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The transition of a detached to attached plasma experiment has been performed in GAMMA 10/PDX by applying an additional plasma heating pulse of electron cyclotron heating (ECH). In a plasma detachment experiment, a short pulse (25 ms) of ECH was applied at the east plug-cell to examine the effects of electron heating on the plasma parameters in the D-module. It was found that the ion flux increased significantly during ECH injection. In the ECH injection period, the ion flux increased with the increasing impurity injection, which indicates the impurity ion components are enhanced by ionization in the D-module due to the application of ECH. During ECH injection period, the increase of the ion flux near the corner of the target plate shows a clear dependence on the gas species. The 2D visible emission has been captured by the high-speed camera and a bright emission near the corner of the target has been observed. The spectroscopic measurement in the D-module shows that the impurity ion emission increases remarkably during ECH injection. These results indicate the detached plasma change to the attached state.

窒素などのガスを入射して熱流低減を行う放射ダイバータは核融合炉オペレーションの有望なシナリオの一つである．放射ダイバータでは冷却ガスの圧力を計測・制御することが重要だが，現在行われているイオンゲージ方式の計測ではガス種間の相互作用により計測感度に誤差が生じることが考えられる．そこで本研究では窒素と水素を混合した際の高速イオンゲージによるガス圧力評価について調べた．, 第36回 プラズマ・核融合学会 年会

JT-60SAの統合コミッショニングを効率良く進めるため、プラズマ対向壁に蓄積した燃料ガスの除去手法の開発を計画している。燃料ガスの除去効率等を定量的に評価するためには、真空容器に導入したガス量及び真空容器から排気されたガスの種類とその量を評価する必要があるため、ペニング真空計と分光計測を組み合わせたペニング真空計測器を設計した。, 第36回 プラズマ・核融合学会 年会

JT-60SAのファーストプラズマに向けて真空容器内機器の製作と設置を行った。真空容器内機器は、プラズマ対向壁、保護リミタ、グロー電極、および磁気センサーで構成される。これらは、主に有限要素法を用いた電磁力及び熱解析などに基づき設計されており、試作や製造までも含めその詳細について記述する。

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Overview of plasma facing components (PFCs) in JT-60SA is introduced, including upper divertor, lower divertor, inboard first wall and outboard first wall. These PFCs are upgraded in 4 stages along plasma experiment of JT-60SA; In the Stage1, only partial inboard first wall and upper divertor are installed with graphite tiles and inertial cooling. In the Stage 2, remaining PFCs including outboard first wall and lower divertor are installed, and the inboard surface is fully covered. In the Stage 3, vertical targets of lower divertor are replaced by CFC monoblock targets with water cooling. In the Stage 4, whole carbon wall is replaced by tungsten wall, and remote handling for lower divertor is introduced. Three R&D on major issues concerning PFCs are presented. Mock-ups of CFC monoblock target were fabricated and it showed good heat removal of the expected maximum heat load of 15 MW/m2 without degradation of performance. Samples tungsten coating on CFC were fabricated and they showed no severe damage by surface temperature up to 2000 C. Laser welded samples showed good appearance and no defect was found by RT.

In this paper, the detailed results of the effect of additional plasma heating under the condition of plasma detachment produced in the large tandem mirror GAMMA 10/PDX. In this experiment, the ECH pulse of 150 kW was applied to the upstream region of detached plasmas established by injecting heavy noble gases (Ar, Kr and Xe) and the significant phenomena on detached to attached transition were measured with Langmuir probes, calorimeters, spectrometers and a high-speed camera. In the presentation, detailed behavior of the plasma parameters is described and the effect of ECH is discussed in terms of radiation loss power and ionization and recombination processes. During the plasma detachment experiments by impurity gas seeding, a short pulse (25 ms) of ECH was applied at the east plug/barriercell to examine the effects of ECH on the detached plasma. A brief summary of the outcomes is given below: ECH heating pulse significantly increases the heat flux at the west end-cell, which indicates detached to attached transition phenomena. During ECH injection period, the ion flux also increases with the increasing gas injection. The emission from the impurity ion enhances significantly during ECH injection period. The emission intensity captured with fast camera also shows a clear dependence on the gas throughput of N2 gas. Comparison of the results using light impurities (N2 and Ne) to those by a heavy impurity gas (Ar) indicates that detached plasma with N2 seeding has a certain tolerance for the additional heating. These outcomes also indicate to consider the sustainability of the detached plasma during ELM., The 23rd International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI-23)

This paper describes the characteristics of detached plasma produced by using hydrogen and noble gases together with the progress of high-heat and particle flux generation experiments in the GAMMA 10/PDX end-cell. In the Plasma Research Center, University of Tsukuba, divertor simulation experiments have been started at the end-cell of GAMMA 10/PDX (E-divertor). In the GAMMA 10/PDX end-cell, plasma flow with high temperature (Ti=100–400 eV, Te=30 eV), heat and particle fluxes (>10 MW/m2, >1023/m2s, respectively) have been produced under the high magnetic field (~1T), which cannot be attained by conventional liner devices. We have succeeded in achieving detachment of high temperature plasma equivalent to the SOL plasma of tokamaks in spite of using a linear device with short connection length of magnetic field line. Various gases (N2, Ne, Ar, Xe) are examined to evaluate the effect of radiation cooling against the plasma flow of MW/m2 level in a divertor simulation region and the following results are obtained: i) Xe gas was most effective on electron cooling (down to ~2 eV) and reduction of heat and particle fluxes (1%, 3%, respectively). ii) Ne gas was less effective. On the other hand, iii) N2 gas showed more favourable effects than Ar. The above results are almost consistent with the observation from an absolutely calibrated visible spectrometer viewing the inside of D-module, such as i) stronger emission from Xe I and II, ii) significant molecular visible-emission from N2, etc. Furthermore, in the case with a simultaneous injection of hydrogen and Xe gases, the ion flux was almost fully suppressed, which indicates the existence of molecular activated recombination in D-module. In plasma flow generation experiments, ICRF heating in anchor-cell successfully extended the particle flux up to 3.3ˆ1023 /m2s in the end-cell. Superimposing the ECH pulse (380 kWx5 ms) into the ICRF plasma also succeeded in extending the highest heat flux of ~15 MW/m2, which exceeds the ITER divertor heat load in the steady state. These results will contribute to the progress in detached plasma operation and clarification of radiation cooling mechanism towards the development of the future divertor., 26th IAEA Fusion Energy Conference

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