arXiv subjects

R. Mahapatra

Publications and source records attributed to R. Mahapatra.

At least 55 records · Page 3Linked to original sources

arXiv2022

Large-mass, low-threshold sapphire detector for rare event searches

Low mass nuclear recoil dark matter and coherent-elastic-neutrino-nucleus-scattering (CENNS) searches confront similar challenges in choosing ultra-low threshold and large-mass detectors. We report experimental results from the first-of-its-kind 100 g single-crystal sapphire detector design with a diameter of 76 mm and thickness of 4 mm. The detector is designed to be sensitive for low-energy rare interactions with an intention to investigate the low mass region of dark matter phase-space and search for CENNS at the reactor site. Sapphire is a crystal of aluminum oxide (Al2O3) and has been found to be a good candidate for light mass spin-dependent dark matter search experiments due to its lower atomic mass compared to other detector materials such as germanium and silicon. Using the data collected from the test facility at Texas A&M University, we were able to resolve low energy lines from calibration sources and estimated that our newly developed sapphire detector has a baseline recoil energy resolution of 18 eV. These detectors are operated at 0 V with the phonon-assisted detection providing a quenching-free low-threshold operation.

physics.ins-det↗

arXiv2022

A backing detector for order-keV neutrons

We have designed and tested a large-area (0.15~m$^2$) neutron detector based on neutron capture on \ce{^{6}Li}. The neutron detector design has been optimized for the purpose of tagging the scattering angle of keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy ($<$100 eV) nuclear recoil in detectors for dark matter and coherent elastic neutrino nucleus scattering (CE$ν$NS). We describe the design, construction, and characterization of a prototype. The prototype is designed to have a tagging efficiency of $\sim$25\% at the relevant $\mathcal{O}$(keV) neutron energies, and with a mean capture time of $\sim$17$~μ$s. The prototype was characterized using a \ce{^{252}Cf} neutron source and agreement with the simulation was observed within a few percent level.

physics.ins-det↗

arXiv2022

A novel active veto prototype detector with an inner target for improved rare event searches

We report the fabrication and performance of an annular, cryogenic, phonon-mediated veto detector that can host an inner target detector, allowing substantial reduction in radiogenic backgrounds for rare event search experiments. A germanium veto detector of mass $\sim$500 g with an outer diameter of 76 mm and an inner diameter of 28 mm was produced. A 25 mm diameter germanium inner target detector of mass $\sim$10 g was mounted inside the veto detector. The detector was designed using inputs from a GEANT4 based simulation, where it was modeled to be sandwiched between two germanium detectors. The simulation showed that the background rates (dominantly gamma interactions) could be reduced by $>$ 90$\%$, and that such an arrangement is sufficient for aggressive background reduction needed for neutrino and dark matter search experiments. During testing at the experimental site the veto detector prototype achieved a baseline resolution of 1.24 $\pm$ 0.02 keV while hosting a functional inner target detector. The baseline resolution of the inner target detector was 147 $\pm$ 2 eV. The detectors were operated at mK temperatures. The experimental results of an identical detector arrangement are in excellent agreement with the simulation.

physics.ins-det↗

arXiv2022

Constraints on Lightly Ionizing Particles from CDMSlite

The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) achieved efficient detection of very small recoil energies in its germanium target, resulting in sensitivity to Lightly Ionizing Particles (LIPs) in a previously unexplored region of charge, mass, and velocity parameter space. We report first direct-detection limits calculated using the optimum interval method on the vertical intensity of cosmogenically-produced LIPs with an electric charge smaller than $e/(3\times10^5$), as well as the strongest limits for charge $\leq e/160$, with a minimum vertical intensity of $1.36\times10^{-7}$\,cm$^{-2}$s$^{-1}$sr$^{-1}$ at charge $e/160$. These results apply over a wide range of LIP masses (5\,MeV/$c^2$ to 100\,TeV/$c^2$) and cover a wide range of $βγ$ values (0.1 -- $10^6$), thus excluding non-relativistic LIPs with $βγ$ as small as 0.1 for the first time.

hep-ex↗

arXiv2021

Light Dark Matter Search with a High-Resolution Athermal Phonon Detector Operated Above Ground

We present limits on spin-independent dark matter-nucleon interactions using a $10.6$ $\mathrm{g}$ Si athermal phonon detector with a baseline energy resolution of $σ_E=3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.19}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from $93$ to $140$ $\mathrm{MeV}/c^2$, with a raw exposure of $9.9$ $\mathrm{g}\cdot\mathrm{d}$ acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches.

hep-ex↗

arXiv2021

Large-mass single-electron-resolution detector for dark matter and neutrino elastic interaction searches

Large mass single-electron-resolution solid state detectors are desirable to search for low mass dark matter candidates and to measure coherent elastic neutrino nucleus scattering (CE$ν$NS). Here, we present results from a novel 100 g phonon-mediated Si detector with a new interface architecture. This detector gives a baseline resolution of $\sim 1 e^{-}/h^{+}$ pair and a leakage current on the order of $10^{-16}$ A. This was achieved by removing the direct electrical contact between the Si crystal and the metallic electrode, and by increasing the phonon absorption efficiency of the sensors. The phonon signal amplification in the detector shows a linear increase while the signal to noise ratio improves with bias voltage, up to 240 V. This feature enables the detector to operate at a low energy threshold which is beneficial for dark matter and CE$ν$NS like searches.

physics.ins-det↗

arXiv2021

Design and Characterization of a Phonon-Mediated Cryogenic Particle Detector with an eV-Scale Threshold and 100 keV-Scale Dynamic Range

We present the design and characterization of a cryogenic phonon-sensitive 1-gram Si detector exploiting the Neganov-Trofimov-Luke effect to detect single-charge excitations. This device achieved 2.65(2)~eV phonon energy resolution when operated without a voltage bias across the crystal and a corresponding charge resolution of 0.03 electron-hole pairs at 100~V bias. With a continuous-readout data acquisition system and an offline optimum-filter trigger, we obtain a 9.2~eV threshold with a trigger rate of the order of 20~Hz. The detector's energy scale is calibrated up to 120~keV using an energy estimator based on the pulse area. The high performance of this device allows its application to different fields where excellent energy resolution, low threshold, and large dynamic range are required, including dark matter searches, precision measurements of coherent neutrino-nucleus scattering, and ionization yield measurements.

physics.ins-det↗

arXiv2021

BPLight-CNN: A Photonics-based Backpropagation Accelerator for Deep Learning

Training deep learning networks involves continuous weight updates across the various layers of the deep network while using a backpropagation algorithm (BP). This results in expensive computation overheads during training. Consequently, most deep learning accelerators today employ pre-trained weights and focus only on improving the design of the inference phase. The recent trend is to build a complete deep learning accelerator by incorporating the training module. Such efforts require an ultra-fast chip architecture for executing the BP algorithm. In this article, we propose a novel photonics-based backpropagation accelerator for high performance deep learning training. We present the design for a convolutional neural network, BPLight-CNN, which incorporates the silicon photonics-based backpropagation accelerator. BPLight-CNN is a first-of-its-kind photonic and memristor-based CNN architecture for end-to-end training and prediction. We evaluate BPLight-CNN using a photonic CAD framework (IPKISS) on deep learning benchmark models including LeNet and VGG-Net. The proposed design achieves (i) at least 34x speedup, 34x improvement in computational efficiency, and 38.5x energy savings, during training; and (ii) 29x speedup, 31x improvement in computational efficiency, and 38.7x improvement in energy savings, during inference compared to the state-of-the-art designs. All these comparisons are done at a 16-bit resolution; and BPLight-CNN achieves these improvements at a cost of approximately 6% lower accuracy compared to the state-of-the-art.

cs.LG↗

arXiv2021

Constraints on low-mass, relic dark matter candidates from a surface-operated SuperCDMS single-charge sensitive detector

This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axion-like particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 gram Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 gram-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section $\barσ_{e}$ is constrained for dark matter masses from 0.5--$10^{4} $MeV$/c^{2}$; in the mass range from 1.2--50 eV$/c^{2}$ the dark photon kinetic mixing parameter $\varepsilon$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above mentioned mass ranges are $\barσ_{e}\,=\,8.7\times10^{-34}$ cm$^{2}$, $\varepsilon\,=\,3.3\times10^{-14}$, and $g_{ae}\,=\,1.0\times10^{-9}$.

hep-ex↗

arXiv2021

Constraints on dark photons and axion-like particles from SuperCDMS Soudan

We present an analysis of electron recoils in cryogenic germanium detectors operated during the SuperCDMS Soudan experiment. The data are used to set new constraints on the axioelectric coupling of axion-like particles and the kinetic mixing parameter of dark photons, assuming the respective species constitutes all of the galactic dark matter. This study covers the mass range from 40 eV/$c^2$ to 500 eV/$c^2$ for both candidates, excluding previously untested parameter space for masses below ~1 keV/$c^2$. For the kinetic mixing of dark photons, values below $10^{-15}$ are reached for particle masses around 100 eV/$c^2$; for the axioelectric coupling of axion-like particles, values below $10^{-12}$ are reached for particles with masses in the range of a few-hundred eV/$c^2$.

hep-ex↗

arXiv2021

Performance of a Large Area Photon Detector For Rare Event Search Applications

We present the design and characterization of a large-area Cryogenic PhotoDetector (CPD) designed for active particle identification in rare event searches, such as neutrinoless double beta decay and dark matter experiments. The detector consists of a $45.6$ $\mathrm{cm}^2$ surface area by 1-mm-thick $10.6$ $\mathrm{g}$ Si wafer. It is instrumented with a distributed network of Quasiparticle-trap-assisted Electrothermal feedback Transition-edge sensors (QETs) with superconducting critical temperature $T_c=41.5$ $\mathrm{mK}$ to measure athermal phonons released from interactions with photons. The detector is characterized and calibrated with a collimated $^{55}$Fe X-ray source incident on the center of the detector. The noise equivalent power is measured to be $1\times 10^{-17}$ $\mathrm{W}/\sqrt{\mathrm{Hz}}$ in a bandwidth of $2.7$ $\mathrm{kHz}$. The baseline energy resolution is measured to be $σ_E = 3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.23}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$ (RMS). The detector also has an expected timing resolution of $σ_t = 2.3$ $μ\mathrm{s}$ for $5$ $σ_E$ events.

physics.ins-det↗

arXiv2021

Search for Low-Mass Dark Matter with CDMSlite Using a Profile Likelihood Fit

The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) searches for interactions between dark matter particles and germanium nuclei in cryogenic detectors. The experiment has achieved a low energy threshold with improved sensitivity to low-mass (<10 GeV/c$^2$) dark matter particles. We present an analysis of the final CDMSlite data set, taken with a different detector than was used for the two previous CDMSlite data sets. This analysis includes a data "salting" method to protect against bias, improved noise discrimination, background modeling, and the use of profile likelihood methods to search for a dark matter signal in the presence of backgrounds. We achieve an energy threshold of 70 eV and significantly improve the sensitivity for dark matter particles with masses between 2.5 and 10 GeV/c$^2$ compared to previous analyses. We set an upper limit on the dark matter-nucleon scattering cross section in germanium of 5.4$\times$10$^{-42}$ cm$^2$ at 5 GeV/c$^2$, a factor of $\sim$2.5 improvement over the previous CDMSlite result.

astro-ph.CO↗

arXiv2020

First Dark Matter Constraints from a SuperCDMS Single-Charge Sensitive Detector

We present the first limits on inelastic electron-scattering dark matter and dark photon absorption using a prototype SuperCDMS detector having a charge resolution of 0.1 electron-hole pairs (CDMS HVeV, a 0.93 gram CDMS HV device). These electron-recoil limits significantly improve experimental constraints on dark matter particles with masses as low as 1 MeV/$\mathrm{c^2}$. We demonstrate a sensitivity to dark photons competitive with other leading approaches but using substantially less exposure (0.49 gram days). These results demonstrate the scientific potential of phonon-mediated semiconductor detectors that are sensitive to single electronic excitations.

hep-ex↗

arXiv2020

Characterizing TES Power Noise for Future Single Optical-Phonon and Infrared-Photon Detectors

In this letter, we present the performance of a $100~μ\mathrm{m}\times 400~μ\mathrm{m} \times 40~\mathrm{nm}$ tungsten (W) Transition-Edge Sensor (TES) with a critical temperature of 40 mK. This device has a measured noise equivalent power (NEP) of $1.5\times 10^{-18}\ \mathrm{W}/\sqrt{\mathrm{Hz}}$, in a bandwidth of $2.6$ kHz, indicating a resolution for Dirac delta energy depositions of $40\pm 5~\mathrm{meV}$ (rms). The performance demonstrated by this device is a critical step towards developing a $\mathcal{O}(100)~\mathrm{meV}$ threshold athermal phonon detectors for low-mass dark matter searches.

physics.ins-det↗

arXiv2020

Phonon-mediated High-voltage Detector with Background Rejection for Low-mass Dark Matter and Reactor Coherent Neutrino Scattering Experiments

We report the first demonstration of a phonon-mediated silicon detector technology that provides a primary phonon measurement in a low-voltage region, and a simultaneous indirect measurement of the ionization signal through Neganov-Trofimov-Luke amplification in a high voltage region, both in a monolithic crystal. We present characterization of charge and phonon transport between the two stages of the detector and the resulting background discrimination capability at low energies. This new detector technology has the potential to significantly enhance the sensitivity of dark matter and coherent neutrino scattering experiments beyond the capabilities of current technologies that have limited discrimination at low energies.

physics.ins-det↗

arXiv2019

Proceedings of The Magnificent CE$ν$NS Workshop 2018

The Magnificent CE$ν$NS Workshop (2018) was held November 2 & 3 of 2018 on the University of Chicago campus and brought together theorists, phenomenologists, and experimentalists working in numerous areas but sharing a common interest in the process of coherent elastic neutrino-nucleus scattering (CE$ν$NS). This is a collection of abstract-like summaries of the talks given at the meeting, including links to the slides presented. This document and the slides from the meeting provide an overview of the field and a snapshot of the robust CE$ν$NS-related efforts both planned and underway.

hep-ex↗

arXiv2019

Production Rate Measurement of Tritium and Other Cosmogenic Isotopes in Germanium with CDMSlite

Future direct searches for low-mass dark matter particles with germanium detectors, such as SuperCDMS SNOLAB, are expected to be limited by backgrounds from radioactive isotopes activated by cosmogenic radiation inside the germanium. There are limited experimental data available to constrain production rates and a large spread of theoretical predictions. We examine the calculation of expected production rates, and analyze data from the second run of the CDMS low ionization threshold experiment (CDMSlite) to estimate the rates for several isotopes. We model the measured CDMSlite spectrum and fit for contributions from tritium and other isotopes. Using the knowledge of the detector history, these results are converted to cosmogenic production rates at sea level. The production rates in atoms/(kg$\cdot$day) are 74$\pm$9 for $^3$H, 1.5$\pm$0.7 for $^{55}$Fe, 17$\pm$5 for $^{65}$Zn, and 30$\pm$18 for $^{68}$Ge.

physics.ins-det↗

arXiv2018

Performance of the First 150 mm Diameter Cryogenic Silicon Ionization Detectors with Contact-Free Electrodes

Cryogenic semiconductor detectors operated at temperatures below 100 mK are commonly used in particle physics experiments searching for dark matter. The largest such germanium and silicon detectors, with diameters of 100 mm and thickness of 33 mm, are planned for use by the Super Cryogenic Dark Matter Search (SuperCDMS) experiment at SNOLAB, Canada. In order to scale up the sensitive mass of future experiments, larger individual detectors are being investigated. We present here the first results of testing two prototype 150 mm diameter silicon ionization detectors. The detectors are 25 mm and 33 mm thick with masses 1.7 and 2.2 times larger than those currently planned for SuperCDMS. These devices were operated with contact-free bias electrodes to minimize leakage currents which currently limit operation at high bias voltages. One detector was instrumented to read out ionization signals using a single contact-free readout electrode and the other with an array of electrodes patterned on the crystal surface. The results show promise for the use of both large volume silicon detectors and contact-free electrode arrangements for scaling up solid state cryogenic detector mass and bias voltage.

physics.ins-det↗