Observation of trapped and passing runaway electrons by infrared camera in the EAST tokamak*

Abstract

In EAST, synchrotron radiation is emitted by runaway electrons in the infrared band, which can be observed by infrared cameras. This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV energy. A common feature of radiation dominated by passing runaway electrons is that it is strongest on the high field side. However, the deeply trapped runaway electrons cannot reach the high field side in principle. Therefore, in this case, the high field side radiation is expected to be weak. This paper reports for the first time that the synchrotron radiation from trapped runaway electrons dominates that from passing runaway electrons and is identifiable in an image. Although the synchrotron radiation dominated by trapped runaway electrons can be observed in experiment, the proportion of trapped runaway electrons is very low.

Effect of tearing modes on the confinement of runaway electrons in Experimental Advanced Superconducting Tokamak

“…Figure 4(a) is the synchrotron radiation image from the RE beams around 2.1 s. The intensity of the synchrotron radiation is higher in the high field side, which is related with the large orbit shift of RE beams. [19][20][21] The pixel marked by circle A is located around the location of the TMs ρ 2/1 (r/a) ≈ 0.38. Clearly, it indicates the RE beams are trapped by the magnetic islands, and then confined inside the islands.…”

Calculation of collisionless pitch-angle scattering of runaway electrons with synchrotron radiation via high-order guiding-centre equation

“…2018; Hoppe et al. 2018; Zhang, Zhou & Hu 2018, 2021) is important; when the inductive electric field becomes strong enough, the runaway avalanche (Nilsson et al. 2015; Svensson et al.…”