Abstract
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 (Qtotal) during different NBs heating phases measured by the CNES shows that the edge of Qtotal changes depending on NB directions. Using the simple derivative unfolding technique, the neutron energy spectra were unfolded from the measured Qtotal 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.
Highlights
Understanding fast-ion confinement is one of the issues for obtaining high-performance plasmas because plasmas are auxiliary heated by fast-ions created by neutral beam (NB) injection and/or ion cyclotron heating
A tangential line-of-sight compact neutron emission spectrometer based on an EJ301 liquid scintillation detector is newly implemented in Large Helical Device (LHD) to obtain the energy distribution of beam ions created by tangential NBs
4 Summary The neutron spectroscopy is performed in NB heated LHD plasma by the newly installed compact neutron emission spectrometer (CNES) having the tangential sightlines
Summary
Understanding fast-ion confinement is one of the issues for obtaining high-performance plasmas because plasmas are auxiliary heated by fast-ions created by neutral beam (NB) injection and/or ion cyclotron heating. In the Large Helical Device (LHD), a study of fast-ion transport due to fast-ion-driven MHD instability has been performed using intensive NBs [2]. High-acceleration energy NBs are installed in LHD. The EJ301 liquid scintillator [15], 1-inch in diameter and 1-inch in height, is directly coupled to a conventional 1-inch PMT (H10580-100-01, Hamamatsu Photonics K.K [16].) and is used as a fast-neutron detector Note that the ratio of neutron signal and γ-ray signal is 5:1
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