Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session PE: Undergraduate Research III |
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Chair: Christopher Crawford, University of Kentucky Room: Park & Scollay |
Thursday, October 14, 2021 9:30AM - 9:42AM |
PE.00001: Frequency Stabilization of a Diode Laser to the Rubidium D2 Transition Charlotte Zehnder, William Bodron, Wolfgang Korsch The polarization of dense spin-polarized helium-3 targets can be measured using the Faraday Rotation of alkali metals. Small amounts of the alkali metals Rb and K will be present in the target if the helium-3 nuclei are polarized by spin exchange optical pumping. An external-cavity diode laser emitting frequencies of the D2 transitions of Rb or K will maximize the rotation of linearly polarized light due to the Faraday effect. Small magnetic fields due to the spin-polarized 3He nuclei can be measured because of this effect, given the laser's frequency remains stable over a long enough time frame. However, diode lasers will drift in frequency off the D2 resonance over time. We used a Saturated Absorption method to resolve a Doppler-Free spectrum as a reference for this frequency and optimized the peaks by leveraging polarization changes to overlap the paths of the "probe" and "pump" beams used to measure absorption. Rb85 F=3 transition provided a strong error signal optimal for the laser's Top of Fringe locking method. We successfully reduced drift by locking our laser to this transition using lock-in techniques. |
Thursday, October 14, 2021 9:42AM - 9:54AM |
PE.00002: Beam Stability in PSI MUSE Rujuta Mokal The proton radius puzzle is a 4% discrepancy in the proton radius when measured with muonic hydrogen spectroscopy compared to normal hydrogen spectroscopy or electron proton scattering. For further investigation of the puzzle, the Muon-proton Scattering Experiment (MUSE) is being performed at the Paul Scherrer Institute (PSI). MUSE runs in the PiM1 beamline at PSI, using a beam of electrons (e), muons (μ) and pions (π). The interactions of μ and e with protons allow the proton radius to be determined, along with any differences between the interactions of muons and electrons, which might indicate new physics. I will discuss analysis and observations of the RF time, the time relative to the accelerator RF signal, of the three particles at the experiment’s Beam Hodoscope and Beam Monitor detectors. The e RF time should be constant, since for e’s beta ~ 1, so this measurement serves to check the combined stability of the accelerator and electronics systems. The difference in μ and π RF times reflects the flight paths and momenta of the particles, and its variation with time checks the stability of the PiM1 channel, the detectors, and the electronics. I present studies of the RF times of the particles and their stability, along with the stability of the channel and particle momenta. |
Thursday, October 14, 2021 9:54AM - 10:06AM |
PE.00003: Abstract: Simulation of Silicon Detector Performance for the Nab Experiment Jackson Z Ricketts, Joshua B Hamblen
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Thursday, October 14, 2021 10:06AM - 10:18AM |
PE.00004: Permeability Measurements of Magnetic Shielding for the SNS nEDM Experiment Bailey J Knight, Christopher B Crawford Because CP violation of the neutron electric dipole moment (nEDM) could explain the baryon asymmetry of the universe, the experimental search for an nEDM is a high priority in cosmology and nuclear physics. In order to maximize the sensitivity of such experiments, they must be conducted in a stable magnetic environment, which requires extensive magnetic shielding. A prototype magnetic shield is being constructed at UK to model the full shield in the SNS nEDM experiment. The B-H curve of mu-metal was analyzed by measuring the inductance of a transformer with a mu-metal core vs an air core of the same geometry. The resulting permeability will be used to model degaussing and performance of the prototype shield.- |
Thursday, October 14, 2021 10:18AM - 10:30AM |
PE.00005: Methods of ECDL Frequency Stabilization Will A Bodron, Charlotte Zehnder, Wolfgang K Korsch Resonant Faraday rotation on alkali metals can be used to monitor the polarization of dense spin-polarized helium-3 targets. If spin exchange optical pumping is used to polarize the helium-3 nuclei, sparse amounts of Rb and K will be present in the target. Tuning external-cavity diode lasers (ECDL) to the D2 transitions of Rb or K maximizes the rotation of linearly polarized light due to the Faraday effect; which allowed measurement of small magnetic fields produced by the spin-polarized nuclei. To accomplish this goal, the laser frequencies must remain stable over long periods of time due to various environmental changes. We performed diagnostic interferometry to determine the rate of frequency drift and to locate the D2 transition frequencies via custom methods of automation on data acquisition and laser parameter control. Then, using the doppler free absorption spectrum of Rb or K as a feedback mechanism, a lock-in technique was used to generate an error signal and a PID feedback system allowed us to minimize the frequency drift of our ECDL to provide sufficient laser frequency stability for the Faraday rotation experiment. |
Thursday, October 14, 2021 10:30AM - 10:42AM Not Participating |
PE.00006: GHz Scale Realtime Least Squares Pulse Fitting Yuke Wang, Lars Hebenstiel, Christopher B Crawford Thus far, few-body hadronic parity violation experiments have measured the average current instead resolving individual events. New experiments involving reactions such as n+d → t+γ (NDTGamma) have scattering cross sections 10^3 times smaller than background, which must be filtered out through spectroscopy. However, it is computationally infeasible to fit the energy of each event using standard non-linear least squares techniques at the expected rate of 10^7 events per second. In least squares fitting, the design matrix maps the parameter space into the solution space. By approximating the design matrix using a piecewise polynomial expansion, recursive convolution filters can be used to calculate the fitting parameters at high sample rates (10^9 hz)[1]. The design matrix expansion is optimized using adaptive moment estimation stochastic optimization. We will discuss the implementation of such a system on relatively cheap ∼ $350 commodity hardware. |
Thursday, October 14, 2021 10:42AM - 10:54AM |
PE.00007: Measurement and Modeling of Magnetron Injection Lock to the Stable Bandwidth Gabija Ziemyte, Haipeng Wang Particle accelerators use radio frequency driving forces to accelerate particles close to the speed of light. The RF driving force emits microwaves that cause alternating positive and negative electric fields in RF cavities surrounding the particle beam. Many particle accelerators use klystrons as wave amplifiers for the particle beam, but magnetrons are less costly and more efficient to use. For a magnetron’s output signal to be stabilized, it must be frequency locked to an external signal. However, as power level of the magnetron increases, the frequency pushing characteristic changes the resonant frequency of the magnetron and the locking bandwidth around it. The pushing characteristic is inherent in magnetrons, but the locking bandwidth can be increased to account for changes in the resonant frequency of the magnetron. The locking bandwidth was measured with an injection frequency of 2.439 GHz using a frequency spectrum analyzer for a magnetron with and without an RF cavity at the magnetron test stand at Jefferson Lab. Analysis of experimental data in relation to previously proposed theoretical models and comparison of Chen to Adler model for best fitting of experimental data will be given. |
Thursday, October 14, 2021 10:54AM - 11:06AM |
PE.00008: Convolutional Neural Networks for Shower Energy Prediction in Liquid Argon Time Projection Chambers Kiara Carloni When electrons with energies of O(10) MeV pass through a liquid argon time projection chamber (LArTPC), they deposit energy in the form of electromagnetic showers. Methods to reconstruct the energy of these showers in LArTPCs often rely on the combination of a clustering algorithm and a calibration between the shower energy and charge contained in the cluster. This reconstruction process could be improved through the use of a convolutional neural network (CNN). Here we discuss and compare the performance of various CNN-based models on simulated LArTPC images to that of a traditional clustering algorithm. It is shown that the CNN method is able to account for non-linearity in the charge-energy relationship of the shower and address other inefficiencies of a LArTPC. |
Thursday, October 14, 2021 11:06AM - 11:18AM |
PE.00009: Organic Photo Sensors for Detection of VUV Scintillation Light Sabrina Cheng, Michael T Febbraro Liquid noble gas scintillators are widely used in rare-event physics detectors due to their low cost, high availability and excellent scintillation properties. Typically, they scintillate in the VUV range ($\sim$128 nm for LAr) with the light detected via PMTs or SiPMs. However, there are few optical sensors that can directly detect 128 nm light, so these devices often rely on wavelength shifters. As experiments pursue towards multi ton-scale detectors, these detection schemes become cost prohibitive. Recent work on the development of organic semiconductor photodiodes at ORNL provides a potential solution using low-cost organic photodiodes. Ongoing research into organic photodiodes is addressing transparent and sensor functionality in the liquid noble gas environment (such as LAr $\sim$128 nm, $\sim$ 87 K) by using specific materials that are transparent to VUV light. This talk will outline the fabrication and characterization of conductive polymer:fullerene-based organic photodiodes, with details of the performance of these photodiodes and method of fabrication also being presented. |
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