Single field-of-view tomographic imaging of 3D impurity emission distribution in magnetized edge plasma of LHD

A new tomographic scheme is proposed for reconstructing three dimensional (3D) impurity emission distributions from two dimensional (2D) measurements with a single field-of-view in the magnetized edge plasma in a Large Helical Device (LHD). The 2D image is obtained with a multi-channel fiber array spectrometer, which views the entire region of the edge stochastic magnetic layer of LHD, including divertor plates, divertor legs, the stochastic layer, and the last closed flux surface. The scheme introduces new regularization terms in the Lagrangian function, based on the transport feature in magnetized plasma that the transport parallel to the magnetic field lines is much faster than the transport across the magnetic field, thus assuming smooth distribution in the parallel direction. The scheme is benchmarked with the test data of 3D distribution in the measurement volume, where the effectiveness of the various regularization terms is surveyed and feasibility of the scheme is confirmed. The new scheme is applied to the experimental data in LHD for carbon impurity emissions of C1+ and C3+, where the obtained distributions are discussed taking into account the plasma wall interaction and charge dependence of ionization potentials

小特集：磁場閉じ込め核融合装置における水素原子分子輸送研究の新展開 ３．表面分析と分光計測によって明らかになった 水素原子分子の炉内分布と輸送

プラズマ対向壁の水素吸蔵・放出を評価するための表面・再堆積層・バルクの水素輸送モデルとそのQUESTプラズマ対向壁への適用，およびその結果から構築した炉内粒子循環モデルとQUEST長時間放電に対する解析を紹介する．水素分子の発光スペクトル計測によるQUEST 第一壁近傍やLHD ダイバータ領域における水素分子回転温度計測を紹介する．水素原子の発光スペクトル計測による周辺から炉心までの水素原子輸送ダイナミクスの計測およびそのプラズマ閉じ込めとの関連について紹介する

Analysis of the impurity flow velocity in a wide plasma parameter range for deuterium and hydrogen plasmas in the divertor legs of the stochastic layer in LHD

Impurity flow velocity measurements have been conducted for different magnetic field configurations in a wide plasma parameter range in the divertor leg region of LHD for understanding of the edge impurity transport. In all cases (densities, magnetic configurations, hydrogen (H) & deuterium (D) discharges), flows of several tens of km/s are observed. It is found that the flow in thick stochastic layer is faster than in thin stochastic layer configuration by a factor of 3. Different velocities of different charge states of carbon impurity are observed. The simulation with EMC3-EIRENE code shows similar trend as the experiments, but only qualitatively: faster flow in H compared to D discharges due to the mass effect, faster flow in the case of thick stochastic layer. However, synthetic spectra show discrepancy with experiments in the absolute Doppler shift, where the impurity velocity in the experiments is one order faster compared to the simulations

Application of system analysis in inventory management : annotation to the B.S. graduation work

The aim of the diploma work is to study some models of management, in particular, consider examples of the tasks of the management model reserves of type (s,S) and the task of creating grain stocks. The main emphasis is optimization problem, finding the optimal policy, functions costs and optimal values for the models considered

First Wall Particle Flux Measurements by an F82H Permeation Probe in QUEST

First wall particle flux measurements in the QUEST spherical tokamak have been conducted, using a permeation probe that employs a first wall candidate ferritic steel alloy F82H as the membrane and also SUS304 as a comparative reference membrane. Permeation measurements have been done during the conditioning steady-state discharges heated with 2.45 GHz and 8.2 GHz ECR. Diffusion and recombination coefficients measured in a laboratory-scale plasma device: VEHICLE-1 are used to interpret the results from the permeation probe measurements in QUEST. These permeation membranes have been analyzed with XPS to evaluate the effects of surface impurities

Characteristic of a pdCu membrane as atomic hydrogen probe for QUEST

A permeation probe is a useful device for detecting the atomic hydrogen flux to plasma-facing walls. Recently, we developed a new type of probe using 60Pd-40Cu alloy (PdCu) as the permeation material. The deuterium behaviors in PdCu samples were investigated using nuclear reaction analysis (NRA) and permeation observations, and the diffusion coefficient and recombination coefficients were determined from these observations. It was found that the sensitivity of a 0.02-mm-thick probe was as high as 0.5 below 473K and was independent of the incident flux. The response time at 473K was 0.41s and 1.3s under an incident flux of 1020m−2s−1 and 1019m−2s−1, respectively. Thus, we concluded that the new PdCu probe can effectively detect the incident atomic hydrogen with high sensitivity and a suitable response time

Hydrogen Permeation through Sputter-Deposited Tungsten Coated F82H in QUEST

Hydrogen plasma-driven permeation (PDP) experiments have been performed using a sputter-deposited tungsten (SP-W) coated F82H membrane in the spherical tokamak QUEST. It has been found that SP-W coatings tend to enhance hydrogen PDP compared with that of bare F82H membrane. Surface recombination is a key process determining the PDP flux, suggesting that surface effects on hydrogen PDP should be further investigated