60 Minutes segment last weekend "Cold Fusion"

[Tim Gray]

That low-level energy inputs can be concentrated to produce localised keV energies is now well-established. Two of my favourite recent Nature papers involve making neutrons by gently heating a pyroelectric crystal, and X-rays from sellotape:

I think that's the sticking point for me. It needs to be more than localized for power applications. We've been generating fusion neutrons for years, but it needs to be large scale to get to the point where it can be stuck in a power plant.

Shouldn't this topic be in the lounge?

 

[nworth]

The neutron generators in nuclear weapons utilize D-D and D-T reactions. The acceleration potential used to be on the order of 50KV, and a lot of neutrons were produced.

 

[alanrockwood]

Tim,

Is there an asymptotic formula that does a good job of correlating and extrapolating the data in the chart to low collision energies? Ideally this would be based on some kind of theoretical considerations, and not just an engineering correlation.

As I think about this in terms of a collision problem (from a kind of hybrid view, but largely as a problem in gas-phase kinetics, with a smattering of over-simplified quantum theory thrown in) I see at least several significant factors. They are inter-related, but could be considered somewhat separately. 1) What energy is required to climb the coulomb hill. 2) How long do the nuclei spend near the turning point - probably significantly less than one vibrational period of a "conventional" diatomic vibration, so a vibrational period could be taken as a very conservative upper limit. 3) What is the probability of fusion as a function of internuclear distance - probably determined largely by tunneling. 4) What mechanisms are available for stabilizing the newly formed Helium nucleus, which will be in a highly excited state. 5) What selection rules and/or rates would govern stabilization. 6) What role does angular momentum play, since a direct head-on hit will be a low probability event.

 

[Tim Gray]

I don't know of what's out there for low collision energies.

Just to give you an idea of the quantities involved, for thermonuclear fusion of DT, either magnetic or inertial, a triple product is used as a formula to estimate when you will have ignition, which is the goal. At this point, the energetic helium ash can deposit enough energy in the plasma to maintain continued fusion reactions. Anyway, the triple product is basically density * temperature * time. You need to keep enough particles together for long enough that are hot enough to fuse. You can reach ignition from different approaches. Inertial fusion jacks up the density at the expense of the time the atoms are held close together (confinement time). Densities are 1000 times solid densities, confinement times are extremely short (ns-us, not exactly sure). Magnetic fusion goes the opposite way, long confinement times (seconds) and lower densities (10^20 particles / m^3). Temperatures are roughly the same - 10's of keV.

I just did a quick search ('low energy fusion cross section') and saw a couple papers out there which talk about the cross section down to about 4 keV. I didn't see anything much lower than that.


nworth: I assume you have some experience with this stuff, noting your location

 

[Bob F.]

The broadcast did miss alot . I wanted to hear more about the company they mentioned called Energetics Technologies.
I checked them out on the web and it turns our it is an American company
and their work has been replicated by the other 2 labs show in the story.
Here is is a link to their website.
www.energeticstechnologies.com

Lol! - I wonder what company Mr OldGeek works for? Do a google: he has spammed this all over the 'net...

 

[Ole]

Interesting titles they use in that company - "Chief Visionary Officer", anyone?

But the CVO is no anyone - he's Dr. Irving Dardik, MD!

 

[Joe VanCleave]

Sandia's Z-Pinch Program

The Z-Pinch inertial confinement method being researched at Sandia promises a long-term road map to a functioning fusion power plant.

Here's a link to a lengthy PDF of the program overview.

Here's Wikipedia's overview of the Z-Pinch Sandia machine.

~Joe

 

[Struan Gray]

I think that's the sticking point for me. It needs to be more than localized for power applications.

True, but there are some interesting applications for a tunable benchtop neutron source, and that's before you get into the wilder power-source-on-a-chip dreams of the nano-technologists.

Lund is in the final stages of bidding and raising funding for both a new synchrotron lab and the European Spallation Source. If funded they will be built all over one of my favourite lunchtime photo-hunting areas. If I can persuade the powers that be that all we really need is a Bunsen burner and a roll of sellotape I'll be happy

 

[Tim Gray]

True, but there are some interesting applications for a tunable benchtop neutron source, and that's before you get into the wilder power-source-on-a-chip dreams of the nano-technologists.

No doubt. And that's ample reason to study these kinds of configurations.

 

[alanrockwood]

... there are some interesting applications for a tunable benchtop neutron source...

There is actually a benchtop neutron source, though I don't know how tunable it is. I believe it has been commercialized by a German company.

The device is called a "fusor". It was invented by Philo T. Farnsworth, the person largely credited with inventing television. Interestingly (for me at least) Philo was my grandmother's cousin, and I met his widow at a family party some years ago.

 

[alanrockwood]

Some twenty years ago I worked at a company where a Cornell PhD graduate also worked. He told me that in the fusion program they scheduled their "breakthroughs". It was all part of the funding process.

This all reminds me of the saying: "fusion is the energy source of the future. Always has been. Always will be."

 

[alanrockwood]

If you could shorten the D-D bond length by a bit (I don't remember how much, but I did research this back when cold fusion was in the news, and as I recall it was a few tens of percent) fusion rates would become significant. In that kind of a system you don't need to have a high tunneling rate, unlike in a collisional process, because the nuclei would be close together for a long long long time, unlike in a collision where they are in proximity for picoseconds or less (probably much much much less.)

 

[spark]

PhD's at universities publish grad student research to get more grants to hire more grad students to do more research. Its a terrific energy source that bypasses the laws of thermodynamics and economics by using those of P. T. Barnum.

 

[Tim Gray]

Some twenty years ago I worked at a company where a Cornell PhD graduate also worked. He told me that in the fusion program they scheduled their "breakthroughs". It was all part of the funding process.

This all reminds me of the saying: "fusion is the energy source of the future. Always has been. Always will be."

I have to call bull on this. A lot of people work really hard on it. Nobody schedules breakthroughs. The larger projects (10's of millions of dollars/year) do have milestones each year, and like in any large bureaucratic system, they are set conservatively so there is little chance of failure. However, at least since the late 70's/early 80's, the whole 'fusion will be here in 20-30 years' was dependent on an Apollo style funding scheme. Budgets that grew every year, as needed. Needless to say, that didn't happen, and instead large cuts happened. Even now, 25 years later, the US fusion budget is only a fraction of what it was in the early 80's (in real dollars).

Personally, I think it's ridiculous that we only budget about $300 million a year for this kind of research. Oil won't last forever. And if you think $300 million/year sounds like a lot of money, look into to how much fission reactors cost to build now and how long they take to be built. The last plant built in the US took 23 years to build. I've also read that new plant cost estimates are in the $15 billion range.

The rest of the world seems to have a clue. Japan has two billion dollar class projects, and they fought tooth and nail with France to host ITER, just to be able to foot 50-60% of the $10 billion in costs (ITER is the international collaboration to build a tokamak that reaches a Q of 10; 10 times the energy out that was put in). France fought back and is the host. The EU has several large devices in operation. The US on the other hand rejoined ITER late as a minor partner, after we helped start it all in the late 80's. We wanted nothing to do with hosting it. The US's most advance fusion project was initially built in the mid-80's. Though it has been upgraded... way to go USA.

 

[nworth]

An interesting, truly tabletop device is available commercially for neutron production. It is the Zetatron (http://en.wikipedia.org/wiki/Zetatron), and it was derived fron the neutron generators used in nuclear weapons. But this device is a long term laboratory tool rather than a one shot device. Some models are tunable, at least to some extent.

 

[keithwms]

Not quite sure how we got onto the subject of tabletop neutron sources, but if it were me, I make up a little H2 plasma bottle, strip off electrons to get protons, accelerate the protons across whatever potential I choose, and then slam them into paraffin. Neutrons aplenty. Looking at that 'zetatron' schematic, I'd guess that the "target" is a paraffin block. As I learned form my visit yesterday, if you want gobs of neutrons but don't want a reactor, then you'd use the technique at the SNS in Oak Ridge- liquid mercury getting slammed with protons from a simple linac. A cuter and more compact technology is the DWA (dielectric wall accelerator) now under development for medical applications at Livermore in collaboration with Tomotherapy. That proton therapy device will be in every cancer hospital within 2-3 decades, mark my words.

I am skeptical that one would want all that zetatron complication in a weapon... it's easy to generate a shower of neutrons from fission. OTOH maybe the zetatron finds application in the baby nukes that contain a net sub-critical mass. But I digress

 

[alanrockwood]

I have to call bull on this... Nobody schedules breakthroughs. The larger projects (10's of millions of dollars/year) do have milestones each year, and like in any large bureaucratic system, they are set conservatively so there is little chance of failure.

Tim,

You could be right that nobody schedules breakthroughs. All I am doing is propagating an unsubstantiated comment from someone I knew who also had known some of the fusion guys. (I think this is what is known as spreading gossip... guilty as charged.)

On the other hand I once worked on a US department of energy-funded project. It would not be considered a large project on the scale you proposed (10's of millions of dollars per year)... probably more along the lines of a medium sized project (around a million dollars per year.) We had an interesting mandate for the project, which was to design and build an instrument that was beyond the state of the art, and we had to do it with a zero probability of failure. (I realize that those are mutually incompatible requirements, but that was the mandate.) This wasn't exactly scheduling a breakthrough, but it would come pretty close to that characterization.

One of the things that the project required was to acquire a superconducting magnet having a combination of field strength, bore size, and stability significantly beyond anything that had been built to date, and we had to do it with a limited budget. It turned out to be impossible using the then-current state of the art, so we had to scale back the field strength a little. I left before the project was finished, but I understand from those who stayed that the stability of the magnet was a little disappointing. However. in the end the instrument set a new standard for that type of instrument.

 

[John Koehrer]

Many technologies weren't around 100--200-300etc years ago.
When the people working on them were held up to ridicule.
Today, some of those experiments and theories that were off the tradtional
direction of then current science are now everyday things.
I guess the point is "never say never".