Patent GB-1397231-A (GB)
Title: Method of and apparatus for determining radiation energy distri butions
IPC: G01T1/36
Filed: 1972-07-27
Abstract: 1397231 Determining radiation energy distribution PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 27 July 1972 [30 July 1971] 35100/72 Heading G1A A method or apparatus of measuring the energy of an incident pulse (quanta) of radiation 4 employs a detector D connected to a charge sensitive amplifier 10 which converts each pulse into a signal step, the results for each quanta being collected together and sorted to provide a distribution curve. The output of the detector is alternately applied for periods of t n  secs. to integrators 20, 21 and thence to a measuring device M with the aid of switching devices 18, 19, 23 and 24 controlled by a clock 27, the output of the measuring device being fed to a multiple store for storing the measuring informations in time sequence and also to a signal recognition circuit S.H.C. which determines when tp a pulse above a predetermined intensity level has occurred. The multiple store MG and the signal recognition circuit S.H.C. are connected to an arithmetic store RG and a counting circuit TK whereby the step height is determined by subtracting the summed integration results obtained in a predetermined period T before the occurrence of such a pulse tp (an event) from the summed integration results obtained in a period T after said occurrence (where T = nt n ). The final result which is proportional to the step height and thus the energy of the pulse is fed to a register ER, where the step height measurement is registered in one of a plurality of event registers (not shown) each register representing a different energy range in accordance with the height of the signal produced by the event. Thus an energy distribution curve or spectrum is eventually obtained. In one embodiment, Figs. 2-7; Figs. 3-7 (not shown) the measuring device is an analogue to digital converter supplying two digital word shift registers, acting as the multiple store and the signal recognition circuit. The arithmetic store comprises an auxillary results register, an intermediate results register and a final results register Fig. 3 (not shown) provided with a subtraction/  additon counter which is activated via a gate circuit by a start pulse from the signal recognition circuit to perform the computation involving "n" addition operations and "n" subtraction operations. The gate circuit may include a weight register to double or even quadruple the values of the subintervals t n  just before and just after the occurrence of the pulse tp. A flip-flop, Figs. 6 and 7 (not shown) may be used in conjunction with two sets of an arithmetic store (RG1, RG2) and a counting circuit (TK1, TK2) the flip-flops being connected to the signal recognition circuit so that the next counting and computing operation can be started before the first one has finished. In a further embodiment, Fig. 7 (not shown) two successive intervals between events are calculated and a period T smaller than the smaller of the two intervals is formed and used in the calculation of the step height but before the result is fed to the final results register ER, the result is standardized (for example by deviding it by T) so that all the results are comparable.