Collimator system design for a DT neutron beam at the first target room of JAEA/FNS

Onishi, Seiki; Sato, Satoshi; Ochiai, Kentaro; Takakura, Kosuke; Kondo, Keitaro; Konno, Chikara  

There are two target rooms at the Fusion Neutronics Source (FNS) facility in Japan Atomic Energy Agency (JAEA). Recently it becomes increasingly difficult to meet needs for experiments with a DT neutron beam such as instrument development for ITER, because of shortage of the large target. Therefore we plan to construct a neutron beam inside TR1 by using the small tritium target of TR1, which is easier to obtain. We designed the collimator system based on the cylindrical assembly used in the previous ITER shielding experiments at JAEA/FNS. Neutron spectra at the exit of the collimator and at the offset position by 20 cm from the collimator axis were calculated with the two dimensional Sn code DORT and FENDL/MG-2.1 multi-group library in order to investigate the effect of the collimator system.