Calculation of the bootstrap current profile for the TJ-II stellarator

TL;DR

This paper presents detailed calculations of the bootstrap current profile in the TJ-II stellarator using advanced codes, providing the first precise radial profile for a specific configuration and comparing it with other configurations and measurements.

Contribution

It introduces the first precise computation of the bootstrap transport coefficient in TJ-II's long mean free path regime using NEO-MC, and provides the first radial profile for a specific configuration.

Findings

Bootstrap current profile calculated for TJ-II configuration 100_44_64.

Comparison of bootstrap coefficients across different TJ-II configurations.

Qualitative agreement with experimental toroidal current measurements.

Abstract

Calculations of the bootstrap current for the TJ-II stellarator are presented. DKES and NEO-MC codes are employed; the latter has allowed, for the first time, the precise computation of the bootstrap transport coefficient in the long mean free path regime of this device. The low error bars allow a precise convolution of the monoenergetic coefficients, which is confirmed by error analysis. The radial profile of the bootstrap current is presented for the first time for the 100_44_64 configuration of TJ-II for three different collisionality regimes. The bootstrap coefficient is then compared to that of other configurations of TJ-II regularly operated. The results show qualitative agreement with toroidal current measurements; precise comparison with real discharges is ongoing.