Session DN: Instrumentation: Calibration and Electronics

Analysis of dissolved radon calibration sources in EXO-200

The EXO-200 experiment, which ran from 2011 to 2018, used enriched liquid xenon in a low-background single-phase time projection chamber to search for neutrinoless double beta decay of ${}^{136}$Xe. At the end of physics running, the xenon volume was doped first with ${}^{220}$Rn and then several days later with ${}^{222}$Rn to test these alpha-emitting decay chains as light calibration sources. This talk will discuss the source deployments and data collection, analysis of resulting decay chain events in EXO-200, and implications for using injected radon sources to calibrate light response for single-phase liquid xenon time projection chambers.   

Precise Calibration of Laser Frequency for determination of Ni Charge Radius

Collinear laser spectroscopy is commonly used to determine charge radii, and requires accurate and precise knowledge of the laser frequency to a level of roughly 1 MHz. A Doppler-free laser spectroscopic system has been implemented at the BECOLA facility to calibrate the laser frequency against precisely-known transitions in molecular iodine. After calibration, the laser system will be used to determine charge radius of $^{\mathrm{54}}$Ni, which is important to address the soft nature [1] of doubly-magic $^{\mathrm{56}}$Ni as well as to deduce the slope parameter, $L$, in the symmetry energy of the nuclear equation of state [2]. The performance characteristics of the laser frequency calibration system will be presented and the results will be discussed. [1] M. Honma et al., Phys. Rev. C 65, 061301 (2002). [2] B. A. Brown et al., Phys. Rev. Research 2, 022035 (R) (2020).   

Shallow underground lab for low-background measurements

This talk will discuss both the design and operation of a low-background germanium detector for various sensitive measurements. The detector system is located in a shallow underground facility, with approximately 300 feet of overburden, reducing cosmogenic backgrounds considerably from ground level. The design of the shield and veto system are described, as well as the efficiency measurement and simulations performed. This detector system is now acting to produce sensitive assay of materials for the LEGEND collaboration.   

Applied Optimization on Mixed Mode Systems for Pulse Shape Discrimination

Pulse-shape discrimination (PSD) is a technique that has long been used for n/$\gamma$ discrimination. Traditionally PSD capable systems are designed using pure analog techniques, or pure digital-signal processing (DSP). Pure analog designs reduce system complexity allowing for higher detector channel counts. These pure analog systems are algorithm locked however, generally using fixed integration gates to do PSD giving minimal flexibility. Pure DSP systems allow for more advanced algorithms to be employed but suffer from linear time logic due to fixed frequency clock sampling. This poses a problem since pulse information is nonlinear in time. We are investigating mixed-mode systems that act as a middle ground between these two extremes. We will optimize this design topology to minimize system complexity, maximize detector channel counts, and maximize dynamic range. We will use test cases including liquid organic scintillators and plastic scintillators with n/$\gamma$ PSD.   

Study of High Voltage Noise in Germanium SuperCDMS Prototype Detector

We studied the resolution of a germanium high voltage SuperCDMS prototype detector, 100 mm diameter and 33 mm thickness. To investigate the sources of noise, the detector was run in three different high voltage bias modes: first, with standard biasing of a grid on the detector surface; second, with an external bias electrode and vacuum gap of about 0.5 mm; and third, with the external electrode and with the metal grid removed. We calculated the total absorbed phonon energy at the transition edge sensors (TES) for events in the 13.95 keV peak~from an Am-241 source placed near the detector, using measured characteristics of the sensors and applying corrections for nonlinear TES response. We calculated the effective Luke gain to estimate the detector bias and compared to estimates based on the electrode bias corrected by the potential difference across the gap and the buildup of charge on the detector surface while biased. For positive biases the two methods agree, with approximately (2-5) {\%} fluctuation at lower bias and to about 10{\%} at higher bias. At 0V we measured an unexpected non-zero Luke gain, indicating some residual charges on the surface of detector. At negative electrode bias the Luke gain was much lower than expected for reasons not yet understood.   

sPHENIX TPC diffuse laser light system

As part of the sPHENIX detector being constructed at RHIC, a diffuse-light laser calibration system for TPC space charge monitoring is being constructed. The sPHENIX detector will measure upsilon states, jets, and jet correlations. In partnership with Brookhaven National Lab, a compact TPC is under construction at Stony Brook University as part of sPHENIX. Space charge is the buildup of charge inside the TPC that distorts the electric field. The Central Membrane of the TPC has a gold substrate with small aluminum stripes in a well-known configuration. The work function of gold is much higher than that of aluminum; in particular we would find approximately 240 times the rate of photo-electron release using a UVC laser. The diffuse laser calibration system will produce an electron signal from these aluminum stripes covering the central membrane. This will allow for the measurement and correction of field distortions present in the TPC drift volume. The current status of the diffuse laser system will be presented.   

Low-cost and modular cosmic ray telescope development and the associated applications

A state-of-the-art portable, low-cost, and modular cosmic ray muon and neutron detector prototype has been developed at Georgia State University for the simultaneous measurement of cosmic ray muon and neutron flux. The detector consists of three layers of plastic scintillator and a neutron-cell with liquid scintillator mounted on an extruded aluminum frame. The scintillation light is collected through embedded wavelength shifting fibers which are coupled to silicon photomultipliers (SiPM). The data acquisition (DAQ) system of this detector consists of a Raspberry PI and a custom-made SiPM interface board. One of the applications of this detector is to study the correlation between the flux variations and the space/earth weather at global scale by installing arrays of this detector around the world. It could also be modified for extensive air shower measurements. In the talk, we will present the details of the detector design and the initial test results from multiple detector prototypes.