The deuterium operation of the Large Helical Device(LHD) began in March 7, 2017, after long-term preparation and commissioning of apparatuses necessary for execution of the deuterium experiment. A comprehensive set of neutron diagnostics was developed and installed onto LHD through numerous efforts in preparation. Neutron diagnostics play an essential role in both neutron yield management for the radiation safety and extension of energetic-particle physics study in LHD. Neutron flux monitor characterized by fast-response and wide dynamic range capabilities is successfully working. Total neutron emission rate reached 3.3×10 15 (n/s) in the first deuterium campaign of LHD. The highest neutron emission rate was recorded in inward shifted configuration. Neutron yield evaluated by neutron activation system agrees with neutron yield measured with neutron flux monitor. Performance of vertical neutron camera was demonstrated. Neutron emission profile was inwardly shifted in the inwardly shifted configuration whereas it was outwardly shifted in the outwardly configuration. Secondary DT neutrons produced by triton burnup in LHD deuterium plasmas were detected for the first time in stellarator/heliotron devices in the world. Similar to total neutron emission rate, the inward shifted configuration provided highest triton burnup ratio.
The deuterium operation of the Large Helical Device (LHD) heliotron started in March 7, 2017, after longterm preparation and commissioning works necessary to execute the deuterium experiment. A comprehensive set of neutron diagnostics was implemented to accelerate energetic-particle physics research in the LHD. The calibrated ex-vessel neutron flux monitor indicated that the total neutron emission rate in the first deuterium campaign reached 3.3×10 15 n/s in inward shifted magnetic field configuration where confinement of helically trapped energetic ions is predicted to be better. Density dependence of measured total neutron emission rate was consistent with that predicted by the calculation. The neutron decay rate analysis following perpendicular deuterium beam blips injection suggested that the confinement of helically trapped beam ions can be understood by the classical slowing down model in relatively high-electron density plasmas at inward shifted magnetic field configuration. On the other hand, loss of helically-trapped beam ions was recognized even in the inward shifted configuration in the case of low density. Performance of the vertical neutron camera was verified by changing the plasma position and/or magnetic field strength. Drastic change of neutron emission profile was observed when the resistive interchange mode driven by helically-trapped beam ions appears. It was successfully demonstrated that the vertical neutron camera can play an important role in revealing radial transport and/or loss of beam ions. Triton burnup study was also conducted. In the first deuterium campaign, the maximum triton burnup ratio of 0.45 % was obtained in inward shifted configuration. The burnup ratio decreased as a plasma was shifted outwardly as expected.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.