Interaction of cosmic protons with interplanetary plasma
Proton beam energy losses to interplanetary plasma electrostatic oscillations
Nikolayev, Yu. M.↗
SEARCH · Engineering Papers
Results for “Beam loss”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Performance of 30-cm ion thrusters with dished accelerator grids
Thirteen sets of dished accelerator grids were treated on five different 30 cm diameter bombardment thrusters to evaluate the effects of grid geometry variations on thruster discharge chamber performance. The dished grid parameters varied were: grid-to-grid spacing, screen and accelerator grid hole diameter, screen and accelerator open area fraction, compensation for beam divergence losses, and accelerator grid thickness. The effects on discharge chamber performance of main magnetic field changes, magnetic baffle current, cathode pole piece length and cathode position were also investigated.
Rawlin, V. K.↗
Performance of 30-cm ion thrusters with dished accelerator grids
Thirteen sets of dished accelerator grids were tested on five different 30-cm diameter bombardment thrustors to evaluate the effects of grid geometry variations on thrustor discharge chamber performance. The dished grid parameters varied were: grid-to-grid spacing, screen and accelerator grid hole-diameter, screen and accelerator open area fraction, compensation for beam divergence losses, and accelerator grid thickness. Also investigated were the effects on discharge chamber performance of main magnetic field changes, magnetic baffle current cathode pole piece length and cathode position.
Rawlin, V. K.↗
Absolute line strengths in nu4, /C-12/H4 - A dual-beam diode laser spectrometer with sweep integration
A tunable diode laser spectrometer with several unique features has been developed for use in the middle IR. The all-reflective optical system has a dual-beam configuration before the dispersive mode selector to eliminate transit-angle errors at the calibration etalon. By maintaining separated beams through the mode selector, beam combiner losses are avoided. Averaging successive sweeps of the current-modulated laser permits stable reproducible spectral integrations, eliminating etalon thermal errors and producing high photometric sensitivity. Line strengths have been measured using this instrument for eleven transitions in nu4 of (C-12)H4. These include R0 and R1 and nine P-branch transitions in the 1202-1263-per cm range. Techniques for measuring strengths with a diode laser are discussed.
Jennings, D. E.↗
The 20 GHz proof-of-concept test model results for a multiple scan beam dual reflector antenna
A full scale 20 GHz antenna model was designed, fabricated and tested. The model is intended to test the low sidelobe beam scanning capability of a new class of an offset dual reflector and feed array configuration. The offset main reflector and subreflector surfaces are custom shaped by a computer synthesis procedure. The derived optics result in beam scan loss under 1 db over the + or - 12.3 beamwidths by + or - 5.8 beamwidths scan volume while maintaining low sidelobes. It is found that the measured and computed patterns are in good agreement.
Roberts, T.↗
Hubble Space Telescope: Faint object spectrograph instrument handbook. Version 1.1
The Faint Object Spectrograph (FOS) has undergone substantial rework since the 1985 FOS Instrument Handbook was published, and we are now more knowledgeable regarding the spacecraft and instrument operations requirements and constraints. The formal system for observation specification has also evolved considerably, as the GTO programs were defined in detail. This supplement to the FOS Instrument Handbook addresses the important aspects of these changes, to facilitate proper selection and specification of FOS observing programs. Since the Handbook was published, the FOS red detector has been replaced twice, first with the best available spare in 1985 (which proved to have a poor, and steadily degrading red response), and later with a newly developed Digicon, which exhibits a high, stable efficiency and a dark-count rate less than half that of its predecessors. Also, the FOS optical train was realigned in 1987-88 to eliminate considerable beam-vignetting losses, and the collimators were both removed and recoated for greater reflectivity. Following the optics and detector rework, the FOS was carefully recalibrated (although only ambient measurements were possible, so the far-UV characteristics could not be re-evaluated directly). The resulting efficiency curves, including improved estimates of the telescope throughput, are shown. A number of changes in the observing-mode specifications and addition of several optional parameters resulted as the Proposal Instructions were honed during the last year. Target-brightness limitations, which have only recently been formulated carefully, are described. Although these restrictions are very conservative, it is imperative that the detector safety be guarded closely, especially during the initial stages of flight operations. Restrictions on the use of the internal calibration lamps and aperture-illumination sources (TA LEDs), also resulting from detector safety considerations, are outlined. Finally, many changes have been made to the instructions for target acquisition specification.
Ford, Holland C.↗
Collision Strengths for Electron Collisional Excitation of S II
Electron collisional excitation strengths for inelastic transitions in S II are calculated using the R-matrix method in a 19-state (3s(sup 2)3p(sup 3)(sup 4)S(sup o), (sup 2)D(sup o), (sup 2)p(sup o), 3s3p(sup 4)(sup 4)P, (sup 2)D, (sup 2)S, 3S(sup 2)3p(sup 2)3d(sup 2)P, (sup 4)F, (sup 4)D, (sup 2)F, (sup 4)P, 3s(sup 2)3p(sup 2)4s(sup 4)P, (sup 2)P, 3s(sup 2)3p(sup 2)4p(sup 2)S(s o), (sup 4)D(sup o), (sup 4)P(sup o), (sup 2)D(sup o), (sup 4)S(sup o), (sup 2)P(sup o)) close-coupling approximation. These target states are represented by extensive configuration-interaction wave functions that give excitation energies and oscillator strengths that are usually in good agreement with the experimental values and the available accurate calculations. The present results for collision strengths are in very good agreement with the recent merged beams energy loss measurement of Liao et al. and agree reasonably well with the 18-state R-matrix calculation of Ramsbottom, Bell, & Stafford, but show significant differences from the 12-state R-matrix calculation of Cai & Pradhan.
Tayal, S. S.↗
Laser-Ablated Ba(0.50)Sr(0.50)TiO3/LaAlO3 Films Analyzed Statistically for Microwave Applications
Scanning phased-array antennas represent a highly desirable solution for futuristic near-Earth and deep space communication scenarios requiring vibration-free, rapid beam steering and enhanced reliability. The current state-of-practice in scanning phased arrays is represented by gallium arsenide (GaAs) monolithic microwave integrated circuit (MMIC) technology or ferrite phase shifters. Cost and weight are significant impediments to space applications. Moreover, conventional manifold-fed arrays suffer from beam-forming loss that places considerable burden on MMIC amplifiers. The inefficiency can result in severe thermal management problems.
Romanofsky, Robert R.↗
Numerical Analysis of High-Order Modes in SRF Resonators for Particle Accelerators
Over the past decades, superconducting technology has rapidly evolved towards high accelerating gradients and low surface resistance, making it possible to operate particle accelerators with high average beam currents and large duty factors. However, RF losses due to coherent excitation of the HOM become the limiting factor for these regimes. Unlike the cavity operating mode, which is tuned separately, the HOM parameters can significantly vary from one cavity to another due to finite mechanical tolerances during the manufacturing process. Thus, it is of utmost importance to know the HOM parameter spread in advance in order to predict unexpected cryogenic losses, overheating of beam line components and maintain stable beam dynamics. In this paper, we present a method for generating cavity geometry with an arbitrary spread of mechanical imperfections and numerically evaluating HOM statistics. Knowing the spread of HOM parameters, we calculated the probability of resonant HOM losses in SRF accelerating cavities used in CW beam current machines such as the PIP-II and LCLS-II linacs, as well as for the SRF crab-cavity for the ILC project. Finally, we present experimental results of HOM spectra measurements in hundreds of 1.3 GHz cavities installed in LCLS-II cryomodules. Studying the effects of HOM excitation results in specifications of the SRF cavity and cryomodule and can significantly impact the efficiency and reliability of the machine operation.
Lunin, Andrei [Fermilab] (ORCID:0000000290096792)↗
Low-loss optical waveguides made with molecular beam epitaxial In(0.012)Ga(0.988)As and In(0.2)Ga(0.8)As-GaAs superlattices
Low-loss optical guiding in In-doped GaAs is demonstrated for the first time. Ridge waveguides are made with single In(0.012)Ga(0.988)As ternary layers and In(0.2)Ga(0.8)As-GaAs superlattices. Attenuation constants of about 1.3 dB/cm are measured and the principal loss mechanism is identified to be scattering at the ridge walls. It is expected that improved fabrication techniques will lead to guides with attenuation less than or equal to 0.5 dB/cm.
Das, U.↗
Power Loss For Multimode Waveguide and its Application to Beam-Waveguide Systems
The conventional way of expressing power loss in dB/meter for a multimode waveguide system with finite wall conductivity (such as a beam-waveguide system with protective shroud) can be incorrect and misleading.
beam-waveguide↗
Power Loss For Multimode Waveguides and its Application to Beam-Waveguide Systems
The conventional way of expressing poer loss in dB/meter for a multimode waveguiding system with finite wall condcutivity (such as a beam-waveguide system with protective shroud) can be incorrect and misleading. The power loss (indB) for a multimode waveguiding system is, in general, not linearly proportional to the length of the waveguide.
Multimode↗
An initial study of using the 34-m antenna for lunar mission support
As a part of the long-range planning of future Mars and lunar missions, a feasibility study was made of a 34-m antenna system with differentially pointed multiple beams. The performance loss mechanisms of the differentially pointed multiple-beam systems were identified and quantified. Techniques that can significantly improve the multiple-beam system performance are identified. The goal is to determine the feasibility of using the 34-m antenna to support widely separated elements associated with lunar missions.
Cha, A.↗
An Initial Study of Using the 34-m Antenna for Lunar Missions Support
As a part of the long-range planning of future Mars and lunar missions, a rudimentary study has been made of a 34-m antenna system with differentially pointed multiple beams. The performance loss mechanisms of the differentially pointed multiple-beam systems were identified and quantified. The goal is to determine the feasibility of using the 34-m antenna to support widely separated elements associated with lunar missions.
lunar↗
Ion Acoustic Wave Frequencies and Onset Times During Type 3 Solar Radio Bursts
Conflicting interpretations exist for the low-frequency ion acoustic (S) waves often observed by ISEE 3 in association with intense Langmuir (L) waves in the source regions of type III solar radio bursts near 1 AU. Two indirect lines of observational evidence, as well as plasma theory, suggest they are produced by the electrostatic (ES) decay L yields L(PRIME) + S. However, contrary to theoretical predictions, an existing analysis of the wave frequencies instead favors the electromagnetic (EM) decays L yields T + S, where T denotes an EM wave near the plasma frequency. This conflict is addressed here by comparing the observed wave frequencies and onset times with theoretical predictions for the ES and EM decays, calculated using the time-variable electron beam and magnetic field orientation data, rather than the nominal values used previously. Field orientation effects and beam speed variations are shown analytically to produce factor-of-three effects, greater than the difference in wave frequencies predicted for the ES and EM decays; effects of similar magnitude occur in the events analyzed here. The S-wave signals are extracted by hand from a sawtooth noise background, greatly improving the association between S waves and intense L waves. Very good agreement exists between the time-varying predictions for the ES decay and the frequencies of most (but not all) wave bursts. The waves occur only after the ES decay becomes kinematically allowed, which is consistent with the ES decay proceeding and producing most of the observed signals. Good agreement exists between the EM decay's predictions and a significant fraction of the S-wave observations while the EM decay is kinematically allowed. The wave data are not consistent, however, with the EM decay being the dominant nonlinear process. Often the observed waves are sufficiently broadband to overlap simultaneously the frequency ranges predicted for the ES and EM decays. Coupling the dominance of the ES decay with this frequency overlap provides support for a previous suggestion that fundamental emission occurs when the EM decay is stimulated by the ES decay product waves. The periods in which the ES and EM decays produce observable S waves are consistent with the observed and (independently) predicted times of fundamental and harmonic radio emission. This supports interpretation of fundamental emission as stimulated EM decay and harmonic emission as the coalescence L + L(prime) yields T of beam-generated L waves and L(prime) waves produced by the ES decay, where T denotes an electromagnetic wave at twice the plasma frequency. Analysis of the electron beam data reveals that the time-varying beam speed is consistent with ballistic beam propagation with minimal energy loss, implying that the beam propagates in a state close to time- and volume-averaged marginal stability. This confirms a central tenet of the stochastic growth theory for type III bursts.
Cairns, Iver H.↗
Electron Excitation Cross Sections for the C II Transitions 2s(exp 2)2p P-2(exp 0) yields 2s2p(exp 2) P-4, D-2, and S-2
Experimental and theoretical excitation cross sections are reported for the transitions 2s(exp 2) 2p-2(exp 0) yield 2s2p(exp 2)P-4, D-2, and S-2 in C II. The transition wavelengths (energies) are 2324 A (5.34 eV), 1335 x (9.29 eV), and 1036 A (11.97 eV), respectively. Use is made of electron energy-loss and merged beams methods. The energy range covered is from below each threshold (4 - 11 eV) to 15-24 eV. As in previous work with O II, care was taken to assess and minimize the metastable fraction in the C II beam, to account for contributions from nearby energy-loss features, and to collect the full angular range of inelastically scattered electrons. A comparison is made for each transition between experiment and new 8-state R-matrix calculations. Subject headings: atomic data ultraviolet: general
Smith, Steven J.↗
Ion-beam-textured and coated surfaces experiment (S1003)
The objective of this LDEF experiment is to measure the effects of exposure to the shuttle launch and near Earth space environments on the optical properties of ion beam textured high absorptance solar thermal control surfaces, the optical and electrical properties of ion beam sputtered conductive solar thermal control surfaces, and the weight loss of ion beam deposited oxide polymer films. The various types of surfaces to be tested include six major categories: (1) ion beam textured surfaces suitable for space solar thermal (solar concentration) application; (2) painted and/or state of the art solar thermal surfaces; (3) ion beam sputtered conductive coatings for thermal and space charge control (e.g., indium-oxide coated metalized FEP Teflon); (4) ion beam sputtered conductive coated solar sail materials for space charge control and cooling through emittance; (5) micrometeoroid sensitive samples whose optical properties change only as a result of micrometeoroid impact; and (6) Kapton coated with oxide polymer films to minimize oxygen degradation at near Earth orbit altitudes.
Mirtich, M. J., Jr.↗
LAMP Emittance Budget, Rev. 1
This report summarizes the performance limits of the LANSCE Coupled-Cavity Linac (CCL). These results are captured or summarized directly from the references cited. This report was written in support of the LANSCE Modernization Project (LAMP). This brief report summarizes the emittance budget for the LANSCE Modernization Project (LAMP). While the project Key Performance Parameters (KPPs) specify threshold and objective requirements for charge delivered to each experimental area, no upper limits on beam emittances are specified. To maintain low losses in the high-energy section of the LANSCE linac and hands-on maintenance, some upper limits on beam emittance need to be specified for the new LAMP front-end performance. The scope of the LAMP project replaces the injector section and drift-tube linac (DTL) up to 100 MeV of the existing LANSCE linac. This new design replacement will be integrated with the remaining coupled cavity linac (CCL) which makes up most of the accelerator at LANSCE and accelerates the beam to a final energy of 800 MeV. The initial approach that has been used to define an emittance budget for the new LAMP front end is based on recent and historical measured beam emittances at 100 MeV for the three beam types accelerated at LANSCE: H+ (protons for isotope production), LBEG (H- beam for delivery to proton radiography and to the Lujan neutron spallation target, and MPEG (H- beam for delivery to the Weapons Neutron Research facility). The emittance budget (upper limit) for each beam type has been selected to maintain the losses in the CCL to a level approximately equivalent to those observed in present operations to first order. However, the goal of the LAMP project is to improve the quality of the beams injected into the CCL, if possible, thus allowing for higher average current operation while also lowering beam losses and activation at high beam energies. The table below summarizes the beam measurements evaluated and used to establish a conservative emittance budget for LAMP based on known historical beam losses and activation. However, based on estimates of the CCL admittance and the Isotope Production Facility (IPF) beamline acceptance, a more relaxed transverse emittance upper limit of 0.095 π-cm-mrad, rms, normalized may be acceptable at 100 MeV while still meeting the LAMP performance requirements for charge delivery to each LANSCE experimental area and maintaining hands-on maintenance. This upper limit is supported by a recent analysis of operational data. Additionally, the present conceptual LAMP front-end design meets this requirement.
43 PARTICLE ACCELERATORS↗