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By Charles Rhodes, P. Eng., Ph.D.

The spheromak injection port valves protect the spheromak generators while enabling axial injection of spheromaks into the spherical pressure vessel. These valves also protect the high vacuum pumps from hot lead vapor and provide a route for high vacuum exhaustion of the spherical pressure vessel. When the spheromak injection port valves are closed the high vacuum pumps, spheromak generators, and plasma injectors are safely isolated from the fusion pressure pulse..

The speed of the spheromak injection port valves is one of the constraints on the Plasma Impact Fusion (PIF) process.

The spheromak injection port valves are realized using custom made ball valves that have a 0.6 m open aperture. The valve operators must move the port from full open to full closed in less than 7 ms. To achieve this objective there may actually be two ball valves in series that move at different rates. One ball valve constantly rotates very fast to meet the 7 ms port closure time. The other ball valve rotates at about half that speed but can hold a sustained open or closed position.

The fast valve is already moving at full speed at the full open position. Hence it has no inertial limitation limiting its 7 ms closure time. However, it will open again about 9 ms after closure. Meanwhile the other valve closes to keep the port closed.

There is a thermal break between each spheromak injection port valve body and the accompanying conical plasma injector because the valve body operates above the melting point of liquid lead whereas the charge injector operates at room temperature. For practical reasons the valve operator must run cool whereas the valve body runs hot. To obtain a high vacuum seal the valve operator should be installed inside the cool portion of the high vacuum system. The linkage between the valve operator and the valve body must contain a thermal break and high torque stress relief.

This web page last updated November 10, 2014.

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