Anode layer ion source. Operation pictures

[Werner Engel]

Hi Andrew!

Great that you still work on the fusor! Thanks for all your posts - great pictures and details!

What kind of "laser density probe" do you use in this case?
Interferometry, reflectometry, scattering, refractive index?

BR,
Werner

[Andrew Seltzman]

Hi Werner,

It's going to be a CO2 interferometer.
http://www.rtftechnologies.org/physics/ ... ometer.htm

Andrew

[Werner Engel]

Hi Andrew!

Congratulations to your final picture (the one showing the interference pattern)!
It's an enormous amount of work doing this @10,6µm with all the special materials. The carbon-pipe is it really stiff enough? What about vibrations from the roughing pump? Or did you switch off pumping during the measurement? Did you choose the 10,6 due to absorption of the plasma to be expected at that density (plasma frequency) or to reduce vibration induced problems?? Thomson Scattering is done @1064 nm (Nd:YAG) at the Tokamak in Garching. It seems they do not care about wavelength. But other refractive index measurements try to use as large as possible wavelengths.
I just built a “normal” HeNe-Michelson to get comfortable with optics. But this will be adapted in several steps.

Attached a Picture of my Michelson and one of the Nd:YAGs in Garching.

BR,
Werner

[Andrew Seltzman]

New modifications to the anode layer ion source:

The old flat anode ring has been replaces with a conical anode ring (6.6 degree inward) for better beam focusing. this should have the focal point about 3" in front of the face of the source, right at the focal point of the fusor. In reality there still is the effect from space charge repelling the beam so it doesn't focus to a point, though the beam is considerably better defined with a tighter focus.

The NdFeB magnet has also been replaced with a SmCo magnet for higher temperature operation(up to 300C instead of 80C for the NdFeB)

Stainless Steel Belleville Disc Spring (mcmaster 9713K437) (6.6 degree inward angle) and jig to bore to correct ID

New and old anode rings

SmCo magnet installed

Modified injector re-assembled

Ion beam

Video of operation
https://www.youtube.com/watch?v=DbfmR5t ... e=youtu.be
https://www.youtube.com/watch?v=UDQ1BAH ... e=youtu.be

[Andrew Seltzman]

Additional pole pieces have been tested to determine the effect of the magnetic field position on beam focusing
Numbers 1,2,and 3 from left, pole piece 1 was the one used in all previous tests
The version 1 has a 1/8" step of 0.5" dia, then a 1/16" step of 0.625" dia, then a 45degree taper over 1/16"
The version 2 has a1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/16"
The version 3 has a 1/16" step of 0.5" dia, then a 15degree taper over 0.1875"

Version 2 pole piece and plasma focus

Version 2 pole piece recessed and plasma focus

Version 3 pole piece and plasma focus

Version 3 pole piece recessed and plasma focus

[Andrew Seltzman]

Further pole pieces tested
Numbers 1,2,and 3 from left, pole piece 1 was the one used in all previous tests
The version 1 has a 1/8" step of 0.5" dia, then a 1/16" step of 0.625" dia, then a 45degree taper over 1/16"
The version 2 has a 1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/16"
The version 3 has a 1/16" step of 0.5" dia, then a 15degree taper over 0.1875"
The version 4 is 7.5mm long 14mm dia
The version 5 has a 1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/8"
Version 4 and 5 have a pump out groove milled in the base to vent the trapped volume inside the magnet

Version 4 pole piece and plasma focus

Version 5 pole piece and plasma focus

Version 5 is going to be the final version used to upgrade the ion sources, it seems to hold the best focus

[Steven Sesselmann]

Andrew,

Once again I commend you on your engineering skills and systematic approach to solving a problem, this work on your anode layer source would be worth writing a paper on.

It will be interesting to see if the narrower beam increases the fusion rate or efficiency.

Steven

[Andrew Seltzman]

Performance curves for the anode layer ion source

[Andrew Seltzman]

I finally got around to converting all the drawing for the ion source from my old cad program (KeyCad, made in 1992) into a modern program (Autodesk Inventor) and made some 3D models:

[Werner Engel]

Did you allready try to focus the beam? Maybe with a Wehnelt cylinder or an einzellens?
Or is this even planned?
Higher luminosity would be nice - I think.