Instrument intercomparison in the pulsed neutron fieldsat the CERN HiRadMat facility

An intercomparison of the performances of active neutron detectors was carried out in pulsed neutron fi elds in the new HiRadMat facility at CERN. Five detectors were employed: four of them (two ionization chambers and two rem counters) are routinely employed in the CERN radiation monitoring system, while the fi fth is a novel instrument, called LUPIN, speci fi cally conceived for applications in pulsed neutron fi elds. The measurements were performed in the stray fi eld generated by a proton beam of very short duration with momentum of 440 GeV/c impinging on a dump. The beam intensity was steadily increased during the experiment by more than three orders of magnitude, with an H*(10) due to neutrons at the detector reference positions varying between a few nSv per burst and a few m Sv per burst, whereas the gamma contribution to the total H*(10) was negligible. The aim of the experiment was to evaluate the linearity of the detector response in extreme pulsed conditions as a function of the neutron burst in- tensity. The results show that the ionization chambers have a quasi-linear response, very close to the ideal behaviour also for values of H*(10) of a few m Sv/burst; the LUPIN response shows a slight deviation from the ideal curve when the H*(10) per burst is higher than 100 nSv; the rem counters response are characterized by a strong deviation from the linearity for H*(10) values higher than a few tens of nSv.