Opus One
pliers or tools to close the valve. Using excessive force to close the valve can permanently
damage the valve mechanism.
B
The cool down procedure steps should be completed in the following order:
1. Evacuate the Opus One unit according to the following procedure.
a) Ensure the green vacuum valve (labeled “Valve”) on the rear of the Opus One unit
is closed by gently applying clockwise torque. The valve should not turn under light
torque. Do not overtighten.
b) Remove the NW25 cap and o-ring from the vacuum port (labeled “Pump/Vent”)
loosening the clamp screw and removing the clamp.
c) Inspect the o-ring to ensure it is dust-free and has no cracks or flaws. If so, replace
the o-ring before proceeding.
d) Using the o-ring and clamp, connect the vacuum pump via an appropriate NW25
vacuum tube (not provided) to the vacuum port and hand tighten the clamp securely.
e) Follow the vacuum pump manufacturer’s recommended procedure for starting the
pump and evacuating the pump tube.
f) Slowly open the vacuum valve on the Opus One unit. The valve is fully open once
rotated counterclockwise approximately two (2) full turns. The valve should remain
open and the pump on until the system has reached 50 K.
2. Ensure the compressor is ready for use, including turning on any required cooling water or
electrical breakers.
3. Turn on the electrical power to the compressor. The hum of the compressor and the 1
cycle-per-second “hiss” of the Opus One unit should begin immediately. If the 1 cycle-per-
second sound from the Opus One is not heard, turn off the compressor and confirm that
the helium line and electrical connections between the Opus One unit and the compressor
are correct, as per Section
4. Confirm that the temperature reading of the Stage 1 thermometer indicates the temperature
has begun to decrease.
5. Wait until the temperature of the Stage 1 thermometer drops below approximately 50 K,
then close the vent valve by turning the green valve knob clockwise until (gently) finger
tight. Do not overtighten.
NOTE
If using a dry pump with strong pumping capabilities such as a turbomolecular
drag pump (i.e., “turbo” pump), you may choose to wait until the system is
fully cold to close the green vacuum valve as there is low risk of backstreaming
contaminants such as air or pump oil into the cryogenic space of the Opus One
unit.
i
6. Once the vacuum valve is closed you may disconnect the pumping line from the Opus One
and turn off the pump, according to the process recommended by the pump manufacturer.
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