Speaker
Dr
Tom Simonen
(Berkeley California)
Description
Recent advances in high-field superconducting technology together with the development of MeV neutral beams and multi-megawatt high-frequency gyrotrons provide motivation to consider Generation II tandem mirror fusion concepts which could burn a range of fuels from DT to DD to possibly p11B. Advanced fuels require high electron temperatures in the end plugs but lower electron temperatures in the center cell to avoid excess Bremstrahlung losses. A new result in this paper shows that strong heating of electrons in the end plugs decouples these temperatures as needed to burn advanced fuels, without the need for externally imposed thermal barriers.
Our considerations incorporate unexploited physics results from past US experiments and recent advances from the GDT facility in Novosibirsk Russia. We envision ignited plasma confined in a simple solenoid with small high-field axisymmetric mirror cells at both ends. Axisymmetric MHD stability can be provided by several methods. Here we consider kinetic stabilization by plasma pressure in the good curvature region just beyond the outermost mirrors. Since magnetic mirror system performance favors high temperature plasmas, (e.g. 100 keV) so it is natural to consider advanced fuel options.
High field circular magnets enables high mirror ratios to improve axial confinement and also enables compact end cells to reduce the auxiliary power required to electrostatically confine the central cell plasma. MeV level neutral beams and high power ECH provides the end cell electrostatic plasma potential that axially confines central cell plasma. Direct energy conversion is considered for untrapped and unneutralized neutral beam energy recovery and to recover plasma end loss energy.
We have evaluated the fusion power gain (Q) as the product of three factors. Q=Lc x C x F. Here Lc is the fusion power producing central cell length, C is a physical size and plasma characterization parameter and F defines the fusion fuel characteristics. For Q = 15 to 20 we find central cell lengths 10 < Lc < 200 m (depending on the magnetic field strength, the design dimensions and the fusion fuel). Example design parameters will be presented together with suggestions for more detailed study such as startup, control of synchrotron radiation and emergence of trapped particle and drift cyclotron modes. The calculation to be presented indicates the existence of an encouraging design space warranting more comprehensive modeling and for experimental investigations.
This work was inspired by our late colleague, Richard F. Post (1918 - 2015).
Primary author
Dr
Ken Fowler
(University of California at Berkeley)
Co-authors
Dr
Ralph Moir
(Vallecitos Molten Salt Research)
Dr
Tom Simonen
(Berkeley California)
