UKAEA Journals

Showing 1 - 10 of 13 Journals Results
2021
UKAEA-CCFE-PR(21)07

A study of a dataset of JET plasma with the Be/W ITER-like wall (JET-ILW) shows that reaching the edge MHD ballooning limit leads to confinement degradation. However, unlike JET plasma with a carbon wall (JET-C), the JET-ILW plasma stays in a marginal dithering phase for a relatively long period, associated with a higher a ( 20%) H-mode density lim…

Preprint
2015
CCFE-PR(15)09

The replacement of the JET carbon wall (C-wall) by a Be/W ITER-like wall (ILW) has affected the plasma energy confinement. To investigate this, experiments have been performed with both the C-wall and ILW to vary the heating power over a wide range for plasmas with different shapes. It was found that the power degradation of thermal energy confinem…

Preprint Published
2012

A new model of the L–H transition in tokamaks is proposed, based on the criterion that the transition occurs when plasma turbulence and shear Alfvén waves compete in the vicinity of the last-closed flux surface. The model is used to predict the scaling of the H-mode access power, PL–H, with magnetic and plasma variables. The predictio…

Published
2012

Recent infra-red measurements of divertor power loads on JET and AUG [1], revealed that the inter-ELM power width at the outer mid-plane in attached ELMy H-modes does not exhibit any noticeable scaling with machine size [1]. Making use of these results to calculate the effective radial heat diffusivity, and then including this in parametrized expre…

Published
2008

The theory of variances of equilibrium reconstruction is presented. It complements existing practices with information regarding what kind of plasma characteristics can be reconstructed, how accurately, and what remains beyond the abilities of diagnostic systems. The -curves, introduced by the present theory, give a quantitative assessment of quali…

Published
2008

An analytical Bayesian inversion of the JET interferometry line integrated densities into density profiles and associated uncertainty information, is demonstrated. These are used, with a detailed model of plasma polarimetry, to predict the rotation and ellipticity for the JET polarimeter. This includes the lateral channels, for over 45,000 time poi…

Published
2007

Principal techniques and trends in the validation and analysis of data in magnetic fusion research are described and examples of applications are given. Wellestablished methods to obtain key physical quantities are outlined, as well as newer techniques employing integrated analysis of multiple diagnostics to improve quality and extract additional i…

Published
2007

A wide range of studies on JET have contributed greatly to the development of the ELMy H-mode as a high-performance scenario for fusion devices and to the understanding of the physical processes that underlie it. Development has focused on the production of a highperformance, high-density, stationary scenario suited to deuterium-tritium operation a…

Published
1998

Detailed ray tracing, of wave propagation in a plasma near electron cyclotron resonances, suggests that refraction can lead to reduced absorption, in some cases. By studying the full wave equation for the ordinary wave near the fundamental, in a slab model, it is shown that such refraction does indeed reduce absorption, for this particular case, bu…

Published
1997

Electron cyclotron absorption (ECA) of electromagnetic radiation at the second harmonic is of interest in Tokamak physics both for plasma heating and current drive, as well as for some diagnostics. Modelling of the linear wave propagation for such problems is usually done by WKB ray tracing, despite the fact that the WKB theory is not strictly vali…

Published