Measurement of the NIEL-scaling factor of thick target p+Be neutrons at Ep = 17.4 MeV proton energy for silicon

Radiation tolerance tests of silicon based devices are regularly done at ATOMKI with thick target p+Be neutrons at Ep = 17.4 MeV. Measurements were done to estimate their NIEL-scaling factor for silicon. The neutron spectrum was measured by the multifoil activation technique. Saturation activities of different neutron induced reactions were measured and the neutron spectrum was unfolded from them. Displacement KERMA data were taken from literature and their energy spectrum averaged value was calculated. The obtained NIEL-scaling factor was = 1.1 ± 0.20. Following the ASTM E1855-05el standard, a second type of measurement was done, too. 2N2222 bipolar transistors were irradiated by p+Be neutrons and by fission neutrons. The emitter current gain of the transistors was measured before and after the irradiation. The NIEL-scaling factor could be determined from the differences of the gains using the Messenger-Spratt equation. The obtained NIEL-scaling factor was 1.1 ± 0.23 from this measurement