Search

The construction of magnet system for the tokamak device of JT-60 super advanced (JT-60SA) was completed in March 2020. The manufacturing of CS had been finished in March 2019. The circularity of 4.0 mm is requirement for CS manufacturing from the point of view of plasma control. The high accurate manufacturing method and jigs had been developed and the circularity of CS achieves 1.44 mm, which meets the requirement of 4.0 mm. The clearance between the CS and the TF coils is very small, only 14 mm in design. The CS touches the TF coils and is subjected to load, the CS can be broken. Thus the surface dimension of the CS and the TF coils was measured before the installation of CS to confirm the clearance sufficient large to avoid the CS crashing in-to the TF coils. The CS was successfully installed to the tokamak center without any damages in December 2019 as the final step of magnet assembly of JT-60SA. In this paper, the manufacturing results and the installation of the CS are described

本小特集は、JT-60SA計画(第1章)、超伝導コイル(第2章)、極低温冷凍機システム(第3章)、電源設備(第4章)、真空容器及び容器内機器(第5章)、本体機器組立(第6章)、プロジェクト管理(第7章)、まとめ(第8章)という構成となっており、JT-60SAの機器の設計・製作・組立などに関する要点を記述するとともに、次期装置に向けての提言や展望も記述している。

A parent-child relationship for Pytagorean triplets are studied. This relationship introduces a directedgraph.First we present a characterization of root nodes of the graph. Next we show every offspring of a root node is an innite subgraph. Then we give a useful program which computes vertices and edges of the graph. Several simulations by using the program suggest that offspring is in fact a tree.

超電導コイルのコミッショニングでは、冷却前試験としてクエンチ検出用の高圧計測線の導通確認や、冷媒の温度計、圧力計、差圧計の動作確認およびコイル・給電機器の耐電圧試験を実施し異常のないことを確認した。冷却開始後は、コイルに20Aの電流を通電し、コイルの抵抗値変化および超伝導遷移温度の測定を実施する。4Kへの冷却が完了した後は、通電試験を実施し、問題なくプラズマ運転が行えることを確認する。発表では、コミッショングの状況・結果について報告した。, 第100回 低温工学・超電導学会研究発表会

The construction of a magnet system for the tokamak device of JT-60 super-advanced (JT-60SA) was completed in March 2020. The manufacturing of central solenoid (CS) had beenfinished in March 2019. The circularity of 4.0 mm is a requirement for CS manufacturing from the point of view of plasma control. The high accurate manufacturing method and jigs had been developed, and the circularity of CS achieves 1.44 mm, which meets the requirement of 4.0 mm. The clearance between the CS and the TF coils is very small, only 14 mm in design. In case the CS touches the TF coils and is subjected to load during operation, the CS can be damaged. Thus the surface dimensions of the CS and the TF coils have been measured before the installation of CS to confirm if the clearance is sufficient large to avoid the CS crashing into the TF coils. The CS was successfully installed to the tokamak center without any damages in December 2019 as the final step of the magnet assembly of JT-60SA. In this paper, the manufacturing results and the installation of the CS are described., Applied Superconductivity Conference 2020 (ASC2020)

The JT-60SA central solenoid (CS), which consists of four stacked modules, is cooled to an operating temperature of 4.5 K by supercritical helium (SHe). During cool-down from room temperature to 4.5 K, in order to avoid a damage on the coil, it is required to reduce thermal stress due to temperature difference in the coil. In the cool-down operation, the CS needs to control the maximum temperature difference in the longitudinal direction of the cable-in-conduit (CIC) conductor below 40 K. However, since that could damage the coil, correctly estimating the temperature distribution in the conductor is important for ensuring the cooldown operation is performed safely. In the present study, the JT- 60SA CS module was prepared and the inlet and outlet temperatures, as well as the SHe mass flow rate, were measured until the CS module was cooled to operating temperature, after which a CS module simulation was performed in order to determine the effect of the inlet temperature on the cool-down speed. From the simulation results, it was concluded that the average cool-down speed was 0.73 K/h and the CS module reached 80 K in approximately 8.3 days while maintaining the maximum temperature difference within 40 K. Furthermore, the temperature difference between the inlet and outlet was kept within 25 K in order to limit the thermal stress. Taken together, the results of our analyses provide fundamental data that can be used to evaluate the safe cool-down operation of the coil and thus protect the coil systems., Applied Superconductivity Conference 2020 (ASC2020)

The construction of the JT-60 Super Advanced (JT-60SA) tokamak has been completed after seven years. In parallel to the tokamak construction, peripheral devices such as vacuum pumping system, gas baking system, wall cleaning system, and so on, that are indispensable for tokamak operation, have been modified for reuse or newly developed. In the JT-60SA, an ultra-high vacuum up to ~10-6Pa is to be realized by eight turbomolecular pumps with a total pumping speed of 6m3/sec for a vacuum vessel. To achieve an ultra-high vacuum condition, a baking operation with 200 ℃ is planned for desorbing water by Nitrogen gas circulation into a double shell of the vacuum vessel. The gas circulation system has a high flow rate of ~18,000 Nm3/h for 200 ℃ baking with four blowers and a heater. Since a radiant heat from the vacuum vessel will be absorbed by an 80 K thermal shield, the system is also utilized to keep vacuum vessel temperature 50 ℃. Moreover, a glow discharge system has been developed for wall conditioning. The system contains three electrodes installed into the vacuum vessel and power supplies with ~3A/600V. The system makes Helium glow discharge where impurities such as Oxygen could be effectively spattered from graphite first wall. In this paper, the completion of JT-60SA construction and the peripheral devices will be reported, focusing on the results of commissioning before the initial operation., 31st Symposium of Fusion Technology (SOFT2020)

日本と欧州が共同で建設している核融合超伝導トカマク型実験装置「JT-60SA」の超伝導マグネットは中心ソレノイド(CS)，6個の平衡磁場コイル(EF)，18個のトロイダル磁場コイル(TF)から構成されている。CSは4つの電気的に独立したモジュールから構成され，1モジュールは8層のパンケーキコイル6個と4層のパンケーキコイル1個から成る。電流は常伝導ブスバーと超伝導フィーダを通して電源から供給される。CSモジュールの絶縁材端子間の電圧設計値は10 kVであり，理想的に分圧した場合，それぞれの層間に約0.38 kVの電圧が印加される。しかし，電源電圧には数kHzの周波数成分が含まれているため，共振現象によりモジュール内に不均一な分布が発生する。その結果，導体間の絶縁が損傷してしまう可能性がある。本研究では，構造物による導体間電圧の影響を評価するため，先行研究で作成した解析モデルにおいて，構造部とモジュール間のキャパシタンスの値を変化させた場合に共振周波数及び層間の最大電圧がどのように変化するか，また，CSを模擬するため，CSモジュールを複数個積み重ねた場合の導体間電圧分布について評価を行った。その結果，構造物キャパシタンスの増加により，共振周波数の減少及び導体間最大電圧の増加が確認した。CS4モジュール解析において層間の最大電圧は絶縁材端子間の電圧設計値(0.38 kV)を超えないことが示された。ゆえに共振現象により絶縁破壊が起こらないことを明らかにした。, 令和２年 電気学会 電力・エネルギー部門大会

The mechanical loading technology has been developed for the pre-compression of central solenoid for the tokamak device of JT-60 super advanced (JT-60SA) being constructed in Japan. Four central solenoid modules were manufactured one by one, then 4 modules were stacked. The pre-compression were conducted to bind stacked 4 modules by support structure called tie-plate as a final process of the central solenoid manufacturing. The pre-compression jigs were designed by using the finite element analysis taking into account of plastic deformation of the jigs and the tie-plate. The pre-compression was performed using developed jigs.The hydraulic jacks and pumps were separately installed to the each tie-plate to control the pre-compress load individually. Since the pre-compress load changed by insulation creeping after initial loading, additional shims were inserted for the tie-plate with small load. Finally, pre-compress load of all tie-plate became within the target range. These results indicate that the pre-compression has been successfully completed using the developed jigs. In this paper, the design and analysis of the pre-compression jigs and the result of the pre-compression are reported.

JT-60SA is a fusion experiment tokamak device with supercon-ducting magnets to be built in Japan. As a unique feature of the JT-60SA cryodistribution system, the main cryogenic transfer line from the helium refrigerator directly inserts into the tokamak cryostat at 12.4 m height, and then it branches to 12 distribution units separately placed around the tokamak through headers in the cryostat. This configuration contributes to the maximization of plasma volume and installation flexibility for heating and measurement devices of plasma experiments but causes compli-cated cooling paths and severe conditions on a mechanical design due to the seismic event and the thermal contraction. In this work, we represent the system design of JT-60SA cryodistribution and several component designs in these severe conditions.

ITER magnets are in the final phases of production and are preparing for the upcoming assembly challenges. The ITER magnet team has expressed the need for close-range support labs in order to perform qualification tests, procedure tuning, mockup testing, site acceptance tests, as well as training of assembly staff and logistics management. In the framework of its general support to the ITER project, CEA's Institute for Magnetic Fusion Research proposed a support structure in line with this need on CEA Cadarache premises. In July 2014, the MIFI agreement (Magnet Infrastructure Facilities for ITER) was signed between ITER organization and CEA. It led to the creation of four laboratories and a storage area dedicated to magnet instrumentation components. This paper gives a general description of the work organization in MIFI, and describes the main ongoing activities with specific focuses on critical qualification activities like high-voltage testing and diagnostic of Glass–Kapton–Glass resin impregnated insulation and the scale 1 mock-up and test of the intermediate outer intercoil structure assembly procedure.