Time-resolved secondary triton burnup 14 MeV neutron measurement by a new scintillating fiber detector in middle total neutron emission ranges in deuterium large helical device plasma experiments

Abstract

A middle-sensitivity scintillating fiber detector (hereafter middle Sci-Fi detector) that works at a deuterium-tritium neutron flux of ~105-107 cm−2s−1 was utilized to measure secondary deuterium-tritium neutron emission rates with high temporal resolution at a total neutron emission rate of 1013 to 1015 n/s, where strong magnetohydrodynamic (MHD) instabilities were observed in the large helical device deuterium plasma experiments. The gain and angular characteristics of the middle Sci-Fi detector were evaluated in an accelerator-based deuterium-tritium neutron source in the intense 14 MeV neutron source facility at Osaka University. Observation of 1 MeV triton transport due to MHD instability was performed by a middle Sci-Fi detector whose deuterium-tritium neutron counting rate was approximately 20 times higher than that of the conventional Sci-Fi detector. Fusion-born triton transport due to energetic-particle-driven MHD instability was observed using the middle Sci-Fi detector due to its high detection efficiency and high discrimination ability of deuterium-tritium neutrons from the sea of deuterium-deuterium neutrons.

Fusion product diagnostics based on commercially available chemical vapor deposition diamond detector in large helical device

“…These were the first deuterium experiments in large-sized stellarator/helical systems. Therefore, advances in energetic particle confinement were expected [38][39][40] through the neutron diagnostics [41][42][43][44][45][46][47][48][49] because neutrons are mainly created by so-called beam-thermal reactions [50]. Energetic particle confinement research, e.g., energetic particle confinement in magnetohydrodynamic quiescent plasmas [51][52][53], visualization of energetic particle transport [54][55][56][57][58][59], and demonstration of MeV ion confinement [60,61], has progressed [62,63].…”

A study of beam ion and deuterium–deuterium fusion-born triton transports due to energetic particle-driven magnetohydrodynamic instability in the large helical device deuterium plasmas

“…A Sci-Fi detector was originated in the Los Alamos National Laboratory and applied in TFTR [45] and JT-60U [13]. Based on the original design of the Sci-Fi detector, we developed several types of Sci-Fi detectors having different detection efficiency to DT neutrons [31,[46][47][48][49]. In this study, the Sci-Fi detector having 456 Sci-Fis, namely the middle Sci-Fi detector, is used to measure S n_DT with the fine time resolution (figure 2).…”

Observation of energetic ion anisotropy using neutron diagnostics in the Large Helical Device

“…The neutrons mainly created by so-called beam thermal reactions possess information regarding energetic ions [48]. Integrated neutron diagnostics [49,50], such as neutron flux monitor [51], neutron activation system [52], vertical neutron cameras [53][54][55], 14 MeV scintillating fiber detector [56][57][58][59], was developed for understanding the neoclassical confinement of energetic ion [60][61][62][63] as well as transport of energetic ion due to energeticion-driven MHD instabilities [64][65][66][67][68][69]. For further study to obtain velocity information for energetic ions, compact neutron energy spectrometers (CNES) were developed [70], such as based on a scintillation detector [71] and the commissioning of a time-of-flight neutron energy spectrometer [72,73].…”