Bolometric imaging of detached plasmas in LHD

Plasma and Fusion Research

Drapiko

Mukai

et al. 2013

The InfraRed imaging Video Bolometer (IRVB) measures the radiation from the plasma in two dimensions, giving an image of the plasma radiation power loss. Using a geometry matrix calculated from a model of the LHD first wall, the IRVB sightline geometry and a three dimensional (3D) plasma grid, a synthetic instrument is developed using the 3D carbon impurity radiation results of the EMC3-EIRENE edge impurity transport code as an input. The output of the synthetic instrument are images of the plasma radiation at the IRVB foil due to the EMC3-EIRENE code, which are qualitatively compared with preliminary experimental images from the IRVB. Such a comparison for detached discharges in LHD in which an externally induced m/n = 1/1 magnetic island is applied shows that when the magnetic island is moved 36 degrees toroidally the enhanced radiation in the x-points of the magnetic island also moves as predicted by the EMC3-EIRENE code.

Section: Comparison Of Synthetic Images and Irvb Datamentioning

confidence: 99%

Imaging Bolometers for Visualization of Plasma Radiation and Cross-Validation of Three Dimensional Impurity Transport Models for the Large Helical Device

Plasma and Fusion Research

Drapiko

Mukai

et al. 2013

“…Addition of the RMP seems to favor the detached plasma regime by localizing the radiating region near the RMP X-point, restricting its movement and penetration into the core, hence avoiding plasma termination by radiative collapse. The localized radiation during the plasma detachment can be effectively studied experimentally [1][2][3] by the InfraRed imaging Video Bolometer (IRVB) [4]. This localization is also confirmed by the EMC3-EIRENE [5,6] edge impurity transport code.…”

Section: Introductionmentioning

confidence: 78%

Measured and Modeled Radiation Profiles for LHD Plasma - A Comparison during Plasma Detachment

Pandya

Plasma and Fusion Research

Kobayashi

et al. 2014

Detached (from the divertors) plasma regime is a very important operational phase for future fusion device operation and is sustained in the Large Helical Device (LHD) by applying an m/n = 1/1 resonant magnetic perturbation (RMP). The radiation from the plasma is found to be localized near the X-point of this RMP during plasma detachment which is confirmed both by the EMC3-EIRENE edge impurity transport code and experiments. This agreement motivates the establishment of a comparison between the results from the transport model and InfraRed imaging Video Bolometer (IRVB) experiments. A synthetic instrument has been developed which can simulate the radiation by tracing the sight lines through the three dimensional carbon impurity radiation results of the EMC3-EIRENE, giving a synthetic image. These synthetic images can be compared with the IRVB image obtained experimentally. Such a comparison is attempted here for two IRVBs installed on LHD for the data from the 2012 and 2013 experimental campaigns. The comparison reveals a fair amount of qualitative agreement but quantitative disagreement among both the approaches. Probable causes for the disagreement are discussed and corrective measures are suggested.

“…[2][3][4] In a tokamak, with the assumption of axis-symmetry, a tangentially viewing IRVB can provide numerous lines of sight to be used in a tomographic reconstruction of the 2D radiation profiles. 5 Also radiation images can be directly compared to synthetic images derived from an impurity transport model 6 such as Scrape Off Layer Plasma Simulation (SOLPS) 7 or EMC3-Eirene. 8,9 In this paper we give information on the design of an imaging bolometer with a tangential view of NSTX-U.…”

Section: Introductionmentioning

confidence: 99%

Preliminary design of a tangentially viewing imaging bolometer for NSTX-U

Review of Scientific Instruments

Sano

Reinke

et al. 2016

The infrared imaging video bolometer (IRVB) measures plasma radiated power images using a thin metal foil. Two different designs with a tangential view of NSTX-U are made assuming a 640 × 480 (1280 × 1024) pixel, 30 (105) fps, 50 (20) mK, IR camera imaging the 9 cm × 9 cm × 2 µm Pt foil. The foil is divided into 40 × 40 (64 × 64) IRVB channels. This gives a spatial resolution of 3.4 (2.2) cm on the machine mid-plane. The noise equivalent power density of the IRVB is given as 113 (46) µW/cm 2 for a time resolution of 33 (20) ms. Synthetic images derived from Scrape Off Layer Plasma Simulation data using the IRVB geometry show peak signal levels ranging from ∼0.8 to ∼80 (∼0.36 to ∼26) mW/cm 2 . Published by AIP Publishing.[http://dx