Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session E4: Instrumentation II |
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Sponsoring Units: DNP Chair: Nilanga Liyanage, University of Virginia Room: Holiday 3 |
Saturday, April 11, 2015 3:30PM - 3:42PM |
E4.00001: Characterization of an amplification read-out gas chamber with stacked GEM and MicromeGas detectors Salvatore Aiola Micro-Pattern Gas Detectors (MPGD) are a relatively new class of devices that allow gas amplification of charges. Amplification is achieved by exploiting the high field density generated in gaps or holes of the order of a few tens of microns. If carefully designed, the field lines are such that the ions produced in the amplification process are trapped by the device, thus avoiding the build-up of space charge (ion back flow) in the gas volume. This is a crucial capability, especially when these devices are employed as read-out chambers of large gaseous tracking detectors, such as a Time Projection Chamber (TPC). We report on a series of measurements aimed at characterizing the performance of an amplification read-out chamber consisting of a stack of two Gas Electron Multipliers (GEMs) on top of a MicromeGas. The combination of these two technologies has proven to be particularly useful: the presence of multiple amplification steps allows operation of the MicromeGas at a relatively low gain, thus suppressing the spark rate; in addition this setup further reduces the overall ion back flow, without hindering the energy resolution. Measurements of the energy resolution, the amplification factor and the ion back flow for different electric field configurations will be presented. [Preview Abstract] |
Saturday, April 11, 2015 3:42PM - 3:54PM |
E4.00002: Characterization of Gas Amplification in Varied Gas Mixtures for Stacked Gas Electron Multiplier and Micromegas Detectors Raymond Ehlers Micropattern Gas Detectors (MPGDs) represent a promising group of gas amplification technologies. Utilizing large electric fields over geometries on the order of tens of micrometers, these elements can achieve large gas amplification while minimizing field distortions by minimizing the number of ions escaping from the amplification stage. Such properties are extremely useful for readout in gaseous detectors such as Time Projection Chambers. Two types of MPGDs are of particular interest, Gas Electron Multipliers (GEMs) and Micro-mesh Gaseous Structure (Micromegas) detectors. These elements may be stacked, which allows for the utilization of the best properties of both, further improving the amplification performance. We report here on the characterization of 2 GEMs stacked on top of a Micromegas. In particular, I will present the dependence of gas amplification on Micromegas voltage in various gas mixtures, as well as an investigation into stability of the elements against sparking. [Preview Abstract] |
Saturday, April 11, 2015 3:54PM - 4:06PM |
E4.00003: Studies of the hadronic calorimeter prototype for sPHENIX Liang Xue During past three years, the RHIC PHENIX collaboration has developed its decade's upgrade refer as sPHENIX, which will incorporate two electromagnetic (EMCAL) and hadronic (HCAL) calorimeters with a large pseudo-rapidity range, and full azimuthal coverage. The HCAL will be first hadronic calorimeter ever be used at RHIC, and will enable a systematic study of jets in QGP. A accordion like HCAL prototype based on scintillator plates and steel absorber plates has been constructed and tested using test beam at Fermilab. It has two longitudinal sections, each has sixteen layers of alternately arranged scintillator and steel plates, with a total depth of 5 interaction length. In this poster, we will present the test beam performance, as well as the single particle GEANT 4 simulation studies for the HCAL prototype. [Preview Abstract] |
Saturday, April 11, 2015 4:06PM - 4:18PM |
E4.00004: Test Beam Results for ALICE TPC Upgrade Prototypes James Mulligan The ALICE detector is one of four major experiments at the Large Hadron Collider (LHC), and its main purpose is to study the quark-gluon plasma created in relativistic heavy ion collisions. The Time Projection Chamber (TPC) is the main tracking detector within ALICE, and currently has an intrinsic rate limitation of 3 kHz. The LHC will be upgraded during Long Shutdown 2 in 2018 to have Pb-Pb collision rates up to 50 kHz, and so the TPC readout must be accordingly upgraded. This will be done by replacing the current Multi-Wire Proportional Chamber assembly, which uses a gating grid to prevent ion backflow, with Micro-Pattern Gas Detectors such as Gas Electron Multipliers (GEMs) and Micro-Mesh Gaseous Structures (MMGs), which allow for continuous rather than gated readout. A substantial R\&D effort is underway for a 4-GEM design, as well as an alternate 2-GEM/MMG design. Prototypes of each design were tested in November-December 2014 at the PS and SPS beams at CERN; the results for the 2-GEM/MMG chambers will be presented. [Preview Abstract] |
Saturday, April 11, 2015 4:18PM - 4:30PM |
E4.00005: Track Finding and Reconstruction for the OLYMPUS Experiment Lauren Ice The OLYMPUS experiment aims at measuring the positron-proton to electron-proton elastic scattering cross section ratio as evidence of a multiple photon exchange contribution to elastic electron-proton scattering. The experiment took place during 2012 using 2.01 GeV electron and positron beams incident on a hydrogen gas target. The cross section ratio is measured with the OLYMPUS spectrometer, comprising six wire chambers arranged in two sectors, surrounded by a time of flight scintillator array. Track finding and reconstruction is based on matching patterns derived from a Monte Carlo simulation followed by an implementation of the elastic arms algorithm. The employed algorithms will be discussed in detail in this talk. [Preview Abstract] |
Saturday, April 11, 2015 4:30PM - 4:42PM |
E4.00006: Parameterization Measurements of a 963 cm$^{3}$ LaBr$_{3}$:Ce Crystal J.C. Marsh, M.S. Litz, C.J. Chiara, J.J. Carroll LaBr$_{3}$:Ce is a relatively new scintillator with characteristics that surpass more commonly used radiation detection scintillators. Published results for small ($<$10 cm$^{3}$) LaBr$_{3}$ detectors (NIMA 683, 46, 2012) describe improved time resolutions ($\sim$35 ps), energy resolutions ($\sim$3.5\% at 662 keV), and optical yields ($\sim$63,000 photons/MeV) compared to NaI and BGO. Here it was possible to assess the characteristics of a 963 cm$^{3}$ (7.6 cm length, 12.7 cm diameter) cylindrical crystal optically coupled to an ET9390KB photomultiplier tube optimized for crystal emissions at 380 nm. A 3$\times$3 array of crystals will be used for neutron-stimulated evaluations of materials for elemental and chemical composition. A custom bleeder chain was designed to minimize current saturation and optimize the energy linearity over a 2-12 MeV energy range. Because large volume crystal characteristics do not always scale linearly, energy resolution, detector efficiency, crystal homogeneity, timing resolution, pulse shape, peak-to-Compton ratios, energy linearity, and self activity were all measured and compared to published results on other LaBr$_{3}$ detectors. Advantages and disadvantages of such large LaBr$_{3}$ crystals will be discussed, and future plans will be described. [Preview Abstract] |
Saturday, April 11, 2015 4:42PM - 4:54PM |
E4.00007: A Cryogenic Target for Compton Scattering Experiments at HI$\gamma$S David Kendellen, Mohammad Ahmed, Henry Weller, Gerald Feldman We have designed, constructed, and tested a cryogenic target for use at the High Intensity $\gamma$-ray Source (HI$\gamma$S). The target is able to liquefy helium (LHe), hydrogen (LH$_2$), and deuterium (LD$_2$). It precools room-temperature gas in two stages with a Gifford-McMahon cryocooler. The precooled gas condenses onto a series of copper fins and drips down to fill a 0.25~L Kapton target cell. The cryotarget will be used to measure nuclear and nucleon electromagnetic polarizabilities. The electromagnetic polarizabilities of the nucleons, $\alpha$ and $\beta$, will be probed by scattering a $\gamma$-ray beam on unpolarized LD$_2$ and LH$_2$ targets. Scattered photons will be detected by the HI$\gamma$S NaI Detector Array (HINDA). We have tested the target with LHe at 3~K and are preparing for LD$_2$ testing and production running. [Preview Abstract] |
Saturday, April 11, 2015 4:54PM - 5:06PM |
E4.00008: The GlueX Start Counter Eric Pooser The GlueX experiment will study meson photoproduction with unprecedented precision. This experiment will use the coherent bremsstrahlung technique to produce a 9 GeV linearly polarized photon beam incident on a liquid $\mathrm{H_{2}}$ target. A Start Counter detector has been fabricated to identify the accelerator electron beam buckets, approximately 2 ns apart, and to provide accurate timing information which is used in the level--1 trigger of the experiment. This detector is designed to operate at photon intensities of up to $\mathrm{10^{8}\gamma/s}$ in the coherent peak and provide a timing resolution $\mathrm{<\ 350\ ps}$ so as to provide successful identification of the electron beam buckets to within 99$\%$ accuracy. Furthermore, the Start Counter detector will provide excellent solid angle coverage, $\sim 90 \%\ \mathrm{of}\ 4 \pi\ \mathrm{hermeticity}$, and a high degree of segmentation for background rejection. It consists of a cylindrical array of 30 scintillators with pointed ends that bend towards the beam at the downstream end. Silicon PhotoMultiplier (SiPM) detectors have been selected as the readout system. The physical properties of the Start Counter have been studied extensively. The results of theses studies are discussed. [Preview Abstract] |
Saturday, April 11, 2015 5:06PM - 5:18PM |
E4.00009: Software Development for the Commissioning of the Jefferson Lab Hall B Silicon Vertex Tracker Justin Ruger, Veronique Ziegler, Yuri Gotra, Gagik Gavalian One of the new additions to Hall B at the Thomas Jefferson National Accelerator Facility is a Silicon Vertex Tracker system that includes 4 regions with 10, 14, 18, 24 sectors of double-sided modules. Recently, the SVT hardware group has completed construction and installation of regions one and two on a cosmic ray test stand. This test setup will be used to preform the first cosmic ray efficiency analysis of the SVT with the availability of 8 measurement layers. In order to study efficiency and module performance, a set of software packages had to be written to decode, analyze and provide feedback on the output from data acquisition. This talk will provide an overview of the software validation suite designed and developed for Hall B and a report on its current utilization for SVT cosmic data analysis. [Preview Abstract] |
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