Development of two color laser diagnostics for the ITER poloidal polarimeter

Abstract

Two color laser diagnostics using terahertz laser sources are under development for a high performance operation of the Large Helical Device and for future fusion devices such as ITER. So far, we have achieved high power laser oscillation lines simultaneously oscillating at 57.2 and 47.7 m by using a twin optically pumped CH 3 OD laser, and confirmed the original function, compensation of mechanical vibration, of the two color laser interferometer. In this article, application of the two color laser diagnostics to the ITER poloidal polarimeter and recent hardware developments will be described.

Polarization properties of a metal corner-cube retroreflector

“…The change in the ellipticity value is usually in the several degree range and therefore is comparable with the change observed at polarimetric systems of tokamaks, coming into being as a result of Cotton-Mouton effect into the plasma. The variations of the azimuth angle are much smaller (tenths of degree) however exceeds the required accuracy of the Faraday rotation angle measurement, at existing polarimetric systems as well as in diagnostic requirement for ITER, which is in several hundredths of degree range [11].…”

Development of an HCN dual laser for the interferometer on EAST

“…The first is to employ two lasers operating atslightly different frequencies via control of the cavity length, and the second is to employ a rotating grating. In the Large Helical Device (LHD), laser sources in the wavelength region around 50 μm have been developed, and high-power lines oscillating simultaneously at 57.2 μm and 47.6 μm in a twin optically pumped FIR CH 3 OD laser have been achieved [4][5][6][7]. In the EAST, a POlarimeter/ INTerferometer (POINT) system which utilizes three optically pumped (at 10.27 μm) HCOOH lasers operating at 432.5 μm as the source power has been successfully established in order to provide accurate measurements [8][9][10].…”

Developments of simultaneously oscillated three-color FIR (48-, 57-, and 119-&#x00B5;m) lasers pumped by two CO<inf>2</inf> lasers for ITER diagnostics

“…In the Large Helical Device (LHD) at National Institute for Fusion Science (NIFS), the plasma electron density profile has been measured by a Michelson type heterodyne interferometer using a 119-μm CH 3 OH laser pumped by a 9P(36) CO 2 laser. We have developed a two color interferometer/polarimeter using 48and 57-μm CH 3 OD lasers pumped by a 9R(8) CO 2 laser in order to apply high density operation of the LHD and future plasma devices such as ITER [1].…”

“…In the Large Helical Device (LHD) at National Institute for Fusion Science (NIFS), the plasma electron density profile has been measured by a Michelson type heterodyne interferometer using a 119-μm CH 3 OH laser pumped by a 9P(36) CO 2 laser. We have developed a two color interferometer/polarimeter using 48and 57-μm CH 3 OD lasers pumped by a 9R(8) CO 2 laser in order to apply high density operation of the LHD and future plasma devices such as ITER [1].If simultaneous oscillations of these lasers from a single laser cavity are realized, it is possible to carry out a suitable measurement for the plasma state. The three-color FIR laser is definitely the right optical source for future plasma diagnostics.…”