We’ve taken the first step in reassembling our FF-2B experimental fusion device with its new anode. We’re applying indium to both the anode, shown here and to the base plate that it attaches to. Indium is vital to decreasing the surface resistance that occurs when two metal pieces meet. No matter how smooth their surfaces are, microscopic hills and valleys mean that only a tiny fraction of the total surface area is actually in contact, greatly increasing resistance.
A standard practice to overcome this problem is to use indium between the surfaces. Indium is a very soft, highly conductive material and molds itself at a microscopic level to metal surfaces. In addition, under pressure, its grain structure changes, making it much stronger, so it does not squeeze out from between the surfaces like toothpaste.
When used with beryllium, special care has to be taken to break up the insulating beryllium oxide layer that forms on the metal. For that, we use an ultrasonic soldering iron that breaks up the beryllium oxide layer into nanoparticles that are dispersed into the indium. If this is done while the indium is heated to close to 130 C, the indium will bond with the beryllium, forming the needed microohm resistance. We can check this resistance with our microohm meter.
The next step will be to take down and clean the cathode.
Indium layer (silver ring between areas covered with aluminum foil) goes onto the new anode to minimize electrical resistance