Development of capillary plate neutron detector filed with liquid scintillator by using recoiled-particle trajectory analyses

New 14 MeV neutron detector using capillary plate with liquid scintillator has been developed aiming at the triton burn-up study on the deuterium plasma experiment of the Large Helical Device (LHD). A capillary plate with 25 mm in diameter, 10 mm in thickness, and 10 μm pitch honeycomb structure is used as a detector head. The scintillating light trajectory is measured by an Electron-Multiplying CCD (EMCCD) via relay lenses. The trajectories for neutrons and gamma-rays are simulated by the Particle and Heavy Ion Transport code System (PHITS). Maximum trajectory length is estimated to be 2 mm and 0.1 mm for 14 MeV neutron and 2.45 MeV neutron, respectively. The trajectory of a proton recoiled by a neutron is linear, and the trajectory length depends on the recoiled proton energy. On the other hand, the trajectory of an electron produced by gamma-ray is not straight due to the random walk of the electron in the scintillator. Therefore, we can identify 14 MeV neutrons from 2.45 MeV neutrons and gamma-rays by the trajectory length and the shape. The developed detector was installed in the basement of the LHD torus hall just under the vertical collimator embedded in the floor concrete for the second deuterium plasma campaign of LHD in 2018. We identify trajectory which is considered due to the proton recoiled by14 MeV neutrons on the LHD deuterium discharge.