The new tungsten anode has a current connection with the silvered steel plate at the edge indicated to by the blue arrow. This current connection is below the red O-ring (yellow arrow) that seals the vacuum chamber indicated by the black arrow. The old current connection was at the location of the red arrow, inside the vacuum chamber and at a small radius, where the concentrated current jumping from one piece of metal to the other could vaporize the anode material and contaminate the plasma.
The first steps have now been completed to begin the re-assembly of FF-1. LPP’s lab team has successfully joined the new monolithic tungsten anode to a steel connector plate, creating a current contact that is outside the vacuum chamber and arcing-proof. Moving the contact outside the vacuum chamber completely eliminates the possibility that vaporization caused by arcing will add impurities to the plasma. In addition, making the contact at a lager radius spreads out the current, making it easier to avoid the intense heating that leads to vaporization.
But additional steps are still needed to be taken to make sure arcing would not occur even as FF-1 device increases its peak current. Arcing outside the chamber can’t hurt the plasma but it can damage the Mylar sheets that insulate the anode plate from the ground plate below it, possibly causing insulator failure. So the LPP team plated this steel with silver and carefully squashed indium metal between the steel and the tungsten to insure low resistance.
Hours of painstaking indium application had finally paid of in the fight against arcing, resulting in the very low resistance of 6 micro -ohms between the silvered steel plate and the inner slightly raised plate in the middle.
Our student intern Taylor Smith from Canada helped improve techniques and with the work of CIO Ivy Karamitsos and Dr. Yousefi we succeeded in reducing resistance below 6 micro-ohms, three times better than our goal. Thanks also to consultant John Thompson and Board of Advisors member Rudy Fritsch for help and designing the anode connection. We will now mount the steel plate and anode onto the FF-1 device. We currently expect assembly to be complete in October.
Taylor and Hamid watch Eric put the steel pressure ring onto the anode assembly. The pressure ring was bolted in place to squeeze the tungsten and steel tightly together, minimizing resistance.