Transition radiation

An improvement in particle separation at low γ (approx. 103) and development of a practical transition radiation detector using a relatively simple electronic count of charge clusters has been described by Fabjan, Willis and collaborators. The count of charge clusters distinguishes rather well between the low number of clusters from ionization of the primary particle and the higher number from transition radiation quanta. The range of the detector is γ approx. 103 - 104. The detector is 10 x 10 cm2 in cross section (MWPC to collect ionization) and 0.5 to 1.0 m long with 12 to 24 sets of radiators. The method requires 4 ADC's and a discriminator/radiator plane, to count the number of clusters with large amplitude collected at each plane. The speed of the device is set by the charge collection time, about 160 nanoseconds. The results are relatively stable over a wide range (2.5 to 4 keV) for the cluster threshold energy, and both π/e and K/π separation is quite good. The π/e separation achieved is approx. 0.2% pion contamination for 90% electron efficiency for 10 to 15 GeV/c π's and electrons, with 12 sets of Li foil radiators spaced over approx. 0.5 m length. For π's and K's at 140 GeV/c, 24 planes of carbon fibers were used as radiators, spaced over a 1.3 m length. With that configuration they reduced the pion contamination to 1 to 2% for 90% kaon efficiency