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My Manhattan Project...

Posted: Tue Sep 06, 2016 10:56 am
by Sven Andersson
During the Manhattan Project the scientists and engineers pursued many leads at the same time; they simply didn't have the time to do any proper R&D and wait for results.

If I had access to a physics lab and colleagues to juggle ideas with and a proper physics education, I could test my ideas easily. Now I have to do many things at the same time and do whatever I can with the equipment I can buy on eBay.

One lead I want to pursue is the method of ionization described in the picture text. How can this be done? Solenoid bought on eBay and a high frequency voltage generator? What is a high frequency voltage generator? From the book Gas Discharge Physics by Yuri P. Raizer:

Re: My Manhattan Project...

Posted: Tue Sep 06, 2016 3:49 pm
by Richard Hull
Carl Willis did this a few years back here and included images of his work. RF coupled energy into gases is very old news. small neon lamps in a microwave oven is a common show of this effect.
Note** The use of microwave ovens in any experiment can be dangerous. A good amateur radio transmitter can be brought to service with a loading coil tuned to excite gases in vacuuo.

Richard Hull

Re: My Manhattan Project...

Posted: Tue Sep 06, 2016 5:03 pm
by Jerry Biehler
Use are rf generator either in 13.56mhz or 450khz, these are ISM bands and you wont need a license to run on them. You will still need a matching network and understanding on how to create the right coil for the load. One of my ion sources for my vacuum system uses inductively coupled plasma.

Re: My Manhattan Project...

Posted: Wed Sep 07, 2016 5:21 am
by Jeroen Vriesman
picture of our home-build plasma cleaning, bell jar with coil, 13.56MHz 350W

Re: My Manhattan Project...

Posted: Thu Sep 08, 2016 10:29 am
by Sven Andersson
Jerry Biehler wrote:You will still need a matching network and understanding on how to create the right coil for the load.
Where can I read up on this subject? Book or online resource?

Re: My Manhattan Project...

Posted: Thu Sep 08, 2016 10:31 am
by Sven Andersson
Jeroen Vriesman wrote:picture of our home-build plasma cleaning, bell jar with coil, 13.56MHz 350W
Very interesting! Where did you get the radio transmitter? Do you have any tips on where to learn more on this?

Re: My Manhattan Project...

Posted: Sun Sep 11, 2016 12:36 pm
by Jeroen Vriesman
Sven,

we got our 350W RF power supply from a vacuum equipment surplus seller.
With the matching network. So we took the easy road :) did cost some money.

The goal of a matching network is to transform the impedance of the load (the plasma) to about 50 ohm load on the coax cable.
That is simple with a fixed load, but a plasma show variations with pressure and other conditions, so sometimes a servo-driven variable capacitor is used, with some control electronics. Not easy.

Anyway, look at T or PI networks to get an idea of impedance matching, you need basic circuit theory (complex number in the frequency domain) to calculate the currents, voltages and impedances.