Response of NE213 liquid scintillation detectors to high-energy photons (7 MeV < Eγ < 20 MeV)

Two NE213 liquid scintillation detectors of 206 and 412 cm3 in volume were calibrated in high-energy photon fields (Eγ > 7 MeV) at the PTB accelerator facility. The measured pulse height spectra are in excellent agreement with the response functions simulated with the EGS4 Monte Carlo code. The generally assumed linear dependence of the electron light output on the energy deposited does not hold for electron energies above 1.6 MeV. The nonlinear electron light output function was therefore included in the calculation of the response functions. The production of high-energy electrons and positrons in the target assembly and in the air was also taken into consideration.