微弱な放射性試料に対するAutomatic Sample Changerとその結果の整理法

抄録

A Simple, low cost automatic sample changer is described.
The instrument is composed of three parts. The sample changing system consists of a turn-table on which six samples are located as shown in Fig. 1, a phono-motor which drives the table and a sample changing vacuum-tube circuit. The time recording system consists of a synchronous motor which generates time signals and six registers each of which records the time required for 64 counts. The scaler is a usual type of scale of 64.
When No. 1 sample is counted by a G-M counter, No. 1 register circuit is closed and it records the time signals. At the moment of the 64th count, a signal from the scaler is sent to trigger the sample changing circuit and A. C. line of the motor is closed and the table begins to turn. No. 1 register circuit is then opened and the time recording is finished. When No. 2 sample is brought to the counting position, No. 2 register circuit is closed and the time signals bigin to be recorded on that register.
A formula is deduced representing the statistical error of the measurement. It is slightly different from that obtained by the usual method, especially when the counting rate is large.
It is found that this instrument is quite adequate for the measurement of samples of low level activity, because it can count the sample and the background alternatively and can record the sum of the counting times of each cycle for each sample.