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Speaker: Cary Forest, University of Wisconsin

Title: The physics basis for a Q≈1 high-field, compact, axisymmetric mirror*

Abstract: A public-private team has been formed to pursue the axisymmetric mirror path to fusion: ARPA-E has funded the construction of an high temperature superconducting prototype called the Wisconsin HTS Axisymmetric Mirror (WHAM), that involves the UW Madison, a new startup company Realta Fusion, MIT and CFS. The 3 step development path begins with a small mirror, WHAM1.0, to establish MHD stable plasmas relying on vortex and FLR stabilization by fast ions of a high mirror ratio simple mirror, a reactor scale simple mirror WHAM++ that uses 100+ keV neutral beam injection to validate the confinement, macro and microstability in a simple mirror, and finally a tandem mirror that uses two WHAM++ configurations with ~1MeV, rf heated ions for the end plugs of a HTS Axisymmetric Magnetic Mirror Reactor (Hammir). This talk will review the physics basis for WHAM++ and address the TRLs for magnets, heating sytems, MHD techniques, and microstability for mirror distribution functions. I will rely on bounce averaged drift kinetic/Fokker-Plank solutions for mirror confined fast ions that show Q>1 is acheivable in a simple mirror with mirror ratio > 10. Direct energy recovery greatly improves prospects even for electrical breakeven. MHD stability will come from FLR stabilization for m>1, and plasma shaping, divertors, vortex and feedback stabilization at high β for m=1. Microinstabilty will rely upon sloshing ions and high mirror ratio. A direct energy convertor appropriate for the axisymmetric exhaust of the mirror should be capable of recovering more than 50% of the lost energy thereby increasing Q even further. Breakeven is possible even for small energy input (several MWs). Applications of WHAM++ include use as a blanket test facility, a minor actinide burner and as a source of efficient process heat. Power production for an industrial scale will be with Hammir.
*This work has been supported by ARPA-E, the Wisconsin Alumni Research Foundation and CFS.

 

Prof. Cary B Forest received a Bachelor of Science degree from the University of Wisconsin in 1986 in the Applied Math, Engineering and Physics program. He received a Magnetic Fusion Energy Science Fellowship from the DoE to attend graduate school at Princeton University where he received a Ph.D. in 1992 in the Astrophysical Sciences department. His thesis, supervised by Dr. Masayuki Ono at the Princeton Plasma Physics Laboratory, received the Simon Ramo Award for Outstanding Doctoral Thesis Research in Plasma Physics} from the APS. In the course of his thesis work he invented and demonstrated a non-inductive method of tokamak formation based upon the bootstrap current. After graduate school he spent 5 years working at General Atomics as a Scientist where his work focused on studies of plasma resistivity, non-inductive current drive, rf heating of plasmas and MHD instabilities in tokamak plasmas (at the time GA operated the largest US tokamak research program). The analysis technique Forest developed during this time for measuring the non-inductive currents driven in tokamaks has since been implemented in most of the world’s large tokamaks and played a central role in validating the heating and current drive models being used to predict their behavior on Iter. At the UW, Forest has received the Romnes Fellowship, the Vilas Associate Award, the Kellett Mid Career Award and most recently a WARF Named Professorship. Nationally, he is the recipient of the Alfred P. Sloan Fellowship, the David and Lucille Packard Foundation Fellowship, and a Research Award from the Alexander von Humboldt Foundation (hosted by the Max Planck Institute for Plasma Physics in Garching, Germany (2005)), and is a Fellow of Merton College, Oxford. He has served as Director of the NSF Physics Frontier Center for Magnetic Self-Organization and currently serves as the Director of the Wisconsin Plasma Physics Laboratory and overseas its operations as a DoE collaborative user facility. He has served and numerous study committees of the National Academies of Science and has Chaired program advisory committees at MIT and Princeton. He is a Fellow of the American Physical Society and has Chaired the the Division of Plasma Physics and also served a an APS Counselor.