Surface Barrier Semiconductor Detector Research Articles

Nuclear Reactions under Irradiation of Deuterated Structures by X Rays

Measurements of emission from nuclear reaction products (neutrons and protons) have been carried out appearing in the deuterated structures of textured CVD diamond, palladium, titanium, and zirconium under irradiation with a beam of X rays using independent methods (neutron detector based on He-3 counters, Si surface-barrier semiconductor detectors and CR-39 track detector). The possibility of enhancement of both DD reaction and multi-particle deuterium fusion by the beam of X rays with energy ranging 20–30 keV in solid deuterated targets has been established. Analysis of X-ray fluorescence spectra of the target bombarded by beams of ions has revealed “additional” peaks, the occurrence of which cannot be related to any of the known elements, and requires separate study.

Development of Two Spectrometers for the Noiseless β Energy Spectrum of Radiocarbon at Room Temperature

In this work, two spectrometric methods are described to have a noiseless β energy spectrum of radiocarbon (14C) as low‐energy β emitter. The spectrometers use two timing techniques with a silicon (Si) surface barrier semiconductor detector. The experimental results are compared; they show that the methods followed in the present work were successful for obtaining a noiseless β energy spectrum.

Fast neutron spectrometer composed of PSPCs and Si(Li)-SSDs with excellent energy resolution and detection efficiency

We have developed a fast neutron spectrometer composed of three position-sensitive proportional counters (PSPCs) with methane gas and two Si(Li) surface barrier semiconductor detectors (SSDs). A collimated incident neutron beam interacts with hydrogen atoms in the methane gas to generate recoil protons. Position information of the recoil protons obtained from the PSPCs gives the recoil angle. At the same time, the energy of the recoil protons is measured with the three PSPCs and the two SSDs. Finally, the neutron energy is derived using the recoil-proton energy and the recoil angle. This spectrometer was experimentally tested using a monoenergetic neutron beam with energy of 5.0 MeV. The energy resolution and the detection efficiency were 3.5% and 1.1 times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> %, respectively. The energy resolution could be achieved better than 2% by selecting events under proper conditions. We also developed a Monte Carlo code to evaluate the characteristics of the spectrometer. The results obtained from these simulations are compared to those obtained through experiments

The effect of temperature on the behavior of semiconductor silicon surface barrier detectors

The operating behavior of a silicon surface barrier semiconductor detector of 5 mm thick depletion depth has been studied over the temperature range from 270 to 313 K by recording the spectrum of 24.8 MeV protons. The temperature of the detector was controlled and measured by a PC-based temperature controller. The analysis of the recorded spectra shows that the centroid of the proton energy peak remains constant up to certain optimum temperature and falls down rapidly to the lower channels beyond the optimum temperature. The % resolution of the detector was found to degrade from 0.5% to 4.9%. The observed degradation is found to be related to the increase in leakage current due to rise in the detector temperature.

THE MEASUREMENTS OF HARD X-RAY FLUCTUATIONS IN THE HT-6B TOKAMAK

Nal(Tl) scintillation detector and Si(Au) surface barrier semiconductor detector are used to measure X-ray fluctuations in the HT-6B Tokamak device. The hard X-ray emission and sawtooth oscillations have been observed. The experiment shows hard X-ray fluctuations are due to MHD disturbances in the frequency range of 2-25 kHz.

The role of nuclear track filters in radon measurements

Track dosimeters in combination with mica nuclear filters have been used to measure radon densities in a mixed atmosphere of radon and thoron. Diffusion studies were carried out in a simulated uranium/thorium mine. Radon gas concentrations were determined by alpha-counting techniques using CR-39 track detectors and surface barrier semiconductor detectors. It has been found that transmission or diffusion of radon through a mica nuclear filter depends on (a) thickness of filter, (b) area of the hole, and (c) density of holes, of the filter. Simultaneously, we studied the effect of mica nuclear filters with tiny holes (40nm<k<440nm) with respect to radon and thoron diffusion.

Measurement of the Fano factor for protons on silicon

The Fano factor for protons has been measured for silicon with a surface barrier semiconductor detector at 87 K over the energy range of E p = 0.989–4.537 MeV. The fwhm of peaks in the spectra observed were corrected for effects of plasma and of charge collection. As a result of the analysis, the value of the Fano factor was obtained as 0.16±0.04. However, the value of the corrected fwhm at E p = 0, estimated by extrapolation, cannot be accounted for by the effect of atomic collision.

Temperature response of silicon surface barrier semiconductor detectors operated in the DC--short circuit configuration.

Temperature response of silicon surface barrier semiconductor detectors operated in the DC--short circuit configuration.

Proton energy distributions from 0.060 to 3.3 Mev at 6.6 Earth radii

Proton differential fluxes are reported for 12 energies from 0.060 to 3.3 Mev at 6.6 earth radii for the time period of October 2 to 13, 1968. The proton energies were measured with a surface barrier semiconductor detector and a stacked discriminator pulse height analyzer on the Air Force Office of Aerospace Research Satellite OV2-5 (1968-81A). The typical quiettime fluxes decreased by 8 orders of magnitude over the measured energy interval. During this time the energy spectrum varied from E−3.5 to E−6.0. Below 200 kev the energy distributions flatten but never peak above the energy of the lowest channel, 68 kev. Energy spectra associated with the two magnetic storms on October 2 and 12 are presented. After the storms the fluxes were higher than before; this is particularly true at the lower energies measured. Quiettime pitch angle distributions near the local noon-midnight meridian clearly show the east-west effect caused by the radial gradient in the fluxes. The pitch angle distributions at local midnight show the ‘drift loss cone’ predicted by Roederer. This experiment provides the first confirmation of the Roederer [1967] model of shell splitting in the earth's magnetic field by measured proton angular distributions.

Silicon detector response functions to monoenergetic positons

Pulse height distributions from a silicon surface barrier semiconductor detector have been recorded for monoenergetic positons in the energy range 100 to 1200 keV. Corresponding distributions for monoenergetic electrons have been recorded for comparison. In addition to the well known low energy tail and full energy peak, the analysis also revealed a high energy pulse height distribution. This effect can be attributed to the production of Compton scattered electrons from annihilation quanta interactions inside the detector. For the detector geometry used this effect represented 4% of the total number of events. The back-scattering probability for positons was deduced and compared with theoretical predictions.

Performance deterioration of surface barrier detectors by fission fraggment bombardment

Performance deterioration of a surface barrier semiconductor detector due to radiation damage induced by fission fragments has been investigated. An increase of reverse current, a decrease of pulseheight for incident particles, and a decrease of resolution power for spectroscopy were observed by the exposure to fission fragments. The increasing rates of the reverse current were 3.8×10 −8 and 4.2×10 −9 μA per fragment for applied biases of 30 and 60 V, respectively. The decreasing rates of the pulseheight for fission fragments from 235U(n th,f) were 4.2×10 −8 and 2.9×10 −8δ% per (fragment/cm 2) for the light group and 3.0×10 −8 and 2.1×10 −8%per(fragment/cm 2 for the heavy group, at applied biases of 30 and 60 V respectively. The decreasing rate for alpha particles of 6.11 MeV was about 1 15 of that for fission fragments The field-dependent part of the pulseheight defect for fission fragments increases linearly and the field-independent part remains constant with the exposure dose of fission fragments. The pulseheight defect and the decrease in pulseheight due to irradiation are discussed with a model which takes into account the recombination loss of charge carriers on recombination centers during a plasma time. The experimental results can be reasonable explained by the model.

Influence of the entrance window on the energy resolution of surface barrier semiconductor detectors

The energy straggling due to the gold layer of the semiconductor surface barrier detector was calculated and measured. This effect on the linewidth is appreciable in the case of α-particles and heavier ions and sets a limit to the resolution. The contribution to the linewidth due to the gold layer is for the usual thicknesses about 10–14 keV in fwhm for 6 MeV α-particles.

Collection time and equivalent circuit of surface barrier semiconductor detectors

The rise time of silicon surface barrier detector pulses was measured, when excited by α-particles. Such a measurements made it possible to check both the collection time of charge carriers in the depletion region and the equivalent circuit of the detector. The measurements were made by comparing, at the output of a fast amplifying chain, the waveforms due respectively to α-particles and to artificial pulses obtained by injecting a calibrated charge ( δ( t)-current pulse) into the detector. The measured parameter T turns out to be equal to T= τ+ R s C 0+ R c C 0; where τ is the collection time, C 0 the depletion layer capacity, R s the bulk resistance due to the undepleted material and R c a series resistance. It was the undepleted that T, according to the theory, is a linear function of V − 1 2 where V is the detector bias.

Fission Fragment Angular Distributions and Cross Sections for Deuteron-Induced Fission

Fission-fragment angular distributions and cross sections have been measured with gold surface barrier semiconductor detectors for fission induced in a group of elements from Tl to Pu by deuterons of 7- to 21- MeV energy. Apart from a pronounced dip in the radium region, the differential fission fragment cross-section ratios $\frac{W(174\ifmmode^\circ\else\textdegree\fi{})}{W(90\ifmmode^\circ\else\textdegree\fi{})}$ at 21 MeV show an increasing trend with decreasing $\frac{{Z}^{2}}{A}$, the values ranging from 1.20 for ${\mathrm{Pu}}^{239}$ to 1.58 for natural Tl. Values of ${{K}_{0}}^{2}$ are calculated from the experimentally determined anisotropies for targets in which single-chance fission prevails, i.e., ${\mathrm{Bi}}^{209}$ and nuclides in the plutonium region. When values of ${{K}_{0}}^{2}$ for plutonium are compared with those from available neutron fission data, there is indicated an anomalous suppression of ${{K}_{0}}^{2}$ in the low-energy region below the values extrapolated from the higher energy data by plausible temperature dependences on excitation energy. Saddle-shape calculations and semiquantitative arguments which are reviewed lend added credence to the view that the saddle shape is independent of the mode of formation. The experimentally observed change in anisotropy with the fissionability parameter $x$ is correlated with the effective moments of inertia at the saddle configuration (vis-\`a-vis scission point), indicating that thermodynamic equilibrium is first established near the saddle point in fission. Fission cross sections measured for ${\mathrm{Th}}^{232}$, ${\mathrm{U}}^{233}$, and ${\mathrm{U}}^{238}$ are supplemented by previously determined spallation cross sections to obtain total deuteron reaction cross sections. At 21 MeV the deuteron reaction cross section of heavy elements is found to be 1800 mb. The experimental reaction cross sections are compared with theoretical values calculated with a volume-absorption optical model.