Sumitomo Marathon CP-8 - Restarting after a Power Failure; System Shutdown

Operation
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Cryopumps having connections that are all copper gasketed can be baked out to 150° C with
the cryopump running. Very low pressures can be achieved with these pumps by using this
method.
See the Parts section for typical replacement parts recommended for ultra-high vacuum (UHV)
service.
Restarting after a Power Failure
The compressor is designed to restart immediately after power has been restored if it is shut
down by a power interruption. The connected cryopump will also start. The gate valve should
not open automatically.
If the compressor stops for other reasons, refer to the Troubleshooting section in the
Compressor manual.
Typical cryopumps operating at less than 14 K have so little heat input that the cold head can be
off for up to 5 minutes without releasing frozen deposits from the panels. If the cold head is
operating at a higher temperature, it has a higher heat load and therefore warms up faster.
Helium or hydrogen may be released from the charcoal before the other gases and thus shorten
the coast time, which is the time after the power shuts off for the pump to warm-up and release
enough gas to break the vacuum. If the pressure has risen to 1 x 10
-2
torr, the cryopump must
be warmed up and regenerated after power has been restored.
In most applications, the operator establishes an upper pressure or temperature limit for
operation that designates when the cryopump should be regenerated or when it should be
allowed to recool after a power interruption. Typical temperature limits are 45 K to 60 K
depending on the gases being pumped.
During power failures, the gate valve and all other valves should be closed to isolate the
cryopump and reduce pressure increases in the vacuum chamber. If regeneration is required,
follow the procedure in the Regeneration section of this manual.
MOUNT THE CRYOPUMP BEHIND A GATE VALVE that closes automatically if
the cold head or compressor shuts down or if there is a power failure.
System Shutdown
1. Close the gate valve to isolate the cryopump from the main vacuum chamber.
2. Stop the compressor. The cryopump will stop.
3. Expect gas release through the cryopump's pressure relief valve as described in the section
Regeneration: Warm-up Phase.
4. Begin nitrogen gas purge of the cryopump as described in Regeneration: Purge Phase, to
dilute hazardous gases.