Dual laser interferometer for plasma density measurements on large tokamaks.
A two-wavelength plasma density interferometer utilizing a CO(2) laser and an HeNe laser is described. The interferometer is being designed for use on Doublet III, a large noncircular cross-section tokamak. The use of the two wavelengths allows the distinction between fringe shifts due to plasma density and fringe shifts due to mirror vibrations. Plasma density fringe shifts of 1/10 of a fringe shift can be measured in the presence of mirror vibrations which cause several fringe shifts. A simple digital phase comparing electronic system is used.
A new method for determining the plasma electron density using three-color interferometer.
A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO(2) laser. Short-time integrations of the fractional fringes enhance the reliability of this method.
CO2 Laser Heterodyne Plasma Diagnostics in an Adverse Environment
A CO2 laser heterodyne system was successfully used to measure plasma density‐length product (DLP) in the 1013–1014‐cm−2 range, with μsec response. This was done in the extremely adverse environment of the Astron‐controlled fusion experimental area at the Lawrence Radiation Laboratory, Livermore. The results indicate that the system is capable of covering a plasma DLP range of 1012–1016 cm−2 with 20‐nsec response.