Loral 5 Dewar Assembly 

This page was assembled by Tim Abbott for the purposes of describing the construction of CFHT dewar heads to Ron Johnson of UBC, 19 Feb 1997.
 
Figure 1: CCD mount, dewar side
This is the CCD mount within the dewar.  The upper surface in the photo attaches to the body of the dewar via the 8 holes visible at the edge, and the lower surface is the mount for the window holder.  Attached to the vacuum-side of the largest ring, is a ring of smaller diameter.  Three screws can be seen holding this in place.  To this smaller ring are attached three standoffs, running back into the dewar, made of PCB material -- these provide thermal isolation from the dewar of the CCD and its mounting surface. The interior ends of the PCB standoffs attach to aluminum legs which run back towards the front face of the dewar and which, at their other ends, attach to a circular disk with an off-center, square hole cut in it.
The square hole has a lip and the CCD package fits into the hole (face down, in this photo) and is prevented from further movement towards the window by the lip.  The hole is cut off-center in the disk because Loral 5 is mounted off-center in its package.
To ensure that the CCD surface coincides with the focal plane, tip-tilt and Z-direction (vertical in this picture) of the circular disk can be adjusted by the use of shims between the two outer rings at the three screws holding them together.
 
 
Figure 2: CCD mount, window side
This is the same component as in Figure 1, viewed from the other side.  The dewar window is attached via the eight inner screw-holes visible in the photo.  The non-anodized ring is the inner ring attached by the three screws described above.
 
Figure 3: Cold finger.
This is the cold finger.  The lower-left (long) end of the aluminium cylinder is attached to the cold end of the dewar via the steel spring and copper leaf assembly described below.  The upper right (short) end of the aluminium cylinder presses on the back of the CCD package, holding it in place and delivering the thermal connection to the N2 reservior.  The three radial arms are made of a single piece of PCB material and are attached to the dewar ends of the aluminium legs described under Figure 1.  When in place, they are under slight tension to apply the required pressure to the back of the CCD package.
 
Figure 4: Cold finger and CCD-mount,
In this photo, the cold-finger is seen in place on the CCD mount, with its three radial arms where they are attached to the aluminium legs.
 
Figure 5: CCD-mount, cold-finger and window-holder.
In my right hand, I am holding the CCD-mount and cold-finger assembly.  The CCD window-holder is in my left hand, as it would be attached to the CCD-mount.
 
Figure 6: CCD housing.
The entire assembly seen in figure 5 fits inside this housing (window up).  The PCB here is the connector for Loral 5.  The two connectors on the outside at lower-left carry the clock and bias signals.
 
Figure 7: Main dewar body.
This is the main dewar body, to which the CCD housing of Figure 6 is attached.  The gold-plated cylinder inside is the N2 reservior and the steal spring and copper-leaf assembly at the center connects to the long end of the cold-finger assembly described above.  Two of three thermally-isolating standoffs are visible.
 
Figure 8: Loral 4's dewar.
This is the fully assembled dewar for Loral 4.  The CCD is visible at the front.  The L-shaped box attached at the right is the preamp box.