Kunihiro Shima

Equilibrium charge fractions of ions of Z = 4–92 emerging from a carbon foil

Based on recent findings that the variation of charge fractions, mean charges, and charge distribution widths with ion energy E and projectile atomic number Z is strongly dependent on the shell structure of the ions, systematic reanalysis of the charge distributions of ions has been performed. Graphs are presented for equilibrium charge fractions thus obtained of ions emerging from a carbon foil as a function of exiting ion energy E ranging from 0.02 to 6 MeV/u. Each graph pertains to one ion species from Z = 4 to 83 and Z = 92. Tables of the mean charges and charge distribution widths are also given for each ion species in the same range of Z and E. Charge fractions of fully stripped ions, H-like ions, and He-like ions are also tabulated from Z = 4 to 20 for fast ions with E up to 40 MeV/u.

Equilibrium charge state distributions of ions (Z1≥4) after passage through foils: compilation of data after 1972

Tables are presented for equilibrium charge distributions, mean charges, and distribution widths of energetic heavy ions (Z/sub 1/> or =4) passing through thin foils. Data reported since May 1972 are included here, updating tables compiled by Wittkower and Betz in AtomIc Data 5, 113 (1973).

Empirical formula for the average equilibrium charge-state of heavy ions behind various foils

A new empirical formula for the average equilibrium charge-state, q, of heavy ions observed after traversal of various foils is presented. The formula is q=[1−exp(−1.25X+0.32X2−0.11X3)]1−0.0019(Z2−6)X+0.00001(Z2−6)2X where Z1 and Z2 are the ion and target foil atomic numbers respectively, and X is the reduced ion velocity as defined by Nikolaev and Dmitriev [1]. The present formula is useful for the collision range Z1 ⩾ 8, 4 ⩽ Z2 ⩽ 79 and E < 6 MeV/amu, to within an accuracy of Δq/Z1 < 0.04.

Response functions of a Si(Li) detector for 1.3–4.0 keV monochromatic photons

Abstract The response functions of a Si(Li) detector have been measured for monochromatic photons in the energy range 1.3–4.0 keV using synchrotron radiation from a 2.5 GeV electron storage ring. The contribution of the low-energy tail, just below the Gaussian full-energy peak, changed drastically at the boundary energy of the Si-K. absorption edge. The structure of the low-energy tail and the tail-to-peak ratio can be described by introducing a new simple geometrical model. The results of a fit based on the model were excellent for all data obtained over a wide energy range.

Si(Li) detector efficiency for 0.7–6 keV X-ray energy region

Abstract Using accelerated proton induced X-rays and some radioisotopes, the Si(Li) detector efficiency has been measured in the X-ray energy region of 0.7–6 keV. The efficiency has been determined by comparing the X-ray counts of a Si(Li) detector and a proportional counter of known efficiency when both are simultaneously irradiated by the emitted characteristic X-ray flux within the evacuated chamber. Obtained results indicate that simple estimation of efficiencies according to the given thickness of the Be window may lead to an error especially in the low energy region of X-rays.

ISOTOPE DEPENDENCE IN K-, L-, AND M-SHELL IONIZATION CROSS SECTIONS BY PROTON AND DEUTERON BOMBARDMENTS.

The ionization cross sections of Al-K, Ti-K, Cu-L, Mo-L, Ag-L and W-M shells have been presented for the incident protons and deuterons in the energy range from 90 to 180 keV/amu. The cross sections are derived from the thick target yields of the respective characteristic X-rays. In contrast with the prediction by Born approximation, isotope dependence is clearly found in the ionization of each target atom. The cross section ratios for K and L shells against the projectile energy per nucleon line up systematically according to the shell binding energies of target atoms. The magnitudes of the K shell ionization cross sections are in good agreement with “binding theory” of Brandt et al. . This means that, in the present energy range, the ionization cross sections depend strongly on the Coulomb deflection of the incident particle and the transient additional binding energy of the K shell electron with the incident particle during the collision.

Measurement of the low energy tail spectra adjacent to the x-ray photopeak in Si(Li) x-ray detectors☆

Abstract Low energy tail spectra, which are inherently observed adjacent to the X-ray photopeak in the use of a Si(Li) X-ray detector, have been measured for the 1.3–3.7 keV X-ray energy range. Three different Si(Li) detectors have been tested. The tail/peak count ratios as a function of incident X-ray energy have exhibited a rapid change at the boundary energy of the Si K absorption edge. From the observed tail/peak count ratios, the thickness of the Si layer which produces the tail spectrum has been estimated; the thicknesses for the three tested detectors are about 0.05, 0.1 and 0.2 μm. In addition to the carrier diffusion effect, it is proposed in the case of a Si(Li) detector that the effect of the escape (penetration) of Auger and phtoelectrons from (into) the intrinsic region plays an important role in the production of the tail spectra.

Quantitative trace element analysis of single fluid inclusions by proton-induced X-ray emission (PIXE): Application to fluid inclusions in hydrothermal quartz

Abstract Single fluid inclusion analogues with known elemental composition and regular shape were analyzed for trace element contents by particle-induced X-ray emission (PIXE)—a nondestructive method for the analysis of single fluid inclusions—to evaluate the accuracy and detection limits of this type of analysis. Elements with concentrations of 10 to 1000 ppm were measured with average estimated relative error of ±7%. For natural fluid inclusions with 30 μm radius and 20 μm depth in quartz, the total analytical errors were estimated to be ±40% relative for Ca, ±16% for Fe, ±13% for Zn, ±12% for Sr, and ±11% for Br and Rb, by considering uncertainties in microscopic measurements of inclusion depths. Detection limits of 4 to 46 ppm for elements of mass numbers 25–50 were achieved for analyses of a spherical fluid inclusion with 30 μm radius and 20 μm depth in quartz, at an integrated charge of 1.0 μC. The trace element compositions of single fluid inclusions in a hydrothermal quartz crystal were also determined. The elemental concentrations in the inclusions varied widely: 0.2–9 wt.% for Ca and Fe, 300–8000 ppm for Mn and Zn, 40–3000 ppm for Cu, 100–4000 ppm for Br, Rb, Sr, and Pb, and less than 100 ppm for Ge. Elemental concentrations of secondary fluid inclusions on the same trail varied over an order of magnitude, even though all these inclusions were formed from the same fluid. Elemental concentrations in inclusions on the same trail are positively correlated with each other, except for Cu and Rb. Ratios of almost all elements in the inclusions on the trail were essentially unchanged; thus, the elemental ratios can provide original information on trace element compositions of a hydrothermal fluid.

Mn and Cu K-shell ionization cross sections by slow electron impact

Abstract Near the threshold energy, electron induced Mn and Cu K-shell ionization cross sections have been measured. Except for energies very close to threshold, the results are in good agreement with the semi-empirical formula of Green and Cosslett.

Thickness measurement of gold contact layers in Si(Li) and Ge x-ray detectors

Four kinds of Si(Li) and a high‐purity Ge x‐ray detectors have been tested to measure the thicknesses of gold contact layers by comparing the response of the primary Rb‐Kα x‐rays with that of the induced Au‐Lα x rays. Observed thicknesses ranged from 140 to 260 A. Near the x‐ray energies of Au‐M subshell absorption edges, the contribution of x‐ray transmission through the observed gold layers to the detection efficiency is greater than or equivalent to that of the inherently attached 7.6‐μm beryllium window. Hence, one must be careful in the determination of the detection efficiency in x‐ray semiconductor detector when low‐energy x rays of less than about 4 keV are measured.