al-CRYOGENICS
HELIX TECHNOLOGY CORPORATION
Section 3
Operation
Do not begin the Model 22C/350C Cryodyne
Cryocooler operation until all steps in the inspection and
installation procedures have been completed and
confirmed.
3.1 Operating Log
It is highly advisable to create and maintain a detailed
operating log. The record will assist in troubleshooting
should problems arise. Appendix A contains a sample
operating log for your use. You may wish to make
photocopies of this sample log.
3.2 Installing the Load
The load can be either attached directly to the cold
station concerned or coupled to it with heat wicks
(braided copper straps). Indium foil that is 0.002 to
0.005 inch thick should be used between the mating
surfaces to improve thermal conduction.
When the installation of the load has been completed,
rough-pump your vacuum chamber down to 5 x 10
-2
torr
or better. Then close the roughing valve prior to starting
the cooldown of the cryocooler. Upon cooldown, the
refrigerator will cryopump residual gases in the chamber
and an insulating vacuum between 10
-4
and 10
5
torr will
be achieved.
3.3 Start-up and Cooldown
Procedures
1.
Ensure the roughing valve is closed.
2.
Turn on the system power ON/OFF switch to operate
the compressor and cold heads. Record helium
pressure and temperature reading during the initial
cooldown.
3.
During cooldown, record the operating log data at
15-minute intervals. To ensure minimum cooldown
time, do not apply electrical power to any load
during the cooldown.
The cooldown time associated with a normal
cooldown with no load attached to the second-stage cold
head is specified in Table 1.1. The cooldown time will
increase approximately 15 minutes for each
pound-of-mass increase of the attached load.
Pressure regulation during a cooldown is automatic.
The compressor will vary during cooldown but will
usually attain steady values nominally within 45 minutes
after cooldown.
P/N 8040272
3-1
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