Optimization of the collective Thomson scattering diagnostic for the GDT open magnetic trap

A G Shalashov; E D Gospodchikov; T A Khusainov; A L Solomakhin

doi:10.1063/5.0175160

Optimization of the collective Thomson scattering diagnostic for the GDT open magnetic trap

Rev Sci Instrum. 2023 Dec 1;94(12):123506. doi: 10.1063/5.0175160.

Authors

A G Shalashov¹, E D Gospodchikov¹, T A Khusainov¹, A L Solomakhin^{1

2}

Affiliations

¹ A.V. Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov str., 603950 Nizhny Novgorod, Russia.
² Budker Institute of Nuclear Physics, 11 Lavrentieva ave., 630090 Novosibirsk, Russia.

PMID: 38088779
DOI: 10.1063/5.0175160

Abstract

The collective Thomson scattering of high-power millimeter-wave radiation on plasma density fluctuations (CTS) is widely used for diagnosing the velocity distribution function of energetic ions in fusion plasma. In this paper, we discuss a non-standard scheme of CTS measurements, which exploits strong refraction of probing and scattered microwave beams when reflecting from the cut-off layer in dense plasma. The scheme may be realized with the existing CTS diagnostic system at the Gas-Dynamic Trap (GDT) facility, a large open magnetic trap operating at Budker Institute (Novosibirsk, Russia). This requires a minor upgrade of the available hardware and essentially increases the range of plasma densities allowed for CTS measurements, as well as its sensitivity and spatial resolution. A detailed study of CTS efficiency for different geometries and plasma conditions at GDT is performed by means of an advanced numerical model that allows for an accurate description of non-Gaussian beam scattering in inhomogeneous plasma. To perform this task, we develop a quasi-optical theory of scattering, which itself may be of general interest.