Precise measurement of Birks kB parameter in plastic scintillators

The scintillation response of different types of plastic scintillators to electrons and protons was studied experimentally with high precision. Equivalent electron and proton energies yielding the same amount of light output have been measured. The results were analyzed in terms of a semiempirical formula proposed by Birks (1951). The results of the present experiment show that the reproducibility of experimentally determined kB values is better than +or-2%. This demonstrates the advantages of the time-of-flight method. As a consequence it was necessary to replace the very simple electron response function, L/sub e/(E) used in earlier publications by a more realistic description. The improved analysis was performed for SCSN-38 and NE 102A. In the present experiment the lowest kB value, i.e., the lowest loss of excitation energy due to radiationless quenching of fluorescence light, was observed for the scintillator SGSN-38 which is used in the ZEUS calorimeter.<>