Statistics and dead time correction of two-particle time-of-flight coincidence experiments

Abstract

The statistics of a specific class of two-particle coincidence experiments are discussed. Detection of the first particle provides for the start of a time-of-flight measurement in which the second particle is analyzed. Dead time of the electronics used for flight time measurements and registration of coincidence signals (time-to-amplitude converter or time-to-digital converter) may cause strong distortion of coincidence spectra. The problem is complicated by the different statistics of true and false coincidences. Without a convenient correction procedure, this effect limits the source strength to a value for which the distortion is small but the measurement duration is long. A calculation method is developed from which the measured coincidence spectra can be corrected for distortion at any source strength thereby separating true and false coincidences. This technique has been successfully applied in an electron-ion coincidence experiment where free atoms were photoionized by synchrotron radiation.