V.H. Chen F.I. Parra J.C. Hillesheim
The Doppler Backscattering (DBS) microwave diagnostic enables the non-perturbative characterisation of density fluctuations and flows, both at the edge and the core of the plasma. The large magnetic pitch angle (up to 35 degrees, compared to 15 degrees in standard tokamaks like JET) and the time-varying magnetic equilibrium make the use of DBS in s…
Preprint PublishedJ.C. Hillesheim D. Dickinson C.M. Roach S. Saarelma R. Scannell A. Kirk N.A. Crocker W.A. Peebles H. Meyer The MAST Team
Measurements of local density and magnetic field fluctuations near the pedestal top, conditionally-averaged over the ELM cycle, have been made in MAST. A Doppler backscattering (DBS) system installed at MAST was used to measure intermediate-k (k ? _i _ 3 - 4) density fluctuations at the top of the pedestal. A novel diagnostic technique combining DB…
Preprint PublishedJ.C. Hillesheim N. A. Crocker W.A. Peebles H. Meyer A. Meakins A.R. Field D. Dunai M. Carr N. Hawkes The MAST Team
The high-k (7 . k??i . 11) wavenumber spectrum of density fluctuations has been measured for the first time in MAST [B. Lloyd et al, Nucl. Fusion 43, 1665 (2003)]. This was accomplished with the first implementation of Doppler backscattering (DBS) for core measurements in a spherical tokamak. DBS has become a well-established and versatile diagnost…
Preprint PublishedJ.C. Hillesheim F.I. Parra M. Barnes N.A. Crocker H. Meyer W.A. Peebles R. Scannell A. Thornton The MAST Team
Tokamak plasmas rotate even without external injection of momentum. A Doppler backscattering system installed at MAST has allowed this intrinsic rotation to be studied in Ohmic L-mode and Hmode plasmas, including the first observation of intrinsic rotation reversals in a spherical tokamak. Experimental results are compared to a novel 1D model, whic…
Preprint PublishedJ. C. Hillesheim E. Delabie H. Meyer C. F. Maggi L. Meneses E. Poli JET Contributors
High spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge . We observe fine-scale spatial structures in the edge well with a wave number kr ? i ˜ 0.4–0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelen…
Preprint PublishedA. Kirk D. Dunai M. Dunne G. Huijsmans S. Pamela M. Becoulet J.R. Harrison J. Hillesheim C. Roach S. Saarelma The Mast Team
The type I ELMy H-mode is the baseline operating scenario for ITER. While it is known that the type I ELM ultimately results from the peeling-ballooning instability, there is growing experimental evidence that a mode grows up before the ELM crash that may modify the edge plasma, which then leads to the ELM event due to the peeling-ballooning mode. …
PublishedJ.C. Hillesheim F.I. Parra,M. Barnes N.A. Crocker H. Meyer W.A. Peebles R. Scannell A. Thornton The Mast Team
Tokamak plasmas rotate even without any external injection of momentum. A Doppler backscattering system installed at MAST has allowed this intrinsic rotation to be studied in Ohmic L-mode and H-mode plasmas, including the first observation of intrinsic rotation reversals in a spherical tokamak. Experimental results are compared to a novel 1D model,…
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