Stopping powers of the noble gases for 300-keV to 10-MeV nitrogen ions were measured using a time-of-flight technique. The stopping power was directly determined from changes in ion time of flight over a fixed distance as a function of the target-gas pressure of a differentially pumped, windowless gas cell. The measured stopping-power values are compared to predictions of the modified Firsov theory of Land and Brennan (FLB) [At. Data Nucl. Data Tables 22, 235 (1978)] and to values compiled by Ziegler et al. [Stopping and Range of Ions in Solids (Pergamon, New York, 1985)]. The measured values are close to the FLB values at v = v0 for low target atomic number Z but are somewhat lower at higher Z. They are systematically smaller than those of Ziegler et al. at nitrogen energies below 2.5 MeV and larger from 2.5 to 10.0 MeV. For projectile velocities greater than v0 the stopping in general is found not to be proportional to velocity.

The Naval Surface Warfare Center (NSWC) at White Oak is completing a major upgrading of its positive-ion accelerator facilities dedicated to the study of ion-atom collisions and ion-beam analysis of materials. At the heart of the facility is a new National Electrostatics Corporation 3 MV tandem accelerator which replaced a 2.5 MV Van de Graaff. There are two ion sources available which will enable the accelerator to produce an ion from nearly any element in the periodic table. Mass-energy control is defined by a 90 ° analyzing magnet. A downstream switching magnet allows for the establishment of five separate beam lines. Currently three beam lines are in operation: an RBS and PIXE analysis system, an NRA analysis system, and an experimental line for measuring the stopping powers of ions in gases. In addition to numerous PCs for data manipulation, a VAX computer system is being upgraded to perform computer-controlled acquisition and analysis of spectral data. Details on the upgrade will be presented as well as recent results of ion-beam analysis.

Stopping powers for 400 to 2400 keV N ions in He and Ar gas targets were measured using a time-of-flight technique. The stopping power was directly determined from changes in ion time-of-flight over a fixed distance after passing through a differentially-pumped, windowless gas cell. Start and stop pulses, derived from secondary electrons produced by passing the ion through thin C foils and detected by microchannel plates, are used to trigger a TAC spectrometer. The measured stopping power values are analyzed as a function of their linearity with projectile velocity and are compared to values compiled by Ziegler et al. and to the predictions of the Firsov-Land-Brennan (FLB) theory. In general, the measured values agree with FLB but are consistently lower than those of Ziegler et al. Comparison of results obtained with 14N and 15N and with N+ and N2+ projectiles are presented. Details of the measurement and detection systems are also given.

The impact-parameter dependence of the K-shell ionization cross section has been measured for protons and $^{3}\mathrm{He}$ ions incident on thin-foil targets of Ti, Ni, and Cu at selected energies in the region from 0.4 to 2.0 MeV/u. Comparison is made of these experimentally determined values with the results of a recently developed theoretical model in which the electron binding energy and initial-state wave function are allowed to respond in a time-dependent fashion to the field of the projectile as a function of its position along a hyperbolic Coulomb trajectory. Generally good agreement between the theoretical and experimental values is obtained. A comparison between the results of this theoretical model and two other published theoretical results and with experimental data for 0.5-MeV p in Cu is also shown. Remarkably close agreement is seen, particularly between the predictions of the rather disparate theoretical models. Measurements for a single system, 2.0-MeV p in Sm, involving ionization from the L shell, are also reported.

Absolute K-shell x-ray production cross sections have been measured for $^{3}\mathrm{He}$ ions in the energy range from 0.175 to 1.6 MeV/u incident on selected thin-foil targets from Ti (Z=22) through Ag (Z=47). A few measurements were made for incident $^{4}\mathrm{He}$ ions at energies from 0.2 to 0.6 MeV/u in order to study the effects of Coulomb deflection and retardation. Newly measured values are also reported for incident protons at energies from 0.5 to 2.5 MeV on numerous target elements from Sc (Z=21) through Zn (Z=30). The x-ray production cross sections were determined from x-ray yields normalized to simultaneous measurements of particle-scattering yields at 75\ifmmode^\circ\else\textdegree\fi{}. The K-shell ionization cross sections inferred from these results are compared with the predictions of the energy-loss Coulomb-deflection perturbed-stationary-state relativistic theory. There is agreement generally to within 10% although a systematic discrepancy, previously observed, is reproduced. Close agreement is obtained for protons with the reference values of Paul and Muhr [Phys. Rep. 135, 47 (1986)]. This investigation is part of an overall experimental-theoretical program whose goals are (1) to enlarge the data base of ion-induced x-ray production cross sections by establishing accurate experimental values and (2) to determine the limitations of the current theoretical descriptions of the inner-shell ionization process and their ability to calculate experimental quantities precisely.

Theoretical calculations for the proton-induced K-shell ionization probability in which the ground-state electron wave function is allowed to be polarized under the influence of the incident projectile are described. These calculations extend the results of a previous theoretical model in which the wave function is allowed only a spherically symmetric distortion. The model is based upon lowest-ord...

Absolute K-shell x-ray-production cross sections have been measured for thin-foil targets of Sc, Ti, V, Cr, Co, Ni, Cu, and Zn for incident protons with energies from 500 to 2200 keV. In order to determine the x-ray production cross sections with high precision (≈ 5%), particular care was necessary in the control of experimental conditions. The overall agreement of the proton-induced cross section...

Densities of porous anodic aluminum oxide coatings have been measured to range from 1.1 to 2.2 g/cm3, values approximately 0.3–0.6 times those of bulk . These measurements are obtained by using two independent techniques for determining film parameters, Rutherford backscatter (RBS) of MeV protons and alpha particles and optical or scanning Auger microscopy. The former gives areal densities in units of g/cm2 and the latter two thicknesses in units of cm. Additional information on the composition of the films studied using ion‐induced x‐ray analysis simultaneously with RBS is: (i) the compositions are mainly with small amounts of or for those anodic layers grown in or electrolytes, respectively; (ii) sulfur is present as a contaminant in layers grown in electrolytes; (iii) there is a reduction in the concentration of the alloying elements in anodized films grown on 7075 T‐73 Al; (iv) atoms from the cathode are deposited on the film surfaces during anodization; (v) chlorine is present throughout the surface of alumina samples severely corroded in solutions.

Calculations of the electronic stopping power for low-velocity ($v<{Z}_{1}^{\frac{2}{3}}{v}_{0}, {v}_{0}=\frac{{e}^{2}}{\ensuremath{\hbar}}$) heavy ions, based upon three models, are performed for two systems for which experimental data are available: 800-keV $^{14}\mathrm{N}^{+}$ ions incident on amorphous solid targets from carbon to tellurium and 100-keV $^{7}\mathrm{Li}^{+}$ ions incident on amorphous targets from carbon to selenium. The results of the models are compared with each other and with the experimental data. The models are found to offer qualitatively better fits to the oscillatory experimental data than the smooth curves of the Lindhard-Scharff theory, with a particular modification of the Firsov theory favored for predictive calculations. All the models, as implemented here, required a parameter to be determined by fitting the calculated curves to the experimental points.