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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

LHCD and ICRF heating experiments in H-mode plasmas on EAST

An ICRF system with power up to 6.0 MW and a LHCD system up to 4MW have been applied for heating and current drive experiments on EAST. Intensive lithium wall coating was intensively used to reduce particle recycling and Hydrogen concentration in Deuterium plasma, which is needed for effective ICRF and LHCD power absorption in high density plasmas. Significant progress has been made with ICRF heating and LHW current drive for realizing the H-mode plasma operation in EAST. In 2010, H-mode was generated and sustained by LHCD alone, where lithium coating and gas puffing launcher mouth were applied to improve the LHCD power coupling and penetration into the core plasmas at high density of H-modes. During the last two experimental campaigns, ICRF Heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H Minority Heating (H-MH) mode, where electrons are predominantly heated by collisions with high energy minority ions. The H-MH mode gave the best plasma performance, and realized H-mode alone in 2012. Combination of ICRF and LHW power injection generated the H-mode plasmas with various ELMy characteristics. The first successful application of the ICRF Heating in the D (He3) plasma was also achieved. The progress on ICRF heating, LHCD experiments and their application in achieving H-mode operation from last two years will be discussed in this report.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas

Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfvén Eigenmodes inside the q = 1 surface (also called “tornado” modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Transverse energy production and charged-particle multiplicity at midrapidity in various systems from s N N = 7.7 to 200 GeV

Measurements of midrapidity charged-particle multiplicity distributions, dN ch /dη, and midrapidity transverse-energy distributions, dE T /dη, are presented for a variety of collision systems and energies. Included are distributions for Au+Au collisions at √s NN =200, 130, 62.4, 39, 27, 19.6, 14.5, and 7.7 GeV, Cu+Cu collisions at √s NN =200 and 62.4 GeV, Cu+Au collisions at √s NN =200 GeV, U+U collisions at√s NN =193 GeV, d+Au collisions at √s NN =200 GeV, He3+Au collisions at √s NN =200 GeV, and p+p collisions at √s NN =200 GeV. We present centrality-dependent distributions at midrapidity in terms of the number of nucleon participants, N part , and the number of constituent quark participants, N qp . For all A+A collisions down to √s NN =7.7 GeV, we observed that the midrapidity data are better described by scaling with N qp than scaling with N part . Finally, our estimates of the Bjorken energy density, ε BJ , and the ratio of dE T /dη to dN ch /dη are presented, the latter of which is seen to be constant as a function of centrality for all systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Design and validation of a cold load for characterization of cosmic microwave background stage 4 detectors

We present the design and validation of a variable temperature cryogenic blackbody source, hereinafter called a cold load, that will be used to characterize detectors to be deployed by cosmic microwave background stage 4 (CMB-S4), the next-generation ground-based cosmic microwave background (CMB) experiment. Although cold loads have been used for detector characterization by previous CMB experiments, this cold load has three innovative design features: (1) the ability to operate from the 1-K stage of a dilution refrigerator (DR), (2) a He3 gas-gap heat switch to reduce cooling time, and (3) the ability to couple small external optical signals to measure detector optical time constants under low optical loading. The efficacy of this design was validated using a 150-GHz detector array previously deployed by the Spider experiment. Thermal tests showed that the cold load can be heated to temperatures required for characterizing CMB-S4’s detectors without significantly impacting the temperatures of other cryogenic stages when mounted to the DR’s 1-K stage. In addition, optical tests demonstrated that external signals can be coupled to a detector array through the cold load without imparting a significant optical load on the detectors, which will enable measurements of the CMB-S4 detectors’ optical time constants.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Benchmarking ICRF Full-wave Solvers for ITER

Abstract Benchmarking of full-wave solvers for ICRF simulations is performed using plasma profiles and equilibria obtained from integrated self-consistent modeling predictions of four ITER plasmas. One is for a high performance baseline (5.3 T, 15 MA) DT H-mode. The others are for half-field, half-current plasmas of interest for the pre-activation phase with bulk plasma ion species being either hydrogen or He4. The predicted profiles are used by six full-wave solver groups to simulate the ICRF electromagnetic fields and heating, and by three of these groups to simulate the current-drive. Approximate agreement is achieved for the predicted heating power for the DT and He4 cases. Factor of two disagreements are found for the cases with second harmonic He3 heating in bulk H cases. Approximate agreement is achieved simulating the ICRF current drive.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Operation of the 56 MHz superconducting RF cavity in RHIC during run 14

A 56 MHz superconducting RF cavity was designed and installed in the Relativistic Heavy Ion Collider (RHIC). It is the first superconducting quarter wave resonator (QWR) operating in a high-energy storage ring. We discuss herein the cavity operation with Au+Au collisions, and with asymmetrical Au+He3 collisions. The cavity is a storage cavity, meaning that it becomes active only at the energy of experiment, after the acceleration cycle is completed. With the cavity at 300 kV, an improvement in luminosity was detected from direct measurements, and the bunch length has been reduced. The uniqueness of the QWR demands an innovative design of the higher order mode dampers with high-pass filters, and a distinctive fundamental mode damper that enables the cavity to be bypassed during the acceleration stage.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Using Inertial Fusion Implosions to Measure the T + 3 He Fusion Cross Section at Nucleosynthesis-Relevant Energies

Light nuclei were created during big-bang nucleosynthesis (BBN). Standard BBN theory, using rates inferred from accelerator-beam data, cannot explain high levels of Li6 in low-metallicity stars. Using high-energy-density plasmas we measure the T(He3,?)Li6 reaction rate, a candidate for anomalously high Li6 production; we find that the rate is too low to explain the observations, and different than values used in common BBN models. This is the first data directly relevant to BBN, and also the first use of laboratory plasmas, at comparable conditions to astrophysical systems, to address a problem in nuclear astrophysics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1971

Tritium trick

Large controlled amounts of helium in uniform concentration in thick samples can be obtained through the radioactive decay of dissolved tritium gas to He3. The term, tritium trick, applies to the case when helium, added by this method, is used to simulate (n,alpha) production of helium in simulated hard flux radiation damage studies.

Green, W. V.↗
NASA NTRS1986

Solar cycle variations of anomalous He-4 as deduced by studies of cosmic ray He-3

Voyager 1 and 2 observations have been used to derive the energy spectrum of 'anomalous' cosmic-ray (ACR) He using a technique based on the separation of the isotopes of He. Previously reported observations show that the ACR oxygen spectrum underwent a change in shape following the solar magnetic field reversal in 1980; in this paper evidence for a corresponding change in the ACR He spectrum is presented. It is found that the energy spectra of ACR He and oxygen and Galactic-cosmic-ray He-4 and He3 can be reproduced both before and after the field reversal using a simple solar modulation model in which the effects of curvature and gradient drifts are arbitrarily neglected.

Cummings, A. C.↗
NASA NTRS1988

Current developments in NASA cryogenic cooler technology

Cooler technologies that are being developed by NASA to meet the varying temperature and cooling power requirements of NASA instruments are described. In addition to providing the desired operating temperature and cooling power by stabilizing temperatures from room temperature down to 0.1 K or less, these coolers will have working lifetimes commensurate with the 10 to 15 year lifetime expected for major future NASA facilities. The types of coolers currently under development are discussed, including radiative coolers, solid cryogen coolers, surface tension confined liquid cryogen coolers, mechanical coolers, liquid helium dewars, He3 adsorption coolers, adiabatic demagnetization refrigerators, and dilution refrigerators.

Castles, Stephen H.↗
NASA NTRS1994

Quantitative understanding of the cycles of oxidized and reduced sulfur on Venus

The evolution of the Venus atmosphere is determined by the supply of gases from the interior of the planet and outer space, and by the loss of particles to space over time. In particular, questions pertaining to the initial inventory of water and the current and past rates of outgassing can be addressed by studying the loss rates of H, D, He3 and He4. The photochemistry of the H2SO4 clouds may also have played an important role in regulating the amount of water above the cloud tops, and hence limit the rate of escape of hydrogen from the planet. Thus the problems of evolution and chemistry are intimately related. In our proposal the principal tasks we undertook to advance our understanding of the origin and evolution of water on Venus included: (1) escape of light atoms from Venus and (2) develop a photochemical model of sulfate formation. In the last two years we have made progress on Task 1 regarding how light atoms can escape from the exosphere of Venus with the development of a Monte Carlo program and in Task 2 have developed a thorough update on the SO2 photochemistry that had been previously carried out.

Yung, Yuk L.↗
NASA NTRS2005

Helium-3 Mining Aerostats in the Atmospheres of the Outer Planets

Imagine an interplanetary future where: a) d-He3 fusion produces most of Earth s energy needs without radioactivity or carbon emissions; b) Space transportation has been revolutionized by an efficient fusion propulsion system with exhaust velocity up to 0.088 c; c) Space commerce is stimulated by the existence of an interplanetary cargo worth $3-M a kilogram; and d) Unmanned probes travel to the nearest star systems with flight times less than a human lifetime.

VanCleve, Jeffrey E.↗
NASA NTRS2011

Use of Apollo 17 Epoch Neutron Spectrum as a Benchmark in Testing LEND Collimated Sensor

The Apollo 17 neutron experiment LPNE provided a unique set of data on production of neutrons in the Lunar soil bombarded by Galactic Cosmic Rays (GCR). It serves as valuable "ground-truth" in the age of orbital remote sensing. We used the neutron data attributed to Apollo 17 epoch as a benchmark for testing the LEND's collimated sensor, as introduced by the geometry of collimator and efficiency of He3 counters. The latter is defined by the size of gas counter and pressure inside it. The intensity and energy spectrum of neutrons escaping the lunar surface are dependent on incident flux of Galactic Cosmic Rays (GCR) whose variability is associated with Solar Cycle and its peculiarities. We obtain first the share of neutrons entering through the field of view of collimator as a fraction of the total neutron flux by using the angular distribution of neutron exiting the Moon described by our Monte Carlo code. We computed next the count rate of the 3He sensor by using the neutron energy spectrum from McKinney et al. [JGR, 2006] and by consider geometry and gas pressure of the LEND sensor. Finally the neutron count rate obtained for the Apollo 17 epoch characterized by intermediate solar activity was adjusted to the LRO epoch characterized by low solar activity. It has been done by taking into account solar modulation potential, which affects the GCR flux, and in turn changes the neutron albedo flux.

Chin, Gordon↗
NASA NTRS2009

Multiplexing of Hot-Electron Nanobolometers Using Microwave SQUIDs

We have obtained the first data on the multiplexed operation of titanium hot-electron bolometers (HEB). Because of their low thermal conductance and small electron heat capacity nanobolometers are particularly interesting as sensors for far-infrared spectroscopy and mid- and near-IR calorimetry. However, the short time constant of these devices (approximately microseconds at 300-400 mK) makes time domain or audio-frequency domain multiplexing impractical. The Microwave SQUID (MSQUID) approach pursued in this work uses dc SQUIDs coupled to X-band microresonators which are, in turn, coupled to a transmission line. We used a 4-element array of Ti HEBs operated at 415 mK in a He3 dewar with an optical fiber access. The microwave signal exhibited 10-MHz wide resonances at individual MSQUD frequencies between 9 GHz and 10 GHz. The resonance depth is modulated by the current through the bolometer via a change of the SQUID flux state. The transmitted signal was amplified by a cryogenic amplifier and downconverted to baseband using an IQ mixer. A 1-dB per ??/2 responsivity was sufficient for keeping the system noise at the level of ~ 2 pA/Hz1/2. This is more than an order of magnitude smaller than phonon noise in the HEB. The devices were able to detect single near- IR photons (1550 nm) with a time constant of 3.5 ?s. Follow-on work will scale the array to larger size and will address the microwave frequency signal generation and processing using a digital transceiver.

microwave readout↗
DOE OSTI2010

Design calculations for NIF convergent ablator experiments.

Design calculations for NIF convergent ablator experiments will be described. The convergent ablator experiments measure the implosion trajectory, velocity, and ablation rate of an x-ray driven capsule and are a important component of the U. S. National Ignition Campaign at NIF. The design calculations are post-processed to provide simulations of the key diagnostics: (1) Dante measurements of hohlraum x-ray flux and spectrum, (2) streaked radiographs of the imploding ablator shell, (3) wedge range filter measurements of D-He3 proton output spectra, and (4) GXD measurements of the imploded core. The simulated diagnostics will be compared to the experimental measurements to provide an assessment of the accuracy of the design code predictions of hohlraum radiation temperature, capsule ablation rate, implosion velocity, shock flash areal density, and x-ray bang time. Post-shot versions of the design calculations are used to enhance the understanding of the experimental measurements and will assist in choosing parameters for subsequent shots and the path towards optimal ignition capsule tuning.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Transducer Signal Noise Analysis for Sensor Authentication

The abstract is being passed through STIMS for submision to the conference. International safeguards organizations charged with promoting the peaceful use of nuclear energy employ unattended and remote monitoring systems supplemented with onsite inspections to ensure nuclear materials are not diverted for weaponization purposes. These systems are left unattended for periods of several months between inspections. During these periods physical security means are the main deterrent used to detect intentional monitoring system tampering. The information gathering components are locked in secure and sealed rooms. The sensor components (i.e. neutron and gamma detectors) are located throughout the plant in unsecure areas where sensor tampering could take place during the periods between inspections. Sensor tampering could allow the diversion of nuclear materials from the accepted and intended use to uses not consistent with the peaceful use of nuclear energy. A method and an apparatus is presented that address the detection of sensor tampering during the periods between inspections. It was developed at the Idaho National Laboratory (INL) for the Department of Energy (DOE) in support of the IAEA. The method is based on the detailed analysis of the sensor noise floor after the sensor signal is removed. The apparatus consists of a 2.1” x 2.6” electronic circuit board containing all signal conditioning and processing components and a laptop computer running an application that acquires and stores the analysis results between inspection periods. The sensors do not require any modification and are remotely located in their normal high radiation zones. The apparatus interfaces with the sensor signal conductors using a simple pass through connector at the normal sensor electronics interface package located in the already secure and sealed rooms. The apparatus does not require hardening against the effects of radiation due to its location. Presented is the apparatus design, the analysis method, and the test results as applied to tamper detection using three HE3 neutron sensors and two gamma sensors designed and built for safeguards monitoring.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗