Vacuum Technology and Vacuum Design Handbook for Accelerator ...

3.5 Flexible design
It is prudent to ensure where practicable designs ensure some redundancy for feedthroughs, access
ports and internal space. A major problem with early chambers was the lack of space allowed for
inserting samples by hand or manually manipulating internal equipment and wiring. It is easier to
design flexibility into the chamber or equipment at the design stage rather than having to dismantle
it and have it reworked in the workshops later.
3.6 Can it be made?
When designing any equipment seek advice from a qualified machinist. Often designs include
machining that may be very expensive or not possible. Early in the design phase ensure that the
resources are available to service the vacuum equipment. It is recommended to consider the
following early in the design stage:
• Power
• Cooling water
• Air cooling
• Signal lines
• Control lines
• Add-on electronic and mechanical instrumentation
3.7 Safe design
There are no cases that the author has been able to find of scientific vacuum chambers or equipment,
like those used in accelerator facilities, failing and causing injury. Vacuum pressure is relatively
low, -100 kPa, or about half the equivalent magnitude in a car tyre.
For safe designs the structure must meet the minimum dimensions as calculated in Appendix 1 –
Structural Calculations for Scientific Vacuum Vessel Design.
Care must be taken with the design of the following:
• Glass view ports (most glass breakages are in the form of a crack which leak to atmospheric
pressure quickly without the spread of shards)
• No internal sharp edges; in the case where a person must insert their hands blindly to access
components.
• Venting limits – pressure relief for positive pressure?
• Evacuation rate regulation; especially in the case where very thin material windows separate
different pressure systems within a single vacuum space for example beryllium windows on
x-ray detectors.
• Equipment mounts/stands; where an operator must climb up high to operate devices on the
system
• If oil type vacuum pumps are used then mist filters must be fitted to the exhausts.
3.8 Cost effective design
All bells and whistles may not be necessary even after considering some design redundancy for
future changes. Where possible, designs should consider integrating components that are available
off the shelf. Designing what has already been designed by someone else is wasting time and effort.
It may be cheaper to modify an existing chamber for use rather than start from the beginning. Many
chambers used around the accelerator area have successfully had one or more lives.
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