Engineering and design of a CO2 phase contrast interferometer system for DIII-D
Abstract
The development of a CO2 laser interferometer system, the engineering, design and installation of the hardware, and the selection of materials specific to the requirements of a CO2 laser diagnostic is discussed. A brief description of the system operation is included. A phase contrast interferometer diagnostic has been designed and installed on the DIII-D tokamak to enhance studies of the physical characteristics of plasma turbulence, and specifically to analyze plasma density fluctuations in the boundary region of the plasma. A 20 watt CO2 laser beam, operating at the 10.6 micron wavelength, is expanded to a diameter of 76 mm and directed through a series of mirrors which provide for entry of the beam into the vessel at a point 70 cm above the midplane at the 285 degree toroidal location. After being reflected from a mirror inside the vessel, the beam is directed downward so that it passes through the edge of the plasma immediately in front of a four-strap fast wave current drive RF antenna. The laser beam is then reflected by a second internal mirror and exits the vessel 70 cm below the midplane (also at 285 degrees) returning to an optical table through a final series of external steering mirrors.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- November 1994
- Bibcode:
- 1994STIN...9524709P
- Keywords:
-
- Carbon Dioxide Lasers;
- Design Analysis;
- Interferometers;
- Phase Contrast;
- Laser Beams;
- Laser Outputs;
- Mirrors;
- Plasma Density;
- Plasma Diagnostics;
- Plasma Turbulence;
- Lasers and Masers