Detection of X-ray transition radiation by the threshold-efficiency method

The threshold-efficiency method for the detection of X-ray transition radiation in gas-filled proportional detectors ∼1 cm thick is discussed. Analysis of experimental data obtained by this method shows that its separation factor is at least as good as that of the traditional method relying on truncated mean energy loss measurements. Arguments showing that the cluster counting method is based on a simplified consideration of the threshold-efficiency method are presented.