First of all a Merry Christmas to all you crazy fusioneers out there, who like me find the festive season to be the perfect time for an antisocial introvert escape into the world of experimental science
LONG STRING OF FAILURES
For those of you who are new to the forum I have the most impressive history of fusion failures, mainly because I refuse to build a proven 6" spherical fusor, instead I have tried a whole bunch of crazy designs all well documented on fusor.net over the last 12 years or so. I shouldn't say total failures, because most of the stuff I built actually produced some neutrons but were not the success I was looking for, however I see it as the challenging path I need to navigate to get to the holy grail of fusion.
BACK TO THE DRAWING BOARD AGAIN
The FICS versions described in this thread were disappointing, so I gave it a break for a few months while I tried to understand the problems (essentially a failure of the plasma to stay lit). I came up with an idea which involved replacing the 6" cathode with a much narrower 30mm disc with embedded neodymium ring magnet (see images).
Effectively this new cathode (D10) is designed to operate in conjunction with the adjoining dynodes (D9 andD11) as a low potential ion source. High voltage is connected to dynodes 9 and 11 either side of the cathode, while the cathode is connected to ground via a 50 kV zener diode. (Yes you read that correct 50 kV).
In operation the HV is set to around 55 kV thereby setting up a potential of around 5kV across (D9+D11) and D10, which is a gap of around 10 mm. At the right pressure of around 5 micron the plasma lights up and a 2 mA current of electrons ionise the deuterium gas at cathode potential, which is what I have been trying to achieve all this time. To understand why this is so important you have to read some of my old posts and try to understand my radical ideas about fusion.
Fortunately the Latex glue I use for these chambers is easy to take apart without breaking the glass. Latex dries into a soft rubber compound and can easily be peeled off without any residue sticking to the glass.
This is the replacement cathode with embedded neodymium magnet. The magnet cost me around $100 online.
A perfectly machined lid covers the magnet and has a centering ring to help align the disc.
This is the whole stack put back together with the new cathode, the latex glue can be seen squeezing out. This method requires at least 1 week to dry and preferably with a bit of heat.
Early results look promising, and I am making neutrons at super low current consumption. I am measuring the current consumption in a slightly unorthodox way, due to the zener diode arrangement. I calculate the current used as;
(input current) - (output current) = Differential Current
Where input current is the current draw of the PSU and the output current is the current going to ground through the Zener diode. Since the latter can be fully recovered I only consider the differential current * voltage to be the energy consumed.
Before conducting the fusion experiment I calibrate the input vs output current by connecting the HV directly to the zener, i.e. bypassing the chamber, and setting the PSU to 55 kV then zeroizing the differential current.
The data below was acquired from my second run on Christmas eve, and looks promising. If you look at the first 300 seconds my neutron output was in the order of 300,000 to 400,000 n/s isotropic with current draw around 0.5 mA. This is a Q of at least an order of magnitude better than a standard fusor at the same voltage.
But as I said this is very early days and I am operating at the low end of efficiency. According to my calculations the optimal Zener value should be 62 kV which is an easy modification to do.
I see light at the end of the tunnel, is that Q1 I see on the horizon?