A much anticipated paper on fusion has appeared on the Arxiv website, High Energy Electron Confinement in a Magnetic Cusp Configuration by Jaeyoung Park, Nicholas A. Krall, Paul E. Sieck, Dustin T. Offermann, Michael Skillicorn, Andrew Sanchez, Kevin Davis, Eric Alderson, and Giovanni Lapenta. The paper has been brought to my attention by John Smith of The Polywell Blog by way of the LinkedIn forum for fusion power.

Here is the abstract of the paper:

We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high beta a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. The current experiment validates this theoretical conjecture for the first time and represents critical progress toward the Polywell fusion concept which combines a high beta cusp configuration with an electrostatic fusion for a compact, economical, power-producing nuclear fusion reactor.

The Polywell fusion concept, which is identified as inertial electrostatic confinement (and also called magnetic cusp confinement), was conceived by Robert W. Bussard of Bussard ramjet fame. In contrast to the ITER project, which employs magnetic bottle confinement, and NIF, which pursues inertial confinement by way of lasers, inertial electrostatic confinement makes use of an electric field to heat plasma to the point of inducing fusion. 

The paper concludes:

In summary, the present experimental results demonstrate for the first time that high β plasma operation can dramatically improve high energy electron confimement in the magnetic cusp system. This result validates the central premise of the Polywell fusion concept which uses high energy beam injected electrons to create an electrostatic potential well for ion acceleration and confinement. The current plan is to extend the present work with increased electron beam power to sustain the high β plasma state and to form an electrostatic well. If the deep potential well can be formed and the scaling of the electron beam confinement is found to be favourable, as conjectured by Grad and others, it may be possible to construct a compact, low cost, high β fusion power reactor based on the Polywell concept.

The Polywell fusion concept has made steady progress both with regard to the science behind the concept and the practical engineering challenges of fusion whenever there has been enough funding to pursue the work. It is intriguing to speculate at the rate of progress that might be possible with serious funding.

In so far as electricity is the lifeblood of industrial-technological civilization (as I recently wrote in another post), the future of this civilization is predicated upon our ability to develop not only sustainable sources of power, but also compact, efficient, and scalable sources of power that can be used to power outposts of civilization beyond Earth and the spacecraft to reach such destinations. Bussard, who initially developed the Polywell fusion concept and the Bussard ramjet for interstellar travel, clearly understood how closely these two are linked.

Polywell Nuclear Fusion

Nuclear fusion can release vast amounts of carbon-free energy from very small amounts of matter.  For example, just two teaspoons of the element boron, reacting with hydrogen, in a p-B11 fusion reaction, can release enough energy to fly an F-16 fighter-bomber to the moon!

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The p-B11 reaction responsible for this amazing feat is shown below.  A hydrogen nucleus (a proton) smashes violently into a boron nucleus.  Now that it has an extra proton, the boron nucleus becomes unstable and it breaks up into three multi MILLION electron volt helium nuclei (aka alpha particles).  The useful energy is extracted from these high energy particles.

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One device that is capable of violently smashing boron nuclei with protons is a polywell reactor.  The US Navy is funding the use of such a polywell for fusion research at a low budget, low profile site in Southern California.

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The hydrogen in the p-B11 reaction is the ordinary hydrogen from H2O and the boron is from Borax (soap). They produce a  nuclear reaction with NO unsafe radiation.  The only product is Helium (as in a child’s balloon).

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A commercial p-B11 polywell reactor will probably produce about 100 megawatts of DEPENDABLE power (enough for all the energy needs of Port Angeles, Washington) at a cost of about $220 million dollars.

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In contrast, because wind is so undependable, many wind turbines would be required at many different locations to make the same amount of power: thus 100 megawatts of DEPENDABLE commercial wind power would cost more than a billion dollars!

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For similar reasons (day and night, cloudy weather, non-optimum angles of the sun) solar would require considerable back-up power and over-engineering, making the cost of 100 megawatts of DEPENDABLE solar power more than $675 million.

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Thus p-B11 nuclear fusion from polywells may well prove to be civilization’s most cost-effective source of safe, carbon-free energy.  Every effort should be made to properly fund and develop this essential source of energy.

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