Yasuto Takenaka

Gamma-ray emission probability measurement by a two-dimensional 4πβ-γ coincidence system

Abstract A two-dimensional data-acquisition system has been applied to a coincidence system composed of a new 4πβ proportional counter operated with CF 4 gas and an HPGe detector. This system was capable of measuring the disintegration rates of short half-life nuclides. Making the most merit of this system, the emission probabilities of the principal γ-rays for 128 I were measured; they are smaller than the evaluated values by about 25% and the uncertainties have been reduced by more than one order.

New position sensing method for position-sensitive proportional counter with neural network algorithm

Abstract We have developed a new position sensing method that can obtain position information directly from the pulse shape of a position-sensitive proportional counter (PSPC). A digital signal processing technique and a neural network algorithm have been used to recognize the pulse shapes and to obtain position information. The method has been applied to a one-sided read-out type PSPC where the pulse shapes depend strongly on the position of radiation interactions. The neural network can recognize the pulse shapes and provide the proper position even for positions that have not been taught in the learning process. The best relative position resolution is 6.4 × 10 −3 . Fairly good integral linearity has been obtained throughout the effective length of the PSPC.

Energy resolution enhancement of CdTe semiconductor detector spectra by using a neural network algorithm

Abstract A neural network algorithm has been applied to improve the energy spectrum and the energy resolution of a CdTe semiconductor detector. In this study, the three-layered perceptron has been chosen as a neural network. The input layer of the neural network consists of four neurons for amplitudes of pulses shaped by linear amplifiers with different time constants (0.5–6 μs), while the output layer consists of one unit for the correction factor by which the amplitude of a pulse shaped with a small time constant (0.5 μs) is multiplied to obtain the proper amplitude. The neural network has learned with the amplitudes of deficient pulses and the amplitude of an ideal pulse with no hole contributions and no effects of trapping and detrapping of the charge carriers. Then the network has been applied to correction of the amplitudes of shaped pulses of events with some hole contributions. The fairly good results obtained showed that the energy resolution and the photopeak efficiency can be improved by using the neural network algorithm.

IMPROVEMENT OF ENERGY RESOLUTION OF CDTE SEMICONDUCTOR DETECTOR BY MEANS OF DIGITAL WAVEFORM PROCESSING WITH NEURAL NETWORK ALGORITHM

We have studied the improvement of energy spectra of a cadmium telluride (CdTe) semiconductor detector by means of a neural network algorithm. The neural network recognized pulse shapes and determined the corrective magnification factors of digitally shaped pulse heights. That is to say, the neural network recognized the difference in the pulse shapes due to the incomplete charge collection and made up for the ballistic deficit of each pulse. We obtained the energy spectra of several gamma ray sources. After the processing, the energy spectra became more ideal profile and the energy resolution (FWHM) changed for the better.

Application of Digital Waveform Processing to Proportional counter

In a charge-division type position-sensitive proportional counter (PSPC) with an anode wire of small resistance, a reflected component from an opposite end and thermal noise involved in signals deteriorate the position resolution of the PSPC. A digital waveform processing method was applied to the reduction of these undesirable effects by skillfully utilizing their signal characteristics that can be observed as inversely correlative signals between two-output signals from both sides of the PSPC. The digital waveform processing could improve the position resolution compared to a conventional pulse height processing method with analog filters. When the digital waveform processing was applied to signals of an equivalent circuit simulating the PSPC, the position resolutions defined by the full width at half maximum were improved to about 30% of those of conventional analog pulse processing. In the case of an actual PSPC, the position resolutions by the digital waveform processing were improved by 4–10% as com...

Reduction of microphonic noise by digital waveform processing

This paper describes a new reduction method of microphonic noises, or some other periodic noises by means of digital waveform processing. This method predicts the microphonic noise shape over the duration of a detector signal by making full use of periodicity of the noise, and then removes the noise component from the detector signal. Experimental results that prove the validity of this method are presented.<<ETX>>

A study on the position resolution of position-sensitive 3He proportional counters

Abstract The influences of wall effects and saturation of the gas multiplication on position resolutions of position-sensitive 3 He proportional counters have been studied by means of numerical calculations, computer simulations and experiments. When the proton produced by the 3 He(n,p)t reaction loses its specific energy in a counter wall by wall effects, a good position resolution is obtained escaping from any effects of a finite range of the proton and the triton. In the case where the gas multiplication is saturated, the best position resolution is obtained by selecting low pulse height events that the protons and the tritons move perpendicularly to the anode wire.

Emission probability for the 443 keV γ-rays of 128I

Abstract The emission probability for the 443 keV γ-rays of 128I was accurately measured, and the result is 0.1267 ± 0.0009, which is smaller than the evaluated values by about 20% and the uncertainty has been reduced by a factor of more than 10.

Reduction of digital errors of digital charge division type position-sensitive detectors

Abstract It is well known that “digital errors”, i.e. differential non-linearity, appear in a position profile of radiation interactions when the profile is obtained with a digital charge-division-type position-sensitive detector. Two methods are presented to reduce the digital errors. They are the methods using logarithmic amplifiers and a weighting function. The validities of these two methods have been evaluated mainly by computer simulation. These methods can considerably reduce the digital errors. The best results are obtained when both methods are applied.