Fusor Forums

Hi,
I justed finished a small neutron source for detector testing. The function was proved with indium- and silver-activation. The source works with a simple canal-ray ion source and a titan target. The working gas is deuterium from a lecture bottle. The accelerating voltage is arround 100 kV, the target current only some 10th microamps. Both HV-supplies, for the ion source (max 25kV) and accelerating (max 120kV) are simple homemade device, flyback inverters with voltage multipliers. The moderator is made of PE-HD. In spite of the low power and current the activation is remarkable, 90 counts for silver and 30 counts for indium.

Thomas

The plastic hose and the small design does solve a lot of Isolation issues - congratulation!
I can't see the RF generator for the ion-source - or am I missing something?
How did you solve the isolation problem between the RF coil and the next KF fitting?
Great work!

Hi Werner,
the copper coil you see is not a rf-coil but a capillary tube to feed the deuterium to the canal ray ion source. The ion source is driven by dc current (20kv, about 200..300µA). Construction drawing will following.

Thomas

Nice work, Rapp, your posts are always an enjoyable read.

Keep the updates coming.

RT

Really sweet beam on target fusion effort! Thanks for your continuing efforts and sharing with the group here.

Richard Hull

Hi,
a schematic of the source



and a image of the tiny ion beam



Thomas

It looks as if the system is, effectively, differentially pumped due to the fine holes in the anode and cathode to the right as the glow in the right half seems rather bright, (higher pressure) and the deuteron stream is nice an dull pink in color, (lower pressure). Am I correct here?

Richard Hull

Hi Richard,

you are quite correct. Mostly because of the fine cannel in the cathode the pressure in the accelerating space is low enough. Otherwise there would be a discharge between cathode and the suppressor. The fine hole in the anode and the long capillary (0.8 mm ID, 50cm long) helps to regulated the pressure with the throttle valve .

Thomas

I'm using a similar device to prevent the plasma from igniting through from the chamber back to the MFC.
It's just a small piece of tiny steel pipe, connected to a KF seal ring.

I think I will call it "plasma backdraft restrictor - design ENGEL"
Sounds nice- does it?

I think Steven Sesselmann could also use it.

I always liked well thought out differential pumping schemes that relied on controlled leaks between chambers, rather than two pumping systems.
Really cool trick, guys.

Richard Hull

Hi,
the tube is becoming cleaner because of beeing evacuated for some days and the flashover rate is decreasing substantially . So the accelerating voltage can be hold a 90 kV and I get rather hot samples. The two shortlife isotopes of silver are nicely seen.



Thomas

Super nice work! Could you provide details (including components) for the high voltage system?

Hi Denis,
like wrote the power supplies are simple inverter circuits.

100kV Supply for accelerating
http://www.rapp-instruments.de/imageurl/neu/100kv.jpg
http://www.rapp-instruments.de/imageurl ... 00kv_1.jpg
http://www.rapp-instruments.de/imageurl ... 00kv_2.jpg

20kV Supply for the Iion source
http://www.rapp-instruments.de/imageurl/neu/20kv.jpg
http://www.rapp-instruments.de/imageurl ... ge20kv.jpg

Thomas

Really impressive work and build!

It's notable that this system, unlike a fusor, does not need a high current high voltage supply.

I am actually thinking of building something in this vein.

While my deuterium accelerator is finished (and has collected dust now for over two years since my efforts were directed to a fusor; which I am very happy to say, was very successful), my rather large voltage multiplier (VM) that I had built for it only reached 60 kV (still haven't tested the giant Van da Graaff I built originally for that purpose - conditions just are never right); I have now added two more stages (this weekend) and then ran the variac to 50% of its scale: the new stack (in air) reached 50 kV. A good sign. So, I will next build a new oil tank and see what this monster will give me.

With a massive resistor (for safety) I will use this new VM for my accelerator; that is, if it can really achieve the +100 kV or higher (maybe.)

In any case, I am now moving on this project again, and we will soon see, I guess. If this VM fails to reach an acceptable voltage I will have to concede it is time to disassemble the accelerator and retask the high vacuum system (not sure for what. Maybe even sell it. I have to say, I like my DP system better for the fusor and have no interest for a turbo in that system.)

I will soon start a new thread and post pics of the new VM once I get this new power supply working in its new oil tank ... .

I am glad to see this thread again - got me motivated once more; still, that is a nice system.