Archived - My setup operating

[John Futter]

Just a quick note to show a substantial ion beam with 100kV acceleration --and yes that is nearly 400 watts of ion energy. power supply is capable of 40mA @ 150kV
pic

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pic control rack with relevant equip to monitor the operating vacuum with ion source running base vacuum is 1 x 10^-7 torr before letting in gas to the ion source. Source is running @ 1.6 x 10^-5 torr
Radiation monitor at the control panel this is now just acceptable it was a 1000 times more than this before substantial mods

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Overview of the experiment containment -filled concrete block 2 deep walls with 1.6mm steel sheet over
radiation levels around the outside are around 5uSv/hr 2 meters or more away while running

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[Richard Hull]

Nice setup, John! What is the ultimate goal? That's a lot of ion capability and a lot of associated x-radiation.

Going for some beam on target fusion?

Richard Hull

[John Futter]

Richard
This is for nitrogen implanting
But I'm hoping to be allowed to try a beam on target of D2 into
Ti target or similar.
The present ion source is a copy of Andrew Seltzmans anode layer source (much simplified). This is capable of around 15mA of ion current but backstreaming electrons are being accelerated by my 8 stage accel tube back to the ion source and of course there are more secondary electrons being redirected to the ion source. This in turn heats the ion source and the magnet losses its lunch. I have put a couple of big magnets near the target in the chamber to mitigate most of the secondary electrons. This change allowed me to go from 1.5mA to 4mA ion current and my x-ray flux is down by a factor of 6.
Next week i'll up the ion current to see when the magnet overheats in the ion source or the x-ray flux becomes unmanageable. All I have to do is open the leak valve a little more.
Not shown in the pics is the two 750L/s diff stacks that are generating the vacuum.

I might put up a few more pics next week

[Dennis P Brown]

Very impressive - just wondering if have you measured the X-ray radiation from the set up both in and out side the shielding? (I can't read the value in the picture.)

[John Futter]

Dennis
The meter is just shy of 2mR/hr just safe for a radiation worker for a few hours per day
inside the enclosure it is about one hundred times this amount.
I did post elsewhere on the progress some time ago
ie here http://www.coultersmithing.com/forums/v ... f=45&t=757
this gives the trials to get to these voltages and mitigate radiation

I'm doing this for work and i'm allowed to share some of it as it pertains to others doing things safely

enjoy

[Dennis P Brown]

Thanks.
Didn't know those two were the same device. Rather high radiation level considering (inside the shielding!) Glade I shielded my system for 750 kV electrons/X-ray (not that my Electro-Static Linear Accelerator (ESLA)) has produce even a single electron at 0.0001 V by thermal emission much less the 250 kV I had hoped for.

Here's to fixing the damn VdG (Van de Graaff.) I've now installed a new belt, redesigned collectors, reworked the rollers, added a newly designed high voltage spray emitter and upgraded the 25 kV power supply to one outputting 75 kV and ... well, the list is long. The previously working VdG stopped producing even 10 kV for no reason I could determine; so, hoping for at least 1 volt out of the thing with all the upgrades ... . The entire instrument is ready except no high voltage field!

I could install a 125 kV power supply I have access to (2 - 5 ma) but realize that is far, far beyond my safe operating abilities and I would rather junk my ESLA system before attempting that level of desperation (lol.) Seriously, no way I'd used that power supply in such an unshielded configuration and no way I'd build the required cable/shield system - the system would still be far too dangerous.

Either it is an operational VdG for me, or the highway; the damn VdG worked fine until the first shorting occurred on the LA tube and I spent a year redesigning the LA tube to prevent that from happening.