Front view of
warm bulkhead. Collimator cold shield has been installed and wrapped
with MLI (aluminum covered mylar -- seen at center). Copper tubing
connects to inlet and outlet of LN2 precool loop. This cooldown used
only LN2. Note that the CTI cold head location (at right, just inside
supporting plate) is filled with a vacuum-sealed plug.
cooling rate was a goal of this cooldown. This was done by capturing
the N2 gas leaving the precool ring outlet, warming it back to room
temperature, and running it through a series of flow gauges (the tall
rectangular pieces mounted to the wooden post). The initially installed
flow gauge stack spanned some three or four powers of ten in flow
rate. We quickly found that only the highest rate gauge (the largest
one) was needed.
Final setup for
first cold test. The front cover has been installed, along with the
aluminum blank replacement for the front lens. Fiber I/O and temperature
monitors and control units are resting on the face of the electronics
rack, not yet installed within the rack. The turbo vacuum pump is
attached to the NW40 valve (at left) leading to the cryostat volume.
LN2 precool loop
outlet fitting, showing location of its temperature sensing silicon
diode (held under the kapton tape [orange]).
temperature sensor (and brass bobbin) attached to the cold optical
and control cables attach to the front of the warm bulkhead using
individually-keyed MIL-spec locking connectors.
sensor wires connect the warm bulkhead MIL-spec connectors to DB15HD
plugs that plug into DB15HD gender changers mounted in the face
of the cold bulkhead. Connected this way, little heat is conducted
into the cold volume via sensor and motor leads and a light-tight
environment is maintained in the cold space.
stainless steel bellows connecting the LN2 precool inlet and outlet
to the loop embedded in the face of the cold bulkhead. Also seen
is the green G10 collar that connects the cold and warm bulkheads.
of the shell heater system. Wrapped in aluminum foil to reduce radiative
heat losses and allow higher shell temperatures.