INNOVATIONS IN THE DESIGN AND CONSTRUCTION OF LARGE VACUUM INFRARED GRATING MONOCHROMATORS

Author Institution: U. S. Naval Ordnance LaboratoryLarge solar spectrographs recently built at Sacramento Peak and Kitt Peak Observatories have certain features which can be used advantageously in laboratory installations. Rotation of the grating about a horizontal axis yields a spectrum dispersed in the vertical direction and allows the use of inexpensive flexural pivots as frictionless bearings. The “over and under” Littrow arrangement of the slits is now to the side and allows reduced off-axis distances. The Girard grill may be coupled with double-pass schemes and with the use of tandem gratings to yield extremely highly resolved spectra even under conditions of low radiance provided the aberration problem can be solved. The use of the achromatic cube corner reflector and parent-daughter gratings in the tandem arrangement offer at least a partial solution to the wavefront curvature problem