Si Semiconductor Detector Research Articles

Use of radioisotope induced X-ray fluorescence for environmental studies

The rapid assay of the trace multi-element content of environmental samples (lake sediment) is described. The method utilized X-ray fluorescence induced by a109Cd radioisotopic source with energy dispersive quantitative detection of the characteristic X-rays of nine elements, ranging from Ti to Zr using Si(Li) semiconductor detector. The method precludes pre-digestion or chemical treatment of the samples, and compairs favorably with the results of atomic absorption assay methods.

Trace element analysis of blood serum by proton-induced x-ray fluorescence

A study of human blood serum is utilized to demonstrate both the x-ray emission caused by electrons dropping into atomic inner-shell vacancies produced by proton bombardment and the application of such x-ray emissions to trace element analysis. Sample preparation consisted solely of pipetting 25 μl of serum onto low-ash filter paper. Characteristic Kα x rays from copper and zinc were detected by a Si(Li) semiconductor detector to determine trace concentrations of these essential biological metals in the blood. The copper and zinc concentrations in the blood serum sample analyzed were found to be 1.16±0.13 and 0.70±0.07 ng/μl, respectively.

Tube-excited energy-dispersive x-ray fluorescence analysis : Part II. Energy-dispersive x-ray fluorescence analysis of air particulate material

The use of monoenergetic exciting radiation of molybdenum obtained with a secondary target set-up, a conventional water-cooled tungsten anode x-ray tube and a Si(Li) semiconductor detector permits many trace and minor constituents from chlorine to strontium to be determined in particulate material collected on cellulose filters. The method is rapid and economical compared to other multielement techniques. The use of one or more single-element thin-film standards to calibrate for the analysis of many elements appears to be possible, but some systematic errors must be prevented. Absorption of the fluorescent radiation is remedied by a simple correction method. The precision and the accuracy of the method were critically examined by independent analysis of a number of samples with instrumental neutron activation analysis and by interlaboratory comparisons on the same samples.

Si(Li) semiconductor detector in angle and energy dispersive X-ray diffractometry

An X-ray diffractometer system is described with which angle dispersive, energy dispersive and combined angle and energy dispersive diffraction measurements can be carried out. The appropriateness and the advantages of these methods under different experimental conditions are discussed. The preliminary measurements have shown promising results in using other than characteristic wavelengths in angle dispersive X-ray diffractometry. A combined angle and energy dispersive method is realized experimentally.

X-ray production by 1.5–11 MeV protons

K-shell ionization and L x-ray production cross-sections by proton impact have been determined from measurements of K x-ray yields from thin targets of Ti, Fe, Co, Cu, Ni and Ag and of L x-ray yields from Au and Pb. The proton energies varied from 1.5 to 11 MeV. A Si(Li) semiconductor detector recorded the x-rays. The total error in the measured cross-sections is mostly less than 5 %. Kβ/Kα, ratios and Lι,β,ƴ/Lα, ratios have been determined. Ionization cross-sections have been compared with predictions of the plane-wave Born approximation (PWBA) and the binary-encounter approximation (BEA). Both theories describe the ionization quite well: PWBA is, however, better for higher proton energies whereas BEA is superior for lower energies. An empirical formula for ionization cross-sections is derived. (Less)

The use of X-ray fluorescence in rapid in vivo measurements of iodine, gold and mercury

Efforts are being directed towards developing a rapid method of in vivo measurements of these elements, requiring simple and fast sample preparations. Several methods of exciting the material of interest have been investigated. 241Am is used as a direct source for irradiating the iodine in solution. The use of rare earths as secondary sources in conjunction with an X-ray tube is also being studied. Also the coincidence counting technique is being investigated. The X-ray fluorescence is measured on a KeVeX Si(Li) semiconductor detector.

A 4 πβ- γ-coincidence spectrometer using Si(Li) and NaI(Tl) detectors

The well-tested method of measuring β-spectra with Si(Li) semiconductor detectors in 4 π geometry is extended to inner β −-spectra and positron decays by applying coincidence techniques. For this purpose a 4 π β- γ-coincidence spectrometer has been constructed. The radioactive source and the two 2 π Si(Li) β-detectors are put together in a sandwichlike arrangement. The γ-quanta, emitted in coincidence with the β-particles, are detected by two large NaI(Tl) scintillation counters, which cover a solid angle of 0.6 × 4 π with respect to the source. A sluice enables the source to be quickly brought into the vacuum chamber, so that short-lived decays with halflives down to one minute can be measured. The characteristics of the coincidence spectrometer are checked by measuring the β −-spectrum of 24Na and the positron spectrum of 22Na. The results are in good agreement with those obtained by other methods and show the reliability of the apparatus.

Adaptation of solid state detector in X‐Ray powder diffractometry

AbstractRapidly recorded X‐ray diffraction powder patterns from some metals and from rock salt have been obtained by using the energy sensitive Si (Li) semiconductor detector with the multichannel pulse height analyser. The measured energy resolution of the detector system was about 210 eV for Cu Kα radiation. A good agreement was obtained between observed and calculated positions and relative intensities of the diffraction lines.

Detector system for the analysis of scattered electrons in Tohoku University 300-MeV linac

The magnetic spectrometer to analyze the elastically and inelastically scattered electrons in combination with the Tohoku University 300-MeV electron linear accelerator is described with emphasis on its electron ladder and the data acquisition system. We employed Si(Li) semiconductor detectors combined with the conventional logic circuits for the coincidence counter telescopes and also for the other circuitry system. Three detector pieces were used per channel and a total of 33 such channels were employed. Data was collected during the beam pulse intervals of about 3.3 msec, after each pulse. The stability of the counting efficiency of the detector channel and the angular constancy of the effective solid angle of the spectrometer were examined.

Search for new islands of fission isomerism

Abstract The spontaneously fissioning isomers of Am and neighboring elements have been explained as nuclei trapped in a secondary minimum in the fission barrier profile. Some recently published calculations suggest the possible existence of another group of such shape isomers near Z = 85, N = 118. An attempt was made to produce isomers of Po, At, Rn and Fr by bombardment of 197 Au with beams of 11 B, 12 C, 14 N, 16 O, from the Berkeley HILAC and to observe their fission mode with Si semiconductor detectors. The cross-section limits were set at 70 nb or less for the half-life range 2 × 10 −9 to 2 × 10 3 s. An attempt was also made to observe fission fragments from nuclei decaying in flight after recoiling out of targets of Ce, Pr, Tm and Au bombarded with heavy ions. No fission fragments were observed from products in the half-life range 1–50 ns above a cross-section limit of ≈ 50 nb. The possible existence of isomers decaying primarily by γ-transitions to the first minimum was not excluded in either set of measurements. The apparatus was tested with known isomers produced by the reactions 238 U(d, pn) 238m U (200 ns) and 238 U( 12 C, α3n) 243m Cm (38 ns).

Electron scattering from silicon semi-conductor detectors

A quantitative investigation of electron scatter from Si semiconductor detectors over the energy range 50–625 keV has been made. All detectors used has depletion depths greater than the electron range in Si. The scatter coefficient, p, was determined in the usual way from the areas under the line and the so-called “low energy tail” which constitute the observed spectrum when mono-energetic electrons fall on a detector. Experimental results are given for the dependence of p on primary electron energy. E 0, on the angle subtended by the detector at the source and on the size and material of any collimating aperture. Measurements of the energy distributions of the scattered electrons are also given. The measured value of p for E 0=625 keV and a detector of area 100 mm 2 is shown to vary from 0.15 ± 0.02 for perpendicular electron incidence to 0.42 ± 0.02 for 35% collection efficiency. No differences in scattering properties were observed between lithium-ion-drift, and surface-barrier detectors and the spread in measurements between detectors was within that due to the experimental method. All experimental results given here, as well as the apparent inconsistencies of those in recent publications 2, 3) are satisfactorily explained on the basis that the value of p measured in this way is not identical with the saturation backscatter coefficient, p b, for Si, as had been assumed hitherto. Instead, p is shown to be a “total scatter coefficient”, p t, incorporating 3 groups of electrons: (a). Those backscattered from the Si; (b). Those which have lost some energy before reaching the detector by being scattered from other parts of the apparatus, and if no aperture is used; (c). Those which are scattered out of the sides of the sensitive volume of the detector. It is shown how the relative contribution of the 3 groups to p t varies with E 0 and the geometry of the experiment and how a knowledge of these factors and of p b can be used to calculate p t for any geometry to agree to within ±0.03 with the measured value.

Die (n, ?)-Reaktion mit 15 MeV-Neutronen an den Kernen138Ba,140Ce und142Nd

Studies of the (n, α)-reactions on138Ba,140Ce and142Nd for a neutron energy of 15 MeV are presented. The energy and angular distribution of the emitted α-particles has been measured with a Si-semiconductor detector. The shape of the energy spectra and the angular distributions predominantly show a direct reaction mechanism in the studied energy regionEα> 16 MeV. The measured total cross sections are 10±3 mb for Nd, 7 ±2 mb for Ce and 3–5 mb for the Ba-reaction. The angular distributions and the values of the total cross sections are discussed.

Decay ofCs129andI131to the Levels inXe129andXe131

The decay schemes of $^{129}\mathrm{Cs}$ and $^{131}\mathrm{I}$ have been investigated using Ge(Li) and Si(Li) semiconductor detectors as well as various coincidence techniques. Gamma-ray energies and relative gamma-ray intensities were determined as well as conversion coefficients for many transitions. In $^{129}\mathrm{Xe}$, levels at 322.0 and 904.9 keV were proposed, which have not been reported earlier. The spin and parity assignments for the 332.0-keV level are probably $\frac{5}{2}$+. In $^{131}\mathrm{Xe}$, a level at 404.8 keV has been found which was not previously known. The spin and parity assignments for this level are \textonehalf{}+ or $\frac{3}{2}$+. Beta-gamma coincidence measurements were used to indicate that the 503-keV $\ensuremath{\gamma}$ ray in $^{131}\mathrm{I}$ decay feeds the 11/2-isomer of $^{131}\mathrm{Xe}$. Decay schemes for both $^{129}\mathrm{Cs}$ and $^{131}\mathrm{I}$ consistent with our observations have been constructed. The levels of $^{129}\mathrm{Xe}$ and $^{131}\mathrm{Xe}$ are compared with each other and with current theoretical calculations.

The decay of Tb 158(150y) to levels in Gd 158 and Dy 158

The long-lived Tb 158 electron-capture decay to levels in Gd 158 and beta-decay to levels in Dy 158 have been studied by means of scintillation spectrometers, Ge and Si semi-conductor detectors, gamma-gamma and negaton coincidence measurements, directional correlation techniques and half-life measurements. The gamma-ray transitions (with total intensities in per cent of total Tb decays) observed are 79.5(83.8%), 182(12.5%), 782(9.9%), 928(0.2%), 946(46.7%), 964(22.2%) 1110(2.2%), and 1190 keV (1.8%), in Gd; 99.0(14.5%) and 218 keV (1.4%) in Dy. The K conversion coefficient measurements and directional correlation measurements are consistent with E1 assignments for the 782, 946 and 964 keV transitions. The following levels in Gd 158 have been established or confirmed: 79.5(2 +, T 1 2 = 2.47 ns) , 262(4 +), 1026(2 −), 1044(3 −, K = 1), and 1190 keV (2 +, K =2). The decay proceeding to the 1190 keV level is >95% L electron capture. An 857±27 KeV beta branch (log ft=12.1) proceeds to the 99.0 keV (2 +, T 1 2 = 1.64 ns) level in Dy. A weak inner beta branch (<1.5%) feeds the 317 KeV (4 +) level in Dy 158. Comparisons are made with the theoretical estimates for the transition branching ratios for K forbidden transitions.

Energy for Electron-Hole Pair Generation in Silicon by Electrons andαParticles

The difference of response of Si semiconductor detectors to $\ensuremath{\alpha}$ particles and electrons has been tested. The mean energy required for electron-hole pair generation by electrons has been found to be different from that for $\ensuremath{\alpha}$ particles. These values are, respectively, ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}=3.79\ifmmode\pm\else\textpm\fi{}0.01$ and ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}=3.61\ifmmode\pm\else\textpm\fi{}0.01$ at a temperature of 300\ifmmode^\circ\else\textdegree\fi{}K for electrons (365 KeV) and $\ensuremath{\alpha}'\mathrm{s}$ (5.477 MeV).