The second major milestone was the delivery of the large e-beam welded cryostat vacuum jacket. The first vacuum tests were successfully completed in early November. Due to the sides of the centre section being made slightly thinner than specified, the sides were found to bend about 5mm under vacuum, less than the elastic limit, but too close for comfort. The addition of two simple stiffener bars to the outside of the jacket has reduced the flexure to less than the specification of 1mm.
Requests for quotation for Phase III of the cryostat fabrication (the spectrograph - light-tight spectrograph box, optical mounts, grating turret, slit wheel and focus stage) were sent to vendors. The contract for Phase III will be awarded next quarter. Final drafting of the drawings for Phase IV of the cryostat fabrication (mechanical components of the fore-optics and slit-viewer) is about to start. (The final phase, Phase V, is the telescope interface and calibration box.)
SSG, Inc., delivered the diamond-turned off-axis parabolic collimator for the spectrograph, and Max Levy Autograph, Inc., delivered the slit mirrors. Optics for Research completed fabrication of the spherical lenses and mirrors, flat mirrors, dichroic substrates, and dewar windows. These will be delivered following optical coating by sub-contractors. SpeX joined a consortium to purchase infrared interference filters from OCLI. These filters are optimized for the dry conditions of Mauna Kea.
As of December, SBRC have processed 18 InSb wafers for PAIDAI, and these have yielded 9 science grade parts. Six wafers remain to be processed. The first six hybridization attempts are now scheduled. The first two hybrids should be ready for cold testing in January 1998. SBRC has successfully used a chemical etching technique to remove three PEDs (see Third Quarter 1997 report) from a Gemini Project array. SBRC will now use this technique to remove PEDs from all potential science grade arrays.