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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Sub-nanosecond time-resolved radiation measurement using x-ray focusing crystal spectrometers

Here, in this paper, we describe a technique using a crystal spectrometer, a silicon-diode detector, and a filtered photoconductive detector to monitor photon energies in the L-shell (0.9–1 keV) and K-shell regimes for nickel and copper hybrid X-pinch x-ray sources. The detectors, system cabling, and an 8 GHz digital oscilloscope in combination enable time resolution better than 200 ps for photoconductive detectors and 700 ps for silicon-diode detectors of the K- and L-shell radiation signals, respectively. We substantially improve the relative timing of signals obtained using the oscilloscope by using an x-ray streak camera with a crystal spectrometer to monitor the L-shell line spectra and, separately, the K-shell line spectra relative to the continuum burst to better than 17 ps time resolution. This combination of instruments enabled and validated a new method by which plasma conditions in nickel and copper X-pinches can be assessed immediately before and after the ~30 ps continuum x-ray burst produced by 370 kA hybrid X-pinches. In general, the method described here can be applied to observe otherwise highly filter-absorbed radiation in the presence of a broad spectrum of higher energy radiation by combining x-ray crystals and detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

High-sensitivity electronic Stark spectrometer featuring a laser-driven light source

We report developmental details of a high-sensitivity Stark absorption spectrometer featuring a laser-driven light source. The light source exhibits intensity fluctuations of ~0.3% over timescales ranging from 1 min to 12 h, minimal drift (≤0.1%/h), and very little 1/f noise at frequencies greater than 200 Hz, which are comparable to or better than an arc-driven light source. Additional features of the spectrometer include balanced detection with multiplex sampling, which yielded lower noise in A, and constant wavelength or wavenumber (energy) spectral bandpass modes. We achieve noise amplitudes of ~7 × 10 –4 and ~6 × 10 –6 in measurements of single A and ΔA spectra (with 92 data points) taking ~7 and ~19 min, respectively.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Monte Carlo toolkit for designing and validating step-range-filter spectrometer designs

Here, we present a Monte Carlo toolkit for validating step range filter (SRF) spectrometer designs. Geant4 is used to transport charged particles through the SRF filters to generate synthetic SRF data that include realistic CR-39 effects. Synthetic SRF spectra generated by this method inherently account for instrument response and allow for the quantification of SRF performance before shots. The usefulness of this toolkit is demonstrated through its application to a number of problems. A new broadband SRF for the ∼10 MeV wide 3He3He proton spectrum is validated, and an analysis method for analyzing 3He3He-p SRF data that accounts for instrument response is put forth. In addition, an SRF design for the compact recoil-proton spectrometer (CRS) on the Z-machine is validated. Finally, a new calibration technique for the DD-p SRF is proposed and validated.

Johnson, T. M. (ORCID:0000000193032949)↗
DOE OSTI2024

Designing ITER motional Stark effect line shift (MSE-LS) spectrometers

As a part of ITER beam aided diagnostics, the design of Motional Stark Effect (MSE) diagnostic observing the emission from the Balmer-α line is underway. The physics of Stark splitting shows that the Stark manifold is polarization dependent, and the energy splitting results in a line shift proportional to the electric field. Due to the challenges of maintaining the calibration of the plasma facing mirrors in ITER, the conventional MSE polarimetry measurement technique is replaced with a spectral approach that is deemed more favorable in the ITER environment. The MSE line shift (LS) diagnostic is designed to quantify the Lorentz electric field magnitude by measuring the Stark manifold using visible spectroscopy. In the presence of large magnetic fields and high energy heating beams of 1 MeV, the expected Stark splitting is much larger than in typical devices. The MSE-LS design has unique challenges requiring careful consideration and modeling of its viewing geometry and photon budget. The MSE-LS approach on ITER is promising but has stringent demands on the allowable errors for the statistical and systematic fitting uncertainties. In this study, a full system model and numerical simulations of data for each sightline are completed. For a range of optical transmission fractions, photon noise analysis is conducted to determine the statistical uncertainties. This provides guidance on the spectrometer throughput, dispersion at the detector, optics, and other design choices. A conceptual design of a high throughput spectrometer with a volume phase transmission grating is presented.

Instruments & Instrumentation↗
DOE OSTI2024

Development of improved higher-order correction for the NIF opacity spectrometer

X-ray opacity measurements on the National Ignition Facility (NIF) are in the process of reproducing earlier measurements from the Sandia Z Facility, in particular for oxygen and iron plasmas. These measurements have the potential to revise our understanding of the “solar problem” and of the hot degenerate Q class white dwarf structure by probing plasma conditions near the base of their convection zones. Accurate opacity measurements using soft x-ray Bragg crystal spectrometers require correction for higher-order diffraction effects. Extending prior work in this area [Dutra et al., Review of Scientific Instruments 93, 113527 (2022)], we have developed a new method to remove higher-order spectral components from NIF opacity spectrometer data. Furthermore, by modeling absorption and backlighting continuum spectra and subtracting the second- and third-order components from the measured data, we are able to perform this correction while avoiding imprinting first-order model line features onto the data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Nonlinear light-output calibration of the oxygenated xylene scintillators used in OMEGA neutron time-of-flight spectrometers

Neutron time-of-flight (nTOF) spectrometers are essential instruments for measuring and evaluating the performance of inertial confinement fusion implosions. The neutron spectrometers utilized for the OMEGA laser include two liquid-based scintillators, each consisting of a large volume filled with xylene that is coupled to four photomultiplier tubes. Analysis of the signal from these detectors requires detailed knowledge of the scintillator’s light output, which is needed to fit the nTOF spectrum, from which the neutron energy spectrum is informed. The light output is nonlinearly proportional to the neutron energy, which, in turn, affects the interpretation of the neutron energy spectrum from a TOF signal. A recent campaign on OMEGA was performed to calibrate the xylene detectors and infer the shape of the light-output curve. The campaign utilized materials with increasing Z placed in the OMEGA target chamber to initiate scattering events with the 14 MeV fusion neutrons. This process leads to the production of backscatter neutrons of varying energies that appear as peaks in the nTOF data. Simulations using a neutron transport code were combined with the measured deuterium–tritium neutron yields to calculate the expected backscattered neutron yields from the well-known scattering cross sections of each material. Furthermore, the neutron-energy dependent light output of the scintillator inferred from the experiment is compared to the light-output curve simulated with a neutron transport code for the following neutron energies: 1.5, 2.5, 6, and 14 MeV.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

X-ray sources for in situ wavelength calibration of x-ray imaging crystal spectrometers

X-ray sources for a range of wavelengths are being considered for in situ calibration of X-ray Imaging Crystal Spectrometers (XICSs) and for monitoring line shifts due to changes in the crystal temperature, which can vary during experimental operation over a day [A. Ince-Cushman et al., Rev. Sci. Instrum. 79, 10E302 (2008), L. Delgado-Aparicio et al., Plasma Phys. Control. Fusion 55, 125011 (2013)]. Such crystal temperature dependent shifts, if not accounted for, could be erroneously interpreted as Doppler shifts leading to errors in plasma flow-velocity measurements. The x-ray sources encompass characteristic x-ray lines falling within the wavelength range of 0.9–4.0 Å, relevant for the XICSs on present and future fusion devices. Several technological challenges associated with the development of x-ray sources for in situ calibration are identified and are being addressed in the design of multiple x-ray tubes, which will be installed inside the spectrometer housing of the XICS for the JT-60SA tokamak. These x-ray sources will be especially useful for in situ calibration between plasma discharges. Here, in this paper, laboratory experiments are described that were conducted with a Cu x-ray source, a heated quartz (102) crystal, and a pixelated Pilatus detector to measure the temperature dependent shifts of the Cu Kα 1 and Kα 2 lines at 1.5405 and 1.5443 Å, respectively, and to evaluate the 2d-lattice constant for the Bragg reflecting crystal planes as a function of temperature, which, in the case of in situ wavelength calibration, would have to be used for numerical analysis of the x-ray spectra from the plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Optical design and efficiency measurement of an extreme ultraviolet high-resolution spectrometer for unresolved transition array research

Understanding the structures of the unresolved transition array (UTA) observed in extreme ultraviolet (EUV) spectra from many-electron atoms is crucial for various applications, including fusion science and nanolithography. Here, to measure the fine structure of the UTA from tungsten and tin at around 5 and 13.5 nm at the Tokyo electron beam ion trap, we developed a high-resolution EUV spectrometer. The designed spectrometer achieves a resolving power of λ/dλ > 5000 at 5 and 13.5 nm. The fabricated large-area grating was experimentally examined at beamline BL5B of the UVSOR synchrotron facility to evaluate the diffraction efficiencies and their variation across the ruled area. The measured diffraction efficiencies are 0.65% ± 0.07% at 5 nm (second order) and 7.9% ± 0.2% at 13.5 nm (first order). The variation in the diffraction efficiency across the ruled area is 2.2%, 13.6%, and 10.0% in zeroth, first, and second order diffractions, respectively. The discrepancies in diffraction efficiencies between the experiments and the calculations were 5.2%, 29%, and 35% for the zeroth, first, and second diffraction orders, respectively.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Calibration of a broadband x-ray crystal spectrometer using a continuum x-ray source and photon-counting detectors

We report measurements of sensitivity of a broadband (≃20–30 keV) x-ray crystal spectrometer using a bremsstrahlung continuum x-ray source and several detectors, including an energy-discriminating photon-counting point detector (Si drift diode, Amptek Inc.), imaging hybrid photon-counting detectors (Eiger2-Si and Eiger2-CdTe, DECTRIS Ltd.), and image plates (SR type). Sensitivity is defined as a ratio of the crystal-reflected energy-position-dispersed spectrum measured by a given detector to the incident non-dispersed spectrum measured using the energy-discriminating point detector. The sensitivity derived from data measured exclusively by the point detector is considered detector-independent and serves as a reference. The sensitivities derived from data collected with the hybrid photon-counting detectors were matched to the reference using a scale factor of 1.05. The image plate-derived sensitivities required a scale factor of 1.16 to match the reference. Furthermore, the resulting mismatch in the shapes of all measured scaled sensitivities in the range of the spectrometer was ≲±10%, while the mismatch between the shapes of the sensitivities corresponding to the Si-based detectors was ≲±2.5%.

Crystal optics↗
DOE OSTI2021

Design of flexible proton beam imaging energy spectrometers (PROBIES)

A simple repeating step-filtered structure has been designed and deployed for the detection of MeV-energy proton beams produced from high-intensity short-pulse laser-driven experiments. Due to the diagnostic's ability to recover energy-resolved images of proton beams, it is called the proton beam imager and energy spectrometer (or PROBIES). The flexible design has two useful applications. First, it can be fielded in a configuration with a scintillator and imaging setup in order to collect proton beam information in high-repetition rate experiments. Here we show a configuration that collects the equivalent of a nine-film radiochromic film (RCF) stack, and a technique for using a neural network (NN) to rapidly analyze the images on millisecond time-scales. Second, when using RCF stacks as the detector, the energy resolution capability is greatly increased compared to traditional RCF stacks, while simultaneously reducing the total number of films required to make each measurement. We demonstrate a configuration that provides up to 90 spatially- and energy-resolved datapoints using just ten films. Both designs presented here can be easily customized for anticipated experimental outputs and manufactured at low cost. Such designs allow for rapid prototyping using modern high-accuracy 3D printers or on-demand computer numerical control machining to reduce the reliance on time-consuming film media, analysis, or bulky electro-magnetically dispersing spectrometers. The analysis of data is discussed and a methodology for constructing a NN that is capable of rapidly analyzing data on-the-fly with greater than 95% accuracy is presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Observations of xenon spectra on the EAST x-ray crystal spectrometer for high-temperature plasma diagnostics

The Xe 44+ 2.7203 Å line, which has been proposed as one of the diagnostic lines for the x-ray imaging crystal spectrometer on ITER, is observed on the EAST tokamak together with its several satellite lines. The observations are made under high electron temperature (T e ) conditions (core T e > 5 keV). Most of the observed xenon lines are identified by comparing the experiment results with the atomic simulation results. The first ion temperature measurements made by the xenon spectra on EAST are also reported in this article. These xenon spectra observations contribute to the justification for using xenon as the diagnostic impurity in x-ray crystal spectrometers in future reactor-scale high-temperature plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Proton reconstruction with the CMS-TOTEM Precision Proton Spectrometer

The Precision Proton Spectrometer (PPS) of the CMS and TOTEM experiments collected 107.7 fb$^{-1}$ in proton-proton (pp) collisions at the LHC at 13 TeV (Run 2). This paper describes the key features of the PPS alignment and optics calibrations, the proton reconstruction procedure, as well as the detector efficiency and the performance of the PPS simulation. The reconstruction and simulation are validated using a sample of (semi)exclusive dilepton events. The performance of PPS has proven the feasibility of continuously operating a near-beam proton spectrometer at a high luminosity hadron collider.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

First full Dalitz plot measurement in neutron 𝛽 decay using the Nab spectrometer and implications for new physics

Precision measurements of observables in neutron 𝛽 decay are used to test the standard model description of the weak interaction and search for evidence of new physics. The Nab experiment at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source was constructed to measure correlations in neutron decay by utilizing an asymmetric spectrometer and novel detection system to accurately reconstruct the proton momentum and electron energy for each 𝛽 decay. This work describes the detection of neutron 𝛽-decay products in the Nab spectrometer and presents the first full Dalitz plot representation of the phase space of neutron 𝛽 decay for all electrons >100 keV. In addition, new constraints are placed on a possible excited neutron state, hypothesized to explain the disagreement between the appearance and disappearance neutron lifetime techniques.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Deciphering Nb 98 β decay with the Modular Total Absorption Spectrometer at ORNL

An assessment done under the auspices of the Organization for Economic Co-operation and Developement Nuclear Energy Agency (OECD-NEA) in 2007 suggested that the β decays of many abundantly produced fission products in nuclear reactors may be incomplete. In this assessment, the fission product 98 Nb was assigned the highest priority for study by total absorption spectroscopy due to its large cumulative fission branching fraction and because the β-decay data from several experiments are discrepant. To obtain the complete β-decay feeding pattern of 98 Nb and determine the impact on the average γ energy per 98 Nb β decay and v¯e emission calculations. The complete 98 Nb β-decay feeding pattern includes ground-state to ground-state β feeding and direct β feeding to the 0 + first-excited state (both have no associated γ rays), and the ground-state to excited-state β transitions followed by γ transitions to the ground state of the daughter nucleus, 98 Mo. The complete β-decay intensities of 98 Nb were measured with the Modular Total Absorption Spectrometer at Oak Ridge National Laboratory (ORNL). Here, the 98 Nb was produced by the β decay of mass 98 fission fragments at ORNL's On-Line Test Facility (OLTF) using proton-induced fission of 238 U. We find that changes to the current ENSDF assessment of 98 Nb β-decay intensity are required. We report improved uncertainties for the β-decay feeding values and report new β feedings to high-energy levels in 98 Mo. A more complete 98 Nb β-feeding pattern with improved accuracy and precision is offered. The impacts of the measured changes to the 98 Nb β-feeding pattern on both reactor decay heat calculations and predicted detection rates of reactor v¯e are presented. The Modular Total Absorption Spectrometer measurements of 98 Nb demonstrate the importance of reexamining and remeasuring complex β-decaying fission products with total absorption spectroscopy, including nuclei very near β stability.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Systematic uncertainties in the measurement of the neutron lifetime using the Lunar Prospector neutron spectrometer

The lifetime of free neutrons measured in the laboratory has a longstanding disparity of ≈9 s. A space-based technique has recently been proposed to independently measure the neutron lifetime using interactions between the galactic cosmic rays and a low atmosphere planetary body. This technique has not produced competitive results yet due to constraints of nonoptimized data that contain large systematic errors. We use data from the neutron spectrometer on-board NASA's Lunar Prospector, and study two large systematics in the measurement of neutron lifetime: the lunar subsurface temperature and the lunar surface composition. We use the HeCd and HeSn neutron spectrometer data when the spacecraft was in a highly elliptical orbit during the orbit insertion period. We report the neutron lifetime using four different models that each have different choices of surface temperature and composition. The 5° [Prettyman et al ., J. Geophys. Res.: Planets 111, 2005JE002656 (2006)] and 2° [Wilson et al., Phys. Rev. C 104, 045501 (2021)] rebinned maps result in 777.6±11.7 s and 739.6±10.8 s, respectively. For the 20° map (Prettyman et al., 2006), constant equatorial and a latitude-dependent temperature model result in 738.6±10.8 s and 767.3±11.2 s, respectively. Increasing the complexities of the models accounting for the systematic effects increase the measured lifetime. However, the reported measurements are not competitive with the laboratory results due to large unaccounted systematics resulting from nonoptimized measurements and modeling assumptions. This work serves as a study of systematic uncertainties for future neutron lifetime measurements using the space-based technique. We estimate the effect on the lifetime from the choice of temperature model to be to be 28.7 ±15.5 s, and choice of compositional map (for 20° and 5° maps) to be 10.3 ±12.2 s.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

IRIXS Spectrograph: an ultra high-resolution spectrometer for tender RIXS

The IRIXS Spectrograph represents a new design of an ultra-high-resolution resonant inelastic X-ray scattering (RIXS) spectrometer that operates at the Ru L 3 -edge (2840 eV). First proposed in the field of hard X-rays by Shvyd'ko [(2015), Phys. Rev. A, 91, 053817], the X-ray spectrograph uses a combination of laterally graded multilayer mirrors and collimating/dispersing Ge(111) crystals optics in a novel spectral imaging approach to overcome the energy resolution limitation of a traditional Rowland-type spectrometer [Gretarsson et al. (2020), J. Synchrotron Rad. 27, 538–544]. In combination with a dispersionless nested four-bounce high-resolution monochromator design that utilizes Si(111) and Al 2 O 3 (110) crystals, an overall energy resolution better than 35 meV full width at half-maximum has been achieved at the Ru L 3 -edge, in excellent agreement with ray-tracing simulations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

The High Rigidity Spectrometer at the FRIB: Magnet Development Status

This paper presents the 2025 progress of the High Rigidity Spectrometer (HRS) project at the Facility for Rare Isotope Beams (FRIB). We report on the construction and testing of the first-article HRS-High Transmission BeamLine (HTBL) magnets. An HTBL dipole magnet has successfully completed cold testing, achieving full magnetic performance without quenching, and is now ready for field mapping at FRIBs offline test bench. HTBL quadrupole triplet coils have been fabricated and tested, with all coils reaching their design currents, some following initial training quenches. Furthermore, the preliminary design of the large-scale, large-aperture SPectrometer Section (SPS) magnets has progressed to determine the baseline of the downstream HRS-SPS subproject in 2025. This includes the introduction of novel magnet designs, such as the sweeper dipole magnet, the sector dipole magnet, and iron-free coil-dominated quadrupole magnets, representing a significant scale breakthrough and a first for FRIB.

Choi, Yoonhyuck↗
DOE OSTI2026

Data-Driven Optimization of Pixelated CdZnTe Spectrometers for Uranium Enrichment Assay

Here, in recent work [Vavrek et al. (2025)], we developed the performance optimization framework spectre-ml for gamma spectrometers with variable performance across many readout channels. The framework uses non-negative matrix factorization (NMF) and clustering to learn groups of similarly-performing channels and sweep through various learned channel combinations to optimize the performance tradeoff of including worse-performing channels for better total efficiency. In this work, we integrate the pyGEM uranium enrichment assay code with our spectre-ml framework, and show that the U-235 enrichment relative uncertainty can be directly used as an optimization target. We find that this optimization reduces relative uncertainties after a 30 -minute measurement by an average of 20%, as tested on six different H3D M400 CdZnTe spectrometers, which can significantly improve uranium non-destructive assay measurement times in nuclear safeguards contexts. Additionally, this work demonstrates that the spect re-ml optimization framework can accommodate arbitrary end-user spectroscopic analysis code and performance metrics, enabling future optimizations for complex Pu spectra.

Gamma-ray detection↗