Abstract
Two scintillating fiber (Sci-Fi) detectors have been operated in the first deuterium plasma campaign of the Large Helical Device in order to investigate the time evolution of the triton burnup through secondary 14 MeV neutron measurement. Two detectors use scintillating fibers of 1 mm diameter embedded in an aluminum matrix with a length of 10 cm connected to the magnetic field resistant photomultiplier. A detector with 91 fibers was developed in the Los Alamos National Laboratory and has been employed on JT-60U. Another detector with 109 fibers has been developed in the National Institute for Fusion Science. The signals are fed into a discriminator of 300 MHz bandwidth with a pulse counter module for online measurement and a digitizer of 1 GHz sampling with 14 bits to acquire pulse shape information for offline data analysis. The triton burnup ratio has been evaluated shot-by-shot by the 14 MeV neutron measurement of Sci-Fi detectors which are calibrated by using the neutron activation system and the total neutron measurement of the neutron flux monitor using 235U fission chambers.
Highlights
MeV neutron yields in the deuterium plasmas
The scintillating fiber (Sci-Fi) detector has been developed by the Los Alamos National Laboratory (LANL) and was utilized for the time-resolved 14 MeV neutron measurement on TFTR15 and JT-60U16
Two detectors use scintillating fibers of 1 mm diameter embedded in an aluminum (Al) matrix with length of 10 cm, which connect to the magnetic field resistant photomultiplier tube (PMT) for signal output
Summary
Activation techniques have been applied to measure the shot integral primary 2.45 MeV neutron yields and secondary 14. The scintillating fiber (Sci-Fi) detector has been developed by the Los Alamos National Laboratory (LANL) and was utilized for the time-resolved 14 MeV neutron measurement on TFTR15 and JT-60U16. The Sci-Fi detector has a high counting rate capability (higher than 107 counts/s) and good discrimination characteristic for 2.45 MeV neutrons and gamma-rays, is suitable for the time-resolved triton burnup measurement. In the first deuterium campaign of LHD, two Sci-Fi detectors work for time evolution of 14 MeV neutron measurement. NAS does not provide time evolution of neutron emission rate, it is absolutely insensitive to gamma-rays and is of great value for performing cross check of the neutron yield evaluated by NFM.[5,6] In the tokamaks such as TFTR7, JET8, ASDEX-U9, JT-60U10, DIII-D11, FT12, PLT13, and KSTAR14, neutron
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