Faculty Profiles - URITANI Akira

Papers - URITANI Akira

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A Multi-Purpose Spherical Neutron Counter Reviewed

H. Toyokawa, A. Uritani, C. Mori. N. Takeda and K. Kudo

IEEE Trans. on Nuclear Science Vol. NS-42 ( 4 ) page： 644-648 1995.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We have developed a unique neutron counter applicable to measurements of fluence, energy distribution and the dose equivalent of neutrons with very wide energy range, and to estimations of incident direction of neutron beams. This 4π sensitive neutron counter consists of a spherical polyethylene moderator and three charge-division-type position-sensitive proportional counters (PSPCs) inserted into the moderator orthogonally with each other. The three PSPCs give thermal neutron distributions in the spherical moderator that bring us the above information. The characteristics of this neutron counter have been studied with Monte Carlo simulations and with experiments using monoenergetic neutrons.

Research for Application of Long Counter with a Position-Sensitive Proportional Counter to Neutron Dosimetry

Reactor Dosimetry Vol. STP1228 1995.8

A Long and Slender Position-Sensitive Helium-3 Proportional Counter with an Anode Wire Supported by a Ladder-Shaped Solid Insulator Reviewed

A. Uritani, Y. Kuniya, Y. Takenaka, H. Toyokawa, Y Yamane, C. Mori, K. Kobayashi, S. Shiroya and C. Ichihara

J. Nucl. Sci. Technol. Vol. 32 ( 8 ) page： 719-726 1995.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A long and slender position-sensitive 3He proportional counter with an outer diameter of 8mm and an effective length of 1.2m has been developed to measure neutron flux distributions in a critical assembly. Because it is difficult to make such a long and slender counter of con- ventional structure where an anode wire is stretched at the center of a cylindrical cathode tube, three prototype electrode systems of which anode wires are supported by insulator plates have been proposed. Among these three electrode systems, the electrode system of which anode wire is stuck on a ladder-shaped insulator has been adopted. The neutron flux distributions in the core of the Kyoto University Critical Assembly (KUCA) have been measured with the counter. Some non-uniformity of the detection efficiency has been observed throughout the counter. This non-uniformity has been corrected by calibrating the position-dependent detection efficiency with a gold wire activation method. A fairly satisfactory distribution, where the relative deviation from the gold wire activation method is 5.0%, has been obtained. Though the non-uniformity of the detection efficiency should be solved for precise measurements, the counter can be used for quick and rough measurements of neutron flux distributions.

Application of Digital Waveform Processing to Position-Sensitive Proportional Counter Reviewed

Y. Takenaka, A. Uritani and C. Mori

J. Nuclear Science and Technology Vol. 32 ( 4 ) page： 295-300 1995.4

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 compared with those of conventional pulse height processing.

中性子位置検出型核分裂計数管の開発

森千鶴夫、安藤彰浩、瓜谷章、羽賀剛

放射線 Vol. 21 ( 1 ) page： 35-42 1995.1

Characterization of Hexafluoroethane as Counting Gas of Position-Sensitive ³He Proportional Counter Reviewed

A. Uritani and C. Mori

Radioisotopes Vol. 44 ( 1 ) page： 23-27 1995.1

シンチレータ塗布・光ファイバーを用いた中性子束分布・位置高分解能迅速測定法の開発

森千鶴夫、三戸祐一郎、柳田勝男、影山一巳、国谷浩、瓜谷章、宮原洋、山根義宏、三澤毅、小林圭二、市原千博、代谷誠治、林正俊、宇根崎博信

京都大学原子炉実験所第２９回学術講演会報文集 page： 193-198 1995

Reduction of Microphonic Noise with Digital Waveform Processing Reviewed

A. Uritani, O. Kubota Y Takenaka and C. Mori

Nuclear Instruments and Methods Vol. A351 ( 2-3 ) page： 598-599 1994.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

This paper describes a new method of microphonic noise reduction by digital waveform processing. This method predicts the microphonic noise shape over the duration of a detector signal by making full use of the periodicity of the noise, and then removes the microphonic noise component from the detector signal. Preliminary experimental results that prove the validity of this method are presented.

Reduction of Digital Errors of Digital Charge Division Type position Sensitive Proportional Counter Reviewed

A. Uritani, K. Yoshimura, Y. Takenaka and C. Mori

Nuclear Instruments and Methods Vol. A353 ( 1-3 ) page： 246-250 1994.12

Measurement of Radioactivity Distribution of Material Surfaces with Imaging Plate Reviewed

C. Mori, T. Suzuki, S. Koido, H. Miyahara, A. Uritani, T. Aoyama and K. Nishizawa

Nuclear Instruments and Methods Vol. A353 ( 1-3 ) page： 371-374 1994.12

Dependence of Position Signal on Pressure of Counting Gas in Charge Division Type Position-Sensitive Proportional Counter Reviewed

Y. Wu, C. Mori, A. Uritani, H. Miyahara, K. Yanagida and M. Yoshida

J. Nuclear Science and Technology Vol. 31 ( 11 ) page： 1194-1201 1994.11

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

In the absolute radioactivity measurement of radioisotope gaseous samples with newly developed position-sensitive proportional counter (PSPC) method, it is necessary to change the counting gas pressure for the correction of the wall effect. The position signal was found to drift depending on the pressure. Theoretical explanation was given for this drift. Rise time of output pulses varies with gas pressure, which leads to a change of ballistic deficit. Consequently, the ballistic deficit differs between pulses from both the ends of the PSPC, which causes the change of position signals. Increasing the pressure of the counting gas from 0.5×105Pa to 4×105Pa, the range of position signals for two position calibration sources became narrower by about 8% under 6μs shaping time.

Reduction of Microphonic Noise by Digital Waveform Processing

A. Uritani, O. Kubota, Y. Takenaka, C. Mori

Nuclear Science Symposium Conference Record, 1994 IEEE Vol. 1 page： 905 - 909 1994.10

A Multipurpose Spherical Neutron Counter

H. Toyokawa, A. Uritani, C. Mori, N. Takeda, K. Kudo

Nuclear Science Symposium Conference Record, 1994 IEEE Vol. 1 page： 968 - 972 1994.10

Language：English

We have developed a unique neutron counter applicable to measurements of fluence, energy distribution and the dose equivalent of neutrons with a very wide energy range, and to estimations of the incident direction of neutron beams. This 4π sensitive neutron counter consists of a spherical polyethylene moderator and three charge-division-type position-sensitive proportional counters (PSPCs) inserted into the moderator orthogonally with each other. The three PSPCs give thermal neutron distributions in the spherical moderator that bring us the above information. The characteristics of this neutron counter have been studied with Monte Carlo simulations and with experiments using monoenergetic neutrons.

A Study on Position Resolution of Position-Sensitive ³He Proportional Counter Reviewed

A. Uritani, N. Marnada, Y. Takenaka, C. Mori and H. Miyahara

Nuclear Instruments and Methods Vol. A350 ( 1-2 ) page： 286-290 1994.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The influences of wall effects and saturation of the gas multiplication on position resolutions of position-sensitive 3He proportional counters have been studied by means of numerical calculations, computer simulations and experiments. When the proton produced by the 3He(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.

Optimization of Counting Time in the Radioactivity Measurement of Gaseous Samples with Inner Counting Method Reviewed

Y. Wu, C. Mori, A. Uritani, K. Yanagida, H. Miyahara, T. Aoyama and M. Yoshida

Nuclear Instruments and Methods Vol. A343 ( 2-3 ) page： 539-544 1994.4

Simple and Quick Measurement of Neutron Flux Distribution by Using an Optical Fiber with Scintillator Reviewed

C. Mori, T. Osada, K. Yanagida, T. Aoyama, A. Uritani, H. Miyahara, Y. Yamane, K. Kobayashi, C. Ichihara and S. Shiroya

J. Nuclear Science and Technology Vol. 31 ( 3 ) page： 248-249 1994.3

Analytical Calculations on Radioactivity Measurements of ¹⁹²Ir-Metallic Sources with a Calibrated Ionization Chamber Reviewed

A. Uritani, T Genka, C. Mori and D. F. G. Reher

Nuclear Instruments and Methods Vol. A339 ( 1-2 ) page： 377-380 1994.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The self-attenuation of photons was analytically calculated for an 192Ir metallic wire source and an aqueous standard source. The influence of the self-attenuation on the current of the calibrated ionization chamber was also evaluated. The self-attenuation did considerably affect the ionization current. It was concluded that the apparent radioactivity must be multiplied by a correction factor larger than unity (1.09±0.01 in the present case) to get the true radioactivity when the radioactivity of the 192Ir metallic wire source was measured with the ionization chamber calibrated with the aqueous standard source of 192Ir.

Radioactivity Measurement of ¹⁹²Ir Wire Sources with a Microcalorimeter Reviewed

T. Genka, S. Iwamoto, N. Takeuchi, A. Uritani and C. Mori

Nuclear Instruments and Methods Vol. A339 ( 1-2 ) page： 398-401 1994.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Radioactivities of metallic 192Ir sources are measured with a microcalorimeter nondestructively. In order to convert the complete decay energy evolved from the source into thermal energy, a tungsten block is used as radiation absorber. The sample sources measured are four thin wires of Ir/Pt alloy with dimensions of 0.1 mmø × 10 mm1, each coated by 0.1 mm thick platinum, giving the final diameter of 0.3 mmø. Overall uncertainty of the measurement for some 60 MBq activity is ±3.2%. Measurements of the wire sources with an ionisation chamber give smaller activities which are smaller by 10% than those from microcalorimetry mainly because of the autoattenuation effect.

Direct Measurement of Gaseous Activities by Diffusion-in Long Proportional Counter Method Reviewed

M. Yoshida, T. Yamamoto, Y. Wu, T. Aratani, A. Uritani

Nuclear Instruments & Methods Vol. A330 ( 1-2 ) page： 158-164 1993.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Direct measurement of gaseous activities by the diffusion-in long proportional counter method (DLPC method) was studied. The measuring time without end effect was estimated by observing the behavior of 37Ar in the counter and was long enough to carry out the accurate activity measurement. The correction for wall effect was also examined on the basis of the measured and calculated correction factors. Among the tested gases of methane, P10 gas and propane, P10 gas was made clear to be a suitable counting gas for the DLPC method because of good diffusion properties and small wall effect. This method is quite effective for standardization of gaseous activities used for tracer experiments and calibration works of radioactive gas monitoring instruments.

Application of Digital Waveform Processing to signals Acquired from Position-sensitive Detector

Vol. 19 ( 2 ) page： 33-40 1993.5

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