UKAEA Journals

Showing 1 - 9 of 9 Journals Results
2015
CCFE-PR(15)27

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 Published
2015
CCFE-PR(15)03

The fuelling of plasmas by shallow frozen pellets with simultaneous mitigation of edge- localised modes (ELM) by external magnetic perturbation is demonstrated on the MAST tokamak. In these plasmas post-pellet particle loss is dominated by ELMs. It is shown that the size of post-pellet ELMs can be controlled by external magnetic perturbations. Post…

Preprint Published
2014

Observations of ion-scale density turbulence of relative amplitude are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging Beam Emission Spectroscopy (BES) diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation …

Published
2014

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. …

Published
2013

Beam emission spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with iontemperature or density gradients, the particle (ion) streaming time along the magnetic field, and the magnetic drift time are consistently comparable, suggesting…

Published
2012

A new beam emission spectroscopy turbulence imaging system has recently been installed onto the MAST spherical tokamak. The system utilises a high-throughput, direct coupled imaging optics, and a single large interference filter for collection of the Doppler shifted emission from the ~2 MW heating beam of ~70 keV injection energy. The collected lig…

Published
2010

The beam emission spectroscopy BES turbulence diagnostic on MAST is to be upgraded in June 2010 from a one-dimensional trial system to a two-dimensional imaging system 8 radial 4 poloidal channels based on a newly developed avalanche photodiode array camera. The spatial resolution of the new system is calculated in terms of the point spread functio…

Published
2010

An avalanche photodiode based APD detector for the visible wavelength range was developed for low light level, high frequency beam emission spectroscopy BES experiments in fusion plasmas. This solid state detector has higher quantum efficiency than photomultiplier tubes, and unlike normal photodiodes, it has internal gain. This paper describes the …

Published
2009

Beam emission spectroscopy BES of the energetic deuterium D 0 heating beams can provide a means of characterizing the density turbulence in tokamak plasmas. First such measurements have been performed on the MAST spherical tokamak using a trial BES system, which shares the collection optics of the charge-exchange recombination spectroscopy system. …

Published