[jamesr]

Steven Sesselmann wrote: How do they measure ion energies?

Steven

From the spread in neutron flight times.

A D-D fusion reaction always releases neutrons with fixed energy (ie. velocity). But this velocity is in the centre of mass frame of the two fusing deuterium ions. So the actual velocity of the neutrons will be spread by the thermal velocity of the ions, ie. whether they were going towards or away from the detector at the time.

Since you know the distance the detector is away you can find the velocity from the flight time. The shape of the velocity curve should be roughly Maxwellian, so by fitting a curve to it you get the equivalent temperature.

[jamesr]

So it does – seems a bit strange though.

Part of my confusion was that LLNL is Lawrence Livermore National Lab http://www.llnl.gov – nothing to do with Eric’s company Lawrenceville Plasma Physics Inc.

[jamesr]

I agree with Keith – there s no way this has a chance of confining a plasma.

First you have the ‘hairy ball problem’ – there is no way to make a 3D spherical rotating field that does not leak at the poles (even if the the axis of rotation is itself rotating along another axis). Also if you have a large mass rotating then conservation of angular momentum ie. gyroscope effect, means you have to exert a large force to tilt the inner rotating sphere about another axis.

Secondly, unless you are at the densities of inertial fusion, then the average distance between ions & electrons colliding at fusion temperatures is huge. In a normal tokamak an ion may go around thousands of times before scattering (or very occasionally fusing) with another ion. This equates to km of distance traveled. So unless you have a magnetic field bending its path back on itself then a ‘hot’ ion will just carry on in a straight line until it hits something else, ie the dense wall.

[jamesr]

MTd2 wrote: http://www.photonmatrix.com/pdf/

It hosts the papers linked from LLNL. Great thing!

Is this your site?

I was trying to figure out why you say they’re from LLNL as there is no reference on the site, and the links are to locally hosted files. Also there is no mention of permission to host journal papers (some journals get very picky about their copyright however old the paper may be).

Although looking at the meta tags for the pages show stuff like:

<meta content=”Advanced Learning Advanced education philosophy e-gold Super Health immortality Technology” name=”description”>
<meta content=”Love Secrets, Brain, healthy, Sky Car, FREE E-books, Magic Story, Magic Letters, Scientific Ads,
News and Weather, Flower CDrom, Accept e-gold, own gold” name=”keywords”>

Not exactly the most inspiring keywords.

[jamesr]

Here are a few sites I have bookmarked:

General news
http://spectrum.ieee.org/energy/nuclear
http://www.world-nuclear-news.org/
http://www.ipp.mpg.de/ippcms/eng/pr/index.html
http://www.sone.org.uk/
http://www.nuclearfuture.info/ibis/nuclearfuture/home

On the more technical side, for anyone wanting to learn about plasma physics:
Journals (need pay/institutional access for full papers but not news or abstracts):
Physics of Plasmas http://pop.aip.org/
Nuclear Fusion http://iopscience.iop.org/0029-5515/
Other IOP Journals: http://iopscience.iop.org/search?searchType=fullText&fieldedquery=plasma+focus&f=titleabs&time=all&submit=Quick+search&navsubmit=Quick+search

http://farside.ph.utexas.edu/teaching/plasma/lectures/lectures.html
Bruce Scott’s homepage http://www.rzg.mpg.de/~bds/
LLNL’s Plasma dictionary http://plasmadictionary.llnl.gov/

and of course I would have to add a link to my own institution
Centre for Fusion Space and Astrophysics, University of Warwick http://www2.warwick.ac.uk/fac/sci/physics/research/cfsa/

I’ve never really used RSS news readers, but appreciate their usefulness. I always prefer some, amount of human interaction in filtering and editorial comment on news items/press releases. This way, where possible, you can try to cite & link to the primary source article/paper – not just the news site item

[jamesr]

You have the mass of a proton, but the atomic masses of the others. Atomic masses include the electrons in a bound atom, ie the rest mass of all the electrons minus their binding energy in the ground state.

http://www.wolframalpha.com/input/?i=mass+of+proton++++mass+of+Boron-11+-++3*++mass+of+alpha+-5*electron+mass
Gets closer at 8.68MeV – but still ignores the binding energy of the 5 electrons in atomic Boron-11

The ionisation energies to strip each of the electrons from the boron are: 8.30, 25.15, 37.93, 259.37, and 340.22eV = 670eV = 0.00067MeV (ie an insignificant correction)

[jamesr]

Another way to look at it is that nuclei have excited states just like atoms do.

You can excite a nucleus to a higher state where the neutrons an protons vibrate more. Often the most efficient way for it to release the energy is not necessarily via photon but via an interaction through the strong force, whereby an alpha particle it emitted. (interaction via the weak nuclear force are far less likely, by far I mean 20 orders of magnitude less likely)

So where the Boron and proton overlap and have a total energy greater than the rest mass of the carbon 12 they combine resulting in an excited C-12 state. The excess is released, on average, as with any radioactive decay, by the most probable route. ie. the C-12 emits one alpha, then shortly after the Be-8 left splits again into to more alphas.

[jamesr]

Do board members need to be US citizens for the charitable status?

[jamesr]

The CNO cycle relies on sufficient confinement time for some of the intermediates products to undergo beta type decay, before fusing with another proton to move to the next link in the chain.

O-15 has a half-life of 122s and N-13’s half-life is 9.9 minutes

in a bound atom these decays are normally via electron capture, but in a plasma this decay time will be different (possibly even longer).

So although the temperature required is in the realm of what a DPF can handle the confinement time needed is impossible for anything other than a gravitationally bound system where the confinement time is essentially infinite (ie a star).

[jamesr]

Do you know what the situation is for non US citizens/taxpayers? It would be good to try to appeal as globally as possible. How can membership benefits be applied universally?

As a UK taxpayer (as I understand it), any donations I give to foreign (non EU) charities are not tax deductible. Also shipping costs of any swag will be higher, and so discourage sending any donated stuff to everyone, regardless of where they may be.

[jamesr]

I like it zapkitty – simple effective logo, with strong typography.

The only thing I would tweak is the kerning slightly, so the C is the same width as the S (or vice versa), then the down stroke of the U would line up with the I below it.

[jamesr]

If you just take for example the turbomolecular pump, developed in 1958. Or from the nuclear viewpoint the various collision cross sections for different elements worked on as a result of the development of the H-Bomb.

It wasn’t until 1941 when Kolmogorov first developed his theories of turbulence, that were later applied to magnetic plasmas that any kind of hypotheses of how macroscopic forces cascaded the energy transport down to smaller scales was considered.

[jamesr]

If you just go back as far as when Filioppov (1961-62) & Mather (1964) came up with the DPF, then if more effort was made into researching them at the time would have meant when progress in understanding plasma phenomena in general was made in the 70s then the DPF would have been better placed to attract funding alongside tokamak projects built in the 80s.

Someone could have come up with the DPF concept before Filioppov & Mather, but not much before. I would say the earliest one could have been built would be maybe 10 years before, but not much more than that – say 1950.

Having said that, I think the whole range of technologies needed to get power from fusion in a DPF mean it could not have been done much before where we are today, maybe 10-15years ago at best.

[jamesr]

I’m sorry to say I didn’t really have much chance to talk about FF with any of the key people. There was only limited time in coffee breaks etc to network, and naturally my first priority had to be my own research. I needed to introduce myself, the code I writing, and try and find potential collaborators as far as what kind of simulations I should run through it once it is more complete (with my supervisor standing next to me half the time).

[jamesr]

Just got back – lots of good talks and posters, as well as usual complement of monotone ones just putting up slide after slide of graphs with no insight into their meaning or implications.

General mood seemed positive for the rate of progress, but still lots of unanswered questions about the understanding of all the phenomena affecting heat and particle transport in tokamaks & stellarators.

Diagnositcs have improved over the last few years on all the various devices round the world like AUG, DIII-D, TEXTOR, TORE SUPRA etc. However there are a lot of phenomena that are seen on some devices and not others. In particular some of the scaling laws do not fit JET (the largest current tokamak) which suggests the understanding of the behaviour once scaled upto ITER’s size is very much in doubt.

Also the role of diffusion coefficients to model the various classical, and turbulent transport mechanisms is becoming more problematic at the plasma edge as the transport here seems to be dominated by blobs of plasma shearing off then being accelerated away towards the wall. If this mechanism is not understood and controlled, too much of the plasma will deposit energy on the proposed beryllium wall of ITER, rather than being safely channeled down to the divertor region at the bottom.

If anyone is interested in any more details on I can try and remember who said what.

Hopefully they’ll post a copy of the group photo taken at the end of the week – I picked that day to wear my FF t-shirt!

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