Naval Research Laboratory, Code 3220, 4555 Overlook Ave. S.W., Washington, D.C. 20375-5326

66 -- FOURIER TRANSFORM INFRARED (FTIR) SPECTROMETER SYSTEM SOL N00173-99-R-AT01 POC Evangelina R. Toledo, Contract Specialist, Code 3220.AT, (202)767-2021, Wayne Carrington, Contracting Officer WEB: click here, http://heron.nrl.navy.mil/contracts/home.htm. This modification is issued to answer technical questions regarding the combination synopsis/solicitation N00173-99-R-AT01 for Fourier Transform Infrared (FTIR) Spectrometer System that was issued on 01 February 1999. Question No. 1: In the RFP it was required to provide "1 radiation input port and 4 output ports." Two of the output ports on the 120 HR are actually internal (allowing access to several detectors), but for the other two, what type of window material would the end user request? What type of window material would the end-user like for the emission input port? Answer: Internal output ports are OK provided all essential components are in-place for use with 2 user-supplied detectors. Collimated output ports can be capped but available for user supplied accessories. No windows are necessary since the user-supplied accessories will be evacuable. All internal optical components necessary to use the ports shall be included in the spectrometer. All components necessary to select which port is usedby external control without breaking vacuum shall be installed in the spectrometer. See also answer to the next question. Question No. 2: The RFP requires an emission input port that will accept an F/4 output from a photoluminescence accessory. How much space outside the PL accessory is available in order to place the mirrors to match our input optic? Answer: As presently configured the focus of the F/4 output of the luminescence attachment is 7.5 cm from the luminescence attachment housing. Conversion optics has available this 7.5 cm before the focus. Mechanical support will be provided for the luminescence attachment which will back the attachment away from the spectrometer to allow insertion of the optical conversion optics. Light exits through a 1 inch diameter hole in the attachment housing which has 4 each #8-32 threaded holes on a 1 inch bolt circle for attaching a mating flange. There is no "O" ring in the housing so an "O" ring should be installed in the mating flange. The luminescence system was originally designed for vacuum operation but has since been modified in a way consistent only with purging of the entire spectrometer by nitrogen gas. That is, although essentially all transmission data is taken under vacuum, at this time, only purge is used for photoluminescence. This means that it must be possible to seal the emission port for vacuum operation with the luminescence accessory in place but open it for purged operation with no window. Question No. 3: We would like you to note that for the F/4 focused input you will only gain energy if the spot size of the PL emission accessory is smaller than the aperture size of the interferometer. (The aperture size that is used depends on the resolution and wavelength being studied.) If the aperture is already overfilled, any optical speed adaption actually reduce the energy due to reflection losses. You indicated the focal point is 75 cm from the PL housing, indicating a focal length of approximately at least 75 to 100 mm or so. This in turn means that the focal spot will be fairly substantial in size. In order to achieve the specified resolution of 0.013 cm-1 this implies a maximal aperture size of ~ 2 mm or so for our 120HR spectrometer, working at a typical mid-infrared wavelengths. If the spot size of the PL accessory is larger than this, it may be more efficient to just directly couple the PL emission in without any adapting optics. Will two off-axis paraboloids (OAPs), to recollimate the focused beam and then focus it into the 120HR, be desirable? Answer: You are correct that the iris may be overfilled at high resolution. But the iris is always overfilled at high resolution even with the internal sources. The critical question is whether the collimating mirror is large enough to collect all the energy at low resolution (e.g. 8 or 4 cm-1) as we frequently use with difficult samples. The IFS 120 HR input optics requires radiation entering with F/6.5 for efficient collection. Our F/4 luminescence system will not overfill the iris at low resolution but it willoverfill the collimating mirror (and suffer an efficiency loss). It is necessary to correct the F/number to 6.5 prior to entering the source housing. Even at F/6.5 the focused image size will be of the order of 0.6 cm and should easily pass through your largest available iris. Therefore, in order to meet the requirements of the RFP, your system will require correction optics in a purgable housing which mates to the spectrometer and our luminescence accessory. For information regarding this solicitation contact Evangelina R. Toledo, Contract Specialist, (202) 767-2021. Posted 03/15/99 (W-SN308487). (0074)

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