Prompt loss of beam ions in KSTAR plasmas

Abstract

For a toroidal plasma facility to realize fusion energy, researching the transport of fast ions is important not only due to its close relation to the heating and current drive efficiencies but also to determine the heat load on the plasma-facing components. We present a theoretical analysis and orbit simulation for the origin of lost fast-ions during neutral beam injection (NBI) heating in Korea Superconducting Tokamak Advanced Research (KSTAR) device. We adopted a two-dimensional phase diagram of the toroidal momentum and magnetic moment and describe detectable momentums at the fast-ion loss detector (FILD) position as a quadratic line. This simple method was used to model birth ions deposited by NBI and drawn as points in the momentum phase space. A Lorentz orbit code was used to calculate the fast-ion orbits and present the prompt loss characteristics of the KSTAR NBI. The scrape-off layer deposition of fast ions produces a significant prompt loss, and the model and experimental results closely agreed on the pitch-angle range of the NBI prompt loss. Our approach can provide wall load information from the fast ion loss. © 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

Interpretation of suprathermal emission at deuteron cyclotron harmonics from deuterium plasmas heated by neutral beam injection in the KSTAR tokamak

“…Turning to the steady state deuteron ICE in 'phase 1', we consider two KSTAR deuterium plasmas, in which beams of 80-100 keV deuterons were injected tangentially with NBI heating power in the range of 2.8-3.8 MW. Detailed calculations of NBI ion losses suggest that some of these NBI deuterons can remain confined on trapped orbits [46]. We therefore investigate whether this small subset of NBI deuterons can give rise to ICE via the MCI in the outer midplane edge plasma.…”

Distinct stages of radio frequency emission at the onset of pedestal collapse in KSTAR H-mode plasmas

“…For the LHD, simulations of ion orbits showed that a small fraction of perpendicular neutral beam-produced fast ions can have specific orbits necessary for MCI [19]. The possibility of fast ions driven by the KSTAR tangential neutral beams [20] as a source of MCI remains as a future research.…”

“…At the same time, the beam driven MCI [19] can be a possible candidate even for the case of tangential NBIs as in the KSTAR in the presence of strong E r . In the KSTAR H-mode discharges, substantial prompt loss (a few %) of the beam ions produced by the tangential NBIs were observed [20], implying that some fraction of the initially tangential beam ions have large orbits encompassing the low-field-side pedestal region. Those fast ions can be influenced by the strong E r , progressively acquiring perpendicular momentum as they circle around the torus, and subsequently drive the MCI.…”

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

“…The location of diamond detectors was decided, based on a collisionless Lorentz orbit following calculation LORBIT, [87] which is widely used in tokamaks [88][89][90][91] and stellarators [91][92][93][94][95].…”