Doublet III Thomson-Scattering-System Hemiconcentric Triplet Lens

摘要

The D-III Thomson Profile System Hemiconcentric Triplet lens is described herein. This objective lens is used to image a 120 cm long segment of a focused TEM sub 00 ruby laser beam onto a curved image plane where the light is collected by fiber optic bundles. This lens has a 100 exp 0 field of view, focal length approx. = 12 inches, and magnification approx. = 1. The small ports on the D-III tokamak make it necessary to situate the objective lens aperture near the front of the lens, and to funnel the light through the narrow port opening. The hemiconcentric triplet lens aperture is located at its front surface and the refraction at this surface acts to funnel the light. The result is excellent light collection (light collection F = 6.7, lens f = 3.9) at the expense of reduced off-axis resolution due to astigmatism. At the edge of the field of view the worst-case resolution along the laser beam is about 3 cm. The excellent correction of spherical and chromatic aberrations of this lens, however, result in minimal additional width of the light collection fiber optic bundles transverse to the beam image. Despite the peculiar geometry for this lens, its relative small size and use of common glasses results in a cost which is less than a comparable concentric design. (ERA citation 07:045261)