Battery-powered Particle Accelerator

[Joe Scherrer]

I understand this topic has probably been brought up before, but I've done some searching and haven't found anything. So, here goes...

In the past couple of years, research groups from UCLA and RPI have been working with pyroelectric crystals in an electrostatic particle accelerator to produce D-D fusion. The crystals generate a potential of about 200 kV, and the current flow during fusion is about 10 nA. This gives us power on the order of milliwatts. And yet they are still pursuing such a device as a portable neutron generator (so far the max count is 5000 n/s).

So, let's say you have a lead-acid battery with a peak power output at, say, 300 watts. Hook it up to an HV transformer to step it up to at least 100 kV, and use the resulting potential in the particle accelerator. I understand the power could be diminished significantly coming out of the transformer, but it's still better than mW from pyroelectrics. Why doesn't this work? If it did, I see no point in pursuing pyroelectric fusion in the first place.

[Carl Willis]

Hi Joe,

Your suggestion of a battery-powered accelerator for DD fusion is a reality, and has been commercially viable and attractive for years, in the form of field-deployable neutron generators. For example:

https://www.thermo.com/com/cda/product/ ... 57,00.html

These devices operate using sealed, pressurized (or fluorocarbon-insulated) Cockroft-Walton generators. There is academic interest in other means of generating high potentials, including the pyroelectric, piezoelectric, and even triboelectric (i.e. Scotch tape) approaches. I suppose it remains to be seen what the real advantages are in comparing these newer practices with the standard C-W generator.

-Carl

[Joe Scherrer]

Wow, I can't believe I have never heard of those! I thought handheld neutron generators were something novel.

It seems like a Cockroft-Walton generator would be more efficient and provide much higher currents than other approaches - of course, no need to speculate when there's experiments to run.

On the other hand, my pyroelectric project now seems a little pointless, considering there's already a solution that functions much better. Unless I can somehow increase the ion current...but I'm not sure I'm willing to spend $700 on crystals when the neutron flux is going to be so low.

[David Geer]

Don't discount yourself so quickly unless you can find research/experimentation results for the exact project you are trying to conduct. With the realm of invention, you'll never know what will randomly work better than all the others, at first glance.

Weigh the pros and cons of the experiment and then make your decision on whether or not to follow through.

[Dan Tibbets]

Two considerations. Your car battery would likely deliver 300 or more Amps for short times (like starting a car) at 12 Volts, which would give you ~ 3,000 or more Watts..
Secondly, the pizoelectric crystals would discharge their energy very quickly, so the neutron output would occur in a very brief period of time. Of course this is a pulsed device, so the average output over a second is much less. I wonder how many cycles they could go through in a second, and if their reported output per second is derived from one or several discharges? This brief, relatively more intense burst of neutrons may have some advantages in certain applications. Also, if small enough, they may cluster dozens of such devices and fire them frequently to achieve relatively much larger near steady state outputs per unit of time.

Dan Tibbets

[Brian McDermott]

The thing about pyroelectric neutron sources is that they can be made extremely light, compact and cheap compared to HV accelerator-based neutron sources due to their simplistic design. If you don't need a high output and you need to make a measurement quickly in the field, it is a very attractive setup indeed. There are already pyroelectric x-ray generators that are used for field radiography and XRF measurements (http://www.amptek.com/coolx.html), and they can quite literally fit in the palm of your hand.

Sure, you can run a compact CW multiplier off a car battery and have a mini-accelerator, but if you're looking for a level of portability comparable to a small radiation detector, that isn't exactly practical. With the pyroelectric system, you only need enough power to run the crystal heaters and controllers for a few minutes, so the battery doesn't need to be all that big or powerful. We're talking the difference between something that costs $10,000 and can fit in a suitcase versus something that costs under $1000 and can potentially fit in your pocket.

I was part of the RPI pyroelectric research group as an undergrad, and it was a very interesting and promising project. There's still a ways to go before a consistent device with a comparably high output is realized, but I think it'll happen someday. I wouldn't be surprised if something comparable in size to the Amptek device showed up on the market someday. It is neither ethical nor lawful to publicly disclose what hasn't been published yet, but if people are interested in reading some of the papers that have been published, let me know and I can point you to a few. It wouldn't be all that hard for an amateur with a vacuum system, neutron detector and some deuterium to replicate the experiments that have done.

[Joe Scherrer]

Dan DT wrote:
> Secondly, the pizoelectric crystals would discharge their energy very quickly, so the neutron output would occur in a very brief period of time. Of course this is a pulsed device, so the average output over a second is much less. I wonder how many cycles they could go through in a second, and if their reported output per second is derived from one or several discharges? This brief, relatively more intense burst of neutrons may have some advantages in certain applications. Also, if small enough, they may cluster dozens of such devices and fire them frequently to achieve relatively much larger near steady state outputs per unit of time.
>

Dan, I think you may be confusing your crystals - this is pyroelectricity, when a crystal subjected to changes in heat accumulates a charge. The cycles tend to be about 300 s long.

Brian, thanks for enlightening me! I saw your name on a few papers, and I was curious as to what you were up to at RPI. I've already gotten five or six papers from various labs (mostly Danon's), but if there are any obscure ones you know of, please let me know.

Initially, I'm just going to recreate RPI's experiment (and get some good vacuum experience) and then expand upon it to see how I can improve output. It seems like, with industrial equipment, building something like the Cool-X wouldn't be impossible. Increasing flux, on the other hand, is another story...