Previous fabrication of ZnSe grisms on the Precision Engineering Research Lathe (PERL II) at LLNL has demonstrated the importance of surface preparation, tool and fixture design, tight thermal control, and backup power sources for the machine. The biggest challenges in machining the RIMAS grisms are the large grooved area, which indicates long machining time, and the relatively steep blaze angle, which means that the grism wavefront error is much more sensitive to lathe metrology errors. Mitigating techniques are described.
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Paul J. Kuzmenko, Steve L. Little, Alexander S. Kutyrev, John I. Capone, "Technique for diamond machining large ZnSe grisms for the Rapid Infrared/Imager Spectrograph (RIMAS)," Proc. SPIE 9912, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 99120C (22 July 2016);