Ikuo Murai

A correction formula for the counting loss in using a time to pulse height converter and experimental verification of the formula

Abstract A correction formula for the counting loss in a TPHC-PHA time analyzer is verified experimentally, after deriving the formula by several methods and obtaining a more refined correction formula. The experiment is made by the application of a gate circuit, which inhibits irrelevant signals, to conventional electronic equipment for measuring the neutron time-of-flight spectra. Lastly we propose the application of the method used in our experiments to general spectra measurement.

A dual-parameter multichannel analyzer using a personal computer

The design of a practical system for measuring two-parameter signals is reported. To obtain constantly changing energy spectral of nuclear reactor assemblies due to repeated insertion of pulsed neutron sources, the simultaneous acquisition of time and energy data is needed. A computer-based dual-parameter multichannel pulse-height analyzer was developed. The analyzer uses a personal computer, two analog-to-digital converters (ADCs), and a parallel interface board for handling these signals. The system is simple to operate, and because the memory size and coincidence resolution time can be changed by software operations, it is highly flexible. >

Calibration measurements for the efficiency and response function of the NE213 scintillator by a /sup 252/Cf spontaneous fission source-application of a two-dimensional pulse height analysis system

The authors describe calibration measurements for the efficiency and response function of the NE213 scintillator as an application of a two-dimensional pulse height analysis system. In this method, a /sup 252/Cf spontaneous fission source with a continuous spectrum is employed by taking each fission event as a pulsed neutron source, and the efficiency and response function of the NE213 scintillator can be estimated by two-dimensional measurements of the time-of-flight spectrum (neutron energy spectrum) and pulse height spectrum. >

A dual-parameter multichannel analyzer by a dual-computer system

The design and feasibility of a simple and practical system for measuring two-parameter signals is reported. A dual-parameter multichannel pulse-height analyzer (MCA) which uses two central processing units (CPUs) is developed and designed. One computer (master computer) controls the other computer (slave computer), and also displays, records, and analyzes the data. The slave computer controls two analog-to-digital converters (ADCs), collects the dual-parameter data, and transfers the collected data to the master computer. Three methods of data transfer between the two CPUs are examined and discussed. The count capacity at the data collection by the slave computer is 2/sup 16/-1/ch (2-B-long data), and this is expanded to 2/sup 32/-a/ch (4-B-long data) at the master computer. The data are analyzed and at any time stored in the storage apparatus by the dual CPU system. The system demonstrates stable operation over long measurement periods. >

Generation and use of parametric X-ray by LINAC

Parametric X-rays (PXR) were generated in the 6˜15keV region to examine the generation and use of PXR by LINAC. The target crystal was a Si single crystal, and the FWHMs of the PXR spectra were obtained at about 350eV by a Si-PIN photo diode detecter with 250eV FWHM at 5.9keV (55Fe). The experiments found that it was possible to select a crystal rotaion angle, detection angle, crystal thickness, crystal material, and interference plane to enhance the PXR intensity. Moreover, in theexperiment for use of PXR, the mass attenuation coefficient around the K-edge could be measured accurately in a narrow range with PXR. The results support that the PXR is a good monochromatic hard X-ray souce, where the energy can be countinuously changed.

DEVELOPMENT OF HIGH SPEED MULTICHANNEL SCALAR USING LINE MEMORIES

Abstract A high speed multichannel scaling mode time analyzer (MCS) for time of flight (TOF) experiments was developed by using high speed serial access memories and a personal computer. The MCS was composed of two memory banks, run alternately for each trigger. The channel width of the MCS was selected from 50 ns to 200 ns (4 stage). The count per channel per trigger signal was one, but the dead time for channel advancing may approach zero. The MCS was tested with linear accelerator (linac)-TOF experiments. The results agreed satisfactorily with the design goal. It was confirmed that the high speed MCS runs normally. A small discrepancy at high energy channels between the time spectrum of the MCS and that of the time-to-pulse-height converter (TPHC)-multichannel pulse height analyzer (PHA) time analyzer was observed. One of the reasons for the discrepancy was the uncertainty of the MCS start time after the trigger signal by linac because of asynchronous crystal oscillations with the linac trigger signal.

Use of a gated counting method for radiation monitoring at a 45-MeV electron LINAC facility.

A fixed-point radiation monitoring system based on the gated counting method, which was previously reported by us, was constructed for a 45-MeV electron LINAC facility. It was tested under different beam intensities of the accelerator both at the current and repetition rates. It showed excellent dynamic response (from 2.5 X 10(-11) to 1.0 X 10(-8) Sv h-1) to the intensity variation of the radiation source. It was demonstrated that the system was very useful in monitoring an extremely low-level radiation from a pulsed source.

Measurement of radiation leaked from a 45-MeV linear accelerator facility by gated counting.

By the gated counting method that had been developed by the authors the spatial dose distributions at the boundary and inside of a 45-MeV electron linear accelerator (linac) facility were obtained using a NaI(Tl) scintillation probe and a counting system. Both distributions of pulse height and radiation propagation time were also measured. At the facility boundary, dose rates measured ranged from 0.16 microR hr-1 to 0.86 microR hr-1, which were less than one-tenth the natural background. At measurement in the linac control room, two different leakage sources, one originating at and around the accelerator and the other at a microwave power system, were discriminated by measuring pulse height and time distributions simultaneously.

Radiation Dosimetry by Dyed Polymethyl Methacrylate

市販のポリメチルメタクリレートに60Coγ線ならびに直線型加速器からの35MeVパルス状電子線を照射し, 誘起される光学的吸収の特性を調べ線量測定に使用可能かどうかについて検討された。その結果600nm～1000nmの領域に光学的吸収が誘起され, 653nmのピーク値の吸光度測定により105～4×106radsの線量測定が可能であることが示され, また35MeV電子線のビームプロフィルの測定が試みられ空間分布の測定にも合理的な結果が得られた。誘起された吸収のフェージソグは653nmのピーク値で24時間以内では2%以下であり, 安価でかつ簡単な線量測定の手法として, 本方法が有用であることが明らかになされた。