Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session K10: Instrumentation I |
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Sponsoring Units: DNP Chair: Gordon Cates, University of Virginia Room: 250B |
Sunday, April 17, 2016 1:30PM - 1:42PM |
K10.00001: Scintillating fiber array for tagging post-bremsstrahlung electrons Philip Cole, Stefan Alef, Bj\"orn-Eric Reitz, Hartmut Schmieden, J\"urgen Hannappel, Thomas Jude, Paolo Levi Sandri We seek to extract the kinematic fingerprints of baryon resonances by making use of a high-quality beam of linearly polarized photons at the BGO-OD experiment at ELSA (Bonn, German). We constructed a unique device for precisely determining the degree of polarization in the coherent bremsstrahlung peak. Deflection of post-bremsstrahlung electrons in the magnetic field of the photon tagger provides precise information on the energy and polarization of the bremsstrahlung photons. And thereby will constrain the overall kinematics of the final-state particles in all decay channels of the photoproduced baryon resonances. We designed, prototyped, built, calibrated, and have been operating a three-layered, multi-stranded, scintillating-fiber detector for ensuring the quality of the linearly polarization of the photon beam. The overlapping 2.00-mm scintillating fibers form an array giving ARGUS over 500 channels. The very befitting name harkens to the mythological all-seeing creature Argus Panoptes, the multi-eyed giant. Our work was supported through a Fulbright Scholarship Award and by the Deutsche Forschungsgemeinschaft through the Collaborative Research Center (Sonderforschungsbereich SFB/TR-16) of the universities in Bonn, Giessen and Bochum, Germany. [Preview Abstract] |
Sunday, April 17, 2016 1:42PM - 1:54PM |
K10.00002: Automated Microwave Frequency Control in Dynamic Nuclear Polarization Experiments Ethan Scott, Ian Johnson, Dustin Keller To achieve highest polarization levels in dynamic nuclear polarization (DNP) experiments, target materials must be subjected to microwave irradiation at a particular frequency determined by the difference in the nuclear Larmor and electron paramagnetic resonance (EPR) frequencies. However, this resonant frequency is variable; it drifts as a result of radiation damage. Manually adjusting the frequency to accommodate for this fluctuation can be difficult, and improper adjustments negatively impact the polarization. In response to this problem, a controller has been developed which automates the process of seeking and maintaining optimal frequency. The creation of such a controller has necessitated research into the correlation between microwave frequency and corresponding polarization growth or decay rates in DNP experiments. Knowledge gained from the research of this unique relationship has additionally lead to the development of a Monte-Carlo simulation which accurately models polarization as a function of frequency and a number of other parameters. The simulation and controller continue to be refined, however, recent DNP experimentation has confirmed the controller's effectiveness. [Preview Abstract] |
Sunday, April 17, 2016 1:54PM - 2:06PM |
K10.00003: Quartz Hodoscope for the SuperHMS Spectrometer Trigger System at Hall-C Jefferson Lab Nouf Alharbi, Abdellah Ahmidouch, Bashar Aljawarneh, Samuel Danagoulian A quartz hodoscope of twenty one fused silica (quartz) bars has been constructed and delivered to Jefferson Lab to be part of the trigger system for the Super High Momentum Spectrometer (SHMS). The quartz bars are 125-cm long, 5.5-cm wide, and 2.5-cm thick and are viewed on each end by a UV-sensitive PMT. The SHMS spectrometer will play a central role in carrying out the 11-GeV physics program at Hall-C Jefferson Lab. The quartz hodoscope task is to provide a clean detection of charged particles, a high level of background suppression, and an accurate tracking efficiency determination. The hodoscope has been tested in situ with cosmic rays. We present final performance results of the hodoscope which include light yield, position resolution and efficiency, as well as plans for its commissioning. [Preview Abstract] |
Sunday, April 17, 2016 2:06PM - 2:18PM |
K10.00004: Gas Ring Cherenkov Detector for High Luminosity and High Background Rates Experiments at Hall-A Jefferson Lab. Bashar Aljawrneh, A Ahmidouch, T Averett, S Danagoulian, B Wojtsekhowski, H Yao A Gas Ring Cherenkov (GRINCH) detector is being developed for the JLab Hall-A BigBite spectrometer. The goal is to accommodate high luminosity and high background rates experiments such as the A1n and the GMn experiments. GRINCH is a 1-atm C4F8O-based Cherenkov counter. The Cherenkov ring is reflected by a set of cylindrical mirrors onto a Photon Detector Array (PDA). It consists of 510 29-mm diameter Electron Tubes 9125B PMTs, which provide timing information. The PMTs are mounted inside a magnetic shielding box to shield against the 15-30 Gauss magnetic field of the spectrometer magnet. Mirrorized plastic reflectors are used to collect the reflected Cherenkov light onto the PMTs. The PDA has been constructed and tested and the GRINCH vessel has been constructed as well. We present the GRINCH design, simulation results, and results of the PDA testing with 15- and 60-gauss magnetic field. [Preview Abstract] |
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