Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.
Forschungszentrum Karlsruhe (FZK) is developing the cryopumps for the ITER heating neutral beam injectors. The system is characterized by high gas flows coming from different sources against which the cryopumps must maintain a pressure between 10-2 and 10-3 Pa in the beam line vessel. In the close arrangement of the beam line the size of the cryopump is limited to a flat rectangular geometry of 8 m length, 2.75 m height and a depth of 0.5 m. Two cryopumps of this size will be included in each beam line. Within gas profile calculations of the detailed beam line geometry it showed up that the gas capture probability of the pumping surface must achieve 30 % to guaranty the beam pulse operation. This paper describes the vacuum requirements given by the ITER heating neutral beam injector and presents gas profile calculations of different beam line configurations to outline the effect on the operation of the cryopump. The design of the novel cryopump is presented and the heat load calculations to the cryogenic circuits will be discussed and summarized for the different operation scenarios. It is shown that the cryopump for the ITER heating neutral beam injectors covers all vacuum requirements and it is adapted to the ITER cryogenic supply.
JT-60SA, the largest tokamak that will operate before ITER, has been designed and built jointly by Japan and Europe, and is due to start operation in 2020. Its main missions are to support ITER exploitation and to contribute to the demonstration fusion reactor machine and scenario design. Peculiar properties of JT-60SA are its capability to produce long-pulse, high-β, and highly shaped plasmas. The preparation of the JT-60SA Research Plan, plasma scenarios, and exploitation are producing physics results that are not only relevant to future JT-60SA experiments, but often constitute original contributions to plasma physics and fusion research. Results of this kind are presented in this paper, in particular in the areas of fast ion physics, highbeta plasma properties and control, and non-linear edge localised mode stability studies.
A large superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMO have been clarified through those studies.
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