Fusor Forums

Hello
Here are the photos I promised in the Introduction-Forum.

pic.1. Overall view of the setup: The flat unit with the black heat sink on it is the zvs-driver I use for powering the flyback-transformer.

pic.2. The vacuum chamber: It has an outer diameter of 2.7 inches. I plan to use something bigger in the future.

pic.3. Three-loop-grid testing:

pic.4. Spiral-grid: I realized that the size of the poisor depends on the current. There two buggle-jets that are very close to each other.

pic.5. One-wire-grid: Due to the heat it moved a bit.

Adrian

Nice pictures adrian. I definitely like how your spiral grid looks.


In the 2nd picture, the one with your three loop grid, what kind of material are you using, and how much power is going through the system. Its glowing red hot I can see, so you might want to experiment with other materials and/or the thickness of your current material. We just had an hour long run with helium where we had about 500w of power being output from the power supply, and we didn't see our grid get red hot like that once. The only time we saw it get red hot is when we used a piece of stainless steel welding rod to connect the grid to the HV feedthrough, because SS welding rod has very high resistivity. So just make sure you're using the proper type of stainless that conducts well.

Great job

-Josh

Hello
Thanks for your feedback.
During the test with the three loop grid an input power of about 200W at 10-15kV was used. The grid has an outer diameter of 1 inch and the thickness of the wire is about 1/2mm.
I think the material is a relatively bad conductor for heat. It was used as heating wire in an infrared emitter before. In future when I get a better vacuum I will use stainless only. By using this grid material I also realized some strange sparks at lower power input. Attached is a photo of a ring-grid that’s made of the same wire. I uploaded a AVI-video of the grid during operation in the fusor part (green link at the bottom of the page) to my website.
http://www.adrian-homelab.de/
Adrian

Adrian,

Those sparks you were seeing were probably arcs from rough edges or such on the wire (probably created from repeated heating and cooling from where you removed it from). After a few hours of operation, you'll stop seeing the sparks.

A good place to buy the stainless steel wire is smallparts.com . We are posting in another thread about laser cut stainless electrodes, which is what I use primarily. After I get a better design worked up, I'd be happy to fabricate one for you.

-Josh

Hello
Nice tips. Thank you. I tested another grid today at 200-250W and was a little surprised to see it glow too. It was a four loop grid made of stainless with an outer diameter of 1 inch an 1 mm thick wire. The size of my grids are limited to 1 inch because of the flange connections. Thank you for the offer of making a grid for me. I’m a bit isolated here in Germany. If there is a good way for you to make a 1 inch grid and ship it to Germany please tell me the costs (including shipping) and I will calculate if I can afford this at the moment. I just bought another rotary pump which needs to be tested when it arrives so I might need some money left for a reducer flange (I have NW25-types only). I looked up your previous posts concerning your grids and was wondering about the grid-size you currently use. Nice setup by the way.
Adrian

SS wire is readily purchased in anyone's home town from welding supply stores who sell it in a large variety of diameters in 3 foot lengths or on spools for MIG welders.

Richard Hull

Hello Adrian,

nice pictures and an interesting setup. I see that you tackle this very systematically. Good luck.
I'd recommend tungsten wire for the grid because the SS wire evaporates too much when hot.

Wilfried

Hi Adrian,

Beautiful diminutive fusor, nice grids. Thanks for sharing this. You are clearly experienced with the various disciplines involved in fusor construction. What are you going to work on next?

-Carl

If this ever fuses it will be the smallest rig ever to do so in amateur hands.

All the best.

Richard Hull

Hello
Thank you for your replies. I want to improve the setup step by step until it can be used as a neutron producing fusor in the far future.
The next task is to set up a better vacuum system.
Except of the single stage pump, which was originally planned to be used for homebuilt lasers, I have a leaking two stage EDM12, a used Alcatel (2030?), which is supposed to arrive tomorrow and a small water-cooled diff-pump (E203S). I will keep u informed.
I always try to find a compromise between costs and performance but sometimes I fail.
I consider using tungsten grids when I achieve starmode.
If it fuses I think the output will be low because of the limited input power. A water cooling for the chamber is required for longer runs above 100 W but the grids can not be cooled that easily so the grid-transparency will be lower than usual or they will melt (I already managed to). Anyway I won’t be able to show fusion results within the next months.
Pic.1. At the moment I’m experimenting with the material, structure and size of different grids.
I scaled down the size of the pictures to about one ninth so the resolution suffered a bit.

Adrian

You are going about this is all the right ways. Learn by doing and constant experiment. Get a feel for the ionized gas and the response of the system over a range of varying pressures, voltages and currents. You will not regret it. When, later, it comes time to fuse, you will own the gas and the system command environment.

Richard Hull