probability, occasionally tunnel through. ​“It’s as if by applying these fields we can change a brick wall into drywall — it’s much easier to go through it,” said Argonne accelerator physicist Jiahang Shao, an author of the study.

    Other methods to generate electrons had involved either thermionic cathodes, which use hot filaments — analogous to those used in incandescent light bulbs — to expel electrons from a solid, or photoelectric cathodes, which use ultrashort laser pulses to spring electrons loose.

    The advantage of field emission cathodes, according to Shao, is that they require neither a heat source nor an expensive laser setup. ​“We’re using electric fields regardless when it comes time to accelerate the electrons,” Shao said. ​“It’s not much more inconvenient to use them to generate them in the first place.”

    To successfully use the field emission technique, the researchers needed to apply a very strongly concentrated electric field directly on the surface of the cathode. To do so, they created a film of diamond that contained diamond pyramids approximately 10 micrometers on a side with nanometer-scale tips on top that were arranged into a one-millimeter equilateral triangle.

    The experimental study is conducted on the Argonne Cathode Test-stand (ACT) beamline at the Argonne Wakefield Accelerator facility. ​“Generating a transversely shaped beam by field emission is the first step of the project, and we are exploring different emitter geometries as well as (radio-frequency) rf gun operation parameters,” Shao said.

    According to Argonne accelerator scientist Manoel Conde, another author of the study, the researchers were trying to balance two separate but competing phenomena by using these diamond field-emitter arrays. The scientists needed to generate as high a current as possible of electrons leaving the material; however, they wanted to mitigate the expelling force between electrons to maintain the triangle shape during emission and transportation.

    An article based on the study, ​“Demonstration of transport of a patterned electron beam produced by diamond pyramid cathode in an rf gun,” appeared in the January 2020 issue of Applied Physics Letters and reported the successful demonstration of generation and transportation of a transversely shaped electron beam from a diamond field-emitter arrays cathode in an rf gun. Another article, ​“Shaped beams from diamond field-emitter array cathodes,” appeared in the July 2020 issue of IEEE Transactions on Plasma Science and reported the continuous geometry optimization of diamond field-emitter arrays. In addition to Shao and Conde, other Argonne authors included Darrel Doran, Gwanghui Ha, Wanming Liu, John Power and Eric Wisniewski. Other authors included Heather Andrews, Kimberley Nichols, Dongsung Kim and Evgenya Simakov from Los Alamos National Laboratory, as well as Sergey Antipov from Euclid Techlabs and Gongxiaohui Chen from the Illinois Institute of Technology.

    This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the DOE Office of Science. There, scientists used Fluorine Inductively Coupled Plasma for silicon etching, Karl Suss Mask Aligner for photolithography and Nova NanoSEM 450 for scanning electron microscopy.

    The work was funded by a Los Alamos National Laboratory Laboratory-Directed Research and Development program.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Los Alamos National Laboratory mission is to solve national security challenges through scientific excellence.

    LANL campus

    Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and URS for the Department of Energy’s National Nuclear Security Administration.
    Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

    Operated by Los Alamos National Security, LLC for the U.S. Dept. of Energy’s NNSA

    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    About the Advanced Photon Source

    The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.

    This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

     
  • richardmitnick 4:51 pm on December 17, 2020 Permalink | Reply
    Tags: "Multi-messenger astronomy offers new estimates of neutron star size and universe expansion", , , , , DOE's Los Alamos National Laboratory, ,   

    From DOE’s Los Alamos National Laboratory via phys.org: “Multi-messenger astronomy offers new estimates of neutron star size and universe expansion” 

    LANL bloc

    From DOE’s Los Alamos National Laboratory

    via


    From phys.org

    December 17, 2020

    1
    Collision of two neutron stars showing the electromagnetic and gravitational-wave emissions during the merger process. The combined interpretation of multiple messengers allows astrophysicists to understand the internal composition of neutron stars and to reveal the properties of matter under the most extreme conditions in the universe. Credit: Tim Dietrich.

    A combination of astrophysical measurements has allowed researchers to put new constraints on the radius of a typical neutron star and provide a novel calculation of the Hubble constant that indicates the rate at which the universe is expanding.

    “We studied signals that came from various sources, for example recently observed mergers of neutron stars,” said Ingo Tews, a theorist in Nuclear and Particle Physics, Astrophysics and Cosmology group at Los Alamos National Laboratory, who worked with an international collaboration of researchers on the analysis to appear in the journal Science on December 18. “We jointly analyzed gravitational-wave signals and electromagnetic emissions from the mergers, and combined them with previous mass measurements of pulsars or recent results from NASA’s Neutron Star Interior Composition Explorer.

    NASA NICER on the ISS.

    We find that the radius of a typical neutron star is about 11.75 kilometers and the Hubble constant is approximately 66.2 kilometers per second per megaparsec.”

    Combining signals to gain insight into distant astrophysical phenomena is known in the field as multi-messenger astronomy. In this case, the researchers’ multi-messenger analysis allowed them to restrict the uncertainty of their estimate of neutron star radii to within 800 meters.

    Their novel approach to measuring the Hubble constant contributes to a debate that has arisen from other, competing determinations of the universe’s expansion. Measurements based on observations of exploding stars known as supernovae are currently at odds with those that come from looking at the Cosmic Microwave Background (CMB), which is essentially the left over energy from the Big Bang. The uncertainties in the new multimessenger Hubble calculation are too large to definitively resolve the disagreement, but the measurement is slightly more supportive of the CMB approach.

    Tews’ primary scientific role in the study was to provide the input from nuclear theory calculations that are the starting point of the analysis. His seven collaborators on the paper comprise an international team of scientists from Germany, the Netherlands, Sweden, France, and the United States.

    A combination of astrophysical measurements has allowed researchers to put novel constraints on the radius of a typical neutron star and provide a new calculation of the Hubble constant that indicates the rate at which the universe is expanding.

    3
    Artist’s impression of two inspiralling neutron stars shortly before their collision. Credit: Nicals Moldenhauer.

    “We studied signals that came from various sources, for example recently observed mergers of neutron stars,” said Ingo Tews, a theorist in Nuclear and Particle Physics, Astrophysics and Cosmology group at Los Alamos National Laboratory, who worked with an international collaboration of researchers on the analysis to appear in the journal Science on December 18. “We jointly analyzed gravitational-wave signals and electromagnetic emissions from the mergers, and combined them with previous mass measurements of pulsars or recent results from NASA’s Neutron Star Interior Composition Explorer. We find that the radius of a typical neutron star is about 11.75 kilometers and the Hubble constant is approximately 66.2 kilometers per second per megaparsec.”

    Combining signals to gain insight into distant astrophysical phenomena is known in the field as multi-messenger astronomy. In this case, the researchers’ multi-messenger analysis allowed them to restrict the uncertainty of their estimate of neutron star radii to within 800 meters.

    Their novel approach to measuring the Hubble constant contributes to a debate that has arisen from other, competing determinations of the universe’s expansion. Measurements based on observations of exploding stars known as supernovae are currently at odds with those that come from looking at the Cosmic Microwave Background (CMB), which is essentially the left over energy from the Big Bang. The uncertainties in the new multimessenger Hubble calculation are too large to definitively resolve the disagreement, but the measurement is slightly more supportive of the CMB approach.

    Tews’ primary scientific role in the study was to provide the input from nuclear theory calculations that are the starting point of the analysis. His seven collaborators on the paper comprise an international team of scientists from Germany, the Netherlands, Sweden, France, and the United States.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Los Alamos National Laboratory mission is to solve national security challenges through scientific excellence.

    LANL campus
    Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and URS for the Department of Energy’s National Nuclear Security Administration.
    Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

    Operated by Los Alamos National Security, LLC for the U.S. Dept. of Energy’s NNSA

     
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