Development of a neutron monitoring system for X-n mixed fields

A dual type ionization chamber system making use of an isotope pair of He-3 and He-4 has been developed to monitor such burst-like X-n mixed fields as those appearing in the vicinity of fusion experiments and accelerators. Specific characteristics of the system have been checked and tested in several different irradiation source facilities, including the D2O-thermalised neutron area of KUR reactor. Useful response coefficients are obtained: X-ray response of a He-4 chamber (1-l 1-atm.) being 13.64 x 10-10 A/(Gy h-1), and response of a He-3 chamber (1-l 1-atm.) to thermal neutron fluence (3.65-1.65) x 10-14 A/(n cm-2 s-1). Further improvements and considerations are discussed. (author)