Year
2001
Abstract
The loss of valid counts from the spectrum due to the system being busy is referred to as counting loss. The traditional method of correcting for the counting losses in spectroscopy applications is the so-called extended live-time correction. The live time is extended to count for a longer clock or real time to compensate for the loss of counts during the counting interval. This method fails to correctly account for the lost counts when count rates and dead times change widely during the time of acquisition of the spectrum. Examples of such cases are when monitoring a rotating waste container with a \"hot spot,\" counting flowing samples in a pipeline or stack, or when counting samples with high levels of short half-life components. So-called \"loss free\" counting methods have been developed in analog-type instruments to correct the spectrum data \"pulse by pulse.\" This avoids the limitations caused by the changing count rates. None of these methods have gained wide acceptance because 1) the difficulty of setup and 2) there is no way to determine the channel-bychannel uncertainty of the spectrum. To overcome both of these shortcomings, a new system was developed based on instruments using digital signal processing (DSP) for the processing of the signals from the germanium detector. This system collects the corrected spectrum and an uncertainty spectrum. The uncertainty spectrum is calculated pulse by pulse, thereby allowing accurate uncertainties of the corrected spectrum to be derived from the uncertainty spectrum. Performance data for both the operation of the correction as a function of count rate and the calculation of the uncertainty will be presented.