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FAQ - Ideal diagram of foreline pump system for a fusor or demo

Posted: Fri Nov 26, 2021 2:24 pm
by Richard Hull
The foreline is where all fusion vacuum systems start out. A poor showing here will kill any demo fusor or full fusion system attempts.

Below is a base level, idealized, diagram with operation instructions. You will need a good mechanical pump, two valves, a "tee" fitting and some hose, plus, some clamps and fittings to mate the hose to the pump, valves and Tee fitting. It is suggested to use KF fittings, but not demanded as long as they are superior vacuum tight seals.

The Main Foreline valve #2 protects the fusor chamber and any secondary pump system from oil back streaming by isolating these follow-on components in the system from mechanical pumping failures or issues in in start-up or shutdown problems.

The up-to-air valve #1 is used after shutdown to keep oil out of the foreline Tee and hosing by releasing the vacuum to avoid back streaming of oil from the turned off pump. As noted, in the diagram, this valve is only opened for 2 seconds to let the mechanical pump up to air but, must remain shut at all other times!!!!

It is critical to keep all hose connection as short as possible to maintain good pump conductance within the foreline system.

Richard Hull