A QUICK RESPONSE IONIZATION SURVEYMETER (in Japanese)
A quick response ionization survey-meter and some problems concerned with alpha contamination are described. To measure small currents a high resistance and a d-c amplifier are used. The time response of such a device was usually improved by the negative feedback, but there is a limitation because of the capacitance parallel to the resistor. This capacitance can be reduced by means of a new device, and the use of a high gain d-c amplifier at the same time makes the response extremely fast. By this method, a time constant less than 0.5 second was accomplished with a resistor of 10/sup 13/ ohms, and 1 mr/h full-scale was realized with a 400-cc air ionization chamber. The response of the device is actually limited by the statistical fluctuations of the ionization current. Theoretical considerations of these problems are discussed and confirmed by measurements using an experimental instrument. Another problem in quickening the response and raising the sensitivity of the survey meter is alpha contamination. Random pulses or spikes are produced by stray alpha emitters in the chamber. By analyzing their pulse height distribution, five causes of random pulses are traced, among which the emitters in the wall material, on the walls, and in the air are in the proportion of 55: 27: 18. These spikes were reduced to 60% after the chamber was left sealed for one year, and this reduced value is nearly equal to the first fiinire of the above ratio. When the response is sufficiently fast, the presence of alpha contamination has no influence on the measurement because recovery to the normal state is fast and the discrimination of these pulses is very easy. (auth)
- Research Organization:
- Hitachi Ltd., Tokyo
- NSA Number:
- NSA-18-004122
- OSTI ID:
- 4126757
- Journal Information:
- Oyo Buturi, Vol. Vol: 32; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- Japanese
Similar Records
Evaluation of ANSI N42-17A by investigating the effects of temperature and humidity on the response of radiological instruments
A DEVICE TO MEASURE LOW LEVELS OF RADIOACTIVE CONTAMINANTS IN ULTRA-CLEAN MATERIALS