P. Mantica D. Van Eester X. Garbet F. Imbeaux L. Laborde M. Mantsinen A. Marinoni D. Mazon D. Moreau N. Hawkes E. Joffrin V. Kiptily S. Pinches A. Salmi S. Sharapov A. Thyagaraja I. Voitsekhovitch P. De Vries K.-D. Zastrow
The first electron temperature modulation experiments in plasmas characterized by strong and longlasting electron and ion internal transport barriers (ITB) have been performed in JET using ion cyclotron resonance heating in mode conversion scheme. The ITB is shown to be a well localized narrow layer with low heat diffusivity, characterized by subcr…
PublishedM. Kuldkepp E. Rachlew N. C. Hawkes B. Schunke
The motional Stark effect ( MSE ) diagnostic on the International Thermonuclear Experimental Reactor will need to guide the light through a labyrinth of mirrors to provide neutron shielding. Knowledge of how the mirrors change the polarization is essential for accurate determination of the q profile. The optical properties of the plasma facing mirr…
PublishedM. R. Siegrist N. Hawkes H. Weisen
This paper presents a feasibility study for a motional Stark effect ( MSE ) [ F. M. Levinton et al. , Phys. Rev. Lett. 63 , 2060 ( 1989 )] diagnostic on the TCV tokamak. A numerical simulation code has been used to identify the optimal port arrangement and geometrical layout. It predicts the expected measurement accuracy for a range of typical plas…
PublishedS. E. Sharapov B. Alper J. Fessey N. C. Hawkes N. P. Young R. Nazikian G. J. Kramer D. N. Borba S. Hacquin E. De La Luna S. D. Pinches J. Rapp D. Testa JET-EFDA Contributors
A microwave interferometry technique is applied for the first time for detecting a discrete spectrum of Alfvén cascade (AC) eigenmodes excited with fast ions in reversed magnetic shear plasmas of the Joint European Torus. The interferometry measurements of plasma density perturbations associated with ACs show an unprecedented frequency and time re…
PublishedG. T. A. Huysmans T. C. Hender N. C. Hawkes X. Litaudon
A region of zero current density in the plasma center has been observed in the advanced tokamak scenarios with off-axis lower-hybrid current drive in the JET and JT-60U tokamak experiments. Significantly, the central current density does not become negative, although this is expected based on conventional current diffusion. In this paper, it is sho…
PublishedN. C. Hawkes B. C. Stratton T. Tala C. D. Challis G. Conway R. Deangelis C. Giroud J. Hobirk E. Joffrin P. Lomas P. Lotte J. Mailloux D. Mazon E. Rachlew S. Reyes-Cortes E. Solano K-D. Zastrow
Simultaneous current ramping and application of lower hybrid heating and current drive (LHCD) have produced a region with zero current density within measurement errors in the core of JET tokamak optimized shear discharges. The reduction of core current density is consistent with a simple physical explanation and numerical simulations of radial cur…
PublishedH. Chen N. C. Hawkes L. C. Ingesson M. Von Hellermann K.-D. Zastrow et al.
Poloidally asymmetric distributions of nickel ions have been observed experimentally in Joint European Torus optimized shear tokamak plasmas following nickel laser injection experiments. Two types of asymmetries occur. In the first type of asymmetry, which has earlier been observed in high-confinement mode plasmas, nickel ions accumulate on the out…
PublishedN. C. Hawkes B. C. Stratton T. Tala C. D. Challis G. Conway R. Deangelis C. Giroud J. Hobirk E. Joffrin P. Lomas P. Lotte J. Mailloux D. Mazon E. Rachlew S. Reyes-Cortes E. Solano K-D. Zastrow
Modern charge-coupled-device (CCD) detectors can achieve peak quantum efficiencies of 90%, compared with less than 10% for the photocathode of an electron multiplier. We report on laboratory tests of examples of these two detector technologies to evaluate their relative performance for precision Doppler spectroscopy of laboratory plasmas. The tests…
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