OPEN THE DEWAR
Set the dewar upside down, using the aluminum ring -(c) above- so
that the openings for LN2 at the dewar top plate are not in contact with
Now, you still can't separate the top and bottom parts of the dewar (let's
call them the two "halves"; and
Unscrew the 9 socket-head screws that tie together the upper and bottom
shells. These are the screws indicated by an arrow
and labelled 1-9 in Drawing 20.
even though the dewar is upside down now, I still call "top" the half
into which you pour LN2 and "bottom" the half that contains the electronics)
because they are attached together by the cold copper straps. The cold
straps are tied to the detector box in the lower half and to the cold plate
in the upper half. You need to free the 2 cold straps AT THE COLD PLATE
END before you can pull the two halves of the dewar apart.
Now you can completely lift the bottom half. Set it on your work space,
since this is what you will be working on and set aside the rest of the
dewar since you will not need it again until you put things back together.
Gently lift the bottom part of the dewar by 3-4 cm (no more!) and place
the two blocks -(d) above- in between the two dewar halves.
Rest the upper half on the blocks.
Place the blocks conveniently so that you can actually do the next step.
Through the gap you have just created, use the correct Allen driver to
reach the screws that tie the cold copper straps to the COLD PLATE. You
DO NOT NEED to COMPLETELY REMOVE THE SCREWS, simply loosen them and pull
the end of the copper straps down and they will slip out. Two of those
4 small screws are labelled A and B in the dewar side view of Drawing 1.