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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

An Artificial Neural Network System for Photon-Based Active Interrogation Applications

Active interrogation (AI) is a promising technique to detect shielded special nuclear materials (SNMs). At the University of Michigan, we are developing a photon-based AI system that uses bremsstrahlung radiation from an electron linear accelerator (linac) as an ionizing source and stilbene organic scintillating detectors for neutron detection. Stilbene scintillators are sensitive to fast neutrons and photons and have excellent pulse shape discrimination (PSD) capabilities. The traditional charge integration (CI) method commonly used for PSD analysis eliminates piled-up pulses and relies on a particle discrimination line to separate neutrons and photons. The presence of the intense photon flux during AI creates a significant number of piled-up events in the stilbene scintillator, thereby posing a great challenge to the traditional CI method. Identifying true single neutron pulses becomes challenging due to the presence of a pile-up cloud and overlapping neutron, photon and pile-up clouds in the PSD analysis. To mitigate the effect of pulse pile up and identify true single neutron pulses from stilbene scintillators, an artificial neural network (ANN) system is developed. The developed ANN system identifies single neutron pulses and neutron-photon combinations from piled-up events. The results obtained from a 252Cf measurement in the presence of the intense photon flux show that the developed ANN system outperforms the traditional CI method. Since many piled-up events lie above the particle discrimination line, they get misclassified as neutrons by the traditional CI method resulting in 25% overestimation of the net neutron count rate during the linac pulse. The overall net neutron count rate (single and restored neutrons) during the linac pulse, estimated by the ANN system is 60% of the ground truth. Energy spectroscopy of the ANN attributed single neutron pulses further provides evidence on the detection of prompt fission neutrons from the 252Cf fission source.

42 ENGINEERING↗
NASA NTRS2000

Photon-Counting Multikilohertz Microlaser Altimeters for Airborne and Spaceborne Topographic Measurements

We consider the optimum design of photon-counting microlaser altimeters operating from airborne and spaceborne platforms under both day and night conditions. Extremely compact Q-switched microlaser transmitters produce trains of low energy pulses at multi-kHz rates and can easily generate subnanosecond pulse-widths for precise ranging. To guide the design, we have modeled the solar noise background and developed simple algorithms, based on Post-Detection Poisson Filtering (PDPF), to optimally extract the weak altimeter signal from a high noise background during daytime operations. Practical technology issues, such as detector and/or receiver dead times, have also been considered in the analysis. We describe an airborne prototype, being developed under NASA's instrument Incubator Program, which is designed to operate at a 10 kHz rate from aircraft cruise altitudes up to 12 km with laser pulse energies on the order of a few microjoules. We also analyze a compact and power efficient system designed to operate from Mars orbit at an altitude of 300 km and sample the Martian surface at rates up to 4.3 kHz using a 1 watt laser transmitter and an 18 cm telescope. This yields a Power-Aperture Product of 0.24 W-square meter, corresponding to a value almost 4 times smaller than the Mars Orbiting Laser Altimeter (0. 88W-square meter), yet the sampling rate is roughly 400 times greater (4 kHz vs 10 Hz) Relative to conventional high power laser altimeters, advantages of photon-counting laser altimeters include: (1) a more efficient use of available laser photons providing up to two orders of magnitude greater surface sampling rates for a given laser power-telescope aperture product; (2) a simultaneous two order of magnitude reduction in the volume, cost and weight of the telescope system; (3) the unique ability to spatially resolve the source of the surface return in a photon counting mode through the use of pixellated or imaging detectors; and (4) improved vertical and transverse spatial resolution resulting from both (1) and (3). Furthermore, because of significantly lower laser pulse energies, the microaltimeter is inherently more eyesafe to observers on the ground and less prone to internal optical damage, which can terminate a space mission prematurely.

Degnan, John J.↗
NASA NTRS1987

Imaging and nondispersive spectroscopy of soft X rays using a laboratory X-ray charge-coupled-device system

This paper describes the design and performance of a laboratory instrument for imaging and nondispersive spectroscopy of soft X-rays (300 eV to 10 keV) utilizing a virtual-phase CCD. This instrument has achieved a spatial resolution of 22 microns (limited by pixel size) with an overall array area of 584 x 390 pixels. It has achieved an energy resolution of about 140 eV FWHM for single-pixel Fe-55 X-ray events (5.9 keV) with the CCD operated at -30 C. The CCD has been operated in photon-counting mode at room temperature, and X-ray spectra with an energy resolution of about 450 eV at 5.9 keV have been obtained. The low energy X-ray sensitivity of the CCD also has been demonstrated by detecting carbon K-alpha X-rays (277eV).

Luppino, Gerard A.↗
DOE OSTI2023

Prompt Photofission Neutron Detection in Depleted Uranium

The detection of prompt photofission neutrons during active interrogation is a strong indication of the presence of special nuclear materials. However, the high-energy photons used for interrogation create a very challenging radiation environment for the detection of prompt fission signatures. These challenges include detector saturation and pulse pile-up. Additionally, there is an elevated neutron background that further challenges the detection of prompt fission neutrons. This background is produced because of (γ, Xn) photonuclear reactions in the surrounding high-Z materials. Here, we demonstrate the detection of prompt photofission neutrons in these challenging environments. Depleted uranium (DU) and lead targets are interrogated with bremsstrahlung photons produced by a 9-MV electron linear accelerator. Fast neutrons are detected with trans-stilbene organic detectors, and scintillation pulses are analyzed using a previously developed and demonstrated artificial neural network system. We observe a 5 times higher photoneutron count rate when the lead target is replaced with the DU target. Additionally, we observe a difference in the photoneutron light-output distributions of lead and DU. Here, this difference in the measured distributions is due to the difference in the photoneutron-energy spectra; DU photoneutrons are emitted with (γ, n) and watt-energy spectra, whereas lead photoneutrons are emitted with only the (γ, n) spectrum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1994

Simultaneous observations of gamma-ray bursts with Phebus/Granat and Ulysses GRB

We compare the characteristics of 35 gamma-ray bursts (GRBs) detected simultaneously by Phebus aboard Granat and the Ulysses GRB experiment. Phebus observes a medium to high energy range (100 keV - 100 MeV), while the Ulysses GRB detector is sensitive to lower energy photons (25 - 150 keV). Comparison of the peak counts recorded by these two instruments shows that the variation in burst intensities is more extended for Phebus (above approximately 150 keV) than for Ulysses GRB. This result confirms similar observations from other instruments (Atteia et al. 1991; Mitrofanov et al. 1992; Belli 1992). We discuss the consequences of this behavior for the statistical properties of GRBs, and for the searches for a possible cosmological redshift.

Atteia, J.-L.↗
DOE OSTI2021

X-ray multi-probe data acquisition: A novel technique for laser pump x-ray transient absorption spectroscopy

We report the development and implementation of a novel data acquisition (DAQ) technique for synchrotron-based laser pump X-ray Transient Absorption (XTA) spectroscopy, called X-ray Multi-Probe DAQ (XMP DAQ). This technique utilizes high performance analog to digital converters and home-built software to efficiently measure and process the XTA signal from all x-ray pulses between laser excitations. XMP DAQ generates a set of time resolved x-ray absorption spectra at thousands of different pump–probe time delays simultaneously. Two distinct XMP DAQ schemes are deployed to accommodate different synchrotron storage ring filling patterns. Current Integration (CI) DAQ is a quasi-analog technique that implements a fitting procedure to extract the time resolved absorption intensity from the averaged fluorescence detector response. The fitting procedure eliminates issues associated with small drifts in the voltage baseline and greatly enhances the accuracy of the technique. Photon Counting (PC) DAQ is a binary technique that uses a time resolved histogram to calculate the XTA spectrum. While PC DAQ is suited to measure XTA data with closely spaced x-ray pulses (~10 ns) and a low count rate (<1 detected photon/pulse), CI DAQ works best for widely spaced pulses (tens of ns or greater) with a high count rate (>1 detected photon/pulse). XMP DAQ produces a two-dimensional XTA dataset, enabling efficient quantitative analysis of photophysical and photochemical processes from the sub-nanosecond timescale to 100 μs and longer.

47 OTHER INSTRUMENTATION↗
NASA NTRS2015

Quantum Dots Microstructured Optical Fiber for X-Ray Detection

A novel concept for the detection of x-rays with microstructured optical fibers containing quantum dots scintillation material comprised of zinc sulfide nanocrystals doped with magnesium sulfide is presented. These quantum dots are applied inside the microstructured optical fibers using capillary action. The x-ray photon counts of these fibers are compared to the output of a collimated CdTe solid state detector over an energy range from 10 to 40 keV. The results of the fiber light output and associated effects of an acrylate coating and the quantum dots application technique are discussed.

DeHaven, S. L.↗
NASA NTRS1989

New measurements of the far ultraviolet scattering properties of interstellar dust

An analysis is presented for the spectra of the diffuse ultraviolet background taken during shuttle flight STS-61C (January 1986). Eight regions of the sky were observed for approximately 20 minutes each, using a spectrograph designed specifically to perform measurements of the UV background. The field of view was 3.8 deg x 8 min, with imaging along the slit to confine stellar contamination. The instrument featured a shutter mechanism to measure internal background during flight, a low-scatter holographically ruled diffraction grating, photon counting microchannel plate detectors, through baffling, and a crystal window to further attenuate stray light. The spectra covered the range 1400 to 1850 A and was binned in 50 A bands. The procedure for substracting the contribution of stars too faint to be detected as discrete sources during the observations (in general this represents a small fraction of the total intensity detected except at the longest wavelengths). A radiative transfer model used to interpret the data and set confidence intervals on the relevant parameters is described. It was found that the continuum component of the diffuse ultraviolet background arises primarily from two sources. One source is scattering of starlight by interstellar dust with an albedo of about 12 percent and a relatively isotropic phase function. A second source consists of about 150 photons/cm/sec/ster/A of extragalactic light which is attenuated by the dust in the galaxy. Although emission features possibly associated with molecular H2 are detected in one look direction, fluorescence of H2 is not a major contributor to the diffuse UV background, at least at galactic latitudes greater than -10 degrees.

Hurwitz, Mark↗
NASA NTRS1977

A photon-counting multichannel spectrometer

A multichannel detector system is described in which the positions of individual photon events in a high-gain image intensifier are decoded in the output of a video detector. The high-gain intensifier consists of a pair of three-stage electrostatic image-tube assemblies each containing three fiber-optically-coupled tubes potted in a rugged package with an internal high-voltage supply. Operation of the electrooptical system is discussed along with the pulse-detection process and the operation of the spectrograph in which the image-tube assembly is mounted. It is noted that the spectrometer detects 1.0 count/sec per A for an object of magnitude 13.0 at the peak of its response in the visual band when no light is lost on the slit, that a 10% coincidence correction is reached at an overall count rate of 860 per sec, and that the response follows an exponential law up to count rates of about 4000 per sec. The measured spectrum of the Seyfert galaxy NGC 5548 is provided as an example of the raw data produced by the instrument on a 1.5 meter telescope.

Shectman, S. A.↗
NASA NTRS1993

Detection of a long-duration solar gamma-ray flare on June 11, 1991 with EGRET on COMPTON-GRO

The detection of high energy photon emission from a long-duration solar gamma-ray flare on June 11, 1991 is reported. Gamma rays were detected up to energies above 1 GeV. The solar origin of this emission is assured by the time profile of the gamma-ray count rate and by time-resolved sky maps, which show a clear maximum at the position of the sun. There are indications for a spectral evolution with time, such that the emission below 100 MeV fades away earlier than the 100-300 MeV radiation, roughly on the time scale of the fast component. The spectrum of the flare can be well fitted with a composite of a proton generated pi exp 0 spectrum and an electron bremsstrahlung component. The latter can be identified with the fast decaying component of the lightcurve.

Kanbach, G.↗
NASA NTRS1994

A loophole-free Bell's inequality experiment

The proof of Nature's nonlocality through Bell-type experiments is a topic of longstanding interest. Nevertheless, no experiments performed thus far have avoided the so-called 'detection loophole,' arising from low detector efficiencies and angular-correlation difficulties. In fact, most, if not all, of the systems employed to date can never close this loophole, even with perfect detectors. In addition, another loophole involving the non-rapid, non-random switching of various parameter settings exists in all past experiments. We discuss a proposal for a potentially loophole-free Bell's inequality experiment. The source of the EPR-correlated pairs consists of two simultaneously-pumped type-2 phase-matched nonlinear crystals and a polarizing beam splitter. The feasibility of such a scheme with current detector technology seems high, and will be discussed. We also present a single-crystal version, motivated by other work presented at this conference. In a separate experiment, we have measured the absolute detection efficiency and time response of four single-photon detectors. The highest observed efficiencies were 70.7 plus or minus 1.9 percent (at 633 nm, with a device from Rockwell International) and 76.4 plus or minus 2.3 percent (at 702 nm, with an EG&G counting module). Possible efficiencies as high as 90 percent were implied. The EG&G devices displayed sub-nanosecond time resolution.

Kwiat, Paul G.↗
NASA NTRS2001

The Ever Changing X-ray Sky: X-ray Transients Observed With BATSE

X-ray transients are typically sources in our own galaxy. They are called "transient" because they usually spend more time in quiescence than in outburst. These transients consist of a compact object and a "normal" star in a binary system. The compact objects in some of these systems are known to be neutron stars because they exhibit X-ray bursts or periodic pulsations, Other systems are believed to contain black holes based upon their outburst behavior and in some cases, optical measurements of their masses. The Burst and Transient Source Experiment (BATSE), one of 4 instruments on the Compton Gamma Ray Observatory, was an all-sky instrument sensitive to photons from about 20 keV to 2 MeV, designed primarily to detect gamma-ray bursts. Transient and persistent hard X-ray point sources were extracted from the data using the Earth occultation method to measure source intensities. In this method, the change in count rate in a BATSE detector was measured just before and just after a source location was occulted by the Earth. For long period pulsars (>1 second) Fourier transforms and epoch-folded searches were used to measure pulse frequency and pulsed flux. Using these methods, 3 black hole candidates and 6 X-ray pulsars were discovered with BATSE during its 9 years in orbit. BATSE provided unprecedented temporal coverage in the 20 keV - 2 MeV band, allowing detection of numerous new outbursts of X-ray transients. In this talk, I will describe the BATSE instrument, discuss methods we use to detect hard X-ray sources, and describe observations of X-ray transients.

Wilson-Hodge, Colleen A.↗
NASA NTRS1982

A PPM modulator and demodulator for the 2.5 bit/detected photon demonstration

In addition to performing the basic pulse position modulation and demodulation, the hardware described also indicates the occurrence of erasures and errors of various types. The analyzer portion of the circuit counts the number of pulses received in a word, demodulates a second input pulse (if one is received), indicates the occurrence of erasures, and detects PPM word errors. Word errors are detected by comparing the modulator input word to the corresponding demodulator output. These functions are provided mainly for testing and diagnosis of the system during the feasibility demonstration period.

Marshall, W. K.↗
DOE OSTI2024

Superconducting nanowire single-photon detector enhanced near-infrared II portable confocal microscopy for tissue imaging with indocyanine green

In this Letter a novel, to our knowledge, approach for near-infrared (NIR) fluorescence portable confocal microscopy is introduced, aiming to enhance fluorescence imaging of biological samples in the NIR-II window. By integrating a superconducting nanowire single-photon detector (SNSPD) into a confocal microscopy, we have significantly leveraged the detection efficiency of the NIR-II fluorescence signal from indocyanine green (ICG), an FDA-approved dye known for its NIR-II fluorescence capabilities. The SNSPD, characterized by its extremely low dark count rate and optimized NIR system detection efficiency, enables the excitation of ICG with 1 mW and the capture of low-light fluorescence signals from deep regions (up to 512 µm). Consequently, our technique was able to produce high-resolution images of bio samples with a superior signal-to-noise ratio, making a substantial advancement in the field of fluorescence microscopy and offering a promising opportunity for future clinical study.

Liu, Yifan (ORCID:0000000328877704)↗
DOE OSTI2025

On the Speed-up of Wave-like Dark Matter Searches with Entangled Qubits

Qubit-based sensing platforms offer promising new directions for wave-like dark matter searches. Recent proposals demonstrate that entangled qubits can achieve quadratic scaling of the signal in the number of qubits. In this work we expand on these proposals to analyze the bandwidth and scan rate performance of entangled qubit protocols across different error regimes. We find that the phase-based readout of entangled protocols preserves the search bandwidth independent of qubit number, in contrast to power-based detection schemes, thereby achieving a genuine scan-rate advantage. We derive coherence time and error rate requirements for qubit systems to realize this advantage. Applying our analysis to dark photon searches, we find that entangled states of approximately 100 qubits can become competitive with benchmark photon-counting cavity experiments for masses $\gtrsim 30{-}40~μ{\rm eV}$, provided sufficiently low error rates are achieved. The advantage increases at higher masses where cavity volume scaling becomes less favorable.

Bodas, Arushi [Fermilab; Chicago U.] (ORCID:000000↗
DOE OSTI2022

A stilbene–strontium iodide based radioxenon detection system for monitoring nuclear explosions

Atmospheric measurement of noble gases has been extensively used for monitoring clandestine nuclear weapon explosions for many years. The ratios of four xenon isotopes of interest ( 131 mXe, 133 mXe, 133 Xe, and 135 Xe) help in discriminating regular reactor operations from nuclear tests. A new coincidence-based detection system using stilbene and strontium iodide [SrI 2 (Eu)] for electron and photon detection respectively was developed at Oregon State University to address some of the challenges of the radioxenon systems deployed in the field such as memory effect, and poor energy resolution. Silicon photomultipliers (SiPMs) were used for sensing optical photons from all scintillation media. Real-time coincidence identification was achieved using the eight-channel digital pulse processor. The detection system was evaluated using lab check sources and Oregon State TRIGA reactor irradiated radioxenon samples. A 48-hour background coincidence spectrum was collected yielding a coincidence count rate and background rejection rate of 0.0174 ± 0.0003 counts per second (cps) and 98.9% respectively. The minimum detectable concentration (MDC) of the system was evaluated to be 0.11 ± 0.01, 0.13 ± 0.02, 0.20 ± 0.02, and 0.73 ± 0.08 for 131 mXe, 133 mXe, 133 Xe, and 135 Xe respectively. The memory effect of the detection system was found to be 0.069 ± 0.015%, which is almost a 70-fold reduction compared to traditional plastic scintillators. Here, the detection elements, custom-designed electronics, and the detector response to radioxenon are detailed in this work.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1994

X-ray emission from PSR 0355+54

We have obtained a 20 ks observation of PSR 0355+54 using the ROSAT position sensitive proportional counter (PSPC). The pulsar is detected with a count rate of 4.2(+/- 1.3) x 10(exp -3)/s above the background. While the approximately 70 source counts are insufficient for spectral fitting, we have derived source parameters for specific cases of power law as well as blackbody spectra. For a Crab-like spectrum (photon index alpha = 2) we find L(sub x)(0.1-2.4 keV) = 1.0 x 10(exp 32) ergs/s, somewhat higher than upper limits reported from Einstein observations but consistent with typical L(sub x) versus E-dot values for other pulsars. For blackbody emission, we derive a temperature upper limit of approximately 9.5 x 10(exp 5) K for emission from the entire neutron star surface, which is consistent with standard models for cooling of the neutron star interior given a characteristic age 10(exp 5.75) yr. No evidence is present for modulation at the 156 ms pulsar period, setting a weak upper limit of approximately 75% for the pulsed fraction of the X-ray signal.

Slane, Patrick↗
NASA NTRS1986

High-resolution pulse-counting array detectors for imaging and spectroscopy at ultraviolet wavelengths

The performance characteristics of multianode microchannel array (MAMA) detector systems which have formats as large as 256 x 1024 pixels and which have application to imaging and spectroscopy at UV wavelengths are evaluated. Sealed and open-structure MAMA detector tubes with opaque CsI photocathodes can determine the arrival time of the detected photon to an accuracy of 100 ns or better. Very large format MAMA detectors with CsI and Cs2Te photocathodes and active areas of 52 x 52 mm (2048 x 2048 pixels) will be used as the UV solar blind detectors for the NASA STIS.

Timothy, J. Gethyn↗