High fusion power steady state operation in JET DT plasmas

Abstract

Because of its large size, single null divertor, and exible magnetic geometry, JET is capable of producing the most reactor-relevant plasmas of any present generation tokamak. In the recent deuterium-tritium experiments the fusion performance of these plasmas was tested for the rst time. Over 4 MW of fusion power was produced in a high power, steady state pulse of 5 s, limited by the duration of the heating power. The fusion Q E , de ned simply as the fusion energy produced divided by the input energy over this 5 s interval, was 0.18. The performance of our DT ELMy Hmode discharges extrapolates to ignition in ITER and thus provides increased con dence in its current design. Operation at low q95 is possible in JET with no degradation in con nement and provides an improved margin to ignition when extrapolated to ITER.

An ITER-like wall for JET

“…The typical timescale for ELM energy deposition at the divertor is of the order of the ion SOL transit time corresponding to the pedestal plasma parameters, covering a range of 100-500 ls in JET. The previous JET high current operation [10,11] indicates that discharges with plasma current I p P 3 MA and input power P inp P 20 MW can reach Type I ELMy H-modes with ELM energy losses DW ELM P 1 MJ. This is e.g.…”

Characteristics of a new class of transport-related MHD modes in JET H-mode plasmas

“…The ELMy H-mode discharges which have been analysed are characterised by a series of large ELMs immediately followed by a series of smaller ELMs and short intermittent ELM-free periods of around 100 msec [2]. WB modes are present in at least the outer part of the plasma during all of this time.…”

“…MHD activity in general has been observed to limit performance at various stages in JET discharges [1,2,3] and in other fusion devices [4,5,6,7]. The modes associated with the performance degradation are usually localised in time, for example Outer Modes, Sawteeth and ELMs [1].…”

Risk Mitigation for ITER by a Prolonged and Joint International Operation of JET

“…This was an important result since for the first time conditions close to breakeven were obtained [2]: 16 MW was produced with 25 MW injected into the reaction chamber (Q = P fusion /P input % 0.6). However, these conditions were maintained only for\1 s. In stationary conditions a total of 4 MW were produced [3], at an input power of 22 MW (hence Q % 0.18). This was done during 5 s, which is longer than the characteristic thermal confinement time scales of the plasma processes.…”