Reply To: Bang or no bang

[markus7]

TimS wrote:

If the problem persists with the knife edge, I wonder if there would be some way to add a slight inductance at the base of the main electrodes so that the current sheath could be created to the knife edge (or pins) all around before lifting off to the electrodes? Perhaps returning to pins and adding a slight inductance in each would slow the current rise through the first pins and allow other pins to become active? I should go back to my old basic electronics class and work out the inductance and timing of the pins as they are…

Although the previous poster’s suggestion of using ‘laser spark plugs’, completely removing the need for high speed synchronized switches and the knife edge or pins, sounds pretty cool.

I had initially thought that the negative side of the capacitors was switched into the cathode electrodes separately, instead of having the positive side of the capacitors switched and then tied together to the anode. That way the shot energy would always be divided evenly between the electrodes. I had thought the circuit worked this way when I saw all those switches, specifically in order to avoid this problem of asymmetric current through the electrodes. I spent some time yesterday confusedly looking at the focus fusion pictures on flickr (aren’t they cool!) trying to figure out why the problem occurs before I realized I had it backwards. I had been wondering how all those separate circuits were synchronized so precisely… A schematic of the focus fusion device would be great.

It had also occurred to me that 16 capacitors, each firing its own cathode rod by individual, synchronized (highly synchronized!) vacuum switches would likely reduce the non-uniformity problem. There might also be an advantage in terms of reduced inductance in the separate circuits and higher peak currents, but I don’t know if that is possible. But that would be a totally new fusor design.

Could you explain what you mean by “add a slight inductance at the base of the main electrodes”?

“Inductance is the property of an electrical circuit causing voltage to be generated proportional to the rate of change in current in a circuit.”