2,45 ghz antenna
Posted: Mon Nov 12, 2012 10:01 amTo go with the maggie to coax adapter (heliax is required for the power levels), here's the in-tank antenna. I'm just fooling around here. I may add some magnets to make a BIG ECR ion source right in the tank (makes ion extraction a bit easier).
The bottom piece is like the one I welded into a 2.75" CF flange, sticking as far in as possible. Above that is the center conductor, which is a 3/16" brass rod with one end drilled 2 mils less than the center conductor of the vacuum adapter size, then split with a metal bandsaw so it's a push on fit (tight!). The outer conductor is 1/2" ID Cu pipe, with a female to female adapter, squished a bit so it is a tight fit on the outside of the SS adapter, with a 1/4 wave ground plane. The antenna center conductor extends about 1.1" out of the end of the Cu pipe - it's tunable to an extent.
Before this, I just put a wire on the center conductor, but it was a little "submarined" into the tank for the tank walls to be a good ground plane. I also added a big screen over my viewport so I don't fry my retinas looking in.
You can see a slight RF leak with an oven leak detector, and you can tell how much plasma etc are floating around in the tank as they absorb some of the RF.
I can also use this as a faraday type probe, and might. It is fairly near "the action" in the fusor.
- Antenna parts
The bottom piece is like the one I welded into a 2.75" CF flange, sticking as far in as possible. Above that is the center conductor, which is a 3/16" brass rod with one end drilled 2 mils less than the center conductor of the vacuum adapter size, then split with a metal bandsaw so it's a push on fit (tight!). The outer conductor is 1/2" ID Cu pipe, with a female to female adapter, squished a bit so it is a tight fit on the outside of the SS adapter, with a 1/4 wave ground plane. The antenna center conductor extends about 1.1" out of the end of the Cu pipe - it's tunable to an extent.
Before this, I just put a wire on the center conductor, but it was a little "submarined" into the tank for the tank walls to be a good ground plane. I also added a big screen over my viewport so I don't fry my retinas looking in.
You can see a slight RF leak with an oven leak detector, and you can tell how much plasma etc are floating around in the tank as they absorb some of the RF.
I can also use this as a faraday type probe, and might. It is fairly near "the action" in the fusor.