Stereo digital image correlation with improved depth of field using tilt-shift photography
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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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Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies
For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising heating method even for the envisaged application in a fusion power plant. Wendelstein 7-X (W7-X) is equipped with a steady-state capable ECRH system, operating at 140 GHz, which corresponds to the 2nd cyclotron harmonic of the electrons at a magnetic field of 2.5 T. Ten gyrotrons are operational and already delivered 7 MW to W7-X plasmas. Combined with pellet injection, the highest triple product (0.68 × 10 20 keV m –3 s), observed up to now in stellarators, was achieved. For the first time, W7-X plasmas were sustained by 2nd harmonic O-mode heating, approaching the collisionality regime for which W7-X was optimized. Power deposition scans did not show any indication of electron temperature profile resilience. In low-density, low-power plasmas a compensation of the bootstrap current with electron-cyclotron current drive (ECCD) was demonstrated. Furthermore, sufficiently strong ECCD close to the plasma centre produced periodic internal plasma-crash events, which coincide with the appearance of low order rationals of the rotational transform.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Cosmic-muon flux and annual modulation in Borexino at 3800 m water-equivalent depth
We have measured the muon flux at the underground Gran Sasso National Laboratory (3800 m w.e.) to be (3.41±0.01)⋅10{sup −4}m{sup −2}s{sup −1} using four years of Borexino data. A modulation of this signal is observed with a period of (366±3) days and a relative amplitude of (1.29±0.07)%. The measured phase is (179±6) days, corresponding to a maximum on the 28{sup th} of June. Using the most complete atmospheric data models available, muon rate fluctuations are shown to be positively correlated with atmospheric temperature, with an effective coefficient α{sub T} = 0.93±0.04. This result represents the most precise study of the muon flux modulation for this site and is in good agreement with expectations.
79 ASTRONOMY AND ASTROPHYSICS↗
Cosmogenic Backgrounds in Borexino at 3800 m water-equivalent depth
The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratories, is in a unique position to study muon-induced backgrounds in an organic liquid scintillator. In this study, a large sample of cosmic muons is identified and tracked by a muon veto detector external to the liquid scintillator, and by the specific light patterns observed when muons cross the scintillator volume. The yield of muon-induced neutrons is found to be Y{sub n} = (3.10±0.11)·10{sup −4} n/(μ·(g/cm{sup 2})). The distance profile between the parent muon track and the neutron capture point has the average value λ = (81.5±2.7) cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for {sup 12}N, {sup 12}B, {sup 8}He, {sup 9}C, {sup 9}Li, {sup 8}B, {sup 6}He, {sup 8}Li, {sup 11}Be, {sup 10}C and {sup 11}C. All results are compared with Monte Carlo simulation predictions using the FLUKA and GEANT4 packages. General agreement between data and simulation is observed for the cosmogenic production yields with a few exceptions, the most prominent case being {sup 11}C yield for which both codes return about 50% lower values. The predicted μ-n distance profile and the neutron multiplicity distribution are found to be overall consistent with data.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Radio measurements of the energy and the depth of the shower maximum of cosmic-ray air showers by Tunka-Rex
We reconstructed the energy and the position of the shower maximum of air showers with energies E ∼> 100 PeV applying a method using radio measurements performed with Tunka-Rex. An event-to-event comparison to air-Cherenkov measurements of the same air showers with the Tunka-133 photomultiplier array confirms that the radio reconstruction works reliably. The Tunka-Rex reconstruction methods and absolute scales have been tuned on CoREAS simulations and yield energy and X{sub max} values consistent with the Tunka-133 measurements. The results of two independent measurement seasons agree within statistical uncertainties, which gives additional confidence in the radio reconstruction. The energy precision of Tunka-Rex is comparable to the Tunka-133 precision of 15%, and exhibits a 20% uncertainty on the absolute scale dominated by the amplitude calibration of the antennas. For X{sub max}, this is the first direct experimental correlation of radio measurements with a different, established method. At the moment, the X{sub max} resolution of Tunka-Rex is approximately 40 g/cm{sup 2}. This resolution can probably be improved by deploying additional antennas and by further development of the reconstruction methods, since the present analysis does not yet reveal any principle limitations.
79 ASTRONOMY AND ASTROPHYSICS↗
In-depth evaluation of 252 Cf absolute calibration by passive neutron correlation counting method
252 Cf neutron sources are particularly convenient, and therefore widely used, to characterize and calibrate many kinds of neutron detectors for both scientific and technological applications. An emerging interest is the use of 252 Cf to calibrate neutron correlation counters for the verification and assay of Pu-items as part of the international effort to safeguard nuclear materials. Passive neutron correlation counting (PNCC) methods, combined with knowledge of the fission neutron multiplicity distribution, can be used as an absolute technique to determine the neutron emission rate of 252 Cf sources. This means that common equipment used by the safeguards community can, in principle, be used to self-certify, to high accuracy, the strength of physically small 252 Cf sealed sources for use in calibration. This is the first step in using 252Cf in place of extensive Pu reference materials for experimental calibration by the safeguards community. The theoretical foundation is already clear but the present work presents the first systematic attempt at demonstrating the practical utility of the concept across a variety of typical instruments. We compare four emission rate estimators for four detector configurations on a common source previously certified by the MnSO 4 -bath technique. We find that the estimator based on the singles to doubles rate ratio provides consistent and precise results across all of the instruments and that these agree with the MnSO 4 -bath technique within combined uncertainties. This success suggests that the absolute PNCC method could become a technically defensible and commonly used, method capable of sub 1% accuracy for routine calibration work.
74 ATOMIC AND MOLECULAR PHYSICS↗
Hydrogen reionization ends by z = 5.3: Lyman-α optical depth measured by the XQR-30 sample
ABSTRACT The presence of excess scatter in the Ly-α forest at z ∼ 5.5, together with the existence of sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end of hydrogen reionization. However, low data quality and systematic uncertainties complicate the use of Ly-α transmission as a precision probe of reionization’s end stages. In this paper, we assemble a sample of 67 quasar sightlines at z > 5.5 with high signal-to-noise ratios of >10 per ≤15 km s−1 spectral pixel, relying largely on the new XQR-30 quasar sample. XQR-30 is a large program on VLT/X-Shooter which obtained deep (SNR > 20 per pixel) spectra of 30 quasars at z > 5.7. We carefully account for systematics in continuum reconstruction, instrumentation, and contamination by damped Ly-α systems. We present improved measurements of the mean Ly-α transmission over 4.9 < z < 6.1. Using all known systematics in a forward modelling analysis, we find excellent agreement between the observed Ly-α transmission distributions and the homogeneous-UVB simulations Sherwood and Nyx up to z ≤ 5.2 (<1σ), and mild tension (∼2.5σ) at z = 5.3. Homogeneous UVB models are ruled out by excess Ly-α transmission scatter at z ≥ 5.4 with high confidence (>3.5σ). Our results indicate that reionization-related fluctuations, whether in the UVB, residual neutral hydrogen fraction, and/or IGM temperature, persist in the intergalactic medium until at least z = 5.3 (t = 1.1 Gyr after the big bang). This is further evidence for a late end to reionization.
79 ASTRONOMY AND ASTROPHYSICS↗
Depth-of-field effects in wiggler radiation sources: Geometrical versus wave optics
N/A
Walker, Richard P.↗
Proposal for a three-dimensional magnetic measurement method with nanometer-scale depth resolution
Not Available
Negi, Devendra↗
Radio measurements of the depth of air-shower maximum at the Pierre Auger Observatory
The (AERA), part of the Pierre Auger Observatory, is currently the largest array of radio antenna stations deployed for the detection of cosmic rays, spanning an area of 17 km 2 with 153 radio stations. It detects the radio emission of extensive air showers produced by cosmic rays in the 30–80 MHz band. Here, we report the AERA measurements of the ( X max ), a probe for mass composition, at cosmic-ray energies between 10 17.5 and 10 18.8 eV , which show agreement with earlier measurements with the fluorescence technique at the Pierre Auger Observatory. We show advancements in the method for radio X max reconstruction by comparison to dedicated sets of / air-shower simulations, including steps of reconstruction-bias identification and correction, which is of particular importance for irregular or sparse radio arrays. Using the largest set of radio air-shower measurements to date, we show the radio X max resolution as a function of energy, reaching a resolution better than 15 g cm − 2 at the highest energies, demonstrating that radio X max measurements are competitive with the established high-precision fluorescence technique. In addition, we developed a procedure for performing an extensive data-driven study of systematic uncertainties, including the effects of acceptance bias, reconstruction bias, and the investigation of possible residual biases. These results have been cross-checked with air showers measured independently with both the radio and fluorescence techniques, a setup unique to the Pierre Auger Observatory. Published by the American Physical Society 2024
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Muons in air showers at the Pierre Auger Observatory: Measurement of atmospheric production depth
Abstract Not Provided
Aab, Alexander↗