The Electric Arc Shock Tube (EAST) facility at NASA Ames performs, among other things, spectroscopic measurements in the Vacuum Ultraviolet. This requires the use of specially fabricated crystal windows that are transparent to Vacuum Ultraviolet radiation. These windows are exposed to shock waves of several atmospheres and thousands of degrees for very short (<1 ms) durations. The windows become damaged during this process and must be periodically replaced. There are two materials which meet our transparency requirements down to 120 nm, Magnesium Fluoride (MgF2) and Lithium Fluoride (LiF). Though we have tested with both types of windows in the past, the MgF2 is preferred due to higher cracking resistance and generally lower fabrication and material cost. The form factors for these windows are as specified in NASA drawing number A329-0802-M47. The drawing also specifies machining tolerances and optical performance metrics. The vendor shall verify optical performance prior to delivery of the components. The material is to be optical quality, vacuum ultraviolet grade MgF2. Parts must be free of color centers. The window must be fabricated perpendicular to its optical axis to minimize birefringence and transmission polarization. The table below specifies the minimum transmittance as a function of wavelength. The transmittance should be verified on parts of full form-factor. Transmittance of fabricated windows will be measured by NASA after receipt. Windows not meeting specification will be returned for replacement or full refund, up to 1 year after receipt. f the vendor is unable to meet all of these requirements, in terms of mechanical precision and/or optical quality, relaxed requirements may be considered. In this case, the vendor must provide alternate values for the specifications they are unable to meet. Quantity Because the windows are fabricated from a larger crystal the batch size a vendor can produce may vary. Therefore the vendor may choose to quote for the quantity that is most consistent with their abilities, with the number of windows required being between 4-8. If the vendor anticipates producing test pieces that are near or slightly off-spec during fabrication the quote may also specify a price and quantity for these pieces as an optional add-on to the procurement. Criteria for Selection Primarily, the selection will be based on cost per window. However, considerations will be given for i) higher transmittances, ii) time of delivery, iii) ability to meet or exceed machining and optical tolerances, and iv) availability of additional windows. erformance Period
Delivery 3 to 4 weeks after receipt of order
S hipping
Shipped in container with appropriate protective material
P lace of Performance
Delivered to NASA Ames
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