Speaker
Mr
Yakov Borissenko
(Budker INP SB RAS)
Description
One of the most important research directions on the Gas Dynamic Trap (GDT) magnetic mirror [1] is a complex study of the divertor physics. The foundation stone of this research program is a study of physical processes in a volume of divertor with expanding magnetic field lines. The exploration of the region near the plasma absorber is also considered. Because of neutralization of the plasma flux on the absorber surface, the adjacent plasma layer is characterized by a high density of atomic and molecular particles. Such a compound considerably affects the whole system particle balance, thus having an effect on the electrostatic potential spatial distribution. Measurement of intensity distributions of light emitted by atoms of plasma offer a direct instrument to observe the dynamics of this plasma component. In this paper, a new visible light tomography diagnostic system is proposed. The two-dimensional tomographic system is designed, constructed and installed on GDT. An avalanche photodiode (APD) based detector for visible light wavelength is used. The optical system, consisting of interference optical filters and gathering lenses, integrates light along 42 lines of sight (LOS). Lines of sight form a pattern laying in the plane that is perpendicular to the plasma flow direction. The entire optical registration system consists of two diagnostic bundles with 21 LOS in each: the first one provides a spatial coverage from the center of the plasma flux to the edge, the second one covers a region from one edge to the opposite one. The light detecting part of the diagnostic is composed of 14 measuring modules. Each detection module has three APDs bound by one pair of lens and narrowband interference filter. The main features of the system are following: (i) a high sensitivity in 650-660 nm wavelength region; (ii) a time resolution better than 1 mks; (iii) a fan-beam geometry of LOS. All measurement modules were absolutely calibrated on a test stand and the optical system throughput was measured to get absolute intensity values. The optimal signal-to-noise ratio of an APD with a fast two-stage transimpedance amplifier reached approximately eighty in the signal bandwidth of 3.2 MHz. This provides a respectable dynamic range, which meets requirements of a physical experiment in GDT divertor plasmas. First measurement results are also discussed in the paper.
1. A.A. Ivanov and V.V. Prikhodko, Plasma Phys. Control. Fusion 55 (2013), 063001.
Primary author
Mr
Yakov Borissenko
(Budker INP SB RAS)
Co-authors
Mr
Aleksandr Khilchenko
(Budker INP SB RAS)
Dr
Andrej Lizunov
(Budker INP SB RAS)
Mr
Denis Moiseev
(Budker INP SB RAS)
Mrs
Natalya Vasileva
(Budker INP SB RAS)
Mr
Petr Zubarev
(Budker INP SB RAS)
