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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The invisible black widow PSR J1720−0534: implications for the electron density towards the North Polar Spur

Radio emission from pulsars can be used to map out their distances through dispersion measure (DM), which quantifies the amount of radio pulse dispersion. However, this method relies on accurately modelling the free electron density in the line of sight. Here, we present a detailed study of the multiwavelength emission from PSR J1720−0534, a black widow compact binary millisecond pulsar discovered in 2021, which the latest electron density model of the Galaxy places at only 191 pc. We obtained and analysed deep multiwavelength observations in the γ-ray ( Fermi -Large Area Telescope, 2008–2022), optical (Las Cumbres Observatory, 2.7 h), near-infrared (Nordic Optical Telescope, 3.5 h), and X-ray ( Swift -X-Ray Telescope, 10 ks) bands. We found no significant detection of γ-ray, optical, near-infrared, or X-ray counterparts around the radio-timing position of PSR J1720−0534, which we thus nickname ‘the invisible black widow’. Employing the most constraining near-infrared limit ( J > 23.4 mag), we established a lower limit on the source distance, d > 1.1 kpc, assuming conservative properties for the black widow companion star. This distance lower limit differs drastically (by a factor of more than 5) from the Yao et al. DM distance estimate. We attribute this difference to the inclusion in the Yao et al. model of a large and dense component towards the North Polar Spur. Considering our results and recent parallax distances to other pulsars in this direction, we argue that such a local and large component in the electron density model of the Galaxy is unnecessary.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Birefringence tests of gravity with multimessenger binaries

Extensions to General Relativity (GR) allow the polarization of gravitational waves (GW) from astrophysical sources to suffer from amplitude and velocity birefringence, which respectively induce changes in the ellipticity and orientation of the polarization tensor. Here, we introduce a multi-messenger approach to test this polarization behavior of GWs during their cosmological propagation using binary sources, for which the initial polarization is determined by the inclination and orientation angles of the orbital angular momentum vector with respect to the line of sight. In particular, we use spatially resolved radio imaging of the jet from a binary neutron star (BNS) merger to constrain the orientation angle and hence the emitted polarization orientation of the GW signal at the site of the merger, and compare to that observed on Earth by GW detectors. For GW170817, using past measurements of the inclination angle, we constrain the deviation from GR due to amplitude birefringence to κ A = $-0.12^{+0.60}_ {-0.61}$, while the velocity birefringence parameter κ V remains unconstrained. The inability to constrain κ V is due to the low amplitude of GW170817 in the Virgo detector, and measurements of the polarization orientation require information from a combination of multiple detectors with different alignments. For this reason, we also mock future BNS mergers with resolved afterglow proper motion and project that κ V could be constrained to a precision of 5 rad (corresponding to an angular shift of the GW polarization of δ φV ≈ 0.2 rad for a BNS at 100 Mpc) by a future network of third-generation ground-based GW detectors such as Cosmic Explorer and the radio High Sensitivity Array. Crucially, this velocity birefringence effect cannot be constrained with dark binary mergers as it requires polarization information at the emission time, which can be provided only by electromagnetic emission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Cavity Qualification and Production Update for SNS-PPU Cryomodules at Jefferson Lab

The Proton Power Upgrade (PPU) project at Oak Ridge National Lab’s Spallation Neutron Source (SNS) currently being constructed will double the proton beam power capability from 1.4 to 2.8 MW by adding seven cryomodules, each containing four six-cell high-beta (β = 0.81) superconducting radio frequency cavities. Research Instruments, located in Germany, built and processed the cavities at the vendor site, including electropolishing as the final active chemistry step. Twenty-eight cavities for seven cryomodules and an additional four cavities for a spare cryomodules were delivered to Jefferson Lab and first qualification tests were completed on all cavities as received from the vendor. The performance largely exceeded the requirements on quality factor and accelerating gradient. Here we present the status of initial cavity qualification tests, rework on unqualified cavities and final cavity qualification with helium vessel prior to installation in cryomodules. In addition, an update on cryomodule production is presented.

Dhakal, P.↗
DOE OSTI2022

Status of SNS Proton Power Upgrade SRF Cavities Production Qualification

The Pro­ton Power Up­grade pro­ject at Oak Ridge Na­tional Lab’s Spal­la­tion Neu­tron Source (SNS PPU) cur­rently being con­structed will dou­ble the pro­ton beam power from 1.4 to 2.8 MW by adding 7 ad­di­tional cry­omod­ules, each con­tains four six-cell high beta (\beta = 0.81) su­per­con­duct­ing radio fre­quency cav­i­ties. The cav­i­ties were built by Re­search In­stru­ments, Ger­many, with all the cav­ity pro­cess­ing done at the ven­dor site, in­clud­ing elec­trop­o­l­ish­ing as the final ac­tive chem­istry step. All 28 cav­i­ties needed for 7 cry­omod­ules were de­liv­ered to Jef­fer­son Lab, ready to be tested. The cryo­genic RF qual­i­fi­ca­tions and he­lium ves­sel weld­ing were done at Jef­fer­son Lab. The per­for­mance largely ex­ceed the re­quire­ments, and greatly ex­ceeded the per­for­mance of the orig­i­nal SNS cav­ity pro­duc­tion se­ries. Here, we pre­sent the sum­mary of RF test on pro­duc­tion cav­i­ties to this date.

Dhakal, P.↗
DOE OSTI2021

Status of SNS Proton Power Upgrade SRF Cavities Production Qualification

The Pro­ton Power Up­grade pro­ject at Oak Ridge Na­tional Lab’s Spal­la­tion Neu­tron Source (SNS PPU) cur­rently being con­structed will dou­ble the pro­ton beam power from 1.4 to 2.8 MW by adding 7 ad­di­tional cry­omod­ules, each con­tains four six-cell high beta (\beta = 0.81) su­per­con­duct­ing radio fre­quency cav­i­ties. The cav­i­ties were built by Re­search In­stru­ments, Ger­many, with all the cav­ity pro­cess­ing done at the ven­dor site, in­clud­ing elec­trop­o­l­ish­ing as the final ac­tive chem­istry step. All 28 cav­i­ties needed for 7 cry­omod­ules were de­liv­ered to Jef­fer­son Lab, ready to be tested. The cryo­genic RF qual­i­fi­ca­tions and he­lium ves­sel weld­ing were done at Jef­fer­son Lab. The per­for­mance largely ex­ceed the re­quire­ments, and greatly ex­ceeded the per­for­mance of the orig­i­nal SNS cav­ity pro­duc­tion se­ries. Here, we pre­sent the sum­mary of RF test on pro­duc­tion cav­i­ties to this date.

Dhakal, P.↗
DOE OSTI2020

Discovery of a Gamma-Ray Black Widow Pulsar by GPU-accelerated Einstein@Home

We report the discovery of 1.97 ms period gamma-ray pulsations from the 75 minute orbital-period binary pulsar now named PSR J1653-0158. The associated Fermi Large Area Telescope gamma-ray source 4FGL J1653.6-0158 has long been expected to harbor a binary millisecond pulsar. Despite the pulsar-like gamma-ray spectrum and candidate optical/X-ray associations—whose periodic brightness modulations suggested an orbit—no radio pulsations had been found in many searches. The pulsar was discovered by directly searching the gamma-ray data using the GPU-accelerated Einstein@Home distributed volunteer computing system. The multidimensional parameter space was bounded by positional and orbital constraints obtained from the optical counterpart. More sensitive analyses of archival and new radio data using knowledge of the pulsar timing solution yield very stringent upper limits on radio emission. Any radio emission is thus either exceptionally weak, or eclipsed for a large fraction of the time. The pulsar has one of the three lowest inferred surface magnetic-field strengths of any known pulsar with B surf ≈ 4 × 10 7 G. The resulting mass function, combined with models of the companion star's optical light curve and spectra, suggests a pulsar mass gsim 2 M ⊙ . The companion is lightweight with mass ~0.01 M ⊙ , and the orbital period is the shortest known for any rotation-powered binary pulsar. This discovery demonstrates the Fermi Large Area Telescope's potential to discover extreme pulsars that would otherwise remain undetected.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

A new probe of μ Hz gravitational waves with FRB timing

We propose Fast Radio Burst (FRB) timing, which uses the precision measurements of the arrival time differences of repeated FRB signals along multiple sightlines, as a new probe of gravitational waves (GWs) around nHz to μ Hz frequencies, with the highest frequency limited by FRB repeating period. The anticipated experiment requires a sightline separation of tens of AU, achieved by sending radio telescopes to space. We find the signal of arrival time difference induced by GWs depends only on the local GWs in the solar system and we can correlate the measurements from different FRB sources or the same source with different repeaters, which leads to a better sensitivity with a larger number of FRB events detected. The projected sensitivity shows this method is a competitive probe in the nHz to μ Hz frequency range. It can fill the ‘ μ Hz gap’ between pulsar timing arrays and Laser Interferometer Space Antenna (LISA) and is complementary to other proposals of GW detection in this frequency band.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Off-line commissioning of the St. Benedict radiofrequency quadrupole cooler-buncher

The St. Benedict ion trapping system, which aims to measure the β - v angular correlation parameter in superallowed-mixed mirror transitions, is under construction at the University of Notre Dame. These measurements will provide much-needed data to improve the accuracy of the V ud element of the CKM matrix. One of the major components of this system is the radio frequency quadrupole cooler-buncher, which is necessary to create low-emittance ion bunches for injection into the measurement Paul trap. The off-line commissioning of the cooler-buncher, using a potassium ion source, determined that the device could produce cooled ion bunches characterized by a 50-ns full-width-half-maximum time width at its exit. The commissioning results also determined the trapping efficiency to be 93(1)% and the trapping half-life to be 20.0(5) s.

Paul trap↗
DOE OSTI2024

O Corona, where art thou? eROSITA’s view of UV-optical-IR variability-selected massive black holes in low-mass galaxies

Finding massive black holes (MBHs,M BH ≈ 10 4 –10 7 M ⊙ ) in the nuclei of low-mass galaxies $\left( {{M_*}\mathop {\mathop < \limits_ }\limits_ {{10}^{10}}{M_ \odot }} \right)$ is crucial to constrain seeding and growth of black holes over cosmic time, but it is particularly challenging due to their low accretion luminosities. Variability selection via long-term photometric ultraviolet, optical, or infrared (UVOIR) light curves has proved effective and identifies lower-Eddington ratios compared to broad and narrow optical spectral lines searches. In the inefficient accretion regime, X-ray and radio searches are effective, but they have been limited to small samples. Therefore, differences between selection techniques have remained uncertain. Here, we present the first large systematic investigation of the X-ray properties of a sample of known MBH candidates in dwarf galaxies. We extracted X-ray photometry and spectra of a sample of ~200 UVOIR variability-selected MBHs and significantly detected 17 of them in the deepest available SRG/eROSITA image, of which four are newly discovered X-ray sources and two are new secure MBHs. This implies that tens to hundreds of LSST MBHs will have SRG/eROSITA counterparts, depending on the seeding model adopted. Surprisingly, the stacked X-ray images of the many non-detected MBHs are incompatible with standard disk-corona relations, typical of active galactic nuclei, inferred from both the optical and radio fluxes. They are instead compatible with the X-ray emission predicted for normal galaxies. After careful consideration of potential biases, we identified that this X-ray weakness needs a physical origin. A possibility is that a canonical X-ray corona might be lacking in the majority of this population of UVOIR-variability selected low-mass galaxies or that unusual accretion modes and spectral energy distributions are in place for MBHs in dwarf galaxies. This result reveals the potential for severe biases in occupation fractions derived from data from only one waveband combined with SEDs and scaling relations of more massive black holes and galaxies.

Astronomy & Astrophysics↗
DOE OSTI2023

Long-term multi-wavelength study of 1ES 0647+250

The BL Lac object 1ES 0647+250 is one of the few distant γ-ray emitting blazars detected at very high energies (VHEs; &100 GeV) during a non-flaring state. It was detected with the MAGIC telescopes during a period of low activity in the years 2009-2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with the highest VHE flux in the last epoch. An extensive multi-instrument data set was collected as part of several coordinated observing campaigns over these years. We aim to characterise the long-term multi-band flux variability of 1ES 0647+250, as well as its broadband spectral energy distribution (SED) during four distinct activity states selected in four different epochs, in order to constrain the physical parameters of the blazar emission region under certain assumptions. We evaluated the variability and correlation of the emission in the different energy bands with the fractional variability and the Z transformed discrete correlation function, as well as its spectral evolution in X-rays and γ rays. Owing to the controversy in the redshift measurements of 1ES 0647+250 reported in the literature, we also estimated its distance in an indirect manner through a comparison of the GeV and TeV spectra from simultaneous observations with Fermi-LAT and MAGIC during the strongest flaring activity detected to date. Moreover, we interpret the SEDs from the four distinct activity states within the framework of one-component and two-component leptonic models, proposing specific scenarios that are able to reproduce the available multi-instrument data. We find significant long-term variability, especially in X-rays and VHE γ rays. Furthermore, significant (3-4σ) correlations were found between the radio, optical, and high-energy (HE) γ-ray fluxes, with the radio emission delayed by about ~400 days with respect to the optical and γ-ray bands. The spectral analysis reveals a harder-when-brighter trend during the non-flaring state in the X-ray domain. However, no clear patterns were observed for either the enhanced states or the HE (30 MeV < E < 100 GeV) and VHE γ-ray emission of the source. The indirect estimation of the redshift yielded a value of z = 0.45 ± 0.05, which is compatible with some of the values reported in the literature. The SEDs related to the low-activity state and the three flaring states of 1ES 0647+250 can be described reasonably well with the both one-component and two-component leptonic scenarios. However, the long-term correlations indicate the need for an additional radio-producing region located about 3.6 pc downstream from the gamma-ray producing region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Fast and flexible control of beam longitudinal phase space for high-repetition-rate x-ray free-electron lasers

The wide-ranging requirements for the photon properties from multiple beamlines in superconducting based free-electron lasers (FELs) demand more challenging beam manipulation techniques. Shot-by-shot control of electron beam bunch length and peak current at high repetition rate up to megahertz is highly desired. In this paper, we present a comprehensive study of a method based on a 2-m-long normal conducting radio-frequency cavity to achieve fast and flexible control of beam compression and realize the full potential of the facility, including theoretical analysis, beam dynamics simulations, and conceptual cavity design for the Linac Coherent Light Source II and its high-energy upgrade. We illustrate the physical mechanism of the chirping cavity on the control of the final beam compression and propose methods to lower the requirements for the cavity parameters. The application of this method will allow tailored photon properties of individual beamlines to optimize their performance and drastically improve the multiplexing capabilities of a high-repetition rate FEL facility.

42 ENGINEERING↗
DOE OSTI2025

Oxygen vacancies in niobium pentoxide as a source of two-level system losses in superconducting niobium

Two-level systems (TLS) have long been a catch-all explanation for RF loss and quantum decoherence in superconducting devices. In our study, the first to directly link TLS losses to a specific physical mechanism, we demonstrate that oxygen vacancies in the naturally formed Nb₂O₅ on oxidized niobium are a major driver of such dissipation. We performed sequential in situ vacuum-baking treatments on niobium superconducting radio-frequency (SRF) cavities and used time-of-flight secondary ion mass spectrometry (TOF-SIMS) to reveal a nonmonotonic evolution in cavity quality factor (Q₀). This behavior correlates with the interplay of Nb₂O₅ vacancy generation and oxide-thickness dissolution. We localize this effect to the oxide itself and present the insignificant role of diffused interstitial oxygen in the underlying Nb by regrowing the oxide via wet oxidation, revealing a mitigation of aggravated TLS losses. We hypothesize that such vacancies in the pentoxide serve as magnetic impurities and are a source of TLS-driven rf loss. Although our measurements center on 3-D SRF cavities, the insights gained here have significant implications for mitigating decoherence in 2-D superconducting qubits.

Bafia, Daniel P. [Fermilab]↗
DOE OSTI2024

Investigation of Materials for Radio Frequency Antenna Plasma Facing Components

Here, the interaction of radio frequency (RF) sheaths with fusion reactor relevant materials (e.g., tungsten and titanium diboride) is being studied on the RF Plasma Interaction Experiment (RF PIE). The RF PIE consists of an electron cyclotron resonance (ECR) plasma source (2.45 GHz, 5 kW) with a biased and heated RF electrode that is used to simulate antenna surfaces in contact with the edge plasma. Helium plasmas (density of ~1e18/m 3 , electron temperature of 4–5 eV) are being used to explore sheath formation on material surfaces with biases up to 500 V. The erosion of a tungsten surface is being studied spectroscopically using a mirror-linked 1 m Czerny-Turner UV imaging spectrometer with a spectral resolution of 0.012 nm for measuring plasma emission in and near the sheath. Tungsten line emission intensity is higher for RF versus dc biasing for similar plasma conditions and average ion energy. RF biasing causes a broadening of the ion energy distribution function (IEDF) due to the RF sheath, as determined from the hPIC2 code, and results in enhanced sputtering. Calculations of the expected sputtering yield for dc and RF biasing are consistent with experimental observations of changes in the 400.9 nm tungsten line emission intensity as a function of ion energy.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Robotic Systems integration for cleanroom SRF assembly at Fermilab

Superconducting Radio Frequency (SRF) cryomodule assembly is a critical process that demands the highest levels of contamination control in a cleanroom to ensure product quality and reliability. Within the cleanroom environment, human-driven activities remain the major source of uncontrolled particulate. Moreover, the precise manual alignment of components often exceeds expected timeframes, increasing the risk of particulate migration into the critical inner space of the SRF resonant cavity, and causing extended discomfort for workers. Automation comes as a natural solution to address these challenges. The goal of this activity is to set up and integrate a robotic system to support cavity coupler installation in the cleanroom environment. Initially, remote control of a 6-axis collaborative robot arm will be implemented as an introductory step towards automation in the cleanroom. Subsequently, the system will be further enhanced by integrating manipulation capabilities through an appropriate end-effector, and computer vision technology to enable accurate pose estimation. This comprehensive approach aims to achieve a fully automated and adaptable assembly process in the partially structured cleanroom environment, thereby enhancing efficiency and mitigating existing challenges for better product quality and workers safety.

42 ENGINEERING↗
DOE OSTI2022

Temperature Mapping analysis of Nitrogen-doped Niobium Radio Frequency Cavity

Nitrogen-doping of niobium superconducting radio-frequency (SRF) cavity has been shown to significantly improve the quality factors as compared to the standard treated niobium cavities. However, the nitrogen-doped cavities generally quench at lower accelerating gradients. To understand the possible sources of rf losses in nitrogen-doped cavities that could reduce the quench field, we used 576 thermometer sensors to map the temperature distribution of the outer cavity surface while increasing the accelerating field. Our measurements have revealed a strong effect of the cavity cooldown rate on the intensity of hot spots and their spatial distribution, indicating a significant contribution from trapped vortices on the RF losses.

Makita, Junki↗
DOE OSTI2025

Radio Frequency Transients Correlated with Electron Flux Measured On-Board the STP-Sat6

We analyzed transient electromagnetic signatures, referred to as spacecraft environment discharges (SEDs) or on-board discharges (OBDs), and the in-situ particle environment simultaneously measured by the Radio Frequency Sensor (RFS) and the Space and Atmospheric Burst Reporting System Z-plasma spectrometer (SABRS-ZPS), respectively. These sensors are on-board the U.S. Department of Defense Space Test Program Satellite 6 (STP-Sat6) in geostationary orbit. Radio frequency signatures of SEDs on STP-Sat6 have relatively high peak amplitudes; they often caused amplitude-saturation in the so-called high band (120–140 MHz frequency range) of the RFS likely due to the proximity of their source to the RFS’s dipole antennas. We examined the occurrence rate of SEDs reported by the RFS and its temporal relationship to electron flux in the 7.9–12.2 keV range. Peaks in SED count rates were time-correlated with peaks in electron flux. The electron-flux peaks appeared to lead the SED count rate peaks by 24–45 min for the 7.9–12.2 keV energies. This indicates that incidence of electrons at this relatively low-energy range likely resulted in ramping up of the charging of the spacecraft leading to periods of high occurrence rates of discharges in and around the spacecraft.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

PRELIMINARY RESULTS OF MAGNETIC AND TEMPERATURE MAP SYSTEM FOR 3 GHz SUPERCONDUCTING RADIO FREQUENCY CAVITIES

Su­per­con­duct­ing radio fre­quency (SRF) cav­i­ties are fun­da­men­tal build­ing blocks of mod­ern par­ti­cle ac­cel­er­a­tors. A sur­face re­sis­tance in the tens of nanoOhm range is achieved when cool­ing these cav­i­ties to liq­uid he­lium tem­per­a­ture, ~2 - 4 K. One of the lead­ing sources of resid­ual losses in SRF cav­i­ties is trapped mag­netic flux. Flux trap­ping mech­a­nism de­pends on dif­fer­ent sur­face prepa­ra­tions and cool-down con­di­tions. We have de­signed, de­vel­oped and com­mis­sioned a com­bined mag­netic and tem­per­a­ture map­ping sys­tem using anisotropic mag­neto-re­sis­tance sen­sors and car­bon re­sis­tors, re­spec­tively, to study the flux trap mech­a­nism in 3 GHz sin­gle-cell nio­bium cav­i­ties. In this con­tri­bu­tion, we will de­scribe the ex­per­i­men­tal ap­pa­ra­tus and pre­sent pre­lim­i­nary test re­sults.

Parajuli, I. P.↗
DOE OSTI2021

Underground Imaging by Sub-Terahertz Radiation

Sub-terahertz ground-penetrating radar systems offer an alternative to radio wave-based systems in the airborne imaging of buried objects. Laboratory prototype systems operating in W-band (75–110 GHz) and F-band (90–140 GHz) are presented, detecting the distance between target and source and imaging metal objects buried in mixed soil. The experimental results show that imaging in the 100–150 GHz frequency range is feasible for underground applications but significantly restricted by the attenuation characteristics of the medium covering the targets. A higher power source and more sensitive receiving components are essential to increase the penetration capability and expand the application settings of this approach.

42 ENGINEERING↗