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  • richardmitnick 2:09 pm on December 2, 2014 Permalink | Reply
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    From Symmetry: “Muon versus the volcano” 


    December 02, 2014
    Glenn Roberts Jr.

    Particles produced by cosmic rays enter volcanoes and live to tell the tale.

    Exploring the innards of Mount Vesuvius, the active volcano that once destroyed the ancient town of Pompeii, sounds like a risky endeavor. Unless you’re a muon.

    Scientists from institutions in Italy, France, Japan and the United States are using muons, the big brothers of electrons, to study the structure of Mount Vesuvius and other volcanoes in Italy, France, Japan and the Caribbean.

    Muons are particles produced in the constant shower of cosmic rays that interact with Earth’s atmosphere. If you hold out your hand, a muon will pass through it about once per second—and it will keep on going. The highest-energy muons can travel more than a mile through solid rock.

    “[Studying volcanoes with muons] should help in giving information on how an eruption would develop,” says scientist Giulio Saracino of INFN, Italy’s National Institute for Nuclear Physics, who is a member of the MU-RAY experiment at Mount Vesuvius. Researchers say the measurements could be used in conjunction with other methods to identify areas of greatest risk based on concentrations of lower-density rock susceptible to fracture in an eruption.

    In May 2013 MU-RAY scientists took a 1-square-meter prototype of a muon detector to a research station at the foot of Mount Vesuvius for a technical run. The detector is an advanced version of technology used in physics experiments at Fermi National Accelerator Laboratory and Gran Sasso National Laboratory. A handful of researchers, assisted by local high school students in the delivery and setup of equipment, completed the installation in about three workdays.

    Courtesy of: MU-RAY collaboration

    Vesuvius is considered the most dangerous volcano on the planet, owing to its well-documented history of incredibly explosive eruptions and the half a million people living in its high-risk “red zone.”

    “If you live in Naples, you feel the presence of Mount Vesuvius as a sleeping giant that could suddenly awaken with tremendous effects,” says MU-RAY scientist Paolo Strolin, also of INFN. “A better understanding of its dangers is worth any challenge.”

    Geologists and volcanologists have amassed an array of tools to study aspects of volcanoes: satellites, seismic readers, laser surveying kits and equipment to monitor gases, gravity fluctuations and electrical and electromagnetic signals.

    Nobel Laureate Luis Alvarez of the University of California, Berkeley, pioneered the muon radiography technique used on volcanoes in the late 1960s when he used it to look for hidden chambers in the Great Pyramid of Chephren in Egypt. In 2007, scientists used it to image the interior of an active volcano, Japan’s Mount Asama, for the first time.

    “This is quite unique compared to other survey methods,” says Valentin Niess of CNRS, the French National Center for Scientific Research, and a member of the TOMUVOL collaboration, a group of about 30 scientists studying the long-dormant Puy de Dôme in France.

    Volcano researchers hope using muons will pay off by helping to identify areas prone to particular risk from eruptions, says TOMUVOL scientist Cristina Cârloganu of CNRS: “That could significantly reduce the volcanic hazards.”

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 8:45 pm on August 5, 2014 Permalink | Reply
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    From SLAC: “Rebooted Muon Experiment Tests Detector Design at SLAC” 

    SLAC Lab

    August 5, 2014
    Last year, a monster magnet set out from Brookhaven National Lab on an epic, 35-day trek by land and sea to its new home at Fermilab, where it will serve as the heart of a search for evidence of new subatomic particles. Last month, with much less fanfare, researchers came to the End Station Test Beam (ESTB) facility at the Department of Energy’s SLAC National Accelerator Laboratory to test the eyes and nerves of the same experiment: a cutting-edge design for a new detector.

    Muon g-2 magnet to be transported to Fermilab.

    The goal of the experiment, called Muon g-2 (pronounced gee-minus-two), is to precisely measure a property of muons by studying the way their spins precess, or wobble like a slowing top, in the grip of a powerful magnet. Researchers can track this spin by observing the muon’s decay into electrons, their lighter, longer-lived siblings.

    In the experiment’s original incarnation at Brookhaven, researchers discovered the spin rate is a tiny bit different from what theory says it should be – a difference that could indicate the influence of unknown virtual particles that pop into existence from the vacuum, affect the muons, and disappear once more.

    However, the researchers at Brookhaven weren’t able to measure the property precisely enough to know for sure. That prompted the relocation of the experiment – including the headline-grabbing move of the giant ring magnet – to Fermilab, with its more powerful muon beam.

    More Muons = More Data

    To take advantage of more muons, and thus more data, a team led by University of Washington physicist David Hertzog developed a new detector design for the experiment, a novel combination of lead-fluoride crystals and silicon photomultiplier chips that they hope will capture more information about the escaping electrons.

    Hertzog and his colleagues brought some of the crystals and silicon chips to SLAC’s ESTB facility, where electrons from the linear accelerator could stand in for the results of muon decays – but controlled and easily tracked muon decays, unlike what the detectors will face during the actual experiment.

    “These detectors will need to catch a tremendous number of muon decays, pinpointing their times and the energies of the electrons,” Hertzog said. “The electrons at ESTB can be delivered one at a time and with known energies, so we can see how the crystals and silicon photomultipliers respond.”

    The tests at ESTB have been much more low-key than the magnet’s 3200-mile trek, but Hertzog said his team can also look back at a successful venture.

    “This experiment has been really enjoyable,” Hertzog said. “We’ve got good data and our system seems to be working well.”

    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 2:55 pm on June 19, 2014 Permalink | Reply
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    From Fermilab- “Frontier Science Result: DZero Shedding light on forward muons 

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

    Thursday, June 19, 2014
    Mark Williams

    The DZero experiment, like all such general-purpose particle detectors, is built from a number of distinct subsystems, each designed to perform a specific task. One such component is the muon system, which forms the outermost layer of the detector. Its job is to identify muons from proton-antiproton collisions and measure their trajectories and timing information for use in both the trigger and the subsequent event reconstruction.

    Fermilab DZero

    In fact, the muon system is itself divided into two complementary parts: three muon tracking layers and three interleaved layers of muon scintillators. The tracking layers provide precise information about the location of muons as they leave the detector, which is used to build the trajectories. The scintillators measure the times that the muons pass through, with excellent precision of less than 1 nanosecond. Together, this is all the information necessary to fully reconstruct muons in the event. A recent limited-authorship publication describes the performance of the muon scintillator counters in the forward region, demonstrating both the excellent performance and the methods used to monitor the system.

    Each layer of forward muon scintillator counters forms an overlapping (“fish-scaled”) set of aluminum-covered plastic plates, which produce a burst of visible light photons when a muon passes through. This light is then fed into photon counters and converted to an electric current. Because the detection medium is light-based, the information is available very soon after the initial proton-antiproton collision and is hence used to make a decision about whether or not to save (trigger) the event for later use. Triggering is essential to select the roughly 100 events per second that can be saved to tape, out of the several million proton-antiproton collisions in this time.

    The timing information is also essential for identifying muons from cosmic-ray sources, which must be removed from the data sample. If a cosmic muon passes directly through the detector, it can look much like a pair of muons originating from the center. However, it will hit the top of the detector around 30 nanoseconds before the bottom, while a genuine muon pair produced in the collision will arrive at the muon system concurrently. By using appropriate timing windows, cosmic-ray muons can be almost completely eliminated from the data without significant reduction of signal efficiency.

    Scientists measured the performance of the forward muon scintillators regularly using a variety of independent methods. The efficiency of the light collection components was tested on a daily basis using built-in LED sources. The scintillating plastic plates were tested with radioactive beta ray (electron) sources. The overall performance of the full system was also tested using reconstructed muons identified by the muon tracking system. All methods show consistent results: a very slow reduction in the signal sizes over time, expected due to the effects of radiation aging. This slow change was anticipated during the detector design and had no effect on the muon identification efficiency.

    Overall, the detector performed very well during its entire life, with typically over 99.9 percent of counters working during data collection, and its excellent design provided extended spatial coverage and outstanding trigger capabilities.

    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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  • richardmitnick 10:36 am on June 13, 2014 Permalink | Reply
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    From Fermilab: “Physics in a Nutshell – Spinning muons” 

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

    Friday, June 13, 2014
    Fermilab Don Lincoln
    This article was written by Don Lincoln

    If you take an electrical charge and set it in motion, you create a magnet. This is true in both the world of ordinary experience and the quantum world, although the details there are a bit trickier. The simplest quantum system is a single, moving charged particle — say an electron or a muon. While I could select either type of particle for this article, for reasons that will become clear, I concentrate on the muon.

    Subatomic particles like the muon have both electrical charge and quantum mechanical spin. Quantum mechanical spin differs a bit from ordinary spin, but it has the same consequence: the spinning muon acts like a magnet. The magnet has a specific strength, determined by the charge of the muon and the fact that it is a spin-1/2 particle. Together, the spin and strength produce an effect that scientists call the magnetic moment.

    The prediction of the magnetic moment of the muon (and electron) was first given by Paul Dirac. The measurement involves something called the g factor, and the value of g was predicted to be 2. The way scientists search for deviations from predictions is to measure the quantity (g-2)/2. If the particle had the exact magnetic moment predicted by Dirac, this quantity would be exactly zero. Early measurements of the muon’s g factor showed that it differed from predictions by 0.1 percent.

    Such a small difference between theory and measurement could be due to measurement or calculation error. However, the predictions and measurements are now very precise. For muons, the measured value of (g-2)/2 is 0.0011659209, where the measurement uncertainty is only in the last “9.” That means that all the other numbers are meaningful: The measurement is accurate to one part in ten billion. This is equivalent to measuring the circumference of the Earth at the equator to a precision of just under a quarter inch.

    So what causes this 0.1 percent difference? There are many names for it, and two such names are virtual particles and quantum foam. In short, empty space isn’t empty space. At the subatomic level, particles are popping in and out of existence like the bubbles in foam. These particles are found in a more concentrated way near particles such as muons. You can think of these virtual particles as bees swarming surrounding a particularly aromatic flower (the muon). These virtual particles alter the strength of the muon’s magnetic field.

    Scientists can calculate the effect of these virtual particles, and they agree very well with data to high precision. However, the theory and experiment don’t agree perfectly. Given the precision of the prediction and the measurement, it is possible that this discrepancy might be the signature of physics beyond the Standard Model. The Fermilab Muon g-2 experiment will study the magnetic moment of muons with greater precision than has been possible in the past. If the discrepancy remains and the uncertainty decreases, it may be that research involving spinning muons might yield the measurement that turns a possible crack in the Standard Model into a broken dam through which a new theory rushes and changes everything.

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

    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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  • richardmitnick 12:34 pm on December 10, 2013 Permalink | Reply
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    From Fermilab: “Mu2e superconducting cable prototype successful” 

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


    Tuesday, Dec. 10, 2013
    Leah Hesla

    Last month, members of the Technical Division conducted final tests on the first batch of prototype superconducting cable for the proposed Mu2e experiment. The cable met every prescribed benchmark, carrying over 6,800 amps of electrical current — well above its design current — at 4.2 Kelvin in a magnetic field of 5 Tesla.

    This aluminum-clad niobium-titanium superconductor is a critical component of one of Mu2e’s three magnets, the transport solenoid. As the name implies, the transport solenoid will help transport a beam of muons from its production source to the detector, where scientists will study the particle interactions.

    “This prototype conductor is an important part of our transport solenoid magnet program,” said Giorgio Ambrosio, who is in charge of the transport solenoid design and development. “We know that no superconducting magnet is better than its conductor.”

    Having met this milestone ahead of schedule, members of the Superconducting Materials and Magnet Systems departments will march ahead with the other three superconducting cable prototypes for Mu2e: one for the production solenoid and two for the detector solenoid. They plan to complete the cable prototyping stage in a few months’ time.

    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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  • richardmitnick 2:32 pm on October 23, 2013 Permalink | Reply
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    From Fermilab: “A step closer to demonstrating muon ionization cooling” 

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

    Wednesday, Oct. 23, 2013
    Mark Palmer

    This month, scientists of the Muon Accelerator Program celebrated the arrival of a U.S.-supplied magnet and six tons of RF hardware at the Muon Ionization Cooling Experiment (MICE), located at Rutherford Appleton Laboratory in the UK. The experiment’s goal is to demonstrate the feasibility of shrinking the size of a muon beam with a process called ionization cooling. Creating compact muon beams is a crucial step toward future muon accelerators and [muon] colliders*.

    Alan Bross works in the MuCool Test Area

    In ionization cooling, muons are cooled by sending them through absorber materials made of light nuclei (such as hydrogen) and then are reaccelerated using RF cavities. This process can be repeated many times and reduces the transverse momentum of each muon relative to its longitudinal momentum.

    In 2015, MICE scientists will begin key experiments that will characterize the interactions of muon beams with various absorbers. The muon trajectories will be carefully measured using scintillating fiber tracking detectors embedded in spectrometer solenoid magnets located at the beginning and end of the cooling beamline. A subsequent experimental configuration, expected to be in operation later in the decade, will employ a full “cooling cell” with suitable absorbers, focusing solenoid magnets and multiple RF cavities to characterize the evolution of the beam’s emittance as the beam travels through a whole sequence of devices.

    In support of these R&D efforts, the DOE-funded U.S. Muon Accelerator Program is providing two spectrometer solenoid magnets and two coupling coil magnets, as well as RF and detector hardware for the experiment. The NSF has provided additional support for U.S. participation in the experiment.

    *A.K.A. “Higgs factories”

    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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