Observation of significant Doppler shift in deuterium-deuterium neutron energy caused by neutral beam injection in the large helical device

• Published in: AAPPS bulletin 2022-02, Vol.32 (1), p.1-8, Article 5
• Main Authors: Sangaroon, S., Ogawa, K., Isobe, M., Kobayashi, M. I., Fujiwara, Y., Kamio, S., Yamaguchi, H., Seki, R., Nuga, H., Takada, E., Murakami, S., Zhong, G. Q., Osakabe, M.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics and Cosmology; Atomic; Compact neutron emission spectrometer; Doppler effect; Large helical device; Liquid scintillator; Molecular; Neutral beam heating; Optical and Plasma Physics; Original Article; Particle and Nuclear Physics; Physics; Physics and Astronomy
• ISSN: 2309-4710; 2309-4710
• DOI: 10.1007/s43673-022-00036-5

The compact neutron emission spectrometer (CNES) having a tangential sightline was installed to observe a significant Doppler shift of the neutron energy due to the high-energy tangential neutral beam (NB) injections in the Large Helical Device (LHD) for understanding of the energy distribution of fast-ion. The CNES is based on a 1-inch diameter and 1-inch height EJ301 liquid scintillator coupled with a conventional 1-inch photomultiplier tube. The histogram of the integrated pulse signal ( Q total ) during different NBs heating phases measured by the CNES shows that the edge of Q total changes depending on NB directions. Using the simple derivative unfolding technique, the neutron energy spectra were unfolded from the measured Q total histogram. Peaks of the neutron energy shift to 2.0 MeV, 2.42 MeV, and 3.0 MeV according to the injection direction of NBs. The obtained neutron energy is almost consistent with the virgin deuterium-deuterium neutron energy evaluated by the simple two-body kinematics considering the sightline of CNES, NB injection angle, and NB injection energy.