Observation of alpha particle loss from JET plasmas during ion cyclotron resonance frequency heating using a thin foil Faraday cup detector array

The loss of MeV alpha particles from JET plasmas has been measured with a set of thin foil Faraday cup detectors during third harmonic heating of helium neutral beam ions. Tail temperatures of ～ 2?MeV have been observed, with radial scrape off lengths of a few centimeters. Operational experience from this system indicates that such detectors are potentially feasible for future large tokamaks, but careful attention to screening rf and MHD induced noise is essential.     

Analysis and improvements of fringe jump corrections by electronics on the JET tokamak far infrared interferometer

For the Tore Supra interferometer phase measurements, an electronics had been developed electronics using field programmable gate array processors. The embedded algorithm can correct the fringe jumps. For comparison, the electronics ran at JET during the 2009 campaign. The first analysis concluded that the electronics was not correcting all the fringe jumps. An analysis of the failures led to improvements in the algorithm, which was tested during the rest of the campaign. In this article, we evaluate the increases in the performance. From the analysis of the remaining faults, further improvements are discussed for designing future boards that are foreseen for JET using the second wavelength and the Cotton–Mouton effect information.     

Detecting non-maxwellian electron velocity distributions at JET by high resolution Thomson scattering

The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6–7 keV, where in some cases the ECE electron temperature measurements can be 15%–20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV.     

“合金装备”2大攻略

……在以一式“直刺“了结了 SOLIDUS 老命的那一瞬间这个世界清净了,痛苦、悲哀、疑惑、愤怒、疯狂、也都随着那首凄美的“不能对往昔说再见“而飞走了。经过20多个小时的苦战、死战,几百次的死而复生……终于将“实体“的 EUROPEAN EX-TREME 难度通关了。如果 SNAKE、雷电、确有其人的话,如果他们是在我的指挥下去完成这次的任务,那么结果一定只有一个,他们肯定已经从这个     

Characterization of the Li beam probe with a beam profile monitor on JET

The lithium beam probe (LBP) is widely used for measurements of the electron density in the edge plasma of magnetically confined fusion experiments. The quality of LBP data strongly depends on the stability and profile shape of the beam. The main beam parameters are as follows: beam energy, beam intensity, beam profile, beam divergence, and the neutralization efficiency. For improved monitoring of the beam parameters, a beam profile monitor (BPM) from the National Electrostatics Corporation (NEC) has been installed in the Li beam line at JET. In the NEC BPM, a single grounded wire formed into a 45° segment of a helix is rotated by a motor about the axis of the helix. During each full revolution, the wire sweeps twice across the beam to give X and Y profiles. In this paper, we will describe the properties of the JET Li beam as measured with the BPM and demonstrate that it facilitates rapid optimization of the gun performance.     

Risk Mitigation for ITER by a Prolonged and Joint International Operation of JET

Prolonged operation of the Joint European Torus (JET) in a set-up involving all ITER partners will be beneficial for ITER. Experiments at JET with its ITER-like wall and using a D–T plasma mixture will help to mitigate risks in the ITER research plan. Training of the ITER operators, technicians and engineers at JET will safe valuable time when ITER comes into operation. Moreover, the way in which the future ITER experiments will be organized can already be experienced at JET, by imposing a similar organisational structure. This paper will present arguments in favour of an extension of JET and additionally briefly discuss a number of enhancements that will make experiments on JET even more relevant for ITER.     

Vacuum problems and solutions related to the tritium experiment at JET

A mixture of deuterium and tritium as fuel was introduced for the first time into a tokamak during the Preliminary Tritium Experiment, carried out successfully at JET in November 1991. The main aims were to produce in excess of 1 MW of fusion power, to validate plasma codes under these conditions, to determine tritium retention in plasma-facing components, to establish procedures for tritium removal from components in contact with the plasma, and to demonstrate the technology related to the safe usage of tritium. The experiments were undertaken within limits imposed by restrictions on vessel activation and tritium usage resulting in a tritium inventory of 0.2 g and a maximum number of neutrons of 1.5 × 10¹⁸. This paper describes the preparations for this experiment with respect to modifications to the vacuum and gas handling system and gives details of materials facing the plasma and conditioning techniques employed. A summary of experimental results is presented together with estimates of the tritium retention in the walls.