Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA

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Steven Sesselmann
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Steven Sesselmann » Mon Jul 04, 2016 10:02 am

Andrew,

Great engineering and incremental improvements and it's obviously working. Your fusion rate and quotient is improving with every iteration, you are now sitting somewhere between Richard Hull and Jon Rosenstiel on the list, despite running at lower voltages then Jon. I shall hold off putting name on the list until you report back again after a 70 kV run.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Andrew Seltzman » Tue Jul 05, 2016 4:27 pm

Best run to date is 1.4e6 n/s, at a slightly increased pressure of 7.8mtorr, 40kV and 8.8mA. 1e6n/s is now easily achievable with 1.4e6 n/s possible with some tweaking. Best to add this Q value to the list for now, it might be a while before the system is capable of 70kV operation.

The molybdenum cap under the grid is also heating up during the runs, getting into the dull red range. I might switch to a stainless cap and braze it onto the grid tubes for better heat conduction to the coolant.
SAM_5073_crop.jpg
Has anyone noticed how the bubbles seem to be clustered towards the center of the dosimeter? Is anyone else seeing this of their BTI?
SAM_5091_count.jpg
rate.jpg
Here is a list of Q values for university fusors, mine is currently at 4e6 n/s/kw
UW-Q.jpg
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Richard Hull
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Richard Hull » Tue Jul 05, 2016 4:48 pm

Keep pushing that pressure!! Old hands who have been here for years, and still working with their fusors, will tell you.......Once you have a fusor working over 35+kv, GO FOR PRESSURE!! My very best runs are always over 10 microns and my best run, ever, of 1.58 e6 neutrons was at 42 kv applied and 15 microns! Right after doing fusion, the secret is to run and run and run and learn with each run. Learn operational technique!

We are working on a ragged edge, bull-heading fusion in a very narrow zone not found or to be had casually for the finest results. Even the finest constructed systems from the best materials have to be considered crude based on our modus operandi in doing fusion. In the end, the science allows it to happen, but operational artifice makes it happen. Improved artifice makes it happen better.

Newbs who come, see, marginally do and then leave, never develop the artifice for any number of reasons. Yes, the fusor, as we typically configure it, can only go so far, but pushing it becomes an art and craft.

I have trumpeted this for years here in numerous postings. It is good to see someone pushing their individual envelope in continued work with a good fusor system.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Steven Sesselmann » Wed Jul 06, 2016 12:08 am

Interesting, I just looked up some information on the SIGFE reactor and I never realised how close the construction is to my current FICS design, as in FICS the cathode is semi enclosed with ions entering through holes, forming almost a hollow cathode, it also has electron suppression. SIGFE and Hirsch design clearly stand above the rest in terms of efficiency.

The only critical mistake they made IMHO is to accelerate the ions into the cathode, obviously they believed ions need speed to overcome a coulomb force and fuse, quite to the contrary I think the ions need to stand still before they can fuse, but time will show.

Steven
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Andrew Seltzman » Mon Jul 11, 2016 3:01 am

Latest run updates:
2.4E6 n/s at 39.8kV, 17.68mA, 9.24mTorr
SAM_5106.JPG
SAM_5109_count.jpg
SAM_5110_count.jpg
neutron-flux.jpg
This higher current run was made possible by paralleling 2 spellman PTV power supplies to double the output current
SAM_5114.JPG
A new plastic insulator was machined that allows 2 HV cables to be plugged into the grid via a splitter adapter. This insulator will also allow use of the 70kV supply that has a larger cable.
SAM_5101.JPG
SAM_5095.JPG
SAM_5111.JPG
A control connector is then made to allow the master supply's current monitor line to drive the slave supply's current program line
SAM_5113.JPG
Both supply's are then run in constant current mode at slightly below the voltage setpoint

There are definitely heating issues on the moly cap, with it now becoming bright red. The macor is still holding up very nicely with no discernible outgassing, even when in contact with the red hot moly cap. I'll probably have to switch to a stainless cap brazed to the grid structure if I want to continue at these current levels.
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Steven Sesselmann » Mon Jul 11, 2016 3:25 am

Andrew,

You are really cooking now, heading towards the 5 meganeutron mark, I trust you are keeping a safe distance.

Even at this emission rate the efficiency has remainded roughly the same.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Andrew Seltzman » Mon Jul 11, 2016 3:37 am

Runs are kept short for safety(and thermal issues)
x-ray rate at the viewport surface is 10-15mR/h through the lead glass shield
neutron rate at the surface of the vacuum vessel is 140mR/h at 2.4E6n/s
Runs are 30s with the two parallel supplies, about 60s with the single supply, and I only run long enough to get good counting statistics from the BTI dosimeter, so about 2-3mR of neutrons at the surface of the fusor(~3.5" from focal point) per run. I'm usually about 1-2ft from it so it drops off a lot due to inverse square law.
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Steven Sesselmann » Mon Jul 11, 2016 3:56 am

Andrew,

I know only too well how fast the minutes pass when one is fiddling with the knobs on a fusor, big difference between 30 seconds and 5 minutes. At those emission rates I would want to be further away than 2 feet.

My new fusor may not achieve 5x10^6 neutrons like yours, in any case I have built it for remote operation with a 10 metre fibre optic control cable extending to my laundry behind a 2 foot sand stone wall.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Andrew Seltzman » Mon Jul 11, 2016 4:08 am

Agreed, adding more shielding is next on the to do list. In this case there isn't really any way to push the runs any longer, the difference between 30s and 40s of operation is the moly cap not glowing and glowing bright red, it's a pretty reliable timer.

More automation is also in progress to allow remote operation, I bought a labjack T7
https://labjack.com/products/t7
to monitor and control the fusor. It has an ethernet interface and numerous digital and analog outputs for control.
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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA

Post by Richard Hull » Mon Jul 11, 2016 4:23 am

Great Work! I guess the best of all current operating fusors!!! Very, very clean system and star. Those ion sources are making a real impact. Plus ultra all the way.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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