Development of a laser imaging system for measuring electron density fluctuations in high temperature plasmas using visible laser

A laser imaging system using an infrared laser is a powerful tool for measuring electron density fluctuations in high temperature plasmas. As an advanced step of the technique, we are developing an imaging system that uses a visible laser. While the visible laser system has advantages over the infrared system, it requires higher accuracy of optical components and improvement on the SN ratio. In this paper, we examine necessary characteristics of optical components and evaluate the noise level experimentally with a noise-eater that reduces optical noise of the laser. A novel He-Ne laser imaging system has been setup based on the results of these studies. Accuracy of measured wavenumber and the minimum detectable intensity of the system are presented. (author)