Speaker
Dr
Marita Mosconi
(Physikalisch-Technische Bundesanstalt)
Description
At IRMM and PTB, several 235U and 238U parallel-plate fission ionization chambers are employed as reference instruments for measuring the spectral neutron fluence in monoenergetic as well as ‘white’ neutron beams with energies up to 200 MeV. Some of these instruments were already manufactured more than 20 years ago. Therefore a comparison exercise was organized at the PTB ion accelerator facility (PIAF) to check the stability of the fissile layers and to verify the efficiencies calculated from the measured properties of the deposits. Neutron fields with mean energies of 8.5 MeV and 15 MeV were produced using the D(d,n) and T(d,n) reactions. The 0° neutron yield was determined relative to the n-p scattering cross section using the PTB recoil telescope RPT1 and a well-characterized 2"x2" NE213 liquid scintillation detector (DD). The time-of-flight method was employed to discriminate the low-energy neutrons resulting from break-up reactions or target scattering. Two long counters and a 3He detector covered with a PE cap were employed as monitors to relate the measurements with RPT1 and DD to those with the various fission ionization chambers under study. The present contribution reports on the actual results obtained for the different instruments and discusses the contribution to the uncertainty budgets as well as the minimum uncertainty which can realistically be achieved using neutrons beams to characterize fission ionization chambers. The models used so far to calculate the neutron detection efficiency as well as the scattering corrections are compared to more recent calculations.
Author
Dr
Marita Mosconi
(Physikalisch-Technische Bundesanstalt)
Co-authors
Dr
Arjan Plompen
(IRRM)
Dr
Chariklia Rouki
(IRRM)
Dr
J.C. Thiry
(IPHC)
Dr
M. Kerveno
(IPHC)
Dr
P. Dessagne
(IPHC)
Dr
Ralf Nolte
(Physikalisch-Technische Bundesanstalt)
