Session Q10: Particle Physics Instrumentation V

Characterization ofHamamatsu VUV4Silicon Photomultipliers using Argon Scintillation Light

For the past several decades, photomultiplier tubes (PMTs) have reigned in noble element time projection chambers (TPCs) as the dominant photosensors in both large scale dark matter experiments and smaller scale test bed systems. Hamamatsu has recently developed VUV-sensitive silicon photomultipliers (SiPMs) as alternative photosensors, which may also be attractive for deployment in TPCs due to their capability of directly detecting VUV scintillation light. At Lawrence Livermore National Laboratory, two types of Hamamatsu VUV4 SiPMs, the S13370-6075 and the S13371-6050CQ-02, have been tested in a pure liquid argon environment to directly observe 128 nm argon scintillation light. In this presentation, I will discuss performance characteristics of these SiPMs such as afterpulsing, crosstalk, and photon detection efficiency.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

IM Release Number: LLNL-ABS-830066   

Characterization of Silicon Photomultipliers for the DarkSide-20k Experiment

DarkSide-20k is a dark matter search experiment using a tonne-scale dual-phase liquid argon TPC that will be capable of confirming a positive observation or of further extending the exclusion limits well beyond any current or presently planned experiment. In order to instrument DarkSide-20k, the Collaboration conducted an intensive program aimed at the development of Silicon Photomultiplier (SiPM) technology to detect the liquid argon scintillation light. The SiPM-based photon detectors have many advantages over the traditional photomultiplier tubes, which are crucial for achieving an unprecedented sensitivity to the WIMP dark matter. In this talk, we will present the complete characterization of the SiPMs produced by Fondazione Bruno Kessler and optimized for cryogenic operation, which will be used in the experiment. Various features, such as dark rate, gain, and correlated noises, were measured in several dedicated setups at 87 K. Additionally, we will present one of the first cryogenic measurements of the Photon Detection Efficiency (PDE) of these devices in the 350-600 nm wavelength range.   

Eos: an integrated testbed for hybrid neutrino detection technology

Hybrid neutrino detectors, capable of leveraging both Cherenkov and scintillation signals simultaneously, have the potential to revolutionize the field of low- and high-energy neutrino detection, offering unprecedented event imaging capabilities and resulting background rejection. These performance characteristics would substantially increase sensitivity to a broad program of fundamental physics, as well as reactor signals for potential nonproliferation applications.  Eos is planned to be a few-ton scale prototype detector, designed to demonstrate the impact of cutting-edge neutrino detection technology.  Leveraging novel scintillating materials and new, fast photon detectors, Eos will be used to explore the impact of detector configuration choices on the potential for hybrid neutrino detection.   

Design, Assembly, and Testing of a Small 3D-printed Thick-GEM

Thick GEMs are a type of gas electron multiplier, a micropattern gaseous detector, with many applications in research. The subject of this study is whether or not a small 3D-printed thick GEM board can be used to form a well-functioning detector. A Thick GEM having three separate board sectors, each having different sized clearance rim annuli around their holes, was designed, printed, and assembled. Several studies to quantify its behavior over both short and long time intervals were conducted, and the results calculated. The THGEM sector with 0.1 mm annulus rims was able to achieve primarily 10² gain, whereas the sector with 0.2 mm annulus rims was able to achieve 10³ gain by going to a higher bias voltage than the 0.1 mm rim sector was able to achieve. The sector with 0.15 mm annulus rims was the only one able to achieve 10⁴ gain. It was shown for the 0.2 mm rim sector that by leaving the Thick GEM powered for at least 10 hours, it is possible to stabilize the gain at an order of magnitude higher than what it would be if it had been in an off state for some time prior. While there were concerns with the overall long-term functionality of the 3D-printed Thick GEM, we show that they are able to perform as functioning GEMs.   

Angular Resolution of Electron Recoils in Gas

Directional recoil detection is highly desirable for neutron detection, neutrino detection, and dark matter searches. Traditionally, the focus has been on directional detection of low-energy nuclear recoils, which offers a method for penetrating the neutrino floor and confirming the galactic origin of a dark matter signal. More recently, there has been growing interest in directional detection of electron recoils, which enable unique neutrino physics capabilities. A particularly interesting example is the possibility of obtaining a firm measurement of the Sun's CNO neutrino flux. It is estimated that an O(10m^3) gas TPC operating at atmospheric pressure can make such a measurement via the electron recoil channel. Given the direction to the Sun and the combined measurement of recoil energy and direction, event-by-event reconstruction of the neutrino energy spectrum is possible. This requires a good understanding of the detector's energy resolution and the angular resolution of electron recoils. However, electron recoils have complex trajectories and the angular resolution that can be achieved is not well understood. We discuss a general method for approximating and optimizing the angular resolution of electron recoils in gas, including both scattering and detector effects.   

Results from a Digital Tension Measurement Instrument for Multi-Wire Particle Detectors

 Currently, one of the most common means of assessing wire tensions in physics detectors is to individually pluck each wire and use a laser to measure its natural frequency. Our new instrument uses a recently developed method that places an AC current and DC bias on alternating wires, inducing vibrations in the wires between them. The instrument reads out the voltage of each vibrating wire while sweeping through AC frequencies, and uses the resonance peak that occurs at a wire's fundamental frequency to determine that wire's tension. The automation and parallelization built into the instrument allow it to greatly exceed the speed at which tensions are measured using the common method. In this talk, we present results from a successful tension measurement of a physics detector that contains thousands of individual wires.   

Searching for ultra-light dark photon dark matter using optical transitions in atomic systems.

Precision measurements at atomic scales can be a powerful tool in the search for new particles that could make up the dark matter in the universe. To that end, optical transitions in atomic systems have been used previously to set leading constraints on models of dark matter than induce a time variation in the value of the fine structure "constant". We use the same systems to study an analoguous effect in a dark sector model where the Standard Model is augemented by a U(1) field which, when light enough, can constitute all the dark matter. This ultra-light dark photon does not cause a shift in the frequency of the fine-structure constant directly, but instead acts as a background electromagnetic field and induces a time varying shift in the frequency of photons emitted in transitions of ions or atoms such as Al⁺, Sr, and Yb. The latter are used as optical clocks and their transition frequency measurements have been performed to Ο( 10^-17 ) levels of relative systematic uncertainty. These experiments therefore offer unparalled sensitivity to small time-varying shifts in their respective transition frequencies. The ultra-light dark photon, acting as a background electric field, induces a tiny time varying Stark shift in the transition frequencies of, for example, Al⁺: 3s² → 3s3p or Sr: 5s² → 5s5p which can be constrained using the measured transition frequency ratio, ν_Al⁺ / v_Sr.  We exploit this to set the first direct detection constraints on dark photon dark matter lighter than 10^-15 eV and also project the sensitivity reachable by future experiments in frequency metrology, such as those using Highly Charged Ions (HCI), such dark matter candidates.    

Energy calibration of a KID-based phonon detector optimized for sub-GeV dark matter

Detection of sub-GeV dark matter candidates require sub-eV detector thresholds on deposited energy. We provide an update on a gram-scale phonon-mediated KID-based device that was designed for a dark matter search in this mass range at the Northwestern Experimental Underground Site. Currently, the device is demonstrating 6 eV resolution on the energy absorbed by the resonator. We show that TLS noise dominates this energy resolution estimate. After modifying the design to mitigate TLS noise, we project 1.5 eV on energy absorbed by the resonator for an amplifier white-noise dominated device. We also detail a photon-based technique to measure the resolution on energy deposited in the substrate, which we project to be roughly three times greater than the resolution on energy absorbed by the resonator, depending on the phonon collection efficiency of the resonator. This technique deposits photons in the substrate via a 475nm LED laser. Finally, we present a clear path forward to sub-eV thresholds, which includes installation of a quantum-limited superconducting parametric amplifier and adjustments to the material makeup of our resonators.