Visible light tomography system for a high-beta field-reversed configuration plasma

Abstract

A simple and adjustable tomographic system has been developed for studying the time evolution of the internal structure of a field-reversed configuration plasma. The optical diagnostic system consists of 35 collimators. In each collimator, a plane-convex lens made of BK7 with a focal length of 100mm collimates emissions from the plasma and focuses them onto the end of an optical-fiber tube. The collimator system gives a spatial resolution of 6mm at the center of the 0.256m diameter discharge chamber. The collimated light is transmitted through the optical-fiber tube to a photomultiplier tube (PMT) detector. In this system, the wavelength is selected by a bandpass interference filter with a central wavelength of 550nm and bandwidth of 10nm to eliminate impurities and deuterium-line spectra. The window is verified to be free of impurity lines (Matsuzawa et al., Rev. Sci. Instrum., these proceedings). Thus, only bremsstrahlung is detected by the PMTs. The 35 collimators are arranged on five holders in a fan-shaped arrangement with seven collimators per fan. A profile of the emissivity has been reconstructed by using the algebraic reconstruction technique, without any assumption regarding the symmetry of the plasma.

Optical tomography diagnostic for study of neutral plasma component in the gas dynamic trap

“…Then a tomography reconstruction can be used to obtain the local emissivity distribution. Various tomography diagnostics in optical to soft X-ray range are being widely used in experiments with magnetically confined plasmas for decades [7][8][9][10][11][12][13][14][15]. The paper discusses the recently developed visible range optical diagnostic, which is installed in the GDT expander to monitor dynamics of atomic plasma component spatial profile.…”

Theoretical Study of Relation between Anomalous Resistivity and Toroidal Spin-Up of Field-Reversed Configurations

“…The spontaneous toroidal rotation of a Field-Reversed Configuration (FRC) plasma [1,2] is a phenomenon which is often observed in the conventional field-reversed thetapinch experiment [3,4] and it is known that the occurrence of rotational instability of n = 2 [4][5][6][7] due to this toroidal rotation leads to the collapse of the FRC plasma. Experimentally, it is indicated that the observation result of the line integral density has a sinusoidal waveform with respect to time [4].…”

Onion-peeling inversion of stellarator images

“…Tomography has succeeded at this in tokamaks 1 and stellarators 2 , primarily for X-ray and visible emission 3,4 . Tomography does not require knowledge of the flux surface geometry, although the geometry can constrain the tomography for better results.…”