Wave Power Could Contain Fusion Plasma

[Matt M]

Researchers at the University of Warwick’s Centre for Fusion Space and Astrophysics and the UK Atomic Energy Authority’s Culham Centre for Fusion Energy may have found a way to channel the flux and fury of a nuclear fusion plasma into a means to help sustain the electric current needed to contain that very same fusion plasma.
http://www2.warwick.ac.uk/newsandevents/pressreleases/wave_power_could/

This article refers to computer simulations. The modeling is done for future Tokamak development.
But, it underscores that we have a lot to learn about how plasma behaves.

[MTd2]

Pre print for the paper is here:

http://arxiv.org/abs/1009.1041

[jamesr]

I am in the same group as the author James Cook. He started a couple of years before me and is just finishing his PhD and this short PRL (Physics Review Letters) paper should be followed up by a longer paper going into more detail fairly soon.

For reference; the final published version is here http://prl.aps.org/abstract/PRL/v105/i25/e255003

[Brian H]

Will the alpha waves rip the containment vessel to smithereenies?
😉

[jamesr]

Brian H wrote: Will the alpha waves rip the containment vessel to smithereenies?
😉

No – if anything it is the opposite. Showing a mechanism by which the alpha energy is deposited in the core plasma rather than escaping.

Plasmas are full of different waves at a vast range of wavelengths and timescales. It is the interaction of these various oscillations mechanisms with each other and with individual ions/electrons that is the main focus of plasma physics. In this case it is the collisionless coupling of the alpha motion with the Lower Hybrid wave that was being studied. The lower hybrid wave is just one particular resonant oscillation at a particular frequency combination of the ion and electron cyclotron frequencies. See http://en.wikipedia.org/wiki/Lower_hybrid_oscillation

[Brian H]

jamesr wrote:

Will the alpha waves rip the containment vessel to smithereenies?
😉

No – if anything it is the opposite. Showing a mechanism by which the alpha energy is deposited in the core plasma rather than escaping.

Plasmas are full of different waves at a vast range of wavelengths and timescales. It is the interaction of these various oscillations mechanisms with each other and with individual ions/electrons that is the main focus of plasma physics. In this case it is the collisionless coupling of the alpha motion with the Lower Hybrid wave that was being studied. The lower hybrid wave is just one particular resonant oscillation at a particular frequency combination of the ion and electron cyclotron frequencies. See http://en.wikipedia.org/wiki/Lower_hybrid_oscillation
When I first started reading, I was looking for the appearance of alpha particles, but no He ions showed up. Didn’t get that (I assume) the alpha wave referred to is the protons plus some deuterium ions(?). Or is it a particular frequency range?

[jamesr]

Brian H wrote:
When I first started reading, I was looking for the appearance of alpha particles, but no He ions showed up. Didn’t get that (I assume) the alpha wave referred to is the protons plus some deuterium ions(?). Or is it a particular frequency range?

The opening sentence says

Optimal exploitation of the free energy of fusion products, for example, the alpha particles born at 3.5 MeV

Nowhere is the phrase “alpha wave” used. The plasma wave is a collective phenomena of the ions, electrons, and the electric & magnetic fields.

The model, as far as I understand, is based on the fusion born alphas having inital collision(s) with some bulk ions transferring their energy to them. Creating a population of high velocity ions. For simplicity this is modelled as bump-on-tail distribution of protons/deuterons, with the bump at 3MeV directed at an angle to the magnetic field. The system is then evolved to see how the energy is redistributed. They then found

Collective instability gives
rise to electromagnetic field activity in the lower hybrid
(LH) frequency range. The spontaneously excited obliquely
propagating waves undergo Landau damping on resonant
electrons, drawing out an asymmetric tail in the distribution
of electron parallel velocities,which carries a current

[Brian H]

True; I conflated the “alpha channelling scenarios” with “By stage (iv) the wave
amplitude is approaching its saturated level. The magnetic fluctuations contain nearly an order of magnitude
less energy than the electric fluctuations, implying that the waves produced by the instability are largely electro-
static”.

[Author]

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