Exploring Magnetic Mirror Configurations

Tom Simonen Berkeley California [email protected] Exploratory Plasma and Fusion Research Workshop Auburn University February 25, 2016

Outline

• Background • Experimental Progress • A Fusion Power path with Commercial By-Products • The Kinetic Stabilized Tandem Mirror (KSTM) – An Advanced Fuel Fusion Power Concept What if a Magnetic Confinement Concept had: • Only simple circular HT SC High Field magnets • No potentially disruptive plasma current • No divertor embedded within the magnet system • Potential of burning advanced fuels (e.g. cat. DD,...) • Direct energy conversion • No need for tritium breeding • Reduced nuclear damage and activation of materials • Utilized developing technologies Reconsider the magnetic mirror

Axisymmetric Tandem Mirror Why Were Mirrors Discarded 30 Years Ago?

• Drastic Fusion Funding Reductions • Relative to then perceived simple Tokamak – Mirrors Required Technology Development (Complex SC magnets, 1 MeV NBI, Gyrotrons) – Physics Performance lagged Tokamak • Perceived Physics Flaws – Neoclassical radial transport (with min-B) – Prone DCLC micro-Instabilities

– Electron thermal conduction clamps Te <100 eV

So What is New Now 30 Years Later?

• ITER R&D is developing key NBI and ECH Technologies

• High Tc High Field Magnets developing • Experiments in the Novosbirsk GDT device and elsewhere as well as theoretical modeling have over come major physics hurdles. Mirror Concept Evolution

1986 Min-B Thermal Barrier 2016 Axisymmetric Tandem Experimental Progress Gas Dynamic Trap (GDT) BINP Novosibirsk Russia

• Size – Mirror-Mirror = 7m – Plasma Diameter = 0.3m • Magnetic Field – Mirror = 10 Tesla – Mirror Ratio = 30 • Input Power – NBI = 5MW @ 20 keV – 5 ms – ECH = 1 MW @ 54.5 GHz

• Plasma (max)

– Ei: 10 keV Te: 1 keV 20 -3 – Beta: 60% ne: 10 m

2. Skew Neutral Beam Injection Suppresses Micro-Instabilities Hot Ion Density Peaks Off Mid-plane Confined Warm Ions Fill the to Confine Warm Ions(Neutrons) Mirror Loss-Cone 3. GDT Electron Temperature Reaches 1 keV with ECRF

Historical Data 50-700 eV Thomson Scattering Spectrum of Bulk Isotropic Electrons The Impact of the Te Achievement

• GDT 1 keV electron temperature dispels beliefs

that open systems are intrinsically low Te ( < 200 eV).

• The 1 keV Te was achieved by expanding ends to reduce conduction to end walls and inhibit secondary electrons from reaching the confined plasma. • The 1 keV temperature, at higher density, is sufficient for a 2 MW/m2 fusion neutron source.

4. GDT End Plug Reduces End Loss Tandem Mirror End Plug End Loss Reduced x5 Imagine GDT Device as a Torus (T-10)

Rp = 1.2 m, ap = 0.15m Resulting Features • Systems – No Non-circular Coils – No Central Solenoid – No Poloidal Coils – No Plasma Current – No Current Drive Systems – No In-magnet Divertor • Achieved Plasma Parameters – Beta(0) < 60%

– Ei < 10 keV – Te < 1 keV 20 -3 – ne < 10 m A Path to Fusion Power with Commercial By-Products

GDT’s Game-Changing Advances Provides Optimism about Axisymmetric Mirrors as a Path to Fusion Power

• A Path to Fusion Power can be Envisioned (1 MW to 100’s) – Medical and Commercial Isotopes (< 5x1016 DT n/s), – Fusion Materials Testing & Development (2MW/m2), – Fission Fuel Production and/or Waste Burner(Q>1) – Fusion-Fission Hybrid (Q =3-5) – Fusion Electrical Power (Q > 10 with Advanced Fuel)

• An Effort Should be Undertaken to Assess Implications and Potential of the GDT Accomplishments and KSTM Concept – Theory, Simulation, Conceptual Design, GDT Collaboration

Isotope Production for Medical and Commercial Applications

• Same physical size with dimensionless plasma characteristics as existing GDT • Increase NBI from 20 to 80 keV • Double Magnetic field (same gyro radius) • Neutrons per Second over 2 m2 – 2.4 x 1014 DD n/s – 4.8 x 1016 DT n/s

Kinetic Stabilized Tandem Mirror (KSTM)

• MHD Stability Provided by Flaring Field Lines • ECH and NBI Power the End Plugs • The Central Cell is Ignited • R.F. Post, Trans. Fusion Sci. & Tech.,51, 112 (2007) • T.K. Fowler, to be published

Mirrors Favor High Temperatures

Confinement Improves with Ei TMX Tandem Mirror Axial Profile Catalyzed DD Fusion Reactions

Fusion Reaction Rates Fusion Reactions • D + D > n(2.4 MeV) + 3He(0.8 MeV) • D + D > H(3 MeV) + T(1 MeV)

• D + 3He > H(14.6 MeV) + 4He (3.7MeV)

• T > 3He

• D + T > n(14 MeV) + 4He(3.5MeV)

Mirror Confinement Favors High Magnetic Fields & Size 2XIIB Confinement increases with Rp/ai DCLC is stable if Rp/ai > 50 Future Work is Required

• Theory – Trapped Particle Modes • Simulation – Fokker Planck, Monte Carlo – Steady State Scenarios – Startup • Conceptual Design – End Plug – Particle and ECH Control • Experimental – End Plug Database Summary: The KSTM Kinetic Stabilized Tandem Mirror Has:

• Simple circular HT SC High Field magnets • No potentially disruptive plasma current • No divertor embedded within the magnets • Potential for advanced fuels (e.g. DD, D3He, p11B) • No need for tritium breeding • Reduced neutron damage and activation • Option for direct energy conversion • Only developing technologies • Commercial by-products

Thanks for many Communications from the GDT Team in Novosibirsk

• And discussions with Peter Bagryansky, Dimitri Ryutov, • Dick Post, Ken Fowler, Art Molvik, Ralph Moir, and others Recent GDT Publications

• A.A. Ivanov and V.V. Prikhodko, “Gas Dynamic Trap: an overview of the concept and experimental results”, Plasma Physics and Controlled Fusion 55, 063001 (2013). • A.G. Shalashov, et.al., Auxiliary ECR heating system for the gas dynamic trap”, Physics of Plasmas 19, 052503 (2012). • P.A. Bagryansky, et.al., “First results of auxiliary electron resonance heating experiment in GDT magnetic mirror”, Nuclear Fusion, 54, 082001 (2014). • P.A. Bagryansky, et.al., “Overview of ECR plasma heating in the GDT magnetic mirror”, Nuclear Fusion 55, 053009 (2015). • P.A. Bagryansky, et.al., “Threefold Increase of the Bulk Electron Temperature of Plasma Discharges in a Magnetic Mirror Device, Physical Review Letters 114, 205001 (2015). • Physics Today, August 2015