Fast-Particle Diagnostics on LHD

Isobe, M.; Ozaki, T.; Nishiura, M.; Goncharov, Pavel; Veshchev, E.; Ogawa, K.; Nagaoka, K.; Saito, Kenji; Murakami, S.; Saida, T.; Sasao, M.; Toi, K.

doi:10.13182/fst10-a10828

Cited by 26 publications

(22 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An examination of the response of various fast ion diagnostic systems (summarized in [40]) may confirm whether this bursting mode is associated with fast ion redistribution/losses. Several neutral particle analysers are available, which collect CX neutrals from the ambient neutral density.…”

Section: Fast Ion Loss Measurementsmentioning

confidence: 99%

Role of Helium–Hydrogen ratio on energetic interchange mode behaviour and its effect on ion temperature and micro-turbulence in LHD

et al. 2018

Self Cite

View full text Add to dashboard Cite

In the Large helical device, a change of energetic particle mode is observed as He concentration is varied in ion-ITB type experiments, having constant electron density and input heating power but with a clear increase of central ion temperature in He rich discharges. This activity consists of bursty, but damped energetic interchange modes (EICs, X Du et al., Phys. Rev. Lett. 114 p.155003 (2015)), whose occurrence rate is dramatically lower in the He-rich discharges. Mechanisms are discussed for the changes in drive and damping of the modes with He concentration. These EIC bursts consist of marked changes in the radial electric field, which is derived from the phase velocity of turbulence measured with the 2D phase contrast imaging (PCI) system. Similar bursts are detected in edge fast ion diagnostics. Ion thermal transport by gyro-Bohm scaling is recognised as a contribution to the change in ion temperature, though fast ion losses by these EIC modes may also contribute to the ion temperature dependence on He concentration, most particularly controlling the height of an "edge-pedestal" in the Ti profile. The steady-state level of fast ions is shown to be larger in Helium rich discharges on the basis of a compact neutral particle analyser (CNPA), and the fast-ion component of the diamagnetic stored energy. These events also have an influence on turbulence and transport. The large velocity shear induced produced during these events transiently improves confinement and suppresses turbulence, and has a larger net effect when bursts are more frequent in Hydrogen discharges. This exactly offsets the increased gyro-Bohm related turbulence drive in Hydrogen which results in the same time-averaged turbulence level in Hydrogen as in Helium.

show abstract

Section: Fast Ion Loss Measurementsmentioning

confidence: 99%

Role of Helium–Hydrogen ratio on energetic interchange mode behaviour and its effect on ion temperature and micro-turbulence in LHD

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…Approaching a steadystate fusion burning plasma, studies of energetic particle confinement in stellarators and helical systems have been led by the Large Helical Device (LHD) [3,4]. In hydrogen campaigns, the study was mainly conducted using the charge-exchanged neutral particle analyzer [5][6][7][8][9][10][11][12][13] and escaping energetic ion diagnostics [14][15][16][17][18][19][20][21][22][23][24][25]. The deuterium experiment was started in March 2017 to obtain further advances in helical-type plasma performances and to understand plasma physics [26,27].…”

Section: Introductionmentioning

confidence: 99%

Progress on Integrated Neutron Diagnostics for Deuterium Plasma Experiments and Energetic Particle Confinement Studies in the Large Helical Device During the Campaigns from FY2017 to FY2019

Ogawa

Isobe

Osakabe

2021

Plasma and Fusion Research

View full text Add to dashboard Cite

To achieve a steady-state fusion burning plasma, energetic particle confinement studies have been performed in fusion devices. Deuterium plasma experiments in the Large Helical Device starting from March 2017 have expanded the energetic ion confinement study toward a helical-type fusion reactor. To conduct this study, integrated neutron diagnostics, such as a wide dynamic range neutron flux monitor composed of three sets of detectors, a neutron activation system with two irradiation ends, three vertical neutron cameras, four types of scintillating fiber detectors, and a fast time response neutron fluctuation detector, were installed based on the plan and were working stably, as designed. Moreover, an energetic particle confinement study was advanced by utilizing integrated neutron diagnostics. Furthermore, the results of the energetic particle confinement study using neutron diagnostics obtained from FY2017 to FY2019 are reviewed in this paper.

show abstract

“…12 During the hydrogen plasma experiment of Large Helical Device (LHD), the fast ions confinements during the ion cyclotron resonance heating and neutral beam heating were experimentally investigated 13 using a comprehensive set of fast ion diagnostics. 14 In particular, confinement property of the helically trapped proton accelerated by ion cyclotron resonance heating has been studied in the LHD using the natural diamond detectors as a solid-state NPA. 15 In order to sustain the high-temperature state, the study of helically trapped beam ion behavior is important and will provide the crucial information for the deep understanding of energetic ions confinement property.…”

Section: Introductionmentioning

confidence: 99%

Performance of the newly installed vertical neutron cameras for low neutron yield discharges in the Large Helical Device

Sangaroon

Ogawa

Isobe

et al. 2020

Review of Scientific Instruments

Self Cite

View full text Add to dashboard Cite

Two new vertical neutron cameras characterized by high detection efficiency were developed on the Large Helical Device in order to observe poloidal structures of helically trapped beam ions created by the perpendicularly injected positive-ion based neutral beam (P-NB) and are newly operated since 2018. In this work, the neutron fields at the vertical neutron cameras are investigated using the Monte Carlo N-particle transport code to evaluate the performance of its collimators. The results indicate that neutrons are attenuated by the heavy concrete and are well collimated through the collimator to detectors. Neutron spectra at the detector position show over 99% of uncollided 2.45 MeV neutrons. Time evolution of neutron emission profiles during the short pulse of P-NB injection is measured by the vertical neutron cameras. Peaks on the neutron emission profiles corresponding to the helically trapped beam ion are successfully obtained, as designed. The decrease in line integrated neutron flux at the peak positions after the P-NB stops is consistent with the behavior of the total neutron emission rate measured by the neutron flux monitor.

show abstract

Fast-Particle Diagnostics on LHD

Cited by 26 publications

References 59 publications

Role of Helium–Hydrogen ratio on energetic interchange mode behaviour and its effect on ion temperature and micro-turbulence in LHD

Role of Helium–Hydrogen ratio on energetic interchange mode behaviour and its effect on ion temperature and micro-turbulence in LHD

Progress on Integrated Neutron Diagnostics for Deuterium Plasma Experiments and Energetic Particle Confinement Studies in the Large Helical Device During the Campaigns from FY2017 to FY2019

Performance of the newly installed vertical neutron cameras for low neutron yield discharges in the Large Helical Device

Contact Info

Product

Resources

About