L. Bertalot

Analysis of the E × B flow shearing rate in JET ITB discharges

The role of turbulence stabilization by sheared E × B flow is analysed for different types of internal transport barrier (ITB) in JET discharges. After the ITB formation, the shearing rate ωs is found to consistently exceed a rather crude estimate for the ion temperature gradient driven turbulence. The roles played by toroidal plasma rotation and by density and temperature gradients in both the radial electric field Er and the shearing rate ωs are evaluated. It turns out that the major contribution in triggering the positive feedback leading to ITB onset is given by the toroidal rotation.

Density dependence of trace tritium transport in H-mode Joint European Torus plasma

Tritium transport in edge localized mode (ELM) high confinement (H-mode) plasmas is analyzed here as a function of density for discharges from the recent trace tritium experimental campaign performed on Joint European Torus. In this campaign small amounts of tritium have been puffed or injected (with neutral beam injectors) into deuterium plasmas [K.-D. Zastrow, J. M. Adams, Yu. Baranov et al., Plasma Phys. Controlled Fusion 46, B255 (2004)]. Information about the tritium has been obtained from the evolution of the profiles of neutron emission simulated via the TRANSP [R. J. Goldston, D. C. McCune, H. H. Towner, S. L. Davis, R. J. Hawryluk, and G. L. Schmidt, J. Comput. Phys. 43, 61 (1981)] and SANCO (L. Lauro-Taroni, B. Alper, R. Giannella, K. Lawson, F. Marcus, M. Mattioli, P. Smeulders, and M. Von Hellermann, Proceedings of the 21st European Conference on Controlled Fusion and Plasma Physics, Montpelier, France, 1994) codes. A strong inverse correlation of tritium transport with plasma density is found...

New diagnostic techniques and technologies at JET (invited)

The European Fusion Development Agreement’s mission for JET is the development of ITER scenarios exploiting the specific properties of the device. This task requires significant improvements in the measuring techniques. The most innovative diagnostic upgrades are in the fields of edge measurements, detection of fast magnetohydrodynamics modes and “burning plasma” diagnostics. The importance of plasma-wall interactions, and, in particular, the issue of tritium inventory promoted the development of the quartz microbalance, a detector with improved time resolution to measure material redeposition in the remote areas of the inner divertor. Measurement of Alfven cascades with unprecedented spectral resolution, reaching a toroidal n number of up to 16, was obtained using an O-mode microwave reflectometer as an interferometer. For the diagnosis of the fusion products, a new approach is being developed to measure the He ash based on double charge exchange between thermalized particles and neutrals from JET beams....

Neutron Emission Profile And Neutron Spectrum Measurements At JET: Status And Plans

In large tokamak devices, such as JET, TFTR, JT‐60U and ITER, a neutron emission profile monitor is considered as one of the principal diagnostic tools, firstly in providing information to characterize the fusion source in terms of its location, shape, intensity and secondly in developing an understanding of fast ion physics in tokamak plasmas. The JET neutron profile monitor is one of the most advanced such instruments currently operating. It enables 2‐D imaging of the non‐circular plasma neutron source through a tomographic deconvolution of line‐integrated measurements. Historically it was usually assumed that the fusion neutron source is a function of the magnetic flux surfaces (MFS), but recent JET results have clearly demonstrated the influence of non‐uniform fast particle populations on the neutron emission profile.Neutron energy spectroscopy also carries valuable information about fast ion behaviour and the fusion and nuclear reactions taking place in the plasma. Spectrum measurements of neutrons w...

ICRF heating scenarios in JET with emphasis on 4He plasmas for the non-activated phase of ITER

In the initial phase of ITER operation, 4He plasmas could be used in order to avoid activating the machine. The main ICRH scenarios foreseen for ITER 4He plasmas are (3He)4He and (H)4He. ICRH experiments have been carried out on JET using 4He plasmas to validate these scenarios. At the same time, conditions for access to H-mode in plasmas of various isotope compositions from dominantly 4He to dominantly D have been studied. Experiments have also been carried out for the first time in 4He plasmas with the ICRF power added to 4He neutral beam injection at the third harmonic of 4He in order to produce a 4He tail for alpha particle studies.