Koh-ichi Mochiki

Amorphous silicon position-sensitive detector

Abstract A new charge-integrating-type position-sensitive detector which consists of an amorphous silicon linear image sensor with a Gd 2 O 2 S phosphor sheet and a signal processing system has been developed. The sensor is 256 mm long and 100 μm wide with 2048 elements on 125 μm centres. The system has a spatial resolution of 500 μm and a wide dynamic range of more than 66 dB. The minimum rms noise corresponds to 140 photons/s for 8 keV X-rays.

High-count rate position-sensitive detectors for synchrotron radiation experiments

Abstract This paper describes several X-ray position-sensitive detectors developed for use in high-count rate experiments at synchrotron radiation sources; (1) a charge-integrating position-sensitive proportional counter, (2) an amorphous silicon photodiode array as an X-ray PSD, (3) a MWPC with a multiple delay-line encoder and (4) a MWPC with carbon-fiber anode wires. The performance of the detectors is demonstrated in two examples of the application: a time-resolved measurement of a kinetic diffraction diagram from contracting muscle and a two-dimensional diffraction measurement of a powder crystal are presented.

VOID FRACTION DISTRIBUTION MEASUREMENT IN TWO-PHASE FLOW BY REAL-TIME NEUTRON RADIOGRAPHY AND REAL-TIME IMAGE PROCESSING

Abstract A real-time two-dimensional void fraction distribution measurement of gas-liquid two-phase flow was carried out by real-time neutron radiography and real-time image processing. The JRR-3M real-time thermal neutron radiography system and a Musashi dynamic image of processing system were used. Image processing methods to calculate two-dimensional and cross-sectional void fraction distributions were proposed. The void fraction distribution was calculated by non-linear processing of the neutron radiography image and displayed by pseud-color in real-time. A simple gas-liquid two-phase flow induced by injecting gas through needles at the bottom of water pool in a rectangular vessel was tested.

Extension of dynamic range in X-ray radiography using multi-color scintillation detector

Abstract A new imaging system using the multi-color scintillator Gd 2 O 2 S:Eu has been developed for the X-ray radiography. In this method a color Charge Coupled Device detects the weak blue and green photons associated with the transitions from the terms like 5 D 1 and 5 D 2 in the Eu-ions as well as the dominant red photons. As these transitions become appreciable and saturate at quite different intensity levels of the X-ray, we can realize a big extension of the dynamic range of the imaging almost by hundred times in comparison with the conventional monochromatic method. As a result, the new system makes it possible to take a clear image of any complex object, which consists of various parts of the different X-ray penetrability, from plastic to heavy metal, at a single shot.

New neutron detection methods using laser technique

Abstract New neutron detection methods using the 3 HeNe lasing are proposed. These methods are mainly based on two types of lasing: nuclear pumped laser (NPL) and radiation triggered laser (RTL). In the NPL mode, the charged particles produced by neutron reactions directly excite the laser gas, and then the lasing occurs. The direct NPL output power and the optical gain are available as signals to measure the thermal neutron flux. In the RTL mode, the neutron irradiation raises the discharge of the laser gas when a specific voltage is applied, and then the lasing occurs. This method is based on the variation of the lasing voltage by the neutron irradiation. Experimental results, obtained for both of these two methods, show the feasibility of a new neutron detection system, using the laser light signal, and which can be applied to in-core neutron monitoring in the fission reactor.

Electronic imaging for 252Cf based neutron radiography

For 252Cf based neutron radiography, a photon counting method which performed binary image conversion and minimum ranked-order filtering has been applied using a multi-functional electronic imaging system. The contrast and spatial resolution of the radiograph have been improved by the signal processing method.

Charge integrating type position-sensitive proportional chamber for time-resolved measurements using intense X-ray sources

Abstract A position-sensitive detecting system for time-resolved diffraction measurements with very intensive X-ray sources has been developed. It consists of a charge integrating type gas-filled detector, multichannel analog multiplexers, a signal processor and a memory (120 ch.×128 phases×24 bits). The detector is 120 mm long in effective length by 10 mm×10 mm in cross section with a single anode of 20 μm diameter. One of the cathode planes consists of 120 cathode strips with a pitch of 1 mm. The spatial resolution is equal to the pitch under a certain detector current limit. The gas gain is adjustable to an appropriate value according to the X-ray intensity range of interest. For experiments with 8 keV X-ray sources, maximum absorption rates of 9×10 7 photons/s·mm with low applied voltage and minimum absorption rates of about 3 photons/s·mm with high applied voltage can be achieved. This system was applied to a time-resolved X-ray diffraction study on frog muscle using a synchrotron radiation source at the Photon Factory and we could collect diffraction patterns with a time resolution of 10 ms and only 10 stimulations.

Integral Type Position-Sensitive Proportional Chamber with Multiplexer Readout System

A new position-sensitive detector with a multiplexer readout system for synchrotron radiation measurements is described. The detector consists of many proportional chamber cells with capacitors for charge accumulation. Charges delivered from a detector cell are accumulated in an associated capacitor during a measuring time. The accumulated charges are transferred to a charge-sensitive amplifier through a multiplexer channel which is addressed by binary coded signals. This process corresponds to the integral type radiation measurement which has no dead time in the pulse measurement. Each cell is regarded as a memory cell containing information about X-ray photons. Experiments carried out with a direct X-ray beam show that the detecting system is applicable to a wide range of photon rates from 103 cps to 108 cps per cell.

An amorphous silicon imaging detector with a phosphor sheet for nondestructive testing and radiography

An amorphous silicon linear sensor originally manufactured for facsimile has been applied to imaging systems for industrial nondestructive testing and radiography. X-ray images can be measured by scanning of a single linear sensor with a Gd2O2S phosphor sheet set on a sliding stage. To reduce the exposure time a semi-area detector with 16 linear sensors has been also constructed. The spatial resolution of 2.5 line pair/mm was obtained for X-ray images with an area of 30 × 25 cm2.

Imaging system with an amorphous silicon linear sensor

An amorphous silicon (a‐Si) linear image sensor with a long active length and good spatial resolution has been applied to two‐dimensional x‐ray imaging. An area‐to‐line converter using plastic optical fibers (250 μm φ) with a Gd2 O2 S phosphor sheet has been constructed and attached to the sensor. This 2D detector has only 32×32 channels, but there is no technical limit for constructing a larger area detector. An EXAFS experiment is also presented for demonstration of the utility of the detector.