Abstract
The design of plasma facing components (PFCs) requires knowledge of the charged particle heat load in the scrape-off layer (SOL). Ray-tracing codes like PFCFlux can model this heat load assuming that particles follow the magnetic field lines. Calculations on limiter equilibria underestimate the heat load significantly. In fact, not all the power circulating in the SOL is reported on the wall, with 80% of the total power circulating in the SOL missing in the worst cases. This paper explains why some power is missing in this case, and presents different ways to rescale the heat load to recover all the power coming from the SOL. The maximum heat load on the limiter for a given magnetic configuration can change from 1MW/m 2 without rescaling to values to values from 3.5 MW/m 2 to 21.7 MW/m 2 depending on the rescaling method.
Highlights
The shaping of the plasma facing components (PFCs) is a fundamental challenge for future fusion reactors like DEMO
The simplest way to model the charged particle heat load is to assume that it comes from the outer mid plane (OMP), is conducted parallel to the magnetic field lines and decreases exponentially in the scrape-off-layer (SOL) from the last closed flux surface (LCFS)
Codes like PFCFlux [4] or SMARDDA [5] use ray-tracing techniques to estimate the heat load deposited on PFCs in 3D CAD models with this approach and are used to design the DEMO FW
Summary
The shaping of the plasma facing components (PFCs) is a fundamental challenge for future fusion reactors like DEMO. The source of energy likely to cause the greatest power density is charged particles from the scrape-off-layer (SOL), following the magnetic field lines and impacting the PFCs. Design studies need simplified models for fast simulations (couple of minutes) of the heat load, allowing for numerous iterations of the design. The simplest way to model the charged particle heat load is to assume that it comes from the outer mid plane (OMP), is conducted parallel to the magnetic field lines and decreases exponentially (decay length λq) in the scrape-off-layer (SOL) from the last closed flux surface (LCFS). Codes like PFCFlux [4] or SMARDDA [5] use ray-tracing techniques to estimate the heat load deposited on PFCs in 3D CAD models with this approach and are used to design the DEMO FW. The rescaling of the heat flux is applied to the previous limiter equilibrium
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