Abstract
To realise the potential of fusion as an abundant energy source, several challenges remain. The TCV tokamak, featuring high shaping capability and a flexible heating system, is strongly contributing to solving these challenges. A fundamental challenge remains in controlling heat exhaust from the plasma. ITER's currently foreseen operational regime implies heat flows to the plasma facing materials that are not compatible with a commercial fusion reactor. TCV has demonstrated alternative plasma divertor configurations, termed “snowflakes”, that have the potential to strongly reduce the heat flux towards the vessel walls. Measurements of particle fluxes, together with IR camera imaging, show a clear reduction of the peak heat fluxes to the walls when the exhaust power is particularly large and a reduction of the heat fluxes most needed. Another challenge lies in the control of plasma instabilities and turbulence in reactor relevant operational regimes. To address this issue, TCV is presently complementing its electron heating system with an ion heating system: a 1MW neutral beam injector. With these ion and electron heating capabilities, TCV will be able to operate high temperature, reactor relevant, plasmas with of ion to electron temperature ratios.
Highlights
Fusion is the energy that powers the stars
Measurements of particle fluxes, together with IR camera imaging, show a clear reduction of the peak heat fluxes to the walls when the exhaust power is large and a reduction of the heat fluxes most needed. Another challenge lies in the control of plasma instabilities and turbulence in reactor relevant operational regimes
For values below 0.75 (∼17 cm), the secondary X-point becomes active and it is fully operational below approximately 0.3 (∼7 cm). This figure clearly shows the benefit of the snowflake configuration, compared to a traditional diverted configuration, reducing the peak heat flux impinging onto the vessel wall during ELMs, i.e. when a reduction is most needed, by a factor of two
Summary
The Tokamak à Configuration Variable (TCV) at the Ecole Polytechnique Fédérale de Lausanne (EPFL) features 16, independently powered, poloidal field coils and a highly elongated vessel, as shown, making TCV the tokamak with the highest plasma shaping capability in the world [1, 2]. It has a major radius of 0.9 m, a minor radius of 0.25 m. TCV is equipped with a highly versatile Electron Cyclotron Resonance Heating (ECRH) system. The microwaves resonate with the electron cyclotron motion inducing strong and localised electron heating
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