A backward Monte Carlo method for fast-ion-loss simulations

Abstract

This paper presents a novel scheme to improve the statistics of simulated fast-ion loss signals and power loads to plasma-facing components in fusion devices. With the so-called Backward Monte Carlo method, the probabilities of marker particles reaching a chosen target surface can be approximately traced from the target back into the plasma. Utilizing the probabilities as {\it a priori} information for the well-established Forward Monte Carlo method, statistics in fast-ion simulations are significantly improved. For testing purposes, the scheme has been implemented to the ASCOT suite of codes and applied to a realistic ASDEX Upgrade configuration of beam-ion distributions.

Iterative reconstruction methods and the resolution principle for fast-ion loss detector measurements

“…Fast-ion loss detectors (FILDs) measure the velocity distribution of lost fast ions, providing data for interpreting the confinement and transport dynamics within the plasma [19,20]. To identify the spatial origins of these losses, reverse orbit-following techniques are used, tracing the trajectories of ions measured by FILDs back into the plasma [21][22][23][24]. Interpreting the velocity distributions obtained from FILDs involves solving an ill-posed inverse problem, typically approached through regularization techniques.…”