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emmetb wrote: No idea if a plasma focus is powerful enough to be used directly here… They need particles with energies approaching the GeV range: http://www.world-nuclear.org/info/inf35.html

It seems ion energies in the reactor will fall short of that range by a couple orders of magnitude

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Rezwan wrote:

2. this approach to fusion was invented in 1963 and is still in the lead.

In the lead of what? I think what you’re trying to say is that the DPF, invented in 1963, routinely accomplishes fusion. The idea that it could actually achieve net energy from fusion has proponents, and is currently being tested. If the results of this test are positive, then we are in for a wonderful new world.

It’s a race toward break-even. I believe the Polywell will get there within another 5 or 6 years. But DPF is in the lead. In Eric’s words, “we have a bit of an edge”.

The statement places all that “fusion is fifty years away” rhetoric into context. It’s already been 47 years, for DPF, and that research effort has produced results.

5. this thing generates the strongest magnetic fields ever produced, equaling those on a neutron star, without huge external magnets

Where’s this from?

If i recall correctly, Eric mentioned the neutron star in the Google tech talks video. Periodically, we see announcements of “the strongest magnetic field ever produced” and it’s always somewhere between 10 – 200 Tesla. The fields in FF-1 already exceed those, don’t they?

6. the top three fusion research programmes are all funded, and racing toward break-even. it will happen sooner than you think.

Funding is always precarious, for all fusion programs. And LPPX could use more funding.

Try: it “could” happen sooner than you think.

Replacing “will happen” with “could happen” weakens it too much. Though i might append,
“but with your help, it will happen sooner”

For me, the purpose of advertising will be to sell generators, and to negate the lights-out, doom-n-gloom future that’s being flogged so heavily, right now.

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Aeronaut wrote: Wow. 90dB sounds fantastic, but achieving it sounds like a mechanical nightmare. Would welding the enclosures to ground achieve the same results? Also, would locating the DPF below grade increase attenuation enough to be worth considering?

I imagine welding would be okay. The specification prohibits soldering, because high currents will melt it.

You want to make wires as short as is feasible, (including ground wires) to avoid any antenna-like effects. Each device and signal path has its own enclosure, and you want all the enclosures firmly grounded. So if the entire structure is enclosed in a shield, and located below-grade, then yes, that will probably help.

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Brian H wrote:
They’d still have to co-ordinate firing and recharging, etc. I think you just invoked an exponential nightmare.

Doubtful. It should be rather like the workings of a V8 engine, with elements carefully timed, and firing in the appropriate sequence.

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emmetb wrote: how hard is it to breed fissile material using a (modified) plasma focus device?

for that, you need lots of neutrons. DPF isn’t an appreciable neutron source, but that might depend on what fuel you use

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Aeronaut wrote:
The biggest operational safety challenge that I can see is the potential lack of industry-standard NEMA and possibly IEEE approved enclosures and procedures for working with the high voltage pulses and the associated RF noise.

This reminds me of EMP produced by nuclear explosions and lightning strikes, so let’s examine the declassified TEMPEST protection guidelines. These specify that the protective shielding must have 90 dB attenuation, if i recall, which is attainable with enclosures that are bolted to ground each 0.9m, and similar minimum separation between hot electric sources and cool signal paths.

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what are the winning messages? here’s what i’ve been using as teasers:

1. the public is convinced that energy production must be massive, expensive, polluting, and dangerous. but it doesn’t have to be any of these.

2. this approach to fusion was invented in 1963 and is still in the lead.

3. because only charged particles are produced, you can extract energy directly, at high efficiency

4. a proton, accelerated to 600 keV, can smash a lot of things

5. this thing generates the strongest magnetic fields ever produced, equaling those on a neutron star, without huge external magnets

6. the top three fusion research programmes are all funded, and racing toward break-even. it will happen sooner than you think.

7. no, it’s hot fusion. it reaches temperatures in the billions of degrees, all in a tiny micron-size volume

8. it cant explode, it produces no radioactive waste, and the fuel itself isn’t radioactive, either.

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Brian H wrote: Repellant remarks? A malign smear! List some. Those which simply happen to disagree with your personal politics and philosophy don’t qualify, of course. I certainly hope. :zip:

Let’s not bother with that, and instead look to winning messages: those ways of thinking, and arguments that will make mainstream fusion researchers stop dismissing DPF as a side show

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advertisers know that word of mouth has the largest zing

i’d like to have a reactor of my own,
and be the envy of every power company on the block 🙂

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increasing the angular momentum on the external magnetic field might delay the pinch.
i thought the pinch occurred at the end of the pulse, anyway?

but i seem to recall Eric writing something about the possibility of a double pinch if rise times are not closely synchronized.
so it makes sense that rise time is the critical parameter

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let’s see.. search terms could be,
coaxial signal propagation speed; coaxial eddy currents; coaxial velocity factor
much of the discussion is around radio frequency propagation, but the same reasoning should apply to the rising edge of the pulse, here.

the inter-layer coupling capacitance and inductance yields velocity factor,
http://en.wikipedia.org/wiki/Wave_propagation_speed#Calculating_velocity_factor
which depends on respective conductor diameters and dielectric constant of the insulator.

eddy currents are responsible for the skin effect
http://en.wikipedia.org/wiki/Eddy_current#Strength_of_eddy_currents

skin depth depends on the frequency. we’re rather wide-band, here, with the rising edge in ~25 ns, and the pulse lasting microseconds. if 25 ns is 1/2 wave, then f=20 MHz; whereas the bulk of the current is delivered as though it is, say, a ~500 kHz pulse, and skin depth increases through the pulse, as δ = sqrt( (2 ρ) / (ω μ) ).
http://en.wikipedia.org/wiki/Skin_effect

em-field calculations for single and multi-layer coax
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=119816

and there is a book on signal propagation black magic
http://tinyurl.com/33nrh8p

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it is encouraging to see efficiency improve at higher temperatures

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Allan Brewer wrote:
Indeed the whole problem arises because the fast-rising current is only conducted in the outer film of the metal anode. Another possible approach to this might be laminating the metal so there are effectively a very large number of separate parallel metal conductors all of which have an outer film and can carry current?

you have to consider *why* the fast-rising current is only conducted in the outer film: it’s because like-charges repel. they will seek to be as far from each other as possible.

if we had, say, a bunch of separate, concentric, conducting tubes, insulated layer-to-layer, then yes it might be possible to spill high current into each, if we adjust the timing slightly, since the rising edge will travel at different rates in different diameter tubes.

note, also, that this is affected by eddy currents. a moving charge in one tube induces a counter-current in another layer. this is potentially helpful: electrons travelling towards the tips of the cathodes will help induce desired anode counter-currents.

but eddy currents in adjacent layers would be detrimental, so it’s tough to say there would be overall improvement.

the sum of all these effects is a worthy modeling exercise, anyway.

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i like that metric. it’s not about whether someone funds us, so much as whether they fund us again.

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seems to have a preponderance of bio topics. will aneutronic fusion fit in the new paradigm?

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