Deimos Dewar System

Abstract

Design work resumed on the DEIMOS detector system in September 1996. The major change from the initial description is the inclusion of the focus and one axis of the flexure control system inside the vacuum head of the dewar. Traditionally Lick has not included any active stages inside the vacuum vessel on visible light instruments. However the appeal of having these stages inside the vacuum is that the moving mass is greatly reduced, reducing the gravity induced motions and the power requirements to move them. The motion stages inside the vacuum are flexures to avoid the need for lubrication, the drives are outside of the vacuum for the same reason and also to reduce the need to open the vacuum for servicing of components.

The mosaic is in an f/1.3 beam, and is being used spectrographically, thus it must be very flat and stable both with changes in gravity and over time. The design currently being developed includes a mosaic system that has materials matched for their thermal coefficient of expansion