Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session 1WC: Workshop on Instrumentation Beyond the Standard Model |
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Chair: Alan Poon, Lawrence Berkeley National Laboratory Room: Plaza III |
Wednesday, October 24, 2012 8:30AM - 9:00AM |
1WC.00001: Scintillation and Ionization in Liquefied Noble Gases Invited Speaker: Daniel McKinsey This presentation will summarize the fundamental properties of liquefied noble gases as radiation detection media. Liquefied noble gases are used as detector materials in particle physics, nuclear physics, astrophysics and medical imaging experiments. They are easily purified, can be scaled to large masses in a straightforward manner, and scintillate brightly from ionizing radiation. The scintillating species are excited diatomic molecules (excimers), which are efficiently produced in both singlet and triplet spin states. The decay of a noble gas molecule to two free atoms results in photon emission; the energies of these photons are insufficient to excite the ground-state atoms in the bulk liquid, allowing them to travel to the edges of the liquid and be detected. The heavier noble liquids, such as liquid xenon, liquid krypton, and liquid argon also exhibit large ionization yields and electron drift speeds. The noble liquids also allow efficient discrimination against electron recoil backgrounds, both through measurement of the ionization/scintillation ratio and through measurement of the fraction of scintillation light that is emitted by short-lived (singlet) molecules relative to the total (singlet+triplet). [Preview Abstract] |
Wednesday, October 24, 2012 9:00AM - 9:30AM |
1WC.00002: Ultracold Neutron Source Technology: Status in 2012 Invited Speaker: Albert Young We present an overview of the state of the art for ultracold neutron (UCN) sources. Driven by the need for increased UCN density for fundamental physics experiments, there has been a signficant growth in the number and variety of UCN sources either planned or in operation over the past decade. All of these new sources rely either on solid deuterium or superfluid helium converters to produce UCN, so we review the basic principles of UCN production and identify common challenges in extracting useful UCN. Methods for producing the primary neutron flux and premoderating neutrons to optimize the UCN output from the solid deuterium or superfluid He vary, however, with most of these sources taking a unique strategy towards meeting the technological challenge of reaching high useful UCN densities. We survey existing and planned sources, highlighting the achievements of those already operational and the prospects for increased UCN density in each case. We also identify some promising technologies which may provide further gains in UCN production and density in future sources. [Preview Abstract] |
Wednesday, October 24, 2012 9:30AM - 10:00AM |
1WC.00003: High Electric Fields in Cryogenic Liquids for EDM searches Invited Speaker: Takeyasu Ito Experiments to search for the neutron's electric dipole moment (EDM) using ultracold neutrons (UCNs) stored in superfluid liquid helium are under development. In these experiments, being able to achieve a strong and stable electric field in superfluid liquid helium in the region where UCNs are stored is of critically importance because in EDM searches in general the sensitivity depends linearly on the strength of the applied electric field. However, the phenomenon of electric breakdown in liquid helium is poorly understood, and as such major R{\&}D efforts are under way to study it for these experiments. In this talk, the current status of such R{\&}D efforts and the implications of the finings on EDM searches and on possible other applications will be discussed. [Preview Abstract] |
Wednesday, October 24, 2012 10:00AM - 10:30AM |
1WC.00004: Fast Electromagnetic Calorimeters for the New Muon g-2 Experiment Invited Speaker: David Hertzog The Intensity Frontier era brings a host of challenges for detector systems that must both accumulate data at very high rates while also maintaining an unusually high level of performance stability to suppress systematic uncertainties. The new muon g-2 experiment at Fermilab is typical of a group of next-generation measurements that also includes muon-to-electron conversion and rare kaon decay experiments. A common theme is detectors that must endure very high rates embedded in strong magnetic fields. I will focus on our design of the g-2 electromagnetic calorimeters, which must be compact, very fast, and be placed inside the highly uniform muon storage ring magnetic field. No magnetic materials can be used and stringent constraints exist on local current-generating electronics. We examined home-built W/SciFi detectors, PbF2 crystals and a custom undoped PbWO4 crystal using the Fermilab test beam facility. Very fast PMTs and on-board, large-area silicon photomultipliers (SiPMs) were used for readout options. The leading design is based on PbF2, which produces very short pure Cherenkov light pulses that must be optimally coupled to SiPMs directly placed on the downstream surface. Custom electronics for the candidate SiPM arrays has been designed to preserve the intrinsic fast pulse signal. I will report on our test beam and lab results and our iterations with SiPM devices and electronics. [Preview Abstract] |
Wednesday, October 24, 2012 10:30AM - 10:45AM |
1WC.00005: COFFEE BREAK
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Wednesday, October 24, 2012 10:45AM - 11:15AM |
1WC.00006: Frequency Techniques in Future Neutrino Mass Measurements and Axion Searches Invited Speaker: Benjamin Monreal Frequency-domain measurements, though common in atomic physics, remain comparatively rare in nuclear and particle physics. One longstanding exception is axion searches. Another may be beta-decay spectroscopy, including attempts to measure the neutrino mass via tritium beta decay. I will focus on the Project 8 experiment, which attempts to detect the microwave emission of a single beta-decay electron in a magnetic field. These detections enable a nondestructive, high-precision, high-rate electron energy measurement, which may make it possible to do future tritium endpoint neutrino mass measurements. I will describe ongoing Project 8 proof-of-concept work, and plans for a larger tritium experiment. [Preview Abstract] |
Wednesday, October 24, 2012 11:15AM - 11:45AM |
1WC.00007: TPC Detectors for Neutrino-less Double-Beta Decay and Dark Matter Searches Invited Speaker: Azriel Goldschmidt Time Projection Chambers (TPCs) are increasingly becoming the particle detector technology of choice for rare event searches such as neutrino-less double beta decays and direct WIMP dark matter interactions. At present time, experiments using xenon-filled TPCs are producing some of the best limits for both of these searches. TPCs offer 3D ionization-track imaging as well as calorimetric energy measurements both of which are important handles for the identification of the rare sought-after events while discarding background events due to cosmic rays or due to radioactive decays in the detector or surrounding materials. Particle identification, beyond that provided by the particle range and dE/dx information, is also available from the relative amount of ionization and excitation losses and is essential for the WIMP searches. The contiguous gas or liquid volume at the heart of a TPC is continuously purified to remove contaminants that would otherwise deteriorate the detector performance or produce backgrounds. The fiducial volume for the event searches can be defined after the fact and is typically chosen to be well separated from the physical boundaries of the working gas or liquid to avoid surface events that often are problematic and much harder to reject in solid state detectors. The scalability of the TPC is one of its most important advantages in a field where ever increasing detector masses are required to achieve the required sensitivities. Detectors of O(100) kg scale are in operation and construction and ton to multi-ton detectors are being planned and expected to come on-line in the next years. In this talk I will describe the various types of TPCs in use or planned and will discuss their potential for achieving the exciting goals of discovering the dark matter particle and observing neutrino-less double beta decays. [Preview Abstract] |
Wednesday, October 24, 2012 11:45AM - 12:15PM |
1WC.00008: A Bubble Chamber Revival: Superheated Liquid Detectors for Dark Matter Searches and Other Applications Invited Speaker: Andrew Sonnenschein Bubble chambers were recently deemed to be obsolete, of interest only to historians, but a few new applications have unexpectedly emerged in nuclear and particle astrophysics. These include the search for WIMP dark matter and the measurement of a few otherwise intractable nuclear cross sections. The new bubble chambers exploit features of the bubble nucleation process that were unappreciated or irrelevant in the 1950s-1970s when the technology was known for its capability to provide fine-grained tracking of high energy particles in a dense target medium. By carefully tuning the temperature and pressure, a liquid can be made selectively sensitive to particles on the basis of their specific rate of energy loss, enabling a high degree of background rejection power when searching for rare heavily-ionizing tracks. Surprisingly, additional information on the microstructure of particle tracks can be extracted from the acoustic noise produce by bubble nucleation. Other novel features of the new bubble chambers include the use of digital photography, self-triggering, and the achievement of nearly continuous sensitivity by the avoidance of bubble nucleation on internal wetted surfaces. [Preview Abstract] |
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