Measurement of the Energy Spectrum of Short-Pulse Neutron Sources Based on Photonuclear Reactions

The energy spectrum of neutrons generated in the Pb(\(\gamma ,n\)) photonuclear reaction has been experimentally studied using a short-pulse laser-plasma electron source (1 TW, 10 Hz). An electron beam accelerated in a nitrogen jet is incident on a lead converter where bremsstrahlung initiating a photodisintegration reaction is generated. The time-of-flight method has been applied for the first time to measure the neutron spectrum in the neutron-counting mode using a scintillation detector based on a stilbene crystal. An exponential distribution with a characteristic “temperature” of ~2 MeV and a maximum energy of ~8 MeV is observed in the measured spectrum. The developed method is very promising for studying photonuclear reaction cross sections near the threshold using compact laser systems or projected \(\gamma \)-ray sources based on inverse Compton scattering.