Plasma particle lofting:one million g centrifuge

Dust can be found everywhere. Mostly it is just annoying, but sometimes it is more than annoying and dust has to be removed. Dust particles stick to a surface as a consequence of the Van der Waals force. We are interested to know how much force a plasma exerts on a particle and whether it is capable of lofting it. In order to do this we need a reference source. For this, we use a centrifuge that can create a force of a million times the gravitational force. In this way we can measure the centrifugal force needed to remove the particles from the surface with and without plasma. This also gives the means to calculate the plasma force in different conditions. In our experiments we link the frequency of rotation to the moment that a particle is removed from the surface, giving us the possibility to calculate the centrifugal force. It is expected that the particles will loft at different times. This is because the Van der Waals force depends heavily on the shape of the surface and of the particles. We will present the results of the first experiments performed with this new set-up

Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X

| openaire: EC/H2020/633053/EU//EUROfusionThe neutral beam deposition model in the BEAMS3D code is validated against neutral beam attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where the neutral beam injection system of W7-X was utilized were reconstructed. These discharges scanned the magnetic configurations and plasma densities of W7-X. The equilibrium reconstructions were performed using STELLOPT which calculates three-dimensional self-consistent ideal magnetohydrodynamic equilibria and kinetic profiles. These reconstructions leveraged new capabilities to incorporate electron cyclotron emission and X-ray imaging diagnostics in the STELLOPT code. The reconstructed equilibria and profiles served as inputs for BEAMS3D calculations of neutral beam deposition in W7-X. It is found that if reconstructed kinetic profiles are utilized, good agreement between measured and simulated beam attenuation is found. As deposition models provide initial conditions for fast-ion slowing down calculations, this work provides a first steptowards validating our ability to predict fast ion confinement in stellarators.Peer reviewe