From: Donald N.B. Hall <hall@ifa.hawaii.edu>
Date: Tue, Apr 2, 2013 at 11:44 AM
Subject: Don's review items
To: Alan Tokunaga <tokunaga@ifa.hawaii.edu>
Cc: Don Hall <hall@ifa.hawaii.edu>


Hi Alan,

Briefly listed below area few other items I flagged during the review - just let me know if you
need more information on any of them.

1) The closed cycle cooler should be vibration and ground isolated from the vacuum vessel and the
cold fingers should also be vibration and ground isolated from the cold stages (we use mica or
sapphire for the cold electrical isolation).

2) The radiation shield and cryogenic spectrograph enclosure should be separate, electrically
isolated Faraday cages that are tied to ground at a well defined "star" point.

3) All mechanism electrical/sensor circuits should be isolated from the spectrograph ground and
tied back to the star point.

4) Analog and digital ground should be kept separate for each detector array to the controller and
tied together at the controller star point (where the individual cards are grounded together).

5) Most types of Al are good thermal conductors down to LN2 temperature but many are much worse at
40K. This should be factored into the design of the two array assemblies.

6) You need to be sure the LN2 reservoir has adequate thermal coupling for all fill levels and
orientations.

Cheers

      Don