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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

New High Power Test Facility for VHF Power Amplifiers at LANSCE

A new test facility was designed and constructed at Los Alamos Neutron Science Center (LANSCE) for testing the Thales TH628 Diacrode{sup R} and TH781 tetrode power amplifiers. Anode power requirements for the TH628 are 28 kV DC, with peak currents of 190 Amperes in long pulses. A charging power supply was obtained by reconfiguring a 2 MW beam power supply remaining from another project. A traditional ignitron crowbar was designed to rapidly discharge the 88 kJ stored energy. The anode power supply was extensively tested using a pulsed tetrode switch and resistor load. A new Fast Protect and Monitor System (FPMS) was designed to take samples of RF reflected power, anode HV, and various tube currents, with outputs to quench the HV charging supply, remove RF drive and disable the conduction bias pulse to the grid of each tube during fault events. The entire test stand is controlled with a programmable logic controller (PLC), for normal startup sequencing and timing, protection against loss of cooling, and provision for operator GUI.

Accelerator Design, Technology, and Operations↗
DOE OSTI2014

Ultrasonic Nakagami-parameter characterization of parotid-gland injury following head-and-neck radiotherapy: A feasibility study of late toxicity

Purpose: The study aims to investigate whether Nakagami parameters—estimated from the statistical distribution of the backscattered ultrasound radio-frequency (RF) signals—could provide a means for quantitative characterization of parotid-gland injury resulting from head-and-neck radiotherapy. Methods: A preliminary clinical study was conducted with 12 postradiotherapy patients and 12 healthy volunteers. Each participant underwent one ultrasound study in which ultrasound scans were performed in the longitudinal, i.e., vertical orientation on the bilateral parotids. For the 12 patients, the mean radiation dose to the parotid glands was 37.7 ± 9.5 Gy, and the mean follow-up time was 16.3 ± 4.8 months. All enrolled patients experienced grade 1 or 2 late salivary-gland toxicity (RTOG/EORTC morbidity scale). The normal parotid glands served as the control group. The Nakagami-scaling and Nakagami-shape parameters were computed from the RF data to quantify radiation-induced parotid-gland changes. Results: Significant differences in Nakagami parameters were observed between the normal and postradiotherapy parotid glands. Compared with the control group, the Nakagami-scaling parameter of the postradiotherapy group decreased by 25.8% (p < 0.001), and the Nakagami-shape parameter decreased by 31.3% (p < 0.001). The area under the receiver operating characteristic curve was 0.85 for the Nakagami-scaling parameter and was 0.95 for the Nakagami-shape parameter, which further demonstrated the diagnostic efficiency of the Nakagami parameters. Conclusions: Nakagami parameters could be used to quantitatively measure parotid-gland injury following head-and-neck radiotherapy. Moreover, the clinical feasibility was demonstrated and this study provides meaningful preliminary data for future clinical investigation.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2012

Surface plasma source with saddle antenna radio frequency plasma generator

A prototype RF H{sup -} surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA/kW. Control experiments with H{sup -} beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Compact Superconducting RF Accelerators for Water Treatment

Jefferson Lab is actively exploring the environmental applications of compact irradiation facilities utilizing Superconducting Radio Frequency (SRF) accelerator technology ? a well-established technology primarily used in large research machines. Recent advancements, such as the application of thin films of superconducting alloys in radio frequency (RF) resonators and the development of high-capacity cryocoolers, have made it feasible to employ this key technology in compact, standalone irradiation facilities. The main advantage over conventional systems based on normal conducting technology is the significantly enhanced efficiency in beam power generation, enabling exposure to substantially higher radiation doses. In the realm of addressing contaminants in wastewater treatment, particularly concerning persistent substances known as "forever chemicals," this technology presents an attractive solution, given the required considerable effort i.e. dose to break them down. Experiment Numbers:

Vennekate, John↗
DOE OSTI2024

Compact Superconducting RF Accelerators for Water Treatment

Jefferson Lab is actively exploring the environmental applications of compact irradiation facilities utilizing Superconducting Radio Frequency (SRF) accelerator technology ? a well-established technology primarily used in large research machines. Recent advancements, such as the application of thin films of superconducting alloys in radio frequency (RF) resonators and the development of high-capacity cryocoolers, have made it feasible to employ this key technology in compact, standalone irradiation facilities. The main advantage over conventional systems based on normal conducting technology is the significantly enhanced efficiency in beam power generation, enabling exposure to substantially higher radiation doses. In the realm of addressing contaminants in wastewater treatment, particularly concerning persistent substances known as "forever chemicals," this technology presents an attractive solution, given the required considerable effort i.e. dose to break them down. Experiment Numbers:

Vennekate, John↗
NASA NTRS1979

Thermal anomalies of the transmitter experiment package on the communications technology satellite

The causes of four temporary thermal-control-system malfunctions that gave rise to unexpected temperature excursions in the 12-gigahertz, 200-watt transmitter experiment package (TEP) on the Communications Technology Satellite were investigated. The TEP consists of a nominal 200-watt output stage tube (OST), a supporting power-processing system (PPS), and a variable-conductance heat-pipe system (VCHPS). The VCHPS, which uses three heat pipes to conduct heat from the body of the OST to a radiator fin, was designed to maintain the TEP at safe operating temperatures at all operating conditions. On four occasions during 1977, all near the spring and fall equinoxes, the OST body temperature and related temperatures displayed sudden, rapid, and unexpected rises above normal levels while the TEP was operating at essentially constant, normal conditions. The temperature excursions were terminated without TEP damage by reducing the radio frequency (RF) output power of the OST. Between the anomalies and since the fourth, the thermal control system has apparently functioned as designed. The results indicate the most probable cause of the temperature anomalies is depriming of the arteries in the variable-conductance heat pipes. A mode was identified in which the TEP, as presently configured, may operate with stable temperatures and with minimum change in performance level.

Alexovich, R. E.↗
DOE OSTI2012

Beam dynamics studies for transverse electromagnetic mode type rf deflectors

We have performed three-dimensional simulations of beam dynamics for transverse electromagnetic mode (TEM) type rf deflectors: normal and superconducting. The compact size of these cavities as compared to the conventional TM 110 type structures is more attractive particularly at low frequency. Highly concentrated electromagnetic fields between the parallel bars provide strong electrical stability to the beam for any mechanical disturbance. An array of six 2-cell normal conducting cavities or a single cell superconducting structure is enough to produce the required vertical displacement at the target point. Both the normal and superconducting structures show very small emittance dilution due to the vertical kick of the beam.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Investigations Towards Ultra-Low Cost Nb 3 Sn SRF Fabrication via Melt Casted Bronze Route Processing

Here, a novel approach to fabricating Nb 3 Sn SRF cavities and other RF components using an ultra-low-cost melt casting fabrication process has been investigated. This simple, low cost melt casting technique has the potential to be used to fabricate nearly any superconducting Nb3Sn structure using either the Bronze Route (BR), Internal Tin (IT), External Tin (ET) processes as well as normal conducting pure copper (Cu) cavities. Most of the heat treated samples that were examined using SEM/EDX seemed to show a reasonable correlation of T c onset and transition width (ΔT c ) of the ingots initial/starting Sn content to the desired stoichiometric Nb 3 Sn phase, where the lower starting Sn content coupons resulted in lower T c 's with broader transition widths and the higher starting Sn coupons resulted in higher T c 's with narrower ΔT c ’s. The best samples had T c onsets ~17-18 K and ΔT c 's < 2 K. Two samples were further tested for RF surface resistance (R s ) and Quality Factor (Q) at JLAB. Here, these RF measurements were performed at 7.4 GHz using a calorimetric technique and showed two transitions, one at ~ 8 K and another at ~ 14 K; values of R s were at least two orders of magnitude higher than similar high quality Nb 3 Sn films directly deposited substrates by JLAB and with another superconducting transition close to the superconducting transition temperature of niobium. Substantial improvements in the processing variables ranging from higher quality of the initial ingots with higher Sn content, to better electropolishing and reaction heat treatment regimens will be necessary to realize improved RF performance metrics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2006

Comparison of Atomic Oxygen Erosion Yields of Materials at Various Energy and Impact Angles

The atomic oxygen erosion yields of various materials, measured in volume of material oxidized per incident atomic oxygen atom, are compared to the commonly accepted standard of Kapton H (DuPont) polyimide. The ratios of the erosion yield of Kapton H to the erosion yield of various materials are not consistent at different atomic oxygen energies. Although it is most convenient to use isotropic thermal energy RF plasma ashers to assess atomic oxygen durability, the results can be misleading because the relative erosion rates at thermal energies are not necessarily the same as low Earth orbital (LEO) energies of approx.4.5 eV. An experimental investigation of the relative atomic oxygen erosion yields of a wide variety of polymers and carbon was conducted using isotropic thermal energy (approx.0.1 eV) and hyperthermal energy (approx.70 eV) atomic oxygen using an RF plasma asher and an end Hall ion source. For hyperthermal energies, the atomic oxygen erosion yields relative to normal incident Kapton H were compared for sweeping atomic oxygen arrival with that of normal incidence arrival. The results of isotropic thermal energy, normal incident, and sweeping incident atomic oxygen are also compared with measured or projected LEO values.

Banks, Bruce A.↗
DOE OSTI2013

Simulation of non-linear rf losses derived from characteristic Nb topography

A simplified model has been developed to simulate non-linear RF losses on Nb surfaces exclusively due to topographical enhancement of surface magnetic fields. If local sharp edges are small enough, at locations where local surface fields exceed Hc, small volumes of material may become normal conducting without thermal leading to quench. These small volumes of normal material yield increases in the effective surface resistance of the Nb. Using topographic data from typical BCP?d and EP?d fine grain niobium surfaces, we have simulated field-dependent losses and found that when extrapolated to resulting cavity performance, these losses correspond well to characteristic BCP/EP high field Q0 performance differences for fine grain Nb. We describe the structure of the model, its limitations, and the effects of this type of non-linear loss contribution on SRF cavities.

Reece, Charles E.↗
DOE OSTI2019

PNNL Report: New Study Validates Color-Rendition Specification Criteria Based on TM-30

Pacific Northwest National Laboratory (PNNL) has released the results of a study – published in Lighting Research & Technology – that validates color-preference specification criteria based on ANSI/IES TM-30-18. The result provides additional data to support TM-30 Annex E (in press), which will include tiers of recommended specification criteria for different goals (color preference, color vividness, and color fidelity), among other information related to color rendition specification. Standardized methods for evaluating the color rendition of light sources have progressed rapidly in the past five years, beginning with the publication of IES TM-30-15, followed by the adoption of CIE 224:2017, and culminating with the issuance of ANSI/IES TM-30-18 (which revised TM-30-15, made it a national standard, and unified the calculation framework of CIE 224 and IES TM-30). Importantly, none of these documents provided guidance on how to specify color rendition using the included measures; that is, no value or combination of values was identified that leads to any desired quality of the light. Dozens of experiments over the past 60 years have examined subjective evaluations of color quality—such as preference, naturalness, or vividness—although the focus has traditionally been on developing a single-number color quality metric rather than specification criteria. Further, many of these pre-LED and pre-TM-30 studies were limited in their ability to vary the lighting characteristics, preventing them from generating a complete and accurate picture of what influences color rendering quality in architectural spaces. A renewed emphasis in this area of research over the past four years has yielded a growing consensus about how measures of color fidelity (Rf), gamut area (Rg), and red chroma (Rcs,h1) can be used in combination to effectively describe several important perceptual attributes. In the new study, which was the third in a series conducted at PNNL, 90 lighting conditions with systematically varied color rendition and chromaticity were evaluated by 25 participants, who provided ratings for normalness, saturation, preference, and acceptability. The lighting conditions were specifically designed to test the bounds of previously proposed color preference criteria, while simultaneously verifying the applicability of the criteria across different values of CCT and Duv. In line with the preceding work, there were substantial differences in ratings based on color rendition, but minimal differences based on chromaticity. The tested criteria performed well, although after the experiment, some small adjustments in lower limits provided more effective divisions between tiers of performance. The adjusted criteria are: • Level 1: Rf = 78, Rg = 95, -1% = Rcs,h1 = 15% • Level 2: Rf = 74, Rg = 92, -7% = Rcs,h1 = 19% • Level 3: Rf = 70, Rg = 89, -12% = Rcs,h1 = 23%. These criteria were concurrently checked against the results from other, independent experiments, and will be included in ANSI/IES TM-30 Annex E as the specifications for color preference. The new criteria will be a valuable tool for improving lighting quality and balancing the tradeoff between color rendition and energy efficiency.

Royer, Michael P.↗
DOE OSTI2014

Linac4 low energy beam measurements with negative hydrogen ions

Linac4, a 160 MeV normal-conducting H{sup −} linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H{sup −} beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Thermal and Lorentz force analysis of beryllium windows for a rectilinear muon cooling channel

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed with thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of the plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed with thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of the plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Cavity Design, Fabrication and Commission Performance of a 750MHz, 4-rod Separator for CEBAF 4-Hall Beam Delivery System

A short version of the original CEBAF normal conducting 4-rod separator cavity has been developed into a 750MHz one * since the concept of simultaneous 4-hall operation for CEBAF is introduced **. This work has been advanced further based on the EM design optimization, bench measurement and by conducting RF-thermal coupled simulation using CST and ANSYS to confirm the cavity tuning and thermal performance. The cavity fabrication used matured technology like copper plating and machining. The cavity flanges, couplers, tuners and cooling channels adopted consistent/compatible hardware with the existing 500MHz cavities. The electromagnetic and thermal design simulations have greatly reduced the prototyping and bench tuning time of the first prototype. Four production cavities have reached a typical 1.94MV kick voltage or 3.0kW wall loss on each cavity after a minor multipactoring or no processing, 7.5% overhead power than the design specification.

Wang, Haipeng↗
DOE OSTI2018

LCLS-II Gun/Buncher LLRF System Design

For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

JLEIC SRF cavity RF Design

The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchro-tron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback sys-tem will be necessary.

Wang, Shaoheng↗