Fusor Forums

Hello all,

I have good news for all fusioneers. There's a new neutron detector on the market that should be just the ticket for most fusors. It is the "Domino" detector, manufactured by Radiation Detection Technologies, a spinoff from Kansas State U.

It is a small detector (active area about 4 cm^2) with a silicon detector that has microstructured grooves etched into it. The grooves are then filled with 6LiF powder, and the silicon detector counts the charged particle reaction products from the 6Li neutron capture reaction. Onboard electronics output a LVTTL square wave for each neutron detected. Gamma rejection is quite good. The detectors are also "tileable", and can be plugged end-to-end to increase total detection area.

I work in the radiation R&D world, and I have hands-on experience with a few of the V3 Dominos. I have been impressed with the Domino's simplicity and ease of use compared to traditional He-3 tubes. Since the Domino can only drive a 1kohm load, we made our own driver board with a line driver for a 50 ohm load, but I would think Arduinos or a simple digital counter could interface directly with the LVTTL output. RDT also has their own driver board for sale.

Price is reasonable. I can't give a number since I got my quote for a business, but it's on the order of what a few BTI bubble dosimeters are going for. If you are going to request a quote, please be courteous and patient. They are a small company.

http://radectech.com/products/rdt-domino

Very interesting. How would you say it compares to a bubble detector in terms of sensitivity and only detecting neutrons?

Unlike the bubble detectors, this device looks like it's designed to detect thermal neutrons. So like BF3 and HE3 tube users, one would have to place the device in a moderator to detect the fast neutrons emitted by a fusor.

Also, 20% is not great efficiency, 30% is a little better. Remember our flux is close to zero. Who is gonna' blow the big bucks and run a test on one of these?

I notice the cps/nv is low. The 20% model is only .57cps/nv the best 30% is .85cps/nv and the yet to be developed 40% model is only 1.25cps/nv.

My 3He tube is rated at 70cps/nv. I don't think I will be rushing out to lay down the big buck for one of these new detectors.

Pricing? Who knows? No real data on pricing. Betcha' they ain't cheap. Electronically they are great! A simple 5 volt device and a 1kohm output impedance is fantastic. A neutron detect could directly flash an LED if you stretched the pulse length. No amp needed. Fabulous for the electronics simplicity, but what about those rotten cps/nv figures? Buy 'em by the bag full and build the ultimate neutron detection plank or wall to reach 70cps/nv. Do it for under $1000 and you have got something then. I imagine the 30% units are in the 1 grand each range.

Richard Hull

If the amateur is interested in playing with this type of detector, you could make your own. In a previous post regarding a detector meeting, I posted:
"Lithium-6 (usually as lithium fluoride) is also being used in all three types of detectors. The most interesting report in terms of what the amateur might do was a report of putting Li-6 on bare silicon photodetectors (these can be purchased bare). Solutions of LiF were painted on the silicon surface and dried to make thin films. The speaker said he actually did the preparations in his office with no sophisticated facilities. The Li-6 was purchased as LiF from Sigma-Aldrich for $7 per gram (which is quite cheap, and a gram would be enough for lots of thin films) but he bought a kilogram to get this price. It is probably sold in smaller quantities, but another problem for the amateur is that Sigma-Aldrich usually won't sell to individuals."
I subsequently bought a gram of lithium-6 fluoride for $50 (on Amazon!), but I haven't gotten around to trying it yet. A likely problem, however, is that the silicon detectors being commerciallized tend to have etched groves or holes to increase surface area. The home brew detector would only have a plane surface. Nonetheless, they could be made cheaply and one could make a large array of them.

"Price is reasonable. I can't give a number since I got my quote for a business,"
Since no price is listed on the website, what was the quote they gave you?

"Solutions of LiF were painted on the silicon surface "
What would one use to make a solution of LiF?

Like I said, about the cost of two bubble dosimeters. Approximately $350 each, YMMV, get yer own quote.

The detectors are 4 cm^2 active area, and the "low-end" detectors are 20% efficient for thermal neutrons. That puts its thermal neutron efficiency at 0.8 cps/nv. Their data sheet shows that in a real-world test with a Cf-252 neutron source it clocked in at 0.57 cps/nv, which ain't too shabby. What low-output fusor couldn't manage a flux of a few nv to give a solid few counts per second in a block of poly next to the vacuum chamber?

Comparing it to a 70 cps/nv He-3 tube is a bit of a apples-to-oranges thing, as a that's a monster size. Tile enough of these detectors to equal the active area of a He-3 tube, and they can hold their own. Size matters when it comes to neutron detection.

I take a few to mean 5 X $350 or well beyond the $1000.00 per each of these new solid state detectors, as I predicted. And your quote was for industrial or corporate use. (probably got a break on price) Private individuals can expect a bit more pay out to get one of these marvels.

I eagerly await the first report from a Fusioneer with a warranted, working fusor who manages to get his paws on one of these detectors and reports his results. If you have $1500 to spend, I suggest a surplus 3He tube. Only have $300?..... Try a surplus BF3 tube. Only have $150?..... search for one of those old surplus GE boron lined tubes.

The fusor community is a nefariously pocket poor collection of souls. I am sure a couple of old hands here can afford one, provided the wife doesn't catch wind of the purchase. I could easily handle it, but with the nice BF3 I have, it would be tossing money at a completely solved issue.

Richard Hull

Sorry for the confusion, I consider "a few" to be less than five I edited the above post with "two" instead of "a few". Anyways, I think the latest quote for a BTI dosimeter was $160? For the price of two BTI bubble dosimeters, you could buy a Domino.

The Domino costs about $300 - 350 each, depending on quantity and efficiency, which does in fact put it in the range of most penny-pinched fusioneers (at least those contemplating buying some bubble dosimeters). Plus, no HV supply, preamp, amp, scaler, cables . . .

All right guys.. get out there and buy one of these puppies and report back. Just make sure you have a working fusor of at least 250,000 n/s before buying one and reporting back. We will not trust these until a confirmed and accepted report. Specs mean nothing until the rubber has met the road. Remember, neutron detection is easily messed up by the rank amateur and almost always by the newbie with no electronic experience. This is why BTI is king and all electronic systems remain suspect without a highly critical review of all detectors and instrumentation.

Pay very close attention to the recommended moderator by the manufacturer.

Richard Hull

I think I will give them a chance and try the components. I'll keep you informed. But it will take some time ..
BR,
Werner

Most important in a report is about at what point in fusion are these things reporting out of any noise or background. Newbies attempting fusion are typically way down in the fusion level. 5,000 - 20,000 neutrons, isotropic.

Richard Hull

The new device arrived!
Unfortunatly I will not have time to test it within the next weeks.
But working in my head on a test szenario ...

Has anyone else tried to get a hand on the new DOMINO?

We look forward to your future reports on the device. Naturally, we would hope for an older neutron detector reading versus the new solid state detector in a single run for comparison. Thanks

Richard Hull

OK - it took some time - but finally I got some results.
Attached you find the data Philipp and I collected at one of our local research-facility neutron sources.
It seems that the device (within the small red box) is not so much depending on slow neutrons - which is fine!
The source has a very low gamma emission and we hope that the counts we got are almost only from neutrons.

We also did some tests with a Cs-137 source – so we have an idea how sensitive it is to gamma radiation.
We plan to compare it with a brand new detector type (and with a white neutron beam from a nuclear reactor) which is still under development – but this will take a while.

Hope to hear from you - is someone else is going to test it - please come back to me to compare the numbers.

BR,
Werner

Werner
your report would make more sense if the axis on your graphs were labeled properly

... and here is the moderator now containing the new detector.
It will be filled with paraffin today.

Very nice. Looks like you made the entire thing with a 3d printer?

yes, I printed it and filled it with wax.
I can send you the print files (or Inventor files) if you need them.
Attached is a pic of the filling process (with cooling). I used a hose - not the funnel.

There is a group buying effort for these detectors at $469..

https://groupgets.com/campaigns/290-dom ... ector-v5-4

Werner
I did ask you to correct the graphs but after a few months you have not
1./ your data flys in the face of the detector published data
2./ detector sensitvty increases as the neutrons are thermalised your graph shows the opposite??
3./ why a ball for the moderator, the detector is planar so should have been rectangular for best response