Counting Schemes for Nuclear Data Acquisition on Small Computers

In using a small computer for accumulating a pulse height spectrum, it is often the case that the word length is too small to store the counts on a one-word-per-channel basis. The use of double precision to avoid this problem is wasteful of storage space. One way to avoid this waste is to store the differences between counts in two adjacent channels rather than the counts themselves. This can be achieved by adding 1 for each new count to the channel corresponding to that count and subtracting 1 from the next channel. The original spectrum can be recovered by summing the difference counts from one end of the storage array. Overflows can still occur when the original count distribution is increasing or decreasing rapidly (e.g., in the peaks of the spectrum), but these will, in general, not be too frequent and can be given special treatment as they occur. One method of doing this is to tag one bit of the word in the count array corresponding to the channel which has overflowed and using the remainder of the word to give the location of a double word which contains the full value of the count. Another method to avoid the use of double precision involves the use of a stochastic counting scheme for accumulating the spectrum.