Performance analysis for an infrared second harmonics dispersion interferometer

A second harmonics or dispersion interferometer (DI) is a promising approach for the measurement of line-integrated densities on fusion devices. In contrast to a conventional two-color interferometer, the second harmonics (SH) of an interferometer beam, generated by a non-linear optical crystal, is used as the second probing beam. Since a few years, non-linear crystals with a sufficient conversion rate are available for the infrared (IR) spectrum around 10%m. Several types of these IR non-linear crystals have the phase-matching angle range as big as ¿1°, which is a great advantage for SH generation applications. Among other advantages, dispersion interferometers offer the possibility of a highly compact frameless design, which makes a modular approach possible for multi-channel diagnostics. Another unique feature is that vibrations are compensated intrinsically. This work will analyze the performance of a 10.6%m DI currently under construction at the TEXTOR tokamak.