Loss Of Pulse Height Research Articles

Feasibility study of TlBr semiconductor detectors for PIXE applications

Semiconductor detectors for PIXE applications were fabricated using TlBr crystals. The TlBr detectors had a multiple-electrode detector design to minimize the pulse-height loss due to hole trapping. Electrodes containing thallium metal were employed for the TlBr detectors to suppress the polarization phenomena. Energy resolutions of 2.4, 3.3, and 3.8 keV FWHM for 5.9, 22.1, and 59.5 keV photons, respectively, were obtained for a TlBr detector operating at −50 °C.

Pulse-height loss in the signal readout circuit of compound semiconductor detectors

Compound semiconductor detectors such as CdTe, CdZnTe, HgI2 and TlBr are known to exhibit large variations in their charge collection times. This paper considers the effect of such variations on the measurement of induced charge pulses by using resistive feedback charge-sensitive preamplifiers. It is shown that, due to the finite decay-time constant of the preamplifiers, the capacitive decay during the signal readout leads to a variable deficit in the measurement of ballistic signals and a digital pulse processing method is employed to correct for it. The method is experimentally examined by using sampled pulses from a TlBr detector coupled to a charge-sensitive preamplifier with 150 μs of decay-time constant and 20 % improvement in the energy resolution of the detector at 662 keV is achieved. The implications of the capacitive decay on the correction of charge-trapping effect by using depth-sensing technique are also considered.

Non-linearity of recoil pulse height events in He-3 tubes

Regarding neutron spectrometry, energy calibration of a He-3 counter was performed for neutron energies up to about 7 MeV, for various operating voltages in the proportionality region. Full-energy peak position is linearly correlated with neutron energy, while the position of the 3He recoil peak deviates from a linear response, especially in the lower energy region. By means of the linear full-energy peak calibration, recoil peak energies are found to be significantly lower than those resulting from the kinematics of the reaction. The pulse-height loss is attributed to initial recombination. Using the Bragg curve of the recoiling nucleus in the counter gas mixture, it is determined that the pulse-height loss corresponds to a constant portion, 33.5±1.3 %, of the fraction of energy deposited by a 3He nucleus traversing the gas mixture with a stopping power higher than 450 eV/μm. The energy calibration equation for the recoil peaks is derived using the following: (i) the range-energy relation and the stopping power function for a 3He nucleus in the gas mixture where the coefficients of both functions were determined via Monte Carlo calculations, and (ii) the experimentally determined recombination coefficient.

Some studies on the pulse-height loss due to capacitive decay in the detector-circuit of parallel plate ionization chambers

Pulse-type ionization chambers are invariably operated in the electron-sensitive mode where the capacitive decay in the detector-circuit during the electron collection produces loss in the pulse-height. In order to understand and appreciate the effect of this capacitive decay on the detector response, we have carried out Monte Carlo simulations of the response of two-electrode parallel plate ionization chambers with and without the capacitive decay keeping shaping time so large that the ballistic deficit is negligibly small. These simulations have been carried out incorporating the physical processes, namely, emission of charged particles from a point radioactive source, the generation of charge carriers in the active volume, separation and acceleration of the charge carriers, transport of the charge carriers, induction of charges on the electrodes, pulse processing by preamplifier-amplifier network, etc. These simulations have shown that the concerned capacitive decay produces appreciable loss in the pulse-height, if the detector-circuit time constant is of the order of maximum electron collection time. We have also carried out measurements on the pulse-height loss due to the capacitive decay in the detector-circuit during the electron collection for a two-electrode parallel plate ionization chamber. The experimental data on the pulse-height loss match reasonably well with the theoretical predictions.

Construction and operation of an ion chamber consisting of lead plates immersed in 2,2,4,4 tetramethylpentane

A small test ion chamber has been constructed using 2,2,4,4 Tetramethylpentane as the ionizing liquid in direct contact with an array of lead plates used as the high voltage and ground planes. The transient response resulting from the passage of cosmic ray muons through the ion chamber was monitored for a period of 54 weeks to measure possible degradation of the signal due to contamination of the ionizing liquid that may have come from the lead plates. Over the first 17 weeks of the experiment, the loss of pulse height was measured to be less than 11% per year at 95 confidence. During the following 37 weeks, a more sensitive measurement was consistent with zero loss, or a limit of less than 2.9% per year at 95% confidence.

Operation of an ion chamber consisting of lead plates immersed in 2,2,4,4 tetramethylpentane

A small test ion chamber has been constructed using 2,2,4,4 tetramethylpentane as the ionizing liquid and an array of lead plates as the high voltage and ground planes. Signals resulting from ionization deposited in the ion chamber by cosmic-ray muons were monitored for possible degradation from contamination that may have come from the lead plates. At the 95% confidence level, the loss of pulse height was measured over the first 17 weeks of the experiment to be less than 11% per year. A more sensitive measurement over the following 37 weeks was consistent with zero loss, or a limit of less than 2.9% per year at 95% confidence.

Study of localised radiation damage to PIPS detectors by a scanning ion microprobe: Measured effects and the consequences for STIM analysis

Radiation damage effects in a PIPS particle detector have been studied by direct irradiation with a 4 MeV He + focused ion beam, using the Eindhoven scanning ion microprobe set-up. This set-up enables extreme sensitivity and accuracy in pulse-height measurement. Pulse-height dependence on ion dose and the lateral variations of pulse-height response after damaging were studied, for different bias voltages. Pulse height was found to decrease linearly with ion dose and this could be observed after only a few ions per scan position, corresponding to a dose of 10 8/cm 2. Pulse-height loss was found to be restricted to damaged detector areas. Consequences of this pulse-height dependence on ion dose and scan position for the accuracy of STIM analyses are discussed.

Determination of fission fragment energies using solid-state detectors

Abstract A method of correcting for the pulse height defect of fissions fragments in silicon surface barrier detectors is described. Loss of energy in the gold window and by elastic collisions in the silicon are considered as well as loss of pulse height from incompleted charge collection in the detector. The method gives identical results for the degraded energies of fession fragments passing through a given amount of gas when the total defects of the detectors used differ by 15 MeV.

LXXIV. Columnar recombination in nitrogen

Abstract Under normal conditions of use, pulse ionization chambers function by virtue of the collection of free electrons liberated by the incident radiation. It is sometimes found, especially under conditions of high gas pressure, that the recorded pulse is smaller than the initial ionic burst and this loss of pulse height is generally attributed to capture of electrons by electronegative impurities in the gas resulting in the formation of negative ions which, owing to their much smaller mobility, are not collected within the short collection times used.