Improvements in and relating to pulse counting apparatus and to the measurement of radiation from radioactive materials using pulse counting apparatus

摘要

1,111,121. Counters. ISOTOPE DEVELOPMENTS Ltd. 26 April, 1965 [7 April, 1964], No. 14253/64. Heading G4D. [Also in Division G1] In pulse counting apparatus for measuring the radiation from radioactive samples presented sequentially by an automatic sample changer, during any one timed counting interval of a number of intervals which make up a complete sample measurement count, pulses are first counted by a background scaler 7a or 7b until the number of pulses counted becomes equal to a periodically updated, stored background count, and then the rest of the pulses for the interval are fed to the main scaler 3 to obtain the count representing the wanted radiation from the material. After each measurement, a trend follower unit 31 is arranged to receive only background pulses, and it responds to any significant change in the average level of the background radiation impulse rate by preventing the presentation, by the sample changer, of a new sample, and by initiating a fresh measurement of the background. This measurement is recorded in one of the two background scalers 7a, 7b, in a time interval determined by the selector 25. The count previously stored in the scaler 7a or 7b is cancelled and the new count read in. Then a new sample can be presented for measurement. Now, the signals are supplied so that the scaler having the stored background count recorded is reduced to zero, while the scaler previously recording a zero count is made to count upwards. When the background count is attained in the background scaler counting upwards (and zero attained in the other), further pulses are diverted to the main counter 3 to record the radiation from the sample. During the next timing interval, the operation of the scalers 7a, 7b is reversed, the background count afterwards still being retained in one of them. This process is repeated for a number of intervals, as stated above, until a predetermined count or time is attained.