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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Measurement of the centrality and pseudorapidity dependence of the integrated elliptic flow in lead–lead collisions at $\sqrt{s_{\mathrm {NN}}}=2.76$ TeV with the ATLAS detector

The integrated elliptic flow of charged particles produced in Pb+Pb collisions at $\sqrt{s_{\mathrm {NN}}} TeV has been measured with the ATLAS detector using data collected at the Large Hadron Collider. The anisotropy parameter, v 2 , was measured in the pseudorapidity range |η| ≤ 2.5 with the event-plane method. In order to include tracks with very low transverse momentum p T , thus reducing the uncertainty in v 2 integrated over p T , a 1 μ b -1 data sample recorded without a magnetic field in the tracking detectors is used. The centrality dependence of the integrated v 2 is compared to other measurements obtained with higher p T thresholds. The integrated elliptic flow is weakly decreasing with |η|. The integrated v 2 transformed to the rest frame of one of the colliding nuclei is compared to the lower-energy RHIC data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)

A new boron-coated CCD camera is described for direct detection of ultracold neutrons (UCN) through the capture reactions 10 B (n,α0γ) 7 Li (6%) and 10 B(n,α1γ) 7 Li (94%). The experiments, which extend earlier works using a boron-coated ZnS:Ag scintillator, are based on direct detections of the neutron-capture byproducts in silicon. The high position resolution, energy resolution and particle ID performance of a scientific CCD allows for observation and identification of all the byproducts α, 7 Li and γ (electron recoils). A signal-to-noise improvement on the order of 10 4 over the indirect method has been achieved. Sub-pixel position resolution of a few microns is demonstrated. The technology can also be used to build UCN detectors with an area on the order of 1 m 2 . The combination of micrometer scale spatial resolution, few electrons ionization thresholds and large area paves the way to new research avenues including quantum physics of UCN and high-resolution neutron imaging and spectroscopy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1985

Quantum noise and the threshold of hearing

It is argued that the sensitivity of the ear reaches a limit imposed by the uncertainty principle. This is possible only if the receptor cell holds the detector elements in a special nonequilibrium state which has the same noise characteristics as a ground (T = 0 K) state. To accomplish this 'active cooling' the molecular dynamics of the system must maintain quantum mechanical coherence over the time scale of the measurement.

Bialek, W.↗
DOE OSTI2019

A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)

A new boron-coated CCD camera is described for direct detection of ultracold neutrons (UCN) through the capture reactions $^{10}$B (n,$\alpha$0$\gamma$)$^7$Li (6%) and $^{10}$B(n,$\alpha$1$\gamma$)$^7$Li (94%). The experiments, which extend earlier works using a boron-coated ZnS:Ag scintillator, are based on direct detections of the neutron-capture byproducts in silicon. The high position resolution, energy resolution and particle ID performance of a scientific CCD allows for observation and identification of all the byproducts $\alpha$, $^7$Li and $\gamma$ (electron recoils). A signal-to-noise improvement on the order of 10$^4$ over the indirect method has been achieved. Sub-pixel position resolution of a few microns is demonstrated. The technology can also be used to build UCN detectors with an area on the order of 1 m$^2$. The combination of micrometer scale spatial resolution, few electrons ionization thresholds and large area paves the way to new research avenues including quantum physics of UCN and high-resolution neutron imaging and spectroscopy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

An algorithm to correct saturated mass spectrometry ion abundances for enhanced quantitation and mass accuracy in omic studies

The mass accuracy and peak intensity of ions detected by mass spectrometry (MS) measurements are essential to facilitate compound identification and quantitation. However, high concentration species can easily cause problems if their ion intensities reach beyond the limits of the detection system, leading to distorted and non-ideal detector response (e.g. saturation), and largely precluding the calculation of accurate m/z and intensity values. Here we present an open source computational method to correct peaks above a defined intensity (saturated) threshold determined by the MS instrumentation such as the analog-to-digital converters or time-to-digital converters used in conjunction with time-of-flight MS. In this method, the isotopic envelope for each observed ion above the saturation threshold is compared to its expected theoretical isotopic distribution. The most intense isotopic peak for which saturation does not occur is then utilized to re-calculate the precursor m/z and correct the intensity, resulting in both higher mass accuracy and greater dynamic range. The benefits of this approach were evaluated with proteomic and lipidomic datasets of varying complexities. After correcting the high concentration species, reduced mass errors and enhanced dynamic range were observed for both simple and complex omic samples. Specifically, the mass error dropped by more than 50% in most cases with highly saturated species and dynamic range increased by 1-2 orders of magnitude for peptides in a blood serum sample.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

Characterization of Silicon Detector Readout Electronics

Configuration and calibration of the front-end electronics typical of many silicon detector configurations were investigated in a lab activity based on a pair of strip sensors interfaced with FSSR2 read-out chips and an FPGA. This simple hardware configuration, originally developed for a telescope at the Fermilab Test Beam Facility, was used to measure thresholds and noise on individual readout channels and to study the influence that different configurations of the front-end electronics had on the observed levels of noise in the system. An understanding of the calibration and operation of this small detector system provided an opportunity to explore the architecture of larger systems such as those currently in use at LHC experiments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2016

Low-Noise Free-Running High-Rate Photon-Counting for Space Communication and Ranging

We present performance data for low-noise free-running high-rate photon counting method for space optical communication and ranging. NASA GSFC is testing the performance of two types of novel photon-counting detectors 1) a 2x8 mercury cadmium telluride (HgCdTe) avalanche array made by DRS Inc., and a 2) a commercial 2880-element silicon avalanche photodiode (APD) array. We successfully measured real-time communication performance using both the 2 detected-photon threshold and logic AND-gate coincidence methods. Use of these methods allows mitigation of dark count, after-pulsing and background noise effects without using other method of Time Gating The HgCdTe APD array routinely demonstrated very high photon detection efficiencies (50) at near infrared wavelength. The commercial silicon APD array exhibited a fast output with rise times of 300 ps and pulse widths of 600 ps. On-chip individually filtered signals from the entire array were multiplexed onto a single fast output. NASA GSFC has tested both detectors for their potential application for space communications and ranging. We developed and compare their performances using both the 2 detected photon threshold and coincidence methods.

Photons↗
NASA NTRS2016

Low-Noise Free-Running High-Rate Photon-Counting for Space Communication and Ranging

We present performance data for low-noise free-running high-rate photon counting method for space optical communication and ranging. NASA GSFC is testing the performance of two types of novel photon-counting detectors 1) a 2x8 mercury cadmium telluride (HgCdTe) avalanche array made by DRS Inc., and a 2) a commercial 2880-element silicon avalanche photodiode (APD) array. We successfully measured real-time communication performance using both the 2 detected-photon threshold and logic AND-gate coincidence methods. Use of these methods allows mitigation of dark count, after-pulsing and background noise effects without using other method of Time Gating The HgCdTe APD array routinely demonstrated very high photon detection efficiencies ((is) greater than 50%) at near infrared wavelength. The commercial silicon APD array exhibited a fast output with rise times of 300 ps and pulse widths of 600 ps. On-chip individually filtered signals from the entire array were multiplexed onto a single fast output. NASA GSFC has tested both detectors for their potential application for space communications and ranging. We developed and compare their performances using both the 2 detected photon threshold and coincidence methods.

Photons↗
DOE OSTI2018

An Analysis of Frenkel Defects and Backgrounds Modeling for SuperCDMS Dark Matter Searches

Years of astrophysical observations suggest that dark matter comprises more than $\sim$ 80 % of all matter in the universe. Particle physics theories favor a weakly-interacting particle that could be directly detected in terrestrial experiments. The Super Cryogenic Dark Matter Search (SuperCDMS) Collaboration operates world-leading experiments to directly detect dark matter interacting with ordinary matter. The SuperCDMS Soudan experiment searched for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei in low-temperature germanium detectors. During the operation of the SuperCDMS Soudan experiment, $^{210}$Pb sources were installed to study background rejection of the Ge detectors. Data from these sources were used to investigate energy loss associated with Frenkel defect formation in germanium crystals at mK temperatures. The spectrum of $^{206}$Pb nuclear recoils was examined near its expected 103 keV endpoint energy to extract the first experimentally determined average displacement threshold energy of 19.7 $\pm$ 0.5 (stat) $\pm$ 0.1 (syst) eV for germanium. This has implications for the sensitivity of future germanium-based dark matter searches including the SuperCDMS SNOLAB experiment. The SuperCDMS SNOLAB experiment will employ germanium and silicon detectors to improve current WIMP-search results by at least one order of magnitude for masses $\leq$ 10 GeV/c$^2$. This will require substantial shielding against cosmogenic and radiogenic backgrounds. The SuperCDMS SNOLAB passive shield will be permanent for the duration of the experiment so extensive simulations were undertaken to optimize the shield design. This resulted in a design of an outer layer of 60 cm of water, a middle layer of 20 cm of lead, and 30 cm of polyethylene which limits the background rate to that required for the primary physics goals of the experiments. The experiment will begin operations in 2020 and care must be taken during the construction phase to limit exposure to the $\pm$ 135 Bq/m$^3$ radon activity in the laboratory. The daughter products of $^{222}$Rn can attach to nearby surfaces leaving long-lived $^{210}$Pb in place for the duration of the experiment. For non-line-of-sight surfaces of the polyethylene shield, the maximum allowable $^{210}$Pb activity is 10,000 nBq/cm$^2$. A study was conducted to experimentally determine the contamination rate of polyethylene and copper by exposing samples for 83 days at SNOLAB. From the resulting surface activities, obtained from high-sensitivity measurements of alpha emissivity using the XIA UltraLo-1800 spectrometer, the average $^{210}$Pb plate-out rate was determined to be 249 and 423 atoms/day/cm$^2$ for polyethylene and copper, respectively. A time-dependent model of alpha activity was

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Study of γ γ → γ ψ ( 2 S ) at Belle

Using 980 fb -1 of data at and around the Υ(nS)(n = 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e+e- collider, the two-photon process γγ → γψ(2S) is studied from the threshold to 4.2 GeV for the first time. Two structures are seen in the invariant mass distribution of γψ(2S): one at M R 1 = 3922.4 ± 6.5 ± 2.0 MeV/c 2 with a width of Γ R 1 = 22 ± 17 ± 4 MeV, and another at M R 2 = 4014.3 ± 4.0 ± 1.5 MeV/c 2 with a width of Γ R 2 = 4 ± 11 ± 6 MeV; the signals are parametrized with the incoherent sum of two Breit- Wigner functions. The first structure is consistent with the X(3915) or the χ c2 (3930), and the local statistical significance is determined to be 3.1σ with the systematic uncertainties included. The second matches none of the known charmonium or charmonium like states, and its global significance is determined to be 2.8σ including the look-elsewhere effect. The production rates are Γ γγ B(R 1 → γψ(2S)) = 9.8 ± 3.6 ± 1.2 eV assuming (J PC , |λ|) = (0 ++ , 0) or 2.0 ± 0.7 ± 0.2 eV with (2 ++ , 2) for the first structure and Γ γγ B(R 2 → γψ(2S)) = 6.2 ± 2.2 ± 0.8 eV with (0 ++ , 0) or 1.2 ± 0.4 ± 0.2 eV with (2 ++ , 2) for the second one. Furthermore, the first errors are statistical and the second systematic, and λ is the helicity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Measurement of the e + e - → K s 0 K ± π ∓ π 0 and K s 0 K ± π ∓ η cross sections using initial-state radiation

The processes e + e - → K$0\atop{S}$ K ± π ∓ π 0 and e + e - → K$0\atop{S}$ K ± π ∓ η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb -1 of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K* 0 (Kπ) 0 , K *(892) ± (Kπ) ∓ , and K$0\atop{S}$K ± ρ ∓ are studied. Lastly, the J / ψ is observed in all of these channels, and corresponding branching fractions are measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber

We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of 37 Ar, respectively. The 37 Ar source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed 55 Fe x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Status of ProtoDUNE Dual Phase

The Deep Underground Neutrino Experiment (DUNE) is a dual-site experiment for long baseline neutrino oscillation studies, and for neutrino astrophysics and nucleon decay searches. DUNE will comprise four 10 kton fiducial liquid argon time-projection-chamber (LAr TPC) modules placed at the Sanford Underground Research Facility (South Dakota, USA). One of these modules will profit form the dual phase (DP) technology where the charge is extracted, amplified, and detected in gaseous argon above the liquid surface allowing a fine readout pitch, a low energy threshold, and good pattern reconstruction of the events. To gain experience in building and operating such a large-scale DP LAr detector, a prototype is currently being assembled at the CERN Neutrino Platform. The ProtoDUNE-DP detector consists of a 6x6x6 m3 LAr TPC and commissioning started in Summer 2019.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2013

FPGA-Based X-Ray Detection and Measurement for an X-Ray Polarimeter

This technology enables detection and measurement of x-rays in an x-ray polarimeter using a field-programmable gate array (FPGA). The technology was developed for the Gravitational and Extreme Magnetism Small Explorer (GEMS) mission. It performs precision energy and timing measurements, as well as rejection of non-x-ray events. It enables the GEMS polarimeter to detect precisely when an event has taken place so that additional measurements can be made. The technology also enables this function to be performed in an FPGA using limited resources so that mass and power can be minimized while reliability for a space application is maximized and precise real-time operation is achieved. This design requires a low-noise, charge-sensitive preamplifier; a highspeed analog to digital converter (ADC); and an x-ray detector with a cathode terminal. It functions by computing a sum of differences for time-samples whose difference exceeds a programmable threshold. A state machine advances through states as a programmable number of consecutive samples exceeds or fails to exceed this threshold. The pulse height is recorded as the accumulated sum. The track length is also measured based on the time from the start to the end of accumulation. For track lengths longer than a certain length, the algorithm estimates the barycenter of charge deposit by comparing the accumulator value at the midpoint to the final accumulator value. The design also employs a number of techniques for rejecting background events. This innovation enables the function to be performed in space where it can operate autonomously with a rapid response time. This implementation combines advantages of computing system-based approaches with those of pure analog approaches. The result is an implementation that is highly reliable, performs in real-time, rejects background events, and consumes minimal power.

Gregory, Kyle↗
DOE OSTI2018

Two distinct components of the delayed single electron noise in liquid xenon emission detectors

Single electron noise which persists for many milliseconds is known to follow ionizing events in liquid/gas xenon emission detectors. Due to the long timescale, this noise can be mistaken for a genuine signal. Therefore, it is a limiting background to the low-energy threshold of dark matter searches, and could prevent discovery-class searches for MeV scale hidden sector dark matter. A systematic study reveals distinct fast and slow components to the noise. The fast component is compatible with the hypothesis of electrons which were trapped below the liquid surface, and can be reduced by increasing the electric field across the liquid/gas interface. However, the slow component increases linearly with electric field. Hypotheses for the origin of this effect are discussed, and techniques for mitigation are suggested.

47 OTHER INSTRUMENTATION↗
NASA NTRS1977

Signal level detector

Frequency-independent circuits measure amplitude of sine waves via Schmitt-trigger circuits, pair of inverters, and two flip-flop stages. Accuracy of unit is limited by Schmitt trigger threshold levels, which depend on temperature and on component variations from unit to unit.

Anderson, T. O.↗
DOE OSTI2012

Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis

Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Elimination of ghosting artifacts from wavelength-shifting fiber neutron detectors

Misassignment of neutron position (ghosting) produces artifacts, which have been observed in wavelength-shifting (WLS) fiber detectors developed for time-of-flight (TOF) neutron powder diffraction. In position-sensitive detectors (PSDs) with WLS fiber encoding, thermal and cold neutrons interact with a monolithic 6LiF/ZnS:Ag scintillator screen, and scintillation photons are generated and transported through the crossed fibers to photomultipliers (PMTs). The neutron position is determined by photon counts in PMTs within a preset time window. Ghosting occurs when neutrons hit the group boundaries of two neighboring PMTs for x-position multiplexing, which is modeled as resulting from a long travel length (about 3-5 mm) of a small number of scintillation photons. This model is supported by the change observed in aperture images when the threshold number for photon-pulses was adjusted for a neutron event determination. When the threshold number of photon-pulses was set above 10 for each PMT, the ghost peaks in the aperture images and TOF spectra of powder diffraction were strongly suppressed or completely eliminated, and the intrinsic background levels of the WLS detectors were significantly reduced. Our result indicates that WLS fiber detector is a promising alternative for 3He PSDs for neutron scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗