Preliminary Success in Tests of Improved Switch Design

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Fig. 1 LPPFusion’s new Testbed can greatly accelerate our switch redesign. Shown here is a test of a single switch (plastic cylinder with copper top). The switch is charged by the spare capacitor (large blue object) and triggered by the brass and copper spark plug seen inside the white plastic trigger head. Current from the switch flows through the black coaxial cables to the silver-coated steel anode plate ( large circle) which releases an arc harmlessly inside the spare vacuum chamber(seen beneath the Mylar sheets). A high voltage probe (vertical cylinder) measures the pulse, as does an optical fiber on the back side of the switch.

LPPFusion got encouraging results from preliminary tests of a revised switch design. The research team tested a redesigned switch on the new single-capacitor Testbed that LPPFusion Research Scientist Syed Hasan built from our spare capacitor and our old vacuum chamber.

We initially tested a single switch of the pair that is to be mounted on each capacitor. We were testing to see if our new 45-degree angle design eliminated the surface breakdown and prefiring that had prevented us from reaching good firing conditions with the previous switch design. The test showed that if, and only if, we had an air-tight seal of the Teflon insulator to the copper electrode can we eliminate the pre-firing and the surface breakdowns. Fortunately, Teflon is elastic enough that it can stretch over the copper just like an O-ring.  With this good seal, we were able to fire the switch at the 40kV charge we have been using for the main shots.

The test also gave preliminary assurance that with the surface breakdowns eliminated, we can get repeatable enough firing so that we can coordinate each pair of switches within a ns or two—close enough so that one switch firing won’t prevent the other one from doing so. The next step, which we intend to take soon, is to have two switches firing together on the test bed.









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