K. Husimi

Direct synthesis of the Gaussian filter for nuclear pulse amplifiers

Abstract The Gaussian pulse forming networks which can be suitably realized by active filters are derived based on the frequency domain analysis. The frequency characteristics and the output waveforms of the results are calculated, and show the favourable features of the filter for nuclear pulse amplifiers. Calculations on the effects of the rise time variations of the detector signal upon the pulse peak height are also carried out.

Epitaxial Integrated E-dE Silicon Detector with a Buried Low-Resistive Diffused Layer

The epitaxial crystal growth technique combined with the impurity diffusion technique is applied on fabrication of integrated E-dE silicon detectors. Experimental results show that detector produced seems to have enough characteristics for use in practical experiments. This detector is compact and easy to handle, and eliminates the highly technical process of etching the substrate, which is necessary for producing the conventional epitaxial silicon dE detector.

New baseline restorer based on feedforward differential compensation

The noise indices regarding the rectangular shaper have been calculated. The results indicate that the time constant of the BLR should be larger than about 20 times that of the prefilter pulse width. A new feedforward type baseline restorer has been developed for the quasi-rectangular shaper. Its time constant can be designed arbitrarily by the value of its components C and R. Therefore, it is simple to determine the compromising point of the delta noise index and the tracking ability for baseline fluctuation. The equivalent circuit of this restorer has an attenuator following the CR differentiator. The existence of the attenuator in the equivalent circuit is a difference from the others. >

Analog particle identifier with a wide dynamic range of the E/ΔE ratio

Abstract A particle identifier which has a good performance for a wide range of signal ratio E / ΔE has been developed based on the multiplication type formula approximating the Goulding equation. The purpose of this approximation is to utilize an analog summation technique (logarithmic) instead of the analog subtraction circuit, since the performance of the subtraction circuit is one of the limiting factors of the dynamic range, especially when the ΔE signal is small while the E signal is large. The numerical method used for deriving the good approximation formula is also applied to the analyses of the problems of the particle identification.

Trapezoidal filtering of signals realized by the directly synthesized Gaussian filter

A novel time-varying trapezoidal pulse suitable for a high-resolution high-counting-rate spectroscopy system is described. The input signal of the gated integrator has a nearly rectangular waveform approximated by using the directly synthesized Gaussian filter. The product of the delta noise index and the deadtime of this pulse-shaper is less than the best value proposed up to now, which is the theoretical value of that of the triangular waveform. >

Epitaxial integrated dE1 − dE2 silicon detectors

Abstract Epitaxial integrated d E 1 − d E 2 silicon detectors have been developed by using the multilayer epitaxial crystal growth technique combined with the chemical preferential etching technique. These detectors are useful for eliminating events affected by channeling and blocking effects in the identification of heavy ions using multiple detector telescope systems. Characteristics of d E detectors of the integrated d E 1 − d E 2 type are confirmed to as good as those of integrated E − d E detectors.

High Resistivity N-Type Silicon Detectors Produced by Neutron Transmutation Doping

High resistivity N-type silicons produced from high purity P-type silicon by neutron transmutation doping are used for fabrication of surface barrier detectors. It has been shown that the materials tested have properties as good as those produced by the conventional floating-zone (FZ) method. The resistivity distribution in a silicon rod produced by this method is expected to be better compared with those obtained by the FZ method, and the resistivity itself is also easily controlled by an irradiation dose of neutrons. The radiation damage produced by neutron bombardments seems to be removed by an annealing treatment. The residual radio-activity induced by irradiation of neutrons has almost negligible effects on the performance of the detector except for low background applications.

Application of epitaxial crystal growth on silicon radiation detectors

Abstract Silicon radiation detectors produced by application of epitaxial crystal growth are reviewed. The epitaxial crystal growth technique is well developed and widely used in semiconductor industries. Therefore, the thickness and the resistivity of the epitaxial silicon layer are well controlled with good uniformities and reproducibilities. The very thin dE epitaxial silicon detector and the integrated E−dE detector are developed based on the uniformity of the thickness of the silicon layer. The epitaxial silicon position sensitive detector is also produced based not only on the uniformity but also on the controllability of resistivity of the epitaxial silicon layer.

Application of chemical preferential etching on fabrication of epitaxial silicon detectors

Abstract A chemical etching technique is applied to the fabrication of a thin silicon detector with a uniform thickness. The chemical etching has many advantages compared with the electrochemical etching, although good crystals which have high resistivity silicon layers epitaxially grown on heavily doped substrates are required for this purpose.

Neutron transmutation doped silicon detectors

Abstract High resistivity n-type silicons has been produced from ultra-high purity p-type silicon by neutron transmutation doping. The material produced by this method has better dopant homogeneity and controllability than carefully produced floating zone crystals. The characteristics of a variation of detectors made from this material are equivalent to those of the conventional silicon detectors.