Compact fusion reactors Tomas Lind´en Helsinki Institute of Physics NST2016, Helsinki, 3rd of November 2016 Fusion research is currently to a large extent focused on tokamak (ITER) and inertial confinement (NIF) research. In addition to these large international or national efforts there are private companies performing fusion research using alternative concepts, that potentially could result on a faster time scale in smaller and cheaper devices than ITER or NIF. The attempt to achieve fusion energy production through relatively small and compact devices compared to standard tokamaks decreases the costs and building time of the reactors and this has allowed several private companies to enter the field, like EMC2, General Fusion, Helion Energy, LPP Fusion, Lockheed Martin, Tokamak Energy and Tri Alpha Energy. These companies are trying to demonstrate the feasibility of their concept. If that is succesfully done, their next step is to try to demonstrate net energy production and after that to attempt to commercialize their technology. In this presentation a very brief overview of compact fusion reactor research is given. Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 1 / 24 Contents Contents 1 Fusion conditions 2 Plasma confinement 3 The Polywell reactor 4 Lockheed Martin CFR 5 Dense plasma focus 6 MTF 7 Spherical tokamaks 8 Other fusion concepts 9 Summary Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 2 / 24 Fusion conditions Fusion conditions See Antti Hakolas presentation in this conference on mainline fusion. A useful fusion performance metric is the triple product NτT (1) that has to execeed some threshold value for the fusion reaction in question for the fusion power to exceed radiation and other losses and maintain a constant plasma temperature. N is the particle density, the confinement time is τ and the temperature is T . For DT the minimum required value for a thermal plasma is 3·1021 keVs/m3. Several plasma heating methods exist. The required temperature is defined by the desired fusion reaction Achieving stable plasma confinement filling the triple product has proved hard The density and the confinement time can by varied in a large unexplored plane Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 3 / 24 Fusion conditions Fusion conditions The ratio of plasma pressure to magnetic pressure β is a figure of merit of how well the investment in the magnetic field can be utilized. Fusion power is proportional to β2. The achievable value of β is often limited by plasma instabilities. β = pkin=pmag (2) 2 where p = N kT + N kT , p = B . N (T ), N (T ) = ion- kin i i e e mag 2µ0 i i e e respective electron particle density (temperature), k = Boltzmann constant and B = the magnetic field and µ0 = the permeability of vacuum [1]. The ITER β design value is ≈ 0.03 [2] A compact fusion reactor in this context has a significantly smaller plasma volume than a traditional tokamak because of a large value of β. Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 4 / 24 Plasma confinement Plasma confinement Examples of plasma confinement methods: Magnetic Confinement Fusion (MCF) Tokamak (JET, ITER, ...), stellarator (Wendelstein 7-X), ... N ≈ 1014/cm3, τ ≈ 1 s Inertial Confinement Fusion (ICF) Laser fusion (National Ignition Facility, High Power laser Energy Research facility (HiPER), ...) N ≈ 1025/cm3, τ ≈ 1 ns Heavy Ion Fusion (HIF) Inertial Electrostatic Confinement (IEC) Magnetized Target Fusion (MTF) also Magneto Inertial Fusion (MIF) (General Fusion, Helion Energy, ...) [3] N ≈ 1019/cm3, τ ≈ 1 µs Magnetic confinement- and laser fusion get the majority of the funding The emphasis of laser fusion is on military applications Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 5 / 24 Plasma confinement Plasma confinement Plasmoids Self confined plasmas where the magnetic fields are mostly generated by currents circulating in the plasma are called plasmoids or Compact Torii [4]: Field Reversed Configuration (FRC) Spheromak Plasmoid Axial- Poloidal field Toroidal field Bt symmetry Bp Bt on surface FRC yes yes no no Spheromak yes yes yes no The poloidal field is contained in planes through the symmetry axis. The toroidal field circulates the symmetry axis. FRC-plasmoids can reach β ≈ 1. Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 6 / 24 The Polywell reactor The Polywell reactor Figure: An EMC2 Polywell with a side Figure: Polywell field lines for β = 0. length of 21.6 cm built for β=1 studies. Simulated electron trajectories are green. Electrons confined in a magnetic cusp accelerate and confine ions [5, 6, 7, 8, 9] The field geometry has a stable curvature EMC2 has shown: 1995: Electrostatic fusion in a Polywell (a potential well for ions) [10] 2013: High β together with greatly increased electron confinement [2] To show the scientific feasibility of the Polywell for energy production, both of these have to be demonstrated at the same time Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 7 / 24 Lockheed Martin CFR Lockheed Martin CFR Lockheed Martin Compact Fusion Reactor project started in 2011 T4 experiment published in February 2013 by C. Chase, aim 200 MW CFR patents published in 09/2014 [11, 12, 13, 14, 15, 16, 17, 18] T. McGuire leads the development at Skunk Works T4 experiment 1 m * 2 m, nominal reactor core 5.2 m * 15.2 m Axisymmetric, ideas from many concepts, mirrors at ends, DT-fuel Few open magnetic field lines, good field curvature, high β heating power 15 kW (to be increased to 100 kW) 16 17 3 Pulses ≈1 s, Te =10-25 eV, τE =4{100 µs, N=10 {10 /m [19, 20] Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 8 / 24 Dense plasma focus Dense plasma focus LPP Fusion (LPPF), led by E. Lerner [21] Dense Plasma Focus: J.W. Mather 1960s, N.V. Filippov 1954. An electric discharge creates the plasma, which develops through a series of instabilities to a plasmoid Goal P = 5 MWe, f = 200 Hz Figure: LPPF reactor [21]. Landau quantization is expected to decrease bremsstrahlung For a DD-plasma E>150 keV has been measured [22], which is enough for p11B τ ≈ 20 ns, surpasses 8 ns goal Energy transfer to the plasmoid surpasses Figure: Electrode length ≈ 15 cm. goal with 50 % ρ needs to increase with 104 for Q = 1 Worked on reducing electron induced impurities [23] Working on reducing plasma impurities from W electrode Figure: Schematic plasma discharge. Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 9 / 24 MTF Fusion Technologies Plasma Energy Driver Power 1.00E+11 1.00E+15 NIF ITER $6B $20B GJ TW 1.00E+08 1.00E+12 GF MJ $150M GW 1.00E+05 1.00E+09 $ Cost of Driver $ Cost of Confinement kJ MW 1.00E+02 1.00E+06 1.00E+13 1.00E+16 1.00E+19 1.00E+22 1.00E+25 Plasma Density (cm-3) SOFE 2013 2 MTF MTF General Fusion - acoustically heated MTF [24, 25, 26, 27, 28, 29, 30, 31] Based on LINUS concept from the 1970s Chief scientist and founder M. Laberge The planned reactor is a sphere with r = 1,5 m with a rotating molten PbLi mixture, P = 100 MWe, f = 1 Hz, Q = 6 Two plasma injectors create, accelerate and compress spheromaks The spheromaks injected through the vortex in the middle collide The FRC DT-plasma is heated to fusion conditions acoustically with hundreds of computer controlled pneumatic pistons The GF concept has several advantages compared to a tokamak: No "inner wall" problem, no divertor needed PbLi is a coolant and neutron multiplicator for T-generation Can be retrofitted to turbines of existing power plants Potential problems Compression and stability of the injected spheromaks Richtmyer-Meshkov instability Pb,Li-impurities can cool the plasma Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 11 / 24 MTF MTF Figure: General Fusions 14 piston test reactor "Mini-Sphere", with a diameter of one meter, is used for validating compression simulations. Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 12 / 24 MTF MTF The General Fusion development plan: Phase I - Proof of principle 2002 - 2008, < 1 M$ Research and development Phase II - Show net gain ≈ 50 M$ System development Current status [32] Physics validation Full scale prototype ≈ 500 M$ Phase III - Commercialization Alpha and Beta power plants ≈ 2 G$ Then power production Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 13 / 24 MTF MTF Figure: Helion Energy, MSNW LLC Grande experiment [33, 34]. Two colliding FRCs merge to a stationary FRC The FRC is compressed magnetically in the burn chamber Ti ≈ 2,3 keV obtained for D-ions A plasmoid speed of 300 km/s has been achieved Plans to use D+D (3He) fuel Targets 50 MWe prototype in 2019 and commercialization in 2022 ARPA-E: VENTI 12 T & FEP 20 T compression, FEP-G 40 T reactor MSNW develops a fusion driven rocket (FDR) with NIAC funding Lithium compresses the plasma, absorbs neutrons and generates T Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 14 / 24 MTF MTF Figure: Tri Alpha Energy (TAE) experiment C-2U [35, 36, 37, 38, 39]. A FRC is produced by two colliding plasmoids The plasmoid injection speed is 250 km/s The goal is to stabilize the FRC-state with neutral beam injection and with external electric and magnetic fields The C-2 FRC lifetime was 5 ms, Ti ≈ 1 keV With C-2U a stable lifetime of 5 ms was reached C2-W to be completed in mid 2017 will aim for increased temperature TAE plans to use D3He or p11B Tomas Lind´en (HIP) Compact fusion reactors 03.11.2016 15 / 24 Spherical tokamaks Spherical tokamaks Mega Ampere Spherical Tokamak Upgrade (MAST-U) National Spherical Torus eXperiment Upgrade (NSTX-U) Affordable, robust, compact (ARC), high field compact tokamak Tokamak Energy Ltd, high