Multipulse time of flight technique of variable resolution based on linear processing of count pulses

Abstract

A novel method for measuring the count arrival times, which is effective at higher count rates when more than a single event per scan is detected (multipulse performance), is presented. It is based on the direct ADC sampling of normalized counts and their software processing by deriving a reference count shape from randomly arriving counts, determination of arrival times by comparison with the reference shape, histograming, etc. The dead time by this method does not exceed several times the count pulse duration. The method is also free of dead processing times after the event arrivals in contrast to typical TOF-methods with TACs. A temporal accuracy of order of 10−2 of the ADC sampling step (0.5ns at 20MHz/8bits ADC) has been experimentally demonstrated. This method combines the very high time resolution of the best TOF-techniques (operating at very low count rates) with the higher tolerable count rates of the photon counting techniques (operating at lower resolutions). The unique opportunity for direct computer processing of raw acquired data from the discriminator, realizing variable resolution (zooming) of the retrieved time profiles must be noted.