Description
Runaway generation during disruptions in present-day tokamaks usually differs significantly from what is expected in reactor-scale devices. In ITER, a small number of seed runaway electrons are expected to form during the thermal quench (TQ) of disruptions, only to then multiply exponentially by many orders of magnitude during the subsequent current quench (CQ) [1]. On the TCV tokamak, however, the standard disruptive runaway scenario relies on the existence of a population of relativistic electrons prior to the disruption, referred to as the “seed” population [2]. While such a seed population enables the study of post-disruption runaway electron beams, it limits the applicability results concerning TQ and CQ physics on TCV.
In this contribution we use the disruption simulation framework D REAM [3] to study the generation of runaway electrons in disruption experiments on the TCV tokamak. The aim of the work is to find a scenario which yields a post-disruptive runaway electron beam, without relying on a pre-disruption runaway seed. In addition to characterizing the generation in the standard disruption scenario, we also investigate the role of the hot-tail mechanism for runaway generation in a new high-power scenario which is under development. The high-power scenario utilizes an internal transport barrier to achieve temperatures of above 15 keV electron temperatures prior to the disruption, and allows more flexibility in optimizing the temperature for maximal runaway generation. D REAM simulations are used to determine optimal parameter combinations which should allow a maximal runaway beam to form in the TCV experiments.
[1] O. Vallhagen et al, NF 64 086033 doi:10.1088/1741-4326/ad54d7 (2024).
[2] J. Decker et al, NF 62 076038 doi:10.1088/1741-4326/ac544e (2022).
[3] M. Hoppe, O. Embreus, T. Fülöp, CPC 268 10890 doi:10.1016/j.cpc.2021.108098 (2021).