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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Demonstration of Electron Cooling using a Pulsed Beam from an Electrostatic Electron Cooler

Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings in cases where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics *. We show the effect of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrate the detrimental effect of timing jitter as predicted by theory and simulations. Compared to actual RF-based coolers, the simplicity and flexibility of our setup will facilitate further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering.

Bruker, M. W.↗
DOE OSTI2020

In-situ spectroscopic ellipsometry for real-time characterization of the effects of high-flux helium plasmas on tungsten surfaces

Tungsten samples were exposed to He plasmas generated by an RF source (Γ i = 3.5 x 10 16 He cm -2 s -1 , ion energy = 92 eV.) The range of exposure conditions selected here is conducive to the growth of nearsurface He bubbles, and at higher fluence, the formation of W nanotendrils ranging between 50 — 100 nm in diameter. The evolution of these surface features was probed using a fixed-angle ellipsometer (280 — 1000 nm wavelength range) with direct line-of-sight to the sample. Over the parameter space explored here, changes in the two angles (p, S) that define the polarization of the reflected light followed a distinct trajectory with increasing plasma fluence. Ex-situ ellipsometry of 22 additional tungsten specimens tested at a wide range of plasma fluences and temperatures mapped onto these in-situ results well. We used helium ion microscopy and focused ion beam profiling to provide a direct calibration of the ellipsometry measurements. Our results indicate that for a reproducible process such as the growth helium-induced surface morphologies, ellipsometry is a practical in-situ diagnostic to study how fusion plasmas modify materials. To study more general effects of plasmas on surfaces, including co-deposition and sputtering, different approaches to modelling the optical properties of the exposed surfaces are also considered.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Demonstration of Electron Cooling using a Pulsed Beam from an Electrostatic Electron Cooler

Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings in cases where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics *. We show the effect of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrate the detrimental effect of timing jitter as predicted by theory and simulations. Compared to actual RF-based coolers, the simplicity and flexibility of our setup will facilitate further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering.

Bruker, M. W.↗
DOE OSTI2022

Multi-Probe 23A Pre-Shot report

The Multi-Probe Radiography campaign will field a full day of experiments at the Omega EP laser facility. The experiments will consist of shots that alternate between Omega EP’s two short-pulse laser beams to generate proton and deuteron beams from a variety of film and foam targets. The proton beam is intended to be used as a radiographic source, while the deuteron beam will be used as the pitcher in a pitcher-catcher neutron-generation concept. For the proton beam, our goal is to characterize the angular distribution and energy spectra of unwanted x-rays that are generated during proton acceleration and were found to be problematic for simultaneous radiography in MP-22A. As part of this primary goal, we will test whether an x-ray shield, XBLK, can be used to prevent these x-rays from impacting other x-ray diagnostics. For the deuteron beam, our primary goal is to characterize the energy spectra and beam profile of deuterons accelerated from CD foils and foams.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

GEANT4 Simulations on Faraday Cup Design for PIP-II Laser Wire Scanner System

The PIP-II accelerator upgrade at Fermilab represents a groundbreaking leap forward in high-energy physics research. This ambitious initiative involves enhancing Fermilab's accelerator complex by replacing the current linear accelerator with a warm front end (WFE) capable of accelerating H- beams up to 2.1 MeV. Subsequently, a superconducting linac further accelerates these beams up to 800 MeV. To precisely measure the transverse beam profile, a combination of traditional wire scanners at the WFE section and Laser wire scanners along the superconducting linac are planned for implementation. This investigation centers on refining the Faraday cup design for the PIP-II Laser wire scanners by utilizing GEANT4, a Monte Carlo simulation toolkit. Leveraging this method enables a comprehensive analysis of particle trajectories, energy deposition, secondary electron emission, backscattering, etc., facilitating optimization through adjustments to cup geometries, materials, and placement to maximize its efficiency.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Geant4-based Analysis of Faraday Cup Performance for PIP-II Laser Wire Scanner System

The Proton Improvement Plan-II (PIP-II) accelerator upgrade at Fermilab marks a significant advancement in high-energy physics research. This initiative aims to enhance Fermilab's accelerator complex by replacing the existing linear accelerator (linac) with a warm front end (WFE) capable of accelerating H- beams up to 2.1 MeV. Subsequently, a superconducting linac (SCL), that further accelerates these beams up to 800 MeV. To accurately measure the transverse beam profile, traditional wire scanners will be utilized in the WFE section, while Laser wire scanners will be implemented along the SCL. The Faraday cup for the Laser wire scanners has been designed using the GEANT4 simulation toolkit. This poster presents a detailed analysis of its performance along the SCL, focusing on electron absorption, secondary electron emission, backscattering, etc.

Wijethunga, S. A.K.↗
DOE OSTI2025

Pre-Commissioning of the Wide-Dynamic Range Halo Monitor to be Installed in the FERMILAB MI-8 Line

The beam halo can contribute to beam losses in accelerators and is very difficult to measure. With an increase in beam intensity following the PIP-II upgrade at Fermilab, the beam losses are expected to be higher with some coming from the beam halo. Therefore, it is important to measure the sources of beam halo to minimize the beam losses. A modified Halo Monitor developed by J-PARC will be installed in Fermilab MI-8 transfer line to measure the beam halo. In this paper, an update on the beam profile monitor fabrication is covered. The updates include the location selection for the Halo Monitor in the MI-8 transfer line, shielding options for instrumentation, and the next steps in commissioning.

Babacan, B. [IIT, Chicago; Fermilab]↗
NASA NTRS1971

Remote detection of trailing vortices, task 3, modification 3

The operation of a frequency tracker for use with the laser Doppler velocimeter (LDV) is reported. Topics discussed include: laser beam profile, lens matching, and LDV resolution data. It is concluded that the LDV provides good ground wind signals. The loss in sensitivity of the cavity system at high frequencies is partly compensated by an increase in the scattering cross section of the atmosphere due to dust.

Fridman, J.↗
NASA NTRS1972

Determination of Burgers vectors in close-packed metals using g.b = 2 contrast.

Reexamination of dislocation images giving double contrast in the electron microscope for g.b = 2 as a possible means for Burgers vector determinations. In fcc foils which have been cut parallel to an active slip plane, the g.b = 2 criterion provides a quick positive Burgers vector analysis which can be carried out during observation. The method is also applicable to basal dislocations in hcp. A comparison between calculated two-beam profiles and experimental images in aluminum is discussed, and several commonly observed characteristics of g.b = 2 contrast are described.

Kestenbach, H.-J.↗
NASA NTRS1974

Eight-cm mercury ion thruster system technology

The technology status of 8 cm diameter electron bombardment ion thrusters is presented. Much of the technology resulting from the 5 cm diameter thruster has been adapted and improved upon to increase the reliability, durability, and efficiency of the 8 cm thruster. Technology discussed includes: dependence of neutralizer tip erosion upon neutralizer flow rate; impregnated and rolled-foil insert cathode performance and life testing; neutralizer position studies; thruster ion beam profile measurements; high voltage pulse ignition; high utilization ion machined accelerator grids; deposition internal and external to the thruster; thruster vectoring systems; thruster cycling life testing and thruster system weights for typical mission applications.

Source record↗
NASA NTRS1974

8-cm mercury ion thruster system technology

The technology status of 8-cm diameter electron bombardment ion thrusters is presented. Much of the technology resulting from the 5-cm diameter thruster has been adapted and improved upon to increase the reliability, durability, and efficiency of the 8-cm thruster. Technology discussed includes: dependence of neutralizer tip erosion upon neutralizer flow rate; impregnated and rolled-foil insert cathode performance and life testing; neutralizer position studies; thruster ion beam profile measurements; high voltage pulse ignition; high utilization ion machined accelerator grids; deposition internal and external to the thruster; thruster vectoring systems; thruster cycling life testing and thruster system weights for typical mission applications.

Source record↗
NASA NTRS1976

Inert gas thrusters

Inert gases are of interest as possible alternatives to the usual electric thruster propellants of mercury and cesium. The multipole discharge chamber investigated was shown capable of low discharge chamber losses and flat ion beam profiles with a minimum of optimization. Minimum discharge losses were 200 to 250 eV/ion for xenon and 300 to 350 eV/ion for argon, while flatness parameters in the plane of the accelerator grid were 0.85 to 0.95. The design used employs low magnetic field strengths, which permits the use of sheet-metal parts. The corner problem of the discharge chamber was resolved with recessed corner anodes, which approximately equalized both the magnetic field above the anodes and the electron currents to these anodes. Argon hollow cathodes were investigated at currents up to about 5 amperes using internal thermionic emitters. Cathode chamber diameter optimized in the 1.0 to 2.5 cm range, while orifices diameter optimized in the 0.5 to 5 mm range. The use of a bias voltage for the internal emitter extended the operating range and facilitated starting. The masses of 15 and 30 cm flight type thrusters were estimated at about 4.2 and 10.8 kg.

Kaufman, H. R.↗
NASA NTRS1977

Multipole gas thruster design

The development of a low field strength multipole thruster operating on both argon and xenon is described. Experimental results were obtained with a 15-cm diameter multipole thruster and are presented for a wide range of discharge-chamber configurations. Minimum discharge losses were 300-350 eV/ion for argon and 200-250 eV/ion for xenon. Ion beam flatness parameters in the plane of the accelerator grid ranged from 0.85 to 0.93 for both propellants. Thruster performance is correlated for a range of ion chamber sizes and operating conditions as well as propellant type and accelerator system open area. A 30-cm diameter ion source designed and built using the procedure and theory presented here-in is shown capable of low discharge losses and flat ion-beam profiles without optimization. This indicates that by using the low field strength multipole design, as well as general performance correlation information provided herein, it should be possible to rapidly translate initial performance specifications into easily fabricated, high performance prototypes.

Isaacson, G. C.↗
NASA NTRS1976

15 cm multipole gas ion thruster

A 15-cm multipole thruster was operated on argon and xenon. The multipole approach used has been shown capable of low discharge losses and flat ion beam profiles with a minimum of redesign. This approach employs low magnetic field strengths and flat or cylindrical sheet-metal parts, hence is suited to rapid optimization and scaling. Only refractory metal cathodes were used in this investigation.

Isaacson, G. C.↗
NASA NTRS1981

Directionality effects in the transfer of X-rays from a magnetized atmosphere: Beam pulse shape

A formalism is presented for radiation transfer in two normal polarization modes in finite and semiinfinite plane parallel uniform atmospheres with a magnetic field perpendicular to the surface and arbitrary propagation angles. This method is based on the coupled integral equations of transfer, including emission, absorption, and scattering. Calculations are performed for atmosphere parameters typical of X-ray pulsars. The directionality of the escaping radiation is investigated for several cases, varying the input distributions. Theoretical pencil beam profiles and X-ray pulse shapes are obtained assuming the radiation is emitted from the polar caps of spinning neutron stars. Implications for realistic models of accreting magnetized X-ray sources are briefly discussed.

Meszaros, P.↗
NASA NTRS1980

Large volume multiple path nuclear lasing of /He-3/-Ar

Output power of 550 W has been achieved from a nuclear-pumped multiple path laser system containing (He-3)-Ar by using the (He-3)(n, p)3(H) nuclear reaction for power deposition. Lasing was achieved in Ar at 1790 nm. The complex beam profile was resolved by an InAs array detector. Laser output was directly proportional to thermal neutron flux, and also increased proportionally with increasing (He-3) pressure up to 292.6 kPa. The variation of the laser output power with the number of passes through the excited medium was found to peak at 5-7 passes.

De Young, R. J.↗
NASA NTRS1981

An f/35 submillimeter photometer for the NASA infrared telescope facility

The design and performance of an f/35 submillimeter photometer are discussed. It is noted that the instrument provides for both broad- and medium-width passbands between 350 microns and 2 mm and for beam sizes between 28 arcsec and 100 arcsec FWHM. Under good atmospheric conditions, a broad-band 400 micron sensitivity of approximately 1.5 Jy is found to be obtainable in one hour. A description is given of the photometer's support housing, submillimeter radiometer, and electronics and data-handling system. In evaluating the performance, attention is given to sensitivity, beam profiles, and the effect of changes in the aperture on the signal.

Whitcomb, S. E.↗
NASA NTRS1984

High frequency plasma generator for ion thrusters

The results of a program to experimentally develop two new types of plasma generators for 30 cm electrostatic argon ion thrusters are presented. The two plasma generating methods selected for this study were by radio frequency induction (RFI), operating at an input power frequency of 1 MHz, and by electron cyclotron heating (ECH) at an operating frequency of 5.0 GHz. Both of these generators utilize multiline cusp permanent magnet configurations for plasma confinement and beam profile optimization. The program goals were to develop a plasma generator possessing the characteristics of high electrical efficiency (low eV/ion) and simplicity of operation while maintaining the reliability and durability of the conventional hollow cathode plasma sources. The RFI plasma generator has achieved minimum discharge losses of 120 eV/ion while the ECH generator has obtained 145 eV/ion, assuming a 90% ion optical transparency of the electrostatic acceleration system. Details of experimental tests with a variety of magnet configurations are presented.

Goede, H.↗