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Investigation of the emissivity in K of INGRID
 (introduction and working plan)

Oct 2003; T. Gregory, A. Zurita
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Introduction
------------

-The aim of this plan is to investigate the origin of the
 unexpectedly high emissivity in K of INGRID when used  
 with NAOMI.

-Tests performed up to now suggest:

 a/ there is a significant source of K emission which 
    seems to be located  between the INGRID entrance 
    window and the pupil stops (with no foreoptics
    and INGRID looking at a cold source, we measure some 
    900 adu/s at the detector).

 b/ the emissivity in K with NAOMI foreoptics is 
    approx. double than with the Cass foreoptics. 

-It was decided in a AO/INGRID meeting (Aug 03):

 -change entrance window of INGRID (to ensure the material is CaF2)
 -get the NAOMI foreoptics coated 

 Although these actions could reduce the background in K, the source
 of high emissivity is still unknown  (specially because of a/)

Plan before and during the INGRID stand-down
--------------------------------------------

A/ Confirm previous measurements 

   With INGRID cold, repeat experiments with the cold soup ladle 
   to measure the amount of K emissivity reaching the INGRID detector
   with: no foreoptics, Cass foreoptics, NAOMI foreoptics.

 o Requirements: 
  
  -INGRID must be cold
  -Full access to INGRID (Test focal station or aluminising area)
  -Both fore-optics available (Cass and NAOMI)
  -INGRID should be rotated by 180 deg (upside down) to
  simulate both (Cass and NAOMI) orientations (trolley needed ??)


 o Total time needed : 2 days


B/ Examination of the baffling in front of the cold stops

   Examination of the baffling: shape, colours and shininess.
   The pupil stop baffle currently inside INGRID seems to    
   have a wrong shape (i.e. it could be allowing unwanted 
   radiation to reach the detector) 

 o Requirements: INGRID warm and open

 o Total time needed : half a day 


C/ Manufacturing and installation of a new Pupil stop baffle

   From conversation with P. Jolley, it must be possible to 
   fit a new pupil stop baffle inside INGRID (to replace the 
   one mentioned in B/).
   
   **The pupil stop baffle could be manufactured before INGRID 
   is opened up.**

    o Suggested plan (assuming that several cycles (2 at least) 
      will take place):

    -manufacture a new pupil stop baffle (a simple one: not polished 
     nor coated), before INGRID is opened.
    -fit it inside INGRID at first opportunity
     (before the the first cool down)
    -test it (repeat A/) when INGRID is cold
    -if it works, make a new pupil stop baffle (polished and gold 
     coated outside, black inside) and install inside INGRID when open.