131 research outputs found
Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation
WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017–2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m−2 were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described
Magnetohydrodynamics modelling of H-mode plasma response to external resonant magnetic perturbations
The response of an H-mode plasma to Resonant Magnetic Perturbations
(RMPs) generated by so-called I-coils in DIII-D experiments on type I
edge localized modes suppression is modelled using the nonlinear reduced
magnetohydrodynamics (with zero-β, i.e. zero plasma temperature, in
the version used here) code JOREK in X-point geometry. JOREK
self-consistently advances in time the magnetic flux, vorticity, and
plasma density in the presence of the RMPs. Without any toroidal
rotation, the magnetic response from the plasma does not significantly
modify the islands widths. A radial convective E⃗×B⃗ plasma
transport is observed to occur in the presence of the RMPs. The
possibility that this mechanism could explain the enhanced density
transport observed experimentally in DIII-D is discussed. Simulations
with a rigid-body-like rotation at a fixed velocity shows evidence of a
screening of the RMPs. The extension of our results to realistic
parameters is discussed
Quasi-linear MHD modelling of H-mode plasma response to resonant magnetic perturbations
The plasma response to externally imposed resonant magnetic
perturbations (RMPs) is investigated through quasi-linear MHD modelling
in the case where the resonant surfaces are located in the pedestal of
an H-mode plasma. The pedestal is a particular region regarding the
question of plasma response to RMPs because of its strong E × B
and electron diamagnetic rotations. It is found that a strong rotational
screening takes place in most of the pedestal. The RMPs may, however,
penetrate in a narrow layer at the very edge, where the plasma is cold
and resistive. The possibility that one harmonic of the RMPs may also
penetrate if its resonant surface is at a particular location, close to
the top of the pedestal, where the E × B and electron diamagnetic
rotations compensate each other, is discussed. Finally, the RMPs are
found to produce some additional transport, even though they do not
penetrate
The optimization of resonant magnetic perturbation spectra for the COMPASS tokamak
The COMPASS tokamak, recently transferred from UKAEA Culham to IPP
Prague, is equipped with a set of saddle coils for producing controlled
resonant magnetic perturbations (RMPs). In the future experimental
programme of COMPASS we plan to focus on studies of RMPs, especially in
view of their application as an ELM control mechanism and their
considered use in ITER. In the present contribution we describe the
preparatory calculations for the planned experiments. We computed the
spectra of perturbations for several different equilibria predicted by
MHD simulations and determined the positions and sizes of the resulting
islands. It is shown how the saddle coils of COMPASS can be adapted to
our equilibria to obtain good island overlap at the edge, which is
believed to be a key component in the ELM mitigation effect. The
techniques used for adapting the coils to achieve this result are
described. Those are fairly general and could be used in the design of
RMP coils on other machines
- …