An introduction to the use of coincidence counting techniques in the study of   rays

Abstract

A basic coincidence counting system is described and the factors which determine the accuracy of coincidence measurements are assessed. Techniques which enable the energies of coincident y rays to be determined are outlined and the factors which limit the minimum usable coincidence resolving time are then discussed. Applications of the coincidence method to the study of nuclear decay schemes are briefly reviewed. Finally a simple coincidence counting system is described which was developed as an undergraduate laboratory project. It is intended to act as a link between the study of simple basic electronic circuits and the use of electronic equipment ('black boxes') in experimental physics by showing how a scintillation counter coincidence system can be constructed from elementary circuits. The coincidence method is illustrated by measurements, made with the simple system, on the y rays from a 2aNa source. Coincidence countingA basic coincidence counting apparatus consists of two detectors coupled to a system which registers the simultaneous detection of radiation in these two detectors, the simultaneity being determined with a precision of It, the 'resolving time' of the system.Consider two y ray detectors, with detection efficiencies e, and c 2 which subtend solid angles R, and R, respectively at a point source which emits Nphotons/s, a fraction f of which are emitted as time coincident pairs. The counting rate in one detector is NI= N (!2,/4n)e, and if there is no correlation of directions of emission of the coincident photons, the rate at which one photon of a coincident pair is detected in one detector with the other photon detected in the other detector, that is the true coincidence rate N,, isIn addition to the true coincidences, if the counting rates in the two detectors are NI and N Z , then because of the finite resolving time, there can be accidental coincidences due to the chance detection of a photon in one detector within +r of the time of detection of a photon in the other. This accidental or 'random' coincidence rate is

Photon–electron coincidence experiments at synchrotron radiation facilities with arbitrary bunch modes

“…Since its first use in the 1920s, 1,2 coincident particle detection evolved to one of the most powerful tools in various disciplines, e.g., nuclear science, [3][4][5][6][7] high-energy particle physics, 6,[8][9][10] positronemission tomography, 11,12 astrophysics, 13,14 quantum communication, 15,16 or atomic and molecular physics, [17][18][19][20][21][22][23][24][25][26][27] and references therein. The simultaneous detection of multiple particles from decays of radioactive matter or following defined target-projectile interactions allowed the identification and quantification of distinct processes in experiments.…”