Measurement of neutron spectra and neutron doses at the Munich FRM II therapy beam with Bonner spheres

Response functions of a Bonner sphere spectrometer calculated with GEANT4

“…In Ref. [17], for example, gold foils that are activated by thermal neutrons were used inside the Bonner spheres to measure the neutron spectrum of the neutron beam at a nuclear reactor, where a high neutron fluence rate is present. The saturation specific activity A i 1 ½Bq g À1 of the gold foil activated in the i-th Bonner sphere obtained from 198 Au Fg-ray measurements can be expressed as…”

“…In contrast, at high neutron fluence rates, such as those that might occur at nuclear facilities, the less sensitive gold foils are preferred [11][12][13][14]. For example, a BSS system including gold foils as detectors has recently been used to detect the neutrons at the MEDAPP neutron therapy facility at the FRM II in Garching, Germany [17,18].…”

NEUTRON RESPONSE FUNCTION OF BONNER SPHERE SPECTROMETER WITH 6LiI(Eu) DETECTOR

“…The 4 mm × 4 mm of 6 LiI(Eu) scintillator is located at the center of BSS that used as thermal neutron detector. Naturally occurring Lithium isotopes are 92.5% 6 Li and 7.5% 7 Li, while Iodine has only one natural isotope 127 I; all those isotopes are stable. The 6 LiI(Eu) scintillator consist of 6 Li, 7 Li, and 127 I isotopes, with smaller amounts of Eu as impurities [12].…”

“…Naturally occurring Lithium isotopes are 92.5% 6 Li and 7.5% 7 Li, while Iodine has only one natural isotope 127 I; all those isotopes are stable. The 6 LiI(Eu) scintillator consist of 6 Li, 7 Li, and 127 I isotopes, with smaller amounts of Eu as impurities [12]. The reported data in literatures are calculations based on scintillators that has been modeled with different enrichment of 6 Li of 96% to 100% [12].…”

“…A BSS can be used to measure the neutron spectrum with energy up to a few GeV usualy by adding lead in the moderating spheres [3], [4], [5]. Several type of thermal neutron detector are utilized in BSS, such as 6 LiI(Eu) scintillator, pairs of thermoluminiscent dosimeters, activation foils, track detectors, and BF 3 or 3 He filled proportional gas counters [6], [7], [8], [9]. The neutron response and the measured readings of the BSS are associated with the neutron count spectrum by the Fredholm integral equation in Equation 1 (1) where inside a neutron field the detector produces count per time, C, that is related to the response function, R(E), and the neutron spectrum, ΦE(E).…”