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Roberts, A.

Publications and source records attributed to Roberts, A..

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

First Measurement of the Nuclear-Recoil Ionization Yield in Silicon at 100 eV

We measured the nuclear-recoil ionization yield in silicon with a cryogenic phonon-sensitive gram-scale detector. Neutrons from a mono-energetic beam scatter off of the silicon nuclei at angles corresponding to energy depositions from 4 keV down to 100 eV, the lowest energy probed so far. The results show no sign of an ionization production threshold above 100 eV. In conclusion, these results call for further investigation of the ionization yield theory and a comprehensive determination of the detector response function at energies below the keV scale.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Intrinsic Fano factor of nuclear recoils for dark matter searches

Nuclear recoils in germanium and silicon are shown to have much larger variance in electron-hole production than their electron recoil counterparts for recoil energies between 10 and 200 keV. This effect—owing primarily to deviations in the amount of energy given to the crystal lattice in response to a nuclear recoil of a given energy—has been predicted by the Lindhard model. Here, we parametrize the variance in terms of an intrinsic nuclear recoil Fano factor that is 24.3 ± 0.2 and 26 ± 8 at around 25 keV for silicon and germanium, respectively. The variance has important effects on the expected signal shapes for experiments utilizing low-energy nuclear recoils such as direct dark matter searches and coherent neutrino-nucleus scattering measurements.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Ionization yield measurement in a germanium CDMSlite detector using photo-neutron sources

Two photo-neutron sources, Y 88 Be 9 and Sb 124 Be 9 , have been used to investigate the ionization yield of nuclear recoils in the CDMSlite germanium detectors by the SuperCDMS collaboration. In this study, we evaluate the yield for nuclear recoil energies between 1 and 7 keV at a temperature of ~ 50 mK . We use a geant4 simulation to model the neutron spectrum assuming a charge yield model that is a generalization of the standard Lindhard model and consists of two energy dependent parameters. We perform a likelihood analysis using the simulated neutron spectrum, modeled background, and experimental data to obtain the best fit values of the yield model. The ionization yield between recoil energies of 1 and 7 keV is shown to be significantly lower than predicted by the standard Lindhard model for germanium. There is a general lack of agreement among different experiments using a variety of techniques studying the low energy range of the nuclear recoil yield, which is most critical for interpretation of direct dark matter searches. This suggests complexity in the physical process that many direct detection experiments use to model their primary signal detection mechanism and highlights the need for further studies to clarify underlying systematic effects that have not been well understood up to this point.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Constraints on Lightly Ionizing Particles from CDMSlite

The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) achieved effcient 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 on the vertical intensity of cosmogenically-produced LIPs with an electric charge smaller than e/(3x10^5), as well as the strongest limits for charge <= e/160, with a minimum vertical intensity of 1.36 x 10^-7 cm^-2s^-1sr^-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 beta-gamma values (0.1--10^6), thus excluding non-relativistic LIPs with beta-gamma as small as 0.1 for the first time.

Alkhatib, I↗
DOE OSTI2021

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 g silicon athermal phonon detector with a baseline energy resolution of 4.92 +/- 0.01 eV. This exclusion analysis sets the most stringent dark matter-nucleon cross-section limits for masses from 87--140 MeV/c^2 , with a raw exposure of 9.9 g d acquired at an above-ground facility. This work illustrates the scientic potential of athermal phonon sensors with eV-scale energy resolution for future dark matter searches.

Alkhatib, I↗
DOE OSTI2020

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 axionlike particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 g 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 g-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 σ ¯ e is constrained for dark matter masses from 0.5 to 10 4 MeV / c 2 ; in the mass range from 1.2 to 50 eV / c 2 the dark photon kinetic mixing parameter ϵ and the axioelectric coupling constant g a e are constrained. The minimum 90% confidence-level upper limits within the above-mentioned mass ranges are σ ¯ e = 8.7 × 10 - 34 cm 2 , ϵ = 3.3 × 10 - 14 , and g a e = 1.0 × 10 - 9 .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Constraints on dark photons and axionlike particles from the SuperCDMS Soudan experiment

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/$c^2$.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2010

Finding, Browsing and Getting Data Easily Using SPDF Web Services

The NASA GSFC Space Physics Data Facility (5PDF) provides heliophysics science-enabling information services for enhancing scientific research and enabling integration of these services into the Heliophysics Data Environment paradigm, via standards-based approach (SOAP) and Representational State Transfer (REST) web services in addition to web browser, FTP, and OPeNDAP interfaces. We describe these interfaces and the philosophies behind these web services, and show how to call them from various languages, such as IDL and Perl. We are working towards a "one simple line to call" philosophy extolled in the recent VxO discussions. Combining data from many instruments and missions enables broad research analysis and correlation and coordination with other experiments and missions.

Candey, R.↗
NASA NTRS2008

Interoperability of Heliophysics Virtual Observatories

If you'd like to find interrelated heliophysics (also known as space and solar physics) data for a research project that spans, for example, magnetic field data and charged particle data from multiple satellites located near a given place and at approximately the same time, how easy is this to do? There are probably hundreds of data sets scattered in archives around the world that might be relevant. Is there an optimal way to search these archives and find what you want? There are a number of virtual observatories (VOs) now in existence that maintain knowledge of the data available in subdisciplines of heliophysics. The data may be widely scattered among various data centers, but the VOs have knowledge of what is available and how to get to it. The problem is that research projects might require data from a number of subdisciplines. Is there a way to search multiple VOs at once and obtain what is needed quickly? To do this requires a common way of describing the data such that a search using a common term will find all data that relate to the common term. This common language is contained within a data model developed for all of heliophysics and known as the SPASE (Space Physics Archive Search and Extract) Data Model. NASA has funded the main part of the development of SPASE but other groups have put resources into it as well. How well is this working? We will review the use of SPASE and how well the goal of locating and retrieving data within the heliophysics community is being achieved. Can the VOs truly be made interoperable despite being developed by so many diverse groups?

Thieman, J.↗
NASA NTRS1986

Interface Program for Reliability Predictions

CARE3MENU generates input file for CARE III program. Used to predict reliabilities of complex, redundant, fault-tolerant systems, including digital computers, aircraft, and nuclear and chemical control systems. CARE III input file often becomes complicated and not easily formatted with text editor. Provides easy interactive method of creating input file by automatically formatting set of user-supplied inputs for CARE III system. CARE3MENU provides detailed online help for most of its screen formats.

Bavuso, S. J.↗
NASA NTRS1979

DUMAND Summer Workshop, University of California, La Jolla, Calif., July 24-September 2, 1978, Proceedings. Volume 1 - Array studies

Papers are presented concerning the design and implementation of the optical and acoustic sensors that will comprise the DUMAND (Deep Underwater Muon and Neutrino Detector) array. Specific topics include the results of experiments on atmospheric muon and neutrino spectra obtained with various muon and neutrino spectrometers, optical sensors and arrays, optical data handling systems, the simulation of the sound generated by high-energy particles in water, constraints on acoustic arrays, standard ocean parameters for DUMAND calculations, and Monte Carlo investigations of hadronic and electromagnetic cascades in sea water.

Roberts, A.↗
NASA NTRS1979

DUMAND Summer Workshop, University of California, La Jolla, Calif., July 24-September 2, 1978, Proceedings. Volume 2 - UHE interactions, neutrino astronomy

The volume covers categories on inelastic neutrino scattering and the W-boson, and other ultra-high-energy processes, on pulsars, quasars and galactic nuclei, as well as other point sources and constants from gamma ray astronomy. Individual subjects include weak intermediate vector bosons and DUMAND, the Monte Carlo simulation of inelastic neutrino scattering in DUMAND, and Higgs boson production by very high-energy neutrinos. The observability of the neutrino flux from the inner region of the galactic disk, the diffuse fluxes of high-energy neutrinos, as well as the significance of gamma ray observations for neutrino astronomy are also among the topics covered.

Roberts, A.↗