Bulletin of the American Physical Society
2019 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 64, Number 18
Friday–Saturday, October 25–26, 2019; Lubbock, Texas
Session H02: Nuclear & Particle IV |
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Chair: Vinay Hedge, Texas Tech University Room: Student Union Building Lubbock Room |
Saturday, October 26, 2019 10:06AM - 10:18AM |
H02.00001: Design Optimization and Fabrication of a two stage HV-LV SuperCDMS style detector Himangshu Neog, Rupak Mahapatra, Mark Platt, Nader Mirabolfathi SuperCDMS interleaved Z-sensitive Ionization and Phonon(iZIP) detectors have shown great success in discrimination of electronic and nuclear recoils, while the High Voltage (HV) detectors have been reaching to lower and lower energy thresholds by sacrificing that discrimination. This work introduces a two-stage High Voltage-Low Voltage(HV-LV) design to retain both the excellent threshold performance of the HV detector and maintain the iZIP discrimination. We tried to optimize the geometry of the two-stage setup using COMSOL electric field simulations to minimize surface events and charge traps on detector surfaces. One optimized version of the detector has been fabricated and tested in contact-free setup. The preliminary analysis results will be presented. [Preview Abstract] |
Saturday, October 26, 2019 10:18AM - 10:30AM |
H02.00002: Fabrication of CDMS Dark Matter Detector using Bi-layer Lift-off Technique Shubham Verma, Rupak Mahapatra Finding out the nature of Dark Matter is one of the biggest unanswered questions in physics today. One of the various methods for Dark Matter detection is direct detection in which the interaction between Dark Matter and the normal matter is explored. The extremely weak nature of Dark Matter particle makes direct detection very challenging thereby demanding highly sensitive detectors. Super CDMS experiment uses cryogenic superconducting Ge and Si as target materials with Transition Edge Sensors (TES) for direct Dark Matter detection. The classic fabrication technique of CDMS detectors uses chemical etching of Aluminum and Tungsten thin films deposited on Si and Ge crystals to pattern TESs on the detectors. We have explored another technique called bi-layer lift-off process, which does not use any chemical enchants and thus, allows us to explore other target materials like Sapphire which seem to have been affected by using chemical enchants with the older technique. Use of Sapphire as target material results in only nuclear recoil, which can help us to improve the detector sensitivity for better detection of Dark Matter. The lift-off technique can also help in improving the phonon collection efficiency from crystal to aluminum thereby improving the sensitivity of these detectors. [Preview Abstract] |
Saturday, October 26, 2019 10:30AM - 10:42AM |
H02.00003: Electrostatic Mitigation of Radon Daughters Present in Boil-off Gases and Surface Activity Screening of Charged Samples Josephine Kimbrough Radon, being a source of natural radiation, decays and emits, gamma, alpha, and beta rays, including charged daughter particles that mimic dark matter particles in the detector. It is important to mitigate the amount of these radon particles and their daughters that account for background noise in the detection of dark matter. As we can screen materials in the XIA, an alpha particle counter, more carefully with lower background noise, the goal of this experiment is to eliminate as many radon daughters from the screening gas as possible. To do this, I have utilized an electric field to mitigate charged radon daughters from gas. Data collected from these experiments have indicated that with the implementation of an electric field we were able to see an increase in the radon reduction rate beyond the natural rate even when accounting for leakage from the exposure chamber once the electric field was turned on. Though it was impossible to completely eliminate leakage from the exposure chamber, we were able to account for it by isolating the leakage rate to find the rate of natural decay. With the rate of natural decay we graphed the amount of radon we expected to be detected by the Rad7 and compared it to the amount actually detected. The results indicated that there was less radon detected in the chamber with the electric field than when the field was off. We have also done a runs with the XIA in order to better understand the instrument. We compare the effects of running the Th230 sample on differently charged points on a piece of polyethylene to compare the resulting data to a grounded copper control. Though a direct correlation between charge and run results has not yet been quantified we have found a significant deviation in the runs over differently charged locations. [Preview Abstract] |
Saturday, October 26, 2019 10:42AM - 10:54AM |
H02.00004: Examining the Effect of Airflow on Radon Plate-out Rates Taylor Wallace, Daniel Jardin, Robert Calkins, Jodi Cooley The SuperCDMS Generation 2 dark matter experiment is currently being constructed at SNOLAB in Sudbury, Ontario to detect dark matter candidates less than 10 GeV/c$^{2}$ in mass using cryogenic germanium and silicon detectors. One major source of contamination for these detectors is gaseous radon whose progeny decays can “plate-out” (stick) to detector components and limit their sensitivity. Thus, it is imperative that steps be taken to minimize radon plate-out in these experiments. Many environmental factors can affect the rate of radon plate-out, including airflow from wind or ventilation. To understand the role of airflow in radon plate-out rates, controlled plate-out tests were conducted inside an annular cylinder exposure chamber equipped with a variable speed fan and anemometer. The exposure chamber was supplied with a controlled concentration of radon using a Pylon radon flow-through source. Measurements using a copper sample have shown an increase in radon plate-out rate when airflow is present. Findings from this study can be used to aid in handling techniques and storage methods for ultra-sensitive detectors such as those in the next generation SuperCDMS experiment. Additionally, this data can help develop models to predict how plate-out rates depend on airflow. [Preview Abstract] |
Saturday, October 26, 2019 10:54AM - 11:06AM |
H02.00005: Installation and Commission of TAMUTRAP Through Mass Measurement of Stable Isotopes Margaret McDonough, Dan Melconian, Veli Kolhinen, Praveen Shidling Texas A{\&}M University's Cyclotron Institute recently built a Penning trap, coined TAMUTRAP, in order to test the current constraints on the weak interaction as it is described by the Standard Model. This summer, we removed the 90mm-diameter prototype trap and installed the two times larger, full-sized Penning trap. We commissioned the new trap by demonstrating its ability to measure the masses of stable isotopes to better than 60 parts per billion. These mass measurements enabled us to characterize and optimize operation of the trap to ensure proper ion manipulation before the complications of the planned beta decay experiment which will use short-lived radioactive ions. Mass measurements were performed using the time-of-flight ion cyclotron resonance technique: various radiofrequencies are applied to excite the ions in the trap, and when the applied frequency matches the resonant frequency of these ions, they accelerate and we observe a shorter time of flight to the micro-channel plate detector upon their exit from the trap. By analyzing the time of flight of the ions as a function of frequency, we determined the resonant cyclotron frequency of the ions, from which we deduced their masses to better than 60 parts per billion, in agreement with their known values. [Preview Abstract] |
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