Quality assurance and high count rate

A high count rate can distort the expected linear relation between the charge spectrum generated in a semiconductor gamma-ray detector and that recorded in the pulse-height analyzer. The busy time of the analog-to-digital converter (ADC) is accurately compensated for in commercial analyzers by extending the live counting time. As fast successive-approximation ADCs have become more generally used (note that 10{mu}s fixed digitizing time for 8192 channels is equivalent to an 800-MHz Wilkinson ADC), the resolution times of the other components in the counting system have become relatively more important limitations of the throughput of the total system and also more important sources of nonlinearity, which lead to biased measurements. A loss-free counting technique (LFC) has been developed which gives an undistorted spectrum and zero dead time so that decay equations can be solved. Tests of an LFC system have shown that, with systematic calibration, the system can give stable values in practice for a reference spectrum up to at least 100 kHz. To obtain higher quality data with confidence, quality control test are needed.