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  • richardmitnick 3:24 pm on February 22, 2019 Permalink | Reply
    Tags: , , Magnet technology, , Quantum condensed matter, Topological materials and insulators   

    From Discovery at Princeton University: “A quantum magnet with a topological twist” 

    Discovery at Princeton

    Princeton University
    From From Discovery at Princeton University

    February 22, 2019
    Catherine Zandonella

    Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons in these materials have exotic, so-called topological behaviors and others behave somewhat like graphene, another material prized for its potential for new types of electronics.

    Now, an international team led by researchers at Princeton University has observed that some of the electrons in these magnets behave collectively, like an almost infinitely massive electron that is strangely magnetic, rather than like individual particles. The study was published in the journal Nature Physics this week. The science team is Jia-Xin Yin, Songtian S. Zhang, Guoqing Chang, Qi Wang, Stepan S. Tsirkin, Zurab Guguchia, Biao Lian, Huibin Zhou, Kun Jiang, Ilya Belopolski, Nana Shumiya, Daniel Multer, Maksim Litskevich, Tyler A. Cochran, Hsin Lin, Ziqiang Wang, Titus Neupert, Shuang Jia, Hechang Lei and M. Zahid Hasan.

    The team also showed that placing the kagome magnet in a high magnetic field causes the direction of magnetism to reverse. This “negative magnetism” is akin to having a compass that points south instead of north, or a refrigerator magnet that suddenly refuses to stick.

    “We have been searching for super-massive ‘flat band’ electrons that can still conduct electricity for a long time, and finally we have found them,” said M. Zahid Hasan, the Eugene Higgins Professor of Physics at Princeton University, who led the team. “In this system, we also found that due to an internal quantum phase effect, some electrons line up opposite to the magnetic field, producing negative magnetism.”

    The team explored how atoms arranged in a kagome pattern in a crystal give rise to strange electronic properties that can have real-world benefits, such as superconductivity, which allows electricity to flow without loss as heat, or magnetism that can be controlled at the quantum level for use in future electronics.

    The researchers used state-of-the-art scanning tunneling microscopy and spectroscopy (STM/S) to look at the behavior of electrons in a kagome-patterned crystal made from cobalt and tin, sandwiched between two layers of sulfur atoms, which are further sandwiched between two layers of tin.

    Researchers explored a material that has an internal structure, shown in 3D in left panel, that consists of triangles and hexagons arranged in a pattern similar to that of a Japanese (kagome) basket. Credit: Hasan, et al.

    In the kagome layer, the cobalt atoms form triangles around a hexagon with a tin atom in the center. This geometry forces the electrons into some uncomfortable positions – leading this type of material to be called a “frustrated magnet.”

    To explore the electron behavior in this structure, the researchers nicked the top layers to reveal the kagome layer beneath.

    They then used the STM/S technique to detect each electron’s energy profile, or band structure. The band structure describes the range of energies an electron can have within a crystal, and explains, for example, why some materials conduct electricity and others are insulators. The researchers found that some of electrons in the kagome layer have a band structure that, rather than being curved as in most materials, is flat.

    A flat band structure indicates that the electrons have an effective mass that is so large as to be almost infinite. In such a state, the particles act collectively rather than as individual particles.

    Theories have long predicted that the kagome pattern would create a flat band structure, but this study is the first experimental detection of a flat band electron in such a system.

    (Left) Although it is expected that a magnet pointing North would move up when the field is pointing up, it actually moves down. (Middle) Application of a magnetic field shifts the energy levels of electrons. (right, up) Energy shifts of Kagome electrons show a large negative magnetic moment (right, down) Orbital arrangements of Kagome electrons give rise to a geometrical quantum phase factor (Berry phase) which creates an unusual magnetic state.

    One of the general predictions that follows is that a material with a flat band may exhibit negative magnetism.

    Indeed, in the current study, when the researchers applied a strong magnetic field, some of the kagome magnet’s electrons pointed in the opposite direction.

    “Whether the field was applied up or down, the electrons’ energy flipped in the same direction, that was the first thing that was strange in terms of the experiments,” said Songtian Sonia Zhang, a graduate student in physics and one of three co-first-authors on the paper.

    “That puzzled us for about three months,” said Jia-Xin Yin, a postdoctoral research associate and another co-first author on the study. “We were searching for the reason, and with our collaborators we realized that this was the first experimental evidence that this flat band peak in the kagome lattice has a negative magnetic moment.”

    The researchers found that the negative magnetism arises due to the relationship between the kagome flat band, a quantum phenomenon called spin–orbit coupling, magnetism and a quantum factor called the Berry curvature field. Spin-orbit coupling refers to a situation where an electron’s spin, which itself is a quantum property of electrons, becomes linked to the electron’s orbital rotation. The combination of spin-orbital coupling and the magnetic nature of the material leads all the electrons to behave in lock step, like a giant single particle.

    Another intriguing behavior that arises from the tightly coupled spin-orbit interactions is the emergence of topological behaviors. The subject of the 2016 Nobel Prize in Physics, topological materials can have electrons that flow without resistance on their surfaces and are an active area of research. The cobalt-tin-sulfur material is an example of a topological system.

    Two-dimensional patterned lattices can have other desirable types of electron conductance. For example, graphene is a pattern of carbon atoms that has generated considerable interest for its electronic applications over the past two decades. The kagome lattice’s band structure gives rise to electrons that behave similarly to those in graphene.

    Funding for this study was provided as follows: The STM experimental and theoretical work at Princeton University was supported by the Gordon and Betty Moore Foundation (GBMF4547). The ARPES characterization of the sample is supported by the United States Department of Energy under the Basic Energy Sciences program (DE-FG-02–05ER46200). Support was also provided through the Princeton Center for Theoretical Science and the Princeton Institute for the Science and Technology of Materials Imaging and Analysis Center at Princeton University, Lawrence Berkeley National Laboratory and the University of California, Berkeley.

    Authors and affiliations:

    Jia-Xin Yin, Songtian S. Zhang, Guoqing Chang, Zurab Guguchia, Ilya Belopolski, Nana Shumiya, Daniel Multer, Maksim Litskevich, Tyler A. Cochran, Biao Lian and M. Zahid Hasan: Department of Physics, Princeton University
    Qi Wang and Hechang Lei: Renmin University of China
    Stepan S. Tsirkin and Titus Neupert: University of Zurich
    Zurab Guguchia: Paul Scherrer Institute, Villigen PSI, Switzerland
    Huibin Zhou and Shuang Jia: Peking University and Chinese Academy of Sciences
    Kun Jiang and Ziqiang Wang: Boston College
    Hsin Lin: Institute of Physics, Academia Sinica, Taipei
    Zahid Hasan is also affiliated with the Princeton Institute for the Science and Technology of Materials and Lawrence Berkeley National Laboratory.

    See the full article here .


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    Princeton University Campus

    Discovery at Princeton University

    Whatever the controversy of the day, the way forward in science relies on following the evidence, wherever it may lead. Princeton researchers are at the forefront of this path, both through theoretical advances in artificial intelligence and machine learning, and through innovations in data science that are helping to address societal challenges, such as eviction and its impacts, energy-efficient transportation, marine “dead zones,” attitudes on immigration, and many more.

    The search for understanding is at the heart of University research, whether the quest leads to beautiful theorems, practical inventions or a new interpretation of art (page 26). Princeton is a place where all of these aspects of research coexist, cross-fertilize and intermingle. But why take my word for it? Let the pages of Discovery be the data that convince you.

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 7:09 pm on February 13, 2019 Permalink | Reply
    Tags: A key link in CERN’s accelerator complex, A new set of quadrupole magnets will be installed along the Booster-to-PS injection line, , Also delivering particles to several experimental areas such as the Antiproton Decelerator (AD), , , CERN Proton Synchrotron, , It takes ten hours to extract one magnet, Magnet technology, Mainly accelerating protons to 26 GeV before sending them to the Super Proton Synchrotron (SPS), New cooling systems are being installed to increase the cooling capacity of the PS, One major component of the PS that will be consolidated is the magnet system, One of the elements known as the pole-face windings which is located between the beam pipe and the magnet yoke needs replacing, , PS will undergo a major overhaul to prepare it for the higher injection and beam intensities of the LHC’s Run 3 as well as for the High-Luminosity LHC   

    From CERN- “LS2 report: The Proton Synchrotron’s magnets prepare for higher energies” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    From CERN

    13 February, 2019
    Achintya Rao

    CERN Proton Synchrotron

    One of the magnets being driven on a locomotive to the workshop (right) after being extracted from the PS itself (left) (Image: Julien Marius Ordan/Maximilien Brice/CERN)

    The Proton Synchrotron (PS), which was CERN’s first synchrotron and which turns 60 this year, once held the record for the particle accelerator with the highest energy. Today, it forms a key link in CERN’s accelerator complex, mainly accelerating protons to 26 GeV before sending them to the Super Proton Synchrotron (SPS), but also delivering particles to several experimental areas such as the Antiproton Decelerator (AD). Over the course of Long Shutdown 2 (LS2), the PS will undergo a major overhaul to prepare it for the higher injection and beam intensities of the LHC’s Run 3 as well as for the High-Luminosity LHC.

    One major component of the PS that will be consolidated is the magnet system [Many magnets will come from Fermilab and Brookhaven Lab, two US D.O.E. labs]. The synchrotron has a total of 100 main magnets within it (plus one reference magnet unit outside the ring), which bend and focus the particle beams as they whizz around it gaining energy. “During the last long shutdown (LS1) and at the beginning of LS2, the TE-MSC team performed various tests to identify weak points in the magnets,” explains Fernando Pedrosa, who is coordinating the LS2 work on the PS. The team identified 50 magnets needing refurbishment, of which seven were repaired during LS1 itself. “The remaining 43 magnets that need attention will be refurbished this year.”

    Specifically, one of the elements, known as the pole-face windings, which is located between the beam pipe and the magnet yoke, needs replacing. In order to reach into the magnet innards to replace these elements, the magnet units have to be transferred to a workshop in building 151. Once disconnected, each magnet is placed onto a small locomotive system that drives them to the workshops. The locomotives themselves are over 50 years old, and their movement must be delicately managed. It takes ten hours to extract one magnet. So far, six magnets have been taken to the workshop and this work will last until 18 October 2019.

    The workshop where the magnets are being treated is divided into two sections. In the first room, the vacuum chamber of the magnets is cut so as to access the pole-face windings. The magnet units are then taken to the second room, where prefabricated replacements are installed.

    As mentioned in the previous LS2 Report, the PS Booster will see an increase in the energy it imparts to accelerating protons, from 1.4 GeV to 2 GeV. A new set of quadrupole magnets will be installed along the Booster-to-PS injection line, to increase the focusing strength required for the higher-energy beams. Higher-energy beams require higher-energy injection elements; therefore some elements will be replaced in the PS injection region as part of the LHC Injectors Upgrade (LIU) project, namely septum 42, kicker 45 and five bumper magnets.

    Other improvements as part of the LIU project include the new cooling systems being installed to increase the cooling capacity of the PS. A new cooling station is being built at building 355, while one cooling tower in building 255 is being upgraded. The TT2 line, which is involved in the transfer from the PS to the SPS, will have its cooling system decoupled from the Booster’s, to allow the PS to operate independent of the Booster schedule. “The internal dumps of the PS, which are used in case the beam needs to be stopped, are also being changed, as are some other intercepting devices,” explains Pedrosa.

    The LS2 operations are on a tight schedule,” notes Pedrosa, pointing out that works being performed on several interconnected systems create constraints for what can be done concurrently. As LS2 proceeds, we will bring you more news about the PS, including the installation of new instrumentation in wire scanners that help with beam-size measurement, an upgraded transverse-feedback system to stabilise the beam and more.

    See the full article here.

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    Meet CERN in a variety of places:

    Quantum Diaries

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    CERN/ALICE Detector

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    CERN map

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  • richardmitnick 7:40 am on April 4, 2015 Permalink | Reply
    Tags: , , , Magnet technology   

    From FNAL: “New magnet at Fermilab achieves high-field milestone” 

    FNAL Home

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    April 3, 2015
    Emanuela Barzi, Technical Division

    This magnet recently achieved an important milestone, reaching its design field of 11.5 Tesla. It is the first successful niobium-3-tin, twin-aperture accelerator magnet in the world. Photo: Sean Johnson, TD

    Last month, a new superconducting magnet developed and fabricated at Fermilab reached its design field of 11.5 Tesla at a temperature nearly as cold as outer space. It is the first successful twin-aperture accelerator magnet made of niobium-3-tin in the world.

    The advancements in niobium-3-tin, or Nb3Sn, magnet technology and the ongoing U.S. collaboration with CERN on the development of these and other Nb3Sn magnets are enabling the use of this innovative technology for future upgrades of the Large Hadron Collider (LHC).

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    They may also provide the cornerstone for future circular machines of interest to the worldwide high-energy physics community. Because of the exceptional challenges — Nb3Sn is brittle and requires high-temperature processing — this important milestone was achieved at Fermilab after decades of worldwide R&D efforts both in the Nb3Sn conductor itself and in associated magnet technologies.

    Superconducting magnets are at the heart of most particle accelerators for fundamental science as well as other scientific and technological applications. Superconductivity is also being explored for use in biosensors and quantum computing.

    Thanks to Nb3Sn’s stronger superconducting properties, it enables magnets of larger field than any in current particle accelerators. As a comparison, the niobium-titanium dipole magnets built in the early 1980s for the Tevatron particle collider produced about 4 Tesla to bend the proton and antiproton beams around the ring. The most powerful niobium-titanium magnets used in the LHC operate at roughly 8 Tesla. The new niobium-3-tin magnet creates a significantly stronger field.

    FNAL Tevatron machine
    Fermilab CDF
    FNAL DZero
    Tevatron at FNAL

    Because the Tevatron accelerated positively charged protons and negatively charged antiprotons, its magnets had only one aperture. By contrast, the LHC uses two proton beams. This requires two-aperture magnets with fields in opposite directions. And because the LHC collides beams at higher energies, it requires larger magnetic fields.

    In the process of upgrading the LHC and in conceiving future particle accelerators and detectors, the high-energy physics community is investing as never before in high-field magnet technologies. This creative process involves the United States, Europe, Japan and other Asian countries. The latest strategic plan for U.S. high-energy physics, the 2014 report by the Particle Physics Project Prioritization Panel, endorses continued U.S. leadership in superconducting magnet technology for future particle physics programs. The U.S. LHC Accelerator Research Program (LARP), which comprises four DOE national laboratories — Berkeley Lab, Brookhaven Lab, Fermilab and SLAC — plays a key role in this strategy.

    The 15-year investment in Nb3Sn technology places the Fermilab team led by scientist Alexander Zlobin at the forefront of this effort. The Fermilab High-Field Magnet Group, in collaboration with U.S. LARP and CERN, built the first reproducible series in the world of single-aperture 10- to 12-Tesla accelerator-quality dipoles and quadrupoles made of Nb3Sn, establishing a strong foundation for the LHC luminosity upgrade at CERN.

    The laboratory has consistently carried out in parallel an assertive superconductor R&D program as key to the magnet success. Coordination with industry and universities has been critical to improve the performance of the next generation of high-field accelerator magnets.

    The next step is to develop 15-Tesla Nb3Sn accelerator magnets for a future very high-energy proton-proton collider. The use of high-temperature superconductors is also becoming a realistic prospect for generating even larger magnetic fields. An ultimate goal is to develop magnet technologies based on combining high- and low-temperature superconductors for accelerator magnets above 20 Tesla.

    The robust and versatile infrastructure that was developed at Fermilab, together with the expertise acquired by the magnet scientists and engineers in design and analysis tools for superconducting materials and magnets, makes Fermilab an ideal setting to look to the future of high-field magnet research.

    See the full article here.

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    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

  • richardmitnick 11:40 am on July 11, 2013 Permalink | Reply
    Tags: , , Magnet technology, ,   

    From Berkeley Lab: “Successful Test of New U.S. Magnet Puts Large Hadron Collider on Track for Major Upgrade” 

    Berkeley Lab

    U.S. Department of Energy national laboratories – including Berkeley Lab – collaborate to build the new magnets CERN needs to increase LHC luminosity by an order of magnitude

    July 11, 2013
    Lynn Yarris (510) 486-5375 lcyarris@lbl.gov

    “The U.S. LHC Accelerator Program (LARP) has successfully tested a powerful superconducting quadrupole magnet that will play a key role in developing a new beam focusing system for CERN’s Large Hadron Collider (LHC). This advanced system, together with other major upgrades to be implemented over the next decade, will allow the LHC to produce 10 times more high-energy collisions than it was originally designed for.

    HQ02a is a superconducting quadrupole magnet made from high performance niobium tin that will play a key role in developing a new beam focusing system for CERN’s Large Hadron Collider. No image credit.

    Dubbed HQ02a, the latest in LARP’s series of High-Field Quadrupole magnets is wound with cables of the brittle but high-performance superconductor niobium tin (Nb3Sn). Compared to the final-focus quadrupoles presently in place at the LHC, which are made with niobium titanium, HQ02a has a larger aperture and superconducting coils designed to operate at a higher magnetic field. In a recent test at the Fermi National Accelerator Laboratory (Fermilab), HQ02a achieved all its challenging objectives.

    LARP is a collaboration among the U.S Department of Energy’s Brookhaven National Laboratory (Brookhaven), Fermilab, Lawrence Berkeley National Laboratory (Berkeley Lab), and the SLAC National Accelerator Laboratory (SLAC), working in close partnership with CERN. LARP has also supported research at the University of Texas at Austin and Old Dominion University.

    ‘Congratulation to all the LARP team for this brilliant result,’ said Lucio Rossi, leader of the High Luminosity LHC project at CERN. ‘The steady progress by LARP and the other DOE supported programs clearly shows the benefits of long-term investments to make serious advances in accelerator technology.'”

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California


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  • richardmitnick 12:32 pm on April 1, 2013 Permalink | Reply
    Tags: , Magnet technology   

    From Fermilab: “Feature High-field magnets poised to get an upgrade” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Monday, April 1, 2013
    Sarah Khan

    Recently the Technical Division’s High Field Magnet Group identified and tested a new insulating compound that could help superconducting magnets survive under the harsh conditions of many future accelerator projects.

    A 2-meter-long superconducting coil filled with Matrimid® has been shown to be able to stand up to extreme operating environments. Photo: Sarah Khan

    This shows a cross-section of superconducting wires stacked on top of each other. In between the wires is the insulating component Matrimid. Photo: Marianne Bossert, TD

    The new component, called Matrimid® and manufactured by the company Huntsman, can last longer and resist radiation better than the traditional epoxy-based insulation used for magnet coils.

    Recently, engineer Steve Krave and lead engineer Rodger Bossert produced 1- and 2-meter long superconducting coils filled with Matrimid. Tests have shown that the new insulation holds up well to extreme fabrication and operating environments.

    ‘These results are very exciting,’ said Alexander Zlobin, head of the high-field magnet program. ‘This technological development will have a great impact on our field.'”

    See the full article here.

    Fermilab campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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