In situ calibration of neutron activation system on the large helical device

Abstract

In situ calibration of the neutron activation system on the Large Helical Device (LHD) was performed by using an intense Cf neutron source. To simulate a ring-shaped neutron source, we installed a railway inside the LHD vacuum vessel and made a train loaded with theCf source run along a typical magnetic axis position. Three activation capsules loaded with thirty pieces of indium foils stacked with total mass of approximately 18 g were prepared. Each capsule was irradiated over 15 h while the train was circulating. The activation response coefficient (9.4 ± 1.2) × 10 of In(n, n')In reaction obtained from the experiment is in good agreement with results from three-dimensional neutron transport calculations using the Monte Carlo neutron transport simulation code 6. The activation response coefficients of 2.45 MeV birth neutron and secondary 14.1 MeV neutron from deuterium plasma were evaluated from the activation response coefficient obtained in this calibration experiment with results from three-dimensional neutron calculations using the Monte Carlo neutron transport simulation code 6.

Evaluation of a treatment planning system developed for clinical boron neutron capture therapy and validation against an independent Monte Carlo dose calculation system

“…al and Kobayashi et. al showed the self-shielding of gamma-rays by the indium foil was estimated to be negligible [ 29 , 30 ].…”

Prediction of Neutron Emission Anisotropy for Validation of an Analysis Model for Neutron Spectra in Beam-Injected LHD Deuterium Plasmas

“…The NAS measures neutrons during a shot by exposing the activation foils and counting the gamma-rays emitted from the exposed foils [7]. The activation foils are sent by pneumatic control systems to two irradiation ends located at the 2.5-L and 8-O ports.…”

“…As neutrons are emitted mainly from the reaction of energetic ions in neutral beam (NB)-injected deuterium plasmas confined by current experimental devices, we can obtain information on confined energetic ions by neutron measurements. The large helical device (LHD) has several neutron measurement systems, including the neutron flux monitor (NFM) [6] and the neutron activation system (NAS) [7]. The NFM measures the time-dependent total neutron emission rate using a 235 U fission chamber, 10 B, and two 3 He counters, whereas the NAS counts the number of neutrons during a shot using the activation foils.…”

Preparation and Commissioning for the LHD Deuterium Experiment

“…1 [22], [23]. In addition, the Neutron Activation-foil System (NAS) was also installed at two toroidal locations on LHD [24]. The calibration of the NFMs [11] and the NAS [24] were performed circulating a 252 Cf source of 800 MBq in the torus at the midplane.…”

“…In addition, the Neutron Activation-foil System (NAS) was also installed at two toroidal locations on LHD [24]. The calibration of the NFMs [11] and the NAS [24] were performed circulating a 252 Cf source of 800 MBq in the torus at the midplane. The spatial resolution of the VNC was also examined by an experiment using the source and by the three dimensional general-purpose Monte Carlo N-Particle (MCNP) code calculations [23].…”