TY - JOUR
T1 - Estimation of the Fast-Ion Anisotropy Effect on the Neutron Source Intensity Measurement and the Experimental Observation
AU - The LHD Experiment Group
AU - Nishitani, Takeo
AU - Matsuura, Hideaki
AU - Pu, Neng
AU - Ogawa, Kunihiro
AU - Kawase, Hiroki
AU - Isobe, Mitsutaka
N1 - Publisher Copyright:
© 2018 IEEE.
PY - 2019/1
Y1 - 2019/1
N2 - In the large helical device (LHD) deuterium plasma experiment, the neutron emission rate and the shot-integrated neutron yield are measured with the neutron flux monitor (NFM) and the neutron activation system (NAS), respectively, where the neutron emission is assumed to be isotropic in the plasma. The differential cross section of the D(d,n)3He reaction has a large anisotropy for the forward direction of the incident deuteron direction. LHD has intensive tangential neutral beam injectors (NBIs), which may cause an anisotropic neutron emission in the plasma. The angular distribution of the neutron emission is calculated from the fast-ion distribution function evaluated by a code that solves Fokker-Plank equations for the 180-keV tangential NBI. The effect of the anisotropic neutron emission on the NFM and NAS measurements is estimated by a general-purpose Monte Carlo N-particle (MCNP) code calculations. Also, the effect is confirmed experimentally. The neutron emission rate measured with the NFM near the equatorial port is about 10% larger than that with the NFM at the top of the LHD center axis. The shot-integrated neutron yield measured with NAS is 25% larger than that with NFM at the top of the LHD center axis in the case of the tangential neutral beam injection, which is consistent with the MCNP calculation.
AB - In the large helical device (LHD) deuterium plasma experiment, the neutron emission rate and the shot-integrated neutron yield are measured with the neutron flux monitor (NFM) and the neutron activation system (NAS), respectively, where the neutron emission is assumed to be isotropic in the plasma. The differential cross section of the D(d,n)3He reaction has a large anisotropy for the forward direction of the incident deuteron direction. LHD has intensive tangential neutral beam injectors (NBIs), which may cause an anisotropic neutron emission in the plasma. The angular distribution of the neutron emission is calculated from the fast-ion distribution function evaluated by a code that solves Fokker-Plank equations for the 180-keV tangential NBI. The effect of the anisotropic neutron emission on the NFM and NAS measurements is estimated by a general-purpose Monte Carlo N-particle (MCNP) code calculations. Also, the effect is confirmed experimentally. The neutron emission rate measured with the NFM near the equatorial port is about 10% larger than that with the NFM at the top of the LHD center axis. The shot-integrated neutron yield measured with NAS is 25% larger than that with NFM at the top of the LHD center axis in the case of the tangential neutral beam injection, which is consistent with the MCNP calculation.
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U2 - 10.1109/TPS.2018.2846776
DO - 10.1109/TPS.2018.2846776
M3 - Article
AN - SCOPUS:85049461040
SN - 0093-3813
VL - 47
SP - 12
EP - 17
JO - IEEE Transactions on Plasma Science
JF - IEEE Transactions on Plasma Science
IS - 1
M1 - 8401945
ER -