Vacuum Technology and Vacuum Design Handbook for Accelerator ...

• Cryopumps must not be operated without a serviceable pop off valve.
• Cold traps must be warmed and blown dry at least every 6 months to minimise O2
concentrating (and for de-icing as necessary).
5.2 Interlocks
Nearly all vacuum systems on the accelerators are interlocked via a set of integrated relays in a
vacuum gauge controller, to protect equipment. Generally, if a rise in pressure is detected above a
particular set level then the interlock relays will activate to close corresponding gate and line valves.
This is designed to minimise the number of vacuums that must be regenerated in a fault. The
interlock system also protects accelerator tubes from exposure to moisture and in the event of a
catastrophic failure of the accelerator tubes; the vacuum system will close the main accelerator gate
valves to trap SF6 gas.
If an interlocked failed causing a gate valve to stay open in the event of a pressure rise then the next
interlock should activate the next gate valve. If the next interlock fails it is possible that the two
interlocks share the same vacuum gauge controller which is at fault. In that case the next interlock
should activate. If no interlocks activated there would be no increased risk of injury to personnel but
all vacuum systems will require regeneration or a restart after the interlocks were repaired and
tested.
5.3 Fumes from exhausts
There are a number of oil vane pumps in use on the accelerators. In the past, the exhaust on the
pumps has released oil mist into the atmosphere inside the buildings. Now, on nearly all oil vane
pumps in continual service there are mist filters attached or the exhaust is plumbed into an
extraction system that vents the exhaust fumes outside of the building.
5.4 Earthing
Some vacuum gauge controllers are prone to high voltage transient surge damage. These sometimes
cause unnecessary isolation of systems requiring resetting. It is very important that all vacuum
gauge controllers are well earthed.
6. Serviceability
6.1 Access
Most beam lines with the exception to some measurement chambers are static volumes of vacuum
requiring little operator intervention other than during preventative maintenance. Vacuum pumping
systems do require a higher level of intervention during maintenance and operation. With these
points in mind the designer must ensure that all controls and monitoring devices are localised at the
working face of the beam line or chamber.
Due to beam lines being so high above floor level, working on them usually requires some form of
ladder or steps. When designing beam lines, be sure to have pump out ports facing the passageway
beside the beam line. The same applies to vacuum chambers and other large volume vessels.
Measurement chamber will need to have the access port accessible from a location near the control
side of the chamber. A platform is recommended to allow easy reach and eay viewing into the ports.
6.2 Maintenance
A well designed vacuum system will require routine maintenance including:
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