Ionization of multielectron atoms by fast charged particles
Ionization of multielectron atoms by fast charged particles and electron and proton impact
Kyle, H. L.↗
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Proton collisional excitation in the ground configuration of Fe/+12/. II
Improved values of the proton impact excitation cross sections at coronal energies for all the Fe(+12) ground configuration transitions are presented. These were obtained by direct computer integration of the Schroedinger equation (with the states expressed in intermediate coupling) resulting from the semiclassical Coulomb excitation theory formulation of the process. Comparison is made with previous results. The associated rate constants at coronal temperatures are given and compared with the corresponding electron impact excitation rate constants.
Landman, D. A.↗
Minima in generalized oscillator strengths for initially excited hydrogen-like atoms
Generalized oscillator strengths for transitions from an initially excited state of a hydrogenic atom to final states (either discrete or continuum) have complicated structures, including minima and shoulders, as functions of the momentum transfer. Extensive calculations carried out in the present work have revealed certain systematics of these structures. Some implications of the minima to the energy dependence of the inner-shell ionization cross section of heavy atoms by proton impact are discussed.
Matsuzawa, M.↗
Effects of secondary yield parameter variation on predicted equilibrium potential of an object in a charging environment
The sensitivity of predicted equilibrium potential to changes in secondary electron yield parameters was investigated using MATCHG, a simple charging code which incorporates the NASCAP material property formulations. The equilibrium potential was found to be a sensitive function of one of the two parameters specifying secondary electron yield due to proton impact and of essentially all the parameters specifying yield due to electron impact. The information on the electron generated secondary yield parameters was discovered to be obtainable from monoenergetic beam charging data if charging rates as well as equilibrium potentials are accurately recorded.
Purvis, C. K.↗
Effects of secondary yield parameter variation on predicted equilibrium potential of an object in a charging environment
A study is presented in which the sensitivity of predicted equilibrium potential to changes in secondary electron yield parameters is investigated using MATCHG, a simple charging code which incorporates the NASCAP material property formulations. It is found that equilibrium potential is a sensitive function of one of the two parameters specifying secondary electron yield due to proton impact and of essentially all the parameters specifying yield due to electron impact. In addition, it is found that information on the electron generated secondary yield parameters can be obtained from monoenergetic beam charging data if charging rates as well as equilibrium potentials are accurately recorded.
Purvis, C. K.↗
Theoretical studies of radiation effects in composite materials for space use
Tetraglycidyl 4,4'-diamino diphenyl methane epoxy cured with diamino diphenyl sulfone was used as a model compound. Computer programs were developed to calculate (1) energy deposition coefficients of protons and electrons of various energies at different depths of the material; (2) ranges of protons and electrons of various energies in the material; and (3) cumulative doses received by the composite in different geometric shapes placed in orbits of various altitudes and inclination. A preliminary study on accelerated testing was conducted and it was found that an elliptical equitorial orbit of 300 km perigee by 2750 km apogee can accumulate, in 2 years or less, enough radiation dose comparable to geosynchronous environment for 30 years. The local plasma model calculated the mean excitation energies for covalent and ionic compounds. Longitudinal and lateral distributions of excited species by electron and proton impact as well as the probability of overlapping of two tracks due to two charged particles within various time intervals were studied.
Chang, C. K.↗
Analytic representations of secondary-electron spectra
A general method for systematizing a bulk of data on the secondary-electron spectrum into a small number of indices is shown. The method is based on thorough examination of the mathematical physics that governs the spectrum. Several examples of the analysis of recent experimental data on proton impact are presented.
Inokuti, Mitio↗
Phenomenological treatments of cross-sections for proton and hydrogen impact below 1 keV on molecular nitrogen
An analytic independent-particle model is used to construct static potentials to describe the interaction of hydrogen-like ions with atoms and molecules. Parameters of the ion-atom potential are determined from ab initio total energy minimization procedure. The elastic scattering of He(+) from Ne and Ar is investigated as a test case and comparison is made with experiment. The model is then used in conjunction with low energy H(+)-N2 experimental data to construct differential and total cross-sections for the scattering of protons and hydrogen in the energy range of 10 eV to 1 keV from molecular nitrogen. Analytic forms are used to parametrize these cross-sections to facilitate their use in the calculation of energy deposition by protons and hydrogen atoms in atmospheric gases.
Porter, H. S.↗
Energy required for proton production by electron impact in mixtures of atomic and molecular hydrogen
Energy requirements for proton production by electron impact of hydrogen plasma
Monnin, C. F.↗
Energy required for proton production by electron impact in mixtures of atomic and molecular hydrogen.
Energy required for proton and molecular hydrogen ion production by electron impact in tenuous hydrogen plasma using Maxwellian electron gas model
Monnin, C. F.↗
Vacuum ultraviolet emission produced by proton and H-atom impact on H sub 2.
Proton and H atom collisions with H molecules, noting cross sections for vacuum UV emission bands and Lyman alpha radiation
Anderson, D. K.↗
Long-range effects in the 2s and 2p excitations of hydrogen by proton and helium-ion impact
Atomic hydrogen 2s and 2p excitations by proton and He ion impact, considering ion-multipole interactions effect
Flannery, M. R.↗
Optical emission produced by proton and hydrogen-atom impact on nitrogen.
Optical emissions produced in collisions of protons and hydrogen atoms incident on nitrogen molecules studied in 1200 to 6000 angstrom spectral region
Anderson, D. K.↗
Simulation and measurement of the dynamic strain response in a prototypical spallation target
The Second Target Station (STS) at the Spallation Neutron Source (SNS) will address emerging scientific challenges by providing a source of intense cold neutrons to instruments optimized for this source. The STS target will use rotating tungsten blocks and will receive 1.3 GeV proton beam pulses from the SNS accelerator at a repetition rate of 15 Hz. The facility life is planned for 40 years, and each target assembly life is expected to be approximately 10 years. An accurate strain prediction is then critical for fatigue life assessment of STS target blocks because they will be subject to approximately 10 8 beam pulses per lifetime. As an R&D activity, the Los Alamos Neutron Science Center (LANSCE) Weapons Neutron Research (WNR) Target 2 (Blue Room) facility was used to test the strain response of prototypical target blocks to the thermal shock of a proton pulse. The blue room was well suited for a pulsed proton beam impact test of subscale STS target blocks; the 800 MeV proton energy is approximately 60 % of the 1.3 GeV proton energy expected from the SNS accelerator to the STS. The LANSCE Proton Storage Ring (PSR) and SNS are both short-pulse proton beam sources with nominal pulse widths of 250 ns and 661 ns, respectively, so the energy deposition in the target occurs in <1 μs pulse duration. Strain measurements on the outer surface of three target blocks (bare tungsten, tantalum-clad tungsten, niobium-clad tungsten) were recorded for comparison against neutronics and structural simulations. In conclusion, this experiment and the supporting simulations satisfied the following primary research goals for the STS target.
Dynamic strain response↗
Long-term Measurements of Solar Proton Fluxes (1963-present) and the Subsequent Impact on Stratospheric Constituents
The fluxes of solar protons have been measured by satellites for over forty years (1963-present). Eight Interplanetary Monitoring Platform (IMP) satellites measured solar proton fluxes from 1963-1993 and five NOAA Geostationary Operational Environmental Satellites (GOES) were used for the period 1994present. These high energy solar protons precipitate on the Earth's polar atmosphere sporadically, especially during solar proton events (SPEs), which typically last a few days. Solar protons with energies greater than 30 MeV are capable of reaching the stratosphere and causing increases in odd hydrogen (HOx) and odd nitrogen (NOy) constituents at polar latitudes (greater than 60 degrees geomagnetic). The enhanced HOx leads to short-lived ozone depletion (-days) due to the short lifetime of HOx constituents. The enhanced NOy leads to long-lived ozone changes because of the long lifetime of the NOy family in the stratosphere. Several very large SPEs (August 1972, August and October 1989, July and November 2000, September and November 2001, and October 2003) over the 1963-2004 time period were simulated in the GSFC two-dimensional chemistry and transport model and were predicted to cause significant polar upper stratospheric ozone depletion greater than 10%, which lasted for several weeks past the events. Several satellite instruments (BUV, SBUV, SBW/2, SAGE II, HALOE, etc.) have shown constituent changes as a result of SPEs. Long-term (greater than 40 year) model simulations of the influence of the solar protons and satellite measurements during and after some of the very large SPEs will be shown.
Jackman, Charles H.↗
The kinetic energy spectrum of protons produced by the dissociative ionization of H2 by electron impact
The kinetic energy spectra of protons resulting from the dissociative ionization of H2 by electron impact have been measured for electron impact energies from threshold (approximately 17 eV) to 160 eV at 90 deg and 30 deg detection angles, using a crossed-beam experimental arrangement. To check reliability, two separate proton energy analysis methods have been employed, i.e., a time-of-flight proton energy analysis and an electrostatic hemispherical energy analyzer. The present results are compared with previous measurements.
Khakoo, M. A.↗
Effect of H + Exchange and Surface Impurities on Bulk and Interfacial Electrochemistry of Garnet Solid Electrolytes
Contact loss and current constriction pose significant challenges at the Li metal interface of solid-state batteries. For garnet-structured Li 7 La 3 Zr 2 O 12 (LLZO), these effects are amplified by Li + /H + exchange and surface contamination reactions, which lead to conductivity losses and poor Li wetting. In this study, we utilize a variety of surface treatment processes across 37 cells to selectively induce proton exchange and contamination reactions in LLZO. The resulting bulk and surface chemistry is systematically characterized and correlated to changes in electrochemical properties. Additionally, we combine impedance analysis and finite element method modeling to deconvolute sources of impedance contributions at the Li metal interface. Specifically, we show that constriction impedance at the Li metal interface arises not solely from voids, but also from ionically-resistive surface contaminants. Further, these findings emphasize the connection between ionic conductivity and constriction, demonstrating that micron-scale ionically-resistive components increase constriction even with identical contact geometries. Finally, we leverage our comprehensive dataset to highlight unstable overpotential growth as a failure mechanism, additionally showing that the phase of a cell’s impedance is a sensitive indicator for the onset of interfacial instability. Overall, this study clarifies the impacts of proton exchange and surface contamination on electrochemical properties at the Li|solid electrolyte interface and elucidates insights that are generalizable to other solid-state battery systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Extraction and Injection in the Electron Injector for the Electron-Ion Collider
The electron injector for the Electron-Ion Collider (EIC) consists of a linear accelerator, a beam accumulation ring, and the Rapid Cycling Synchrotron (RCS) before the electrons are injected into the Electron Storage Ring (ESR) and collided. Extraction out of the RCS is complicated by limited space and the nominal beam pipe aperture, while injection into the ESR is complicated due to the limitation of kicker strength, so that the kickers will not impact the proton beam in the adjacent Hadron Storage Ring (HSR); additionally, the ESR kickers must also provide enough kick to the stored bunch for the swap-out scheme. This paper covers the injection into and extraction out of the RCS, as well as injection into the ESR, detailing layout, optics, and anticipated parameters of the septa and different kickers.
Deitrick, K. [Thomas Jefferson National Accelerato↗