Achievement of a record electron temperature for a magnetic mirror device

TL;DR

This paper reports a record high electron temperature of around 660 eV in a magnetic mirror device, achieved through advanced heating techniques, marking a significant step towards fusion applications in open magnetic systems.

Contribution

The study demonstrates the highest quasi-stationary electron temperature in an open magnetic mirror trap using combined electron cyclotron resonance and neutral beam heating.

Findings

Electron temperature reached 660 eV on average, exceeding previous records.

Peak electron temperatures surpassed 900 eV in some shots.

High-density plasma confinement with β≈60% was achieved.

Abstract

We demonstrate plasma discharges with extremely high temperature of bulk electrons at the large axially symmetric magnetic mirror device GDT (Budker Institute, Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over several sequential shots is 660 $\pm$ 50 eV with peak values exceeding 900 eV in few shots. This corresponds to at least threefold increase as compared to previous experiments both at the GDT and at other comparable machines, thus demonstrating the maximum quasi-stationary (~1 ms) electron temperature achieved in open traps. The breakthrough is made possible with application of sophisticated electron cyclotron resonance heating in addition to standard heating by neutral beams. The reported increase of the electron temperature along with previous experiments, which demonstrated high-density plasma confinement with $\beta\approx$ 60%, provide a firm basis for extrapolating to fusion relevant applications of open magnetic systems.