An Alternative Optical System for the Motional Stark Effect Diagnostic

The presently used systems for Motional Stark Effect (MSE) diagnostics are complex and include many optical components which can degrade the signal intensity and polarization. We propose a new optical system for MSE measurements which uses only one spherical mirror to image the spectral lines. This alternative system offers the following advantages: (1) it consists of only one optical component; (2) by exploiting the astigmatism of a spherical mirror, it focuses the radiation emitted from an entire line segment, perpendicular to the direction of the neutral beam, onto a point on the detector and provides spatial resolution along the beam direction; (3) due to the symmetry of the system, the polarization of the spectral lines is essentially conserved; (4) only a thin slit at the meridional focus is required as a viewing port to the plasma, which will protect the detector from intense neutron and gamma radiation. Test results verifying the polarization-conserving properties for various angles of incidence will be presented.