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  • richardmitnick 11:16 am on April 15, 2016 Permalink | Reply
    Tags: , , Magnetic remanence, Magnets,   

    From EPFL: “A single-atom magnet breaks new ground for future data storage” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne EPFL

    15.04.16
    Nik Papageorgiou

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    Scientists at EPFL and ETH Zürich have built a single-atom magnet that is the most stable to-date. The breakthrough paves the way for the scalable production of miniature magnetic storage devices.

    Magnetic storage devices such as computer hard drives or memory cards are widespread today. But as computer technology grows smaller, there is a need to also miniaturize data storage. This is epitomized by an effort to build magnets the size of a single atom. However, a magnet that small is very hard to keep “magnetized”, which means that it would be unable to retain information for a meaningful amount time. In a breakthrough study published in Science*, researchers led by EPFL and ETH Zürich have now built a single-atom magnet that, although working at around 40 Kelvin (-233.15 oC), is the smallest and most stable to date.

    Magnets work because of electron spin, which is a complicated motion best imagined as a spinning top. Electrons can spin up or down (something like clockwise or anti-clockwise), which creates a tiny magnetic field. In an atom, electrons usually come in pairs with opposite spins, thus cancelling out each other’s magnetic field. But in a magnet, atoms have unpaired electrons, and their spins create an overall magnetic field.

    A challenge today is to build smaller and smaller magnets that can be implemented in data storage devices. The problem is something called “magnetic remanence”, which describes the ability of a magnet to remain magnetized. Remanence is very difficult to observe from a single atom, because environmental fluctuations can flip its magnetic fields. In terms of technology, a limited remanence would mean limited information storage for atom-sized magnets.

    A team of scientists led by Harald Brune at EPFL and Pietro Gambardella at ETH Zürich, have built a prototypical single-atom magnet based on atoms of the rare-earth element holmium. The researchers, placed single holmium atoms on ultrathin films of magnesium oxide, which were previously grown on a surface of silver. This method allows the formation of single-atom magnets with robust remanence. The reason is that the electron structure of holmium atoms protects the magnetic field from being flipped.

    The magnetic remanence of the holmium atoms is stable at temperatures around 40 Kelvin (-233.15 oC), which, though far from room temperature, are the highest achieved ever. The scientists’ calculations demonstrate that the remanence of single holmium atoms at these temperatures is much higher than the remanence seen in previous magnets, which were also made up of 3-12 atoms. This makes the new single-atom magnet a worldwide record in terms of both size and stability.

    This project involved a collaboration of EPFL’s Institute of Condensed Matter Physics with ETH Zürich, Swiss Light Source (PSI), Vinča Institute of Nuclear Sciences (Belgrade), the Texas A&M University at Qatar and the European Synchrotron Radiation Facility (Grenoble).

    It was funded by the Swiss National Science Foundation, the Swiss Competence Centre for Materials Science and Technology (CCMX), the ETH Zurich, EPFL and the Marie Curie Institute, and the Serbian Ministry of Education and Science.

    Reference

    Donati F, Rusponi S, Stepanow S, Wäckerlin C, Singha A, Persichetti L, Baltic R, Diller K, Patthey F, Fernandes E, Dreiser J, Šljivančanin Ž, Kummer K, Nistor C, Gambardella P, Brune H. Magnetic remanence in single atoms. Science 14 April 2016. DOI: 10.1126/science.aad9898

    *Science paper:P
    Magnetic remanence in single atoms

    Science team:
    F. Donati1, S. Rusponi1, S. Stepanow2, C. Wäckerlin1, A. Singha1, L. Persichetti2, R. Baltic1, K. Diller1, F. Patthey1, E. Fernandes1, J. Dreiser1,3, Ž. Šljivančanin4,5, K. Kummer6, C. Nistor2, P. Gambardella2,*, H. Brune1,*

    Affiliations:
    1Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland.
    2Department of Materials, ETH Zürich, Hönggerbergring 64, CH-8093 Zürich, Switzerland.
    3Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
    4Vinča Institute of Nuclear Sciences (020), Post Office Box 522, 11001 Belgrade, Serbia.
    5Texas A&M University at Qatar, Doha, Qatar.
    6European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France.

    ↵*Corresponding author. E-mail: pietro.gambardella@mat.ethz.ch (P.G.); harald.brune@epfl.ch (H.B.)

    See the full article here .

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    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university with students, professors and staff from over 120 nations. A dynamic environment, open to Switzerland and the world, EPFL is centered on its three missions: teaching, research and technology transfer. EPFL works together with an extensive network of partners including other universities and institutes of technology, developing and emerging countries, secondary schools and colleges, industry and economy, political circles and the general public, to bring about real impact for society.

     
  • richardmitnick 10:40 am on May 28, 2015 Permalink | Reply
    Tags: , , , Magnets   

    From FNAL: “Physics in a Nutshell – Magnets for measurements” 

    FNAL Home

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

    May 28, 2015
    Jim Pivarski

    1
    Magnet systems in modern particle physics experiments are used to analyze particle charge and momentum, but the field is strong enough and covers enough volume to give a whale an MRI exam.

    Broadly speaking, a modern particle physics detector has three main pieces: (1) tracking, which charts the course of charged particles by letting them pass through thin sensors, (2) calorimetry, which measures the energy of charged or neutral particles by making them splat into a wall and (3) a strong magnetic field. Unlike tracking and calorimetry, the magnet doesn’t detect the particles directly — it affects them in revealing ways.

    Magnetic fields curve the paths of charged particles, and the direction of curvature depends on whether the particle is positively or negatively charged. Thus, a tracking system with a magnetic field can distinguish between matter and antimatter. In addition, the deflection is larger for slow, low-momentum particles than it is for fast, high-momentum ones. Fast particles zip right through while slow ones loop around, possibly several times.

    Both effects were used to discover positrons in 1932. A cloud chamber (tracking system) immersed in a strong magnetic field revealed particles that curved the wrong way to be negatively charged electrons, yet were also too fast to be positively charged protons. The experimenters concluded that they had discovered a new particle, similar to electrons, but positively charged. It turned out to be the first evidence of antimatter.

    Today, most particle physics experiments feature a strong magnet. The radius of curvature of each particle’s track precisely determines its momentum. In many experiments, these magnets are stronger than the ones used to conduct MRI scans in hospitals, yet are also large enough to fit a whale inside.

    Most of these magnets work the same way as a hand-held electromagnet: a DC current circulates in a coiled wire to produce a magnetic field. However, particle physics magnets are often made of superconducting materials to achieve extremely high currents and field strengths. Some magnets, such as the one in CMS, are cylindrical for more precision at right angles to the beamline, while others, such as ATLAS’s outer magnet, are toroidal (doughnut-shaped) for more precision close to the beamline.

    CERN CMS Detector
    CMS

    CERN ATLAS New
    ATLAS

    In some cases, an experiment without a built-in magnet can surreptitiously make use of natural magnetic fields: the Fermi-LAT satellite used the Earth’s magnetic field to distinguish positrons from electrons.

    NASA Fermi LAT
    FERMI-LAT

    Since the particle momentum that a magnetized tracking system measures is closely related to the particle energy that a calorimeter measures, the two can cross-check each other, be used in combination or reveal the particles that are invisible to tracking alone. Advances in understanding often come from different ways of measuring similar things.

    See the full article here.

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    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. 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 3:24 pm on April 24, 2015 Permalink | Reply
    Tags: , Magnets,   

    From TRIUMF: “Baartman scores touchdown in magnet design” 

    TRIUMF

    Thursday, 23. April 2015
    Kyla Shauer and Jacqueline Wightman, Communications Assistants

    For years labs all over the world have been using a quadrupole magnet design that works perfectly on paper – that is, in two dimensional space – but less than perfectly in three dimensional reality. These quadrupoles were designed in the 1970s to be used in particle accelerators, and the design has not changed much since. Rick Baartman, head of the Beam Physics group at TRIUMF, re-evaluated the problem and came up with a new and improved quadrupole design.

    Quadrupoles are four-poled magnets with alternating north and south poles. They are used to focus a beam of charged particles and guide it down the beam line. To create a given force on the charged particle beam, quadrupoles can be long and weak or short and strong. It is well known in the particle accelerator community that the shorter your quadrupole magnet, the more efficiently and accurately it works. This is because quadrupoles are made of steel, so they are subject to a lagging effect called “hysteresis.” This effect is more pronounced with weaker magnets, so the quadrupoles should be as short as possible.

    Previous to Rick’s breakthrough, TRIUMF, like many labs all over the world, used a design that was basically derived from the 2-dimensional one, but truncated in the third dimension (See Fig. 2). Engineers knew the ends should be rounded to minimize the non-intended, non-linear field, but the exact optimal shape was unknown.

    Baartman found a key formula in a 1972 Russian paper by Derevjankin [1]. Using Mathematica™ software, he made calculations based on this formula, and found that for the shortest quadrupoles, the poles should ideally look like four American footballs connected end to end in a ring (see Figure 3). However, a “good enough” shape is spherical – just the middle part of the football (see Fig. 4). “I found the way to shape the ends so that you get minimal error from the non-intended field,” says Baartman. “It starts from a complicated idea, but the eventual product is very simple.”

    Baartman’s derivation works well for both long and short quadrupoles; in the long case, the poles are not spherical, but are curved in the beam direction rather than straight.

    Baartman sent his calculations to Buckley Systems Ltd, a manufacturer of precision electromagnets, who perfected his solution using more detailed magnetic field calculations. Buckley manufactured 70 magnets for TRIUMF using Baartman’s new design, and 40 have already been installed in the ARIEL e-linac.

    Triumf ARIEL LINAC
    ARIEL

    Congratulations Rick Baartman on this breakthrough achievement!

    1

    2

    3

    4

    5

    Photos, from top to bottom: 1. Rick Baartman; 2. Example of non-ideal (truncated) magnet shape; 3. Optimal magnet shape; 4. Magnets with new design, built by Buckley; 5. New quadrupoles installed in the e-linac tunnel

    Baartman’s paper
    [1] G. Derevjankin, Zh. Tkh. Fiz. (USSR) 42, 1178 (1972)

    See the full article here.

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    Triumf Campus
    Triumf Campus
    World Class Science at Triumf Lab, British Columbia, Canada
    Canada’s national laboratory for particle and nuclear physics
    Member Universities:
    University of Alberta, University of British Columbia, Carleton University, University of Guelph, University of Manitoba, Université de Montréal, Simon Fraser University,
    Queen’s University, University of Toronto, University of Victoria, York University. Not too shabby, eh?

    Associate Members:
    University of Calgary, McMaster University, University of Northern British Columbia, University of Regina, Saint Mary’s University, University of Winnipeg, How bad is that !!

     
  • richardmitnick 6:41 pm on March 11, 2014 Permalink | Reply
    Tags: , , , , Magnets, ,   

    From SLAC: “SLAC Accelerator Physicists Help Make Sure ILC Will Hit Target” 

    March 7, 2014
    Lori Ann White

    An international team of scientists at Japan’s high-energy accelerator research facility KEK has successfully demonstrated a key component of a future high-power linear collider, such as the International Linear Collider (ILC) under consideration in Japan or the Compact Linear Accelerator (CLIC) being developed at the European facility CERN.

    ILC schematic
    ILC

    CERN CLIC
    CLIC

    The component, called the final focus optics, will help produce precise beams of particles at these future research facilities, said Glen White, the SLAC accelerator physicist who is lead author on a recent paper in Physical Review Letters.

    Optics for an accelerator that boosts charged particles to near light speed aren’t lenses in the typical sense of eyeglass lenses or magnifying lenses. Instead, “optics” refers to the magnets that steer the particles. The final focus optics for an accelerator are a sequence of powerful magnets that concentrate particles into tight beams. The optics demonstrated by the Accelerator Test Facility 2 (ATF2) focused an electron beam down to only a few tens of nanometers tall.

    This special sequence of magnets was developed by former SLAC accelerator physicists Andrei Seryi and Pantaleo Raimondi nearly 15 years ago. Many more SLAC physicists are members of the ATF2 collaboration, an international group of scientists that built and continue to test the structure at the KEK accelerator facility in Japan.

    The optics for a future linear collider must take many different issues into account, said White, including the physics and the economics of extremely energetic beams of tiny particles.

    For example, a magnet will focus charged particles that have slightly different energies to slightly different places.”No bunch of particles in an accelerator is perfectly uniform,” said White. Thus, the particles can “fuzz out” around the focal point, resulting in fewer collisions and less data, unless such differences in position, called chromatic aberrations, are accounted for.

    Previous methods for correcting chromatic aberration, such as those tested during the Final Focus Test Beam experiment at SLAC, required additional lengthy sections of tunnel for the magnets used, thus adding considerable cost, White said. The design the ATF2 collaboration tested involved adding magnets called sextupoles to the focusing magnets, called quadrupoles, already in use. “The sextupoles refocus the particles according to their positions, which are determined by their energies,” he said – essentially reversing the errors introduced by the quadrupoles.

    sextupole
    Sextupole electromagnet as used within the storage ring of the Australian Synchrotron to focus and steer the electron beam

    quad
    A quadrupole electromagnet as used in the storage ring of the Australian Synchrotron

    Seryi, who left SLAC in 2010 to become director of the John Adams Institute for Accelerator Science at Oxford University, is a member of the ATF2 collaboration. “It is extremely gratifying to see the idea realized in practice and know that it works,” he said. “I am also tremendously happy that the ATF2 experiment has trained many young accelerator physics experts. This was actually one of the goals – to create the team who will be able to work on the linear collider’s final focus when the real project starts.”

    Now that they know it works, said White, the next steps are to work on stabilizing the beam and train more young physicists for the real thing.

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 11:52 am on January 17, 2014 Permalink | Reply
    Tags: , , , Magnets,   

    From Fermilab: “Fermilab breaks ground on coil fabrication for Jefferson Lab collaboration” 


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

    Friday, Jan. 17, 2014
    Sarah Witman

    There is perhaps no greater challenge, mentally, than taking on a project that has been attempted previously but not successfully completed.

    This is the position a team of Fermilab engineers and physicists found themselves in more than a year ago, when Jefferson Lab, based in Virginia, came to Fermilab for help on a project: fabricating magnet coils for an upgrade to its CEBAF Large Acceptance Spectrometer (CLAS) experiment.

    It turned out to be a good move. In late November, a Magnet Systems Department fabrication team in the Technical Division successfully wound a full-size coil, called a practice coil, of the type to be installed in the new torus magnet for the upgrade of Jefferson Lab’s CLAS detector. Jefferson Lab’s upgraded facilities will provide scientists with unprecedented precision and reach for studies of atomic nuclei.

    coil
    The Magnet Systems Department recently successfully completed a prototype torus magnet coil for the Jefferson Lab CLAS12 upgrade. They devised a relatively inexpensive system, seen here, for winding the 2,500-pound coil. While the price of a standard coil-winding table that can hold a 4,000-pound fixture is $190,000, the Fermilab team built an adequate system for less than $10,000. One layer of coil, sitting at the winding fixture with a 12-foot-diameter cable spool installed above the fixture, and the second spool on the tensioner, is almost completely wound. Photo: Douglas Howard, TD

    “Now we can say we can definitely do this job,” said Fermilab engineer Sasha Makarov. “It seems like Jefferson Lab is very satisfied with our achievement.”

    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.


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  • richardmitnick 10:22 am on December 20, 2013 Permalink | Reply
    Tags: , , Magnets,   

    From Livermore: “High-pressure studies of rare earth material could lead to lighter, cheaper magnets” 


    Lawrence Livermore National Laboratory

    12/20/2013
    Anne M Stark, LLNL, (925) 422-9799, stark8@llnl.gov

    Sometimes you have to apply a little pressure to get magnetic materials to reveal their secrets. By placing a permanent magnet under high pressures, Lawrence Livermore researchers are exploring how atomic structure enhances magnetic strength and resistance to demagnetization. This fundamental research into magnetic behavior has important implications for engineering stronger, cheaper magnets.

    man
    A Lawrence Livermore researcher prepares a sample at Oak Ridge National Laboratory’s Spallation Neutrons and Pressure Diffractometer (SNAP).

    Permanent magnets based on rare earth elements are in high demand for energy technologies such as windmills and electric motors that generate rotational energy through opposing magnetic forces.

    In September 2013, a team from Lawrence Livermore National Laboratory (LLNL) and the National Institute of Standards and Technology conducted neutron scattering research at Oak Ridge National Laboratory’s Spallation Neutron Source Spallation Neutrons and Pressure (SNAP) Diffractometer to examine the magnetic properties of a rare-earth-based permanent magnet containing the elements lanthanum and cobalt, known as LaCo5.

    “We’re using high pressure to tune the structural and magnetic properties of permanent magnets like LaCo5,” said Jason Jeffries of the LLNL research team. “We can see how the atomic structure of the material changes as the magnetic moment, or the magnetic strength, of the system changes under pressure.”

    Researchers applied 20 GPa — about 200,000 times atmospheric pressure — to a 100 mg sample of LaCo5 with a SNAP pressure cell. The suite of pressure cells available at SNAP includes some that can achieve pressures near 100 GPa and that can be used to study a range of materials under high-pressure conditions applicable to research in solid-state physics, hydrogen storage, planetary ices and geochemistry, among other fields. Jeffries said the LLNL team hopes to expand their research to pressures as high as 25 to 50 GPa.

    One of the team’s most important research goals is to see if expensive, rare earth elements that are increasing in scarcity and driving up the cost of permanent magnets can be substituted with cheaper elements or entirely new, engineered materials.

    See the full article here.

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