Magnetized Target Fusion: Potential Path From Science To Practical Fusion Energy

Summary

This presentation explores Magneto-Inertial Fusion (MIF) and Magnetized Target Fusion (MTF) as potential low-cost, intermediate paths between magnetic and inertial confinement fusion approaches. It details collaborative research between Los Alamos National Laboratory and the Air Force Research Laboratory focusing on Field Reversed Configuration (FRC) formation, translation, and implosion using Shiva Star. The slides address reactor engineering challenges, high-energy-density physics platforms, and magnetic reconnection dynamics.

Title Slide - Page 1

T. Intrator P-24 Plasma Physics, Los Alamos National Laboratory

In collaboration with: C. Adams, J. Dunn, J. Sears, W. Waganaar, T. Weber, G. A. Wurden - Los Alamos National Laboratory, NM, USA J. H. Degnan, M. Domonkos, C. Grabowski, E. L. Ruden, W. White - Air Force Research Laboratory, Kirtland Air Force Base, NM, USA D. G. Gale, M. Kostora, W. Sommars - SAIC, Albuquerque, New Mexico, USA D. J. Amdahl, J. F. Camacho, S. K. Coffey, M. H. Frese, S. D. Frese, N. F. Roderick - NumerEx, Albuquerque, New Mexico, USA B. Bauer, S. Fuelling, R. E. Siemon - University of Nevada, Reno, Nevada, USA R. Clark, M. Gilmore, A. Lynn - University of New Mexico, Albuquerque, NM

24th Symposium on Fusion Engineering 2011 Jul 26-30 Chicago, Illinois, USA

Abstract - Page 2

abstract Magnetized Target Fusion: Potential Path From Science To Practical Fusion Energy T. Intrator Los Alamos National Laboratory, P-24 Plasma Physics

Magneto Inertial Fusion (MIF) inertial adiabatic compression of a plasma fuel target takes advantage of embedded magnetic field to reduce thermal conduction and enhance alpha-particle heating. This allows operation at reduced values of areal density (ρr) for fusion ignition when compared to non magnetized inertial compression approaches. It also relaxes implosion speed (5-100 km/sec), convergence (≈10:1), power, precision, and expense (more efficient pulsed power driver) for requirements for the chosen compression scheme. A wide range of MIF time and length scales can be realized from nearly ICF parameters (time ≈ 100 psec, length ≈ 25µm) to many orders of magnitude larger time scales of micro seconds and cm spatial scales. This versatile set of approaches allows considerable latitude for tackling the engineering and technology problems.

Magnetized Target Fusion (MTF) is a subset of MIF, requiring target plasma formation plus ejection into a solid flux conserving compressor shell or liner that implodes and compresses a plasma target, as shown in Fig. 1. When generalized for MTF the usual ICF burn fraction estimate must include a large tamping correction. The liner has much larger mass than the compressed fuel, which increases the dwell time because it scales as the square root of the total mass. It appears possible to exceed the typical figure of merit ηG > 10 which is the product of (high) driver efficiency η and (small) fusion gain G. We describe a variety of MTF approaches, some conclusions about the scaling characteristics, and show recent data including experimental engineering test shots in a collaboration to realize a physics demonstration of MTF.

*Work supported by the DOE, Office of Science, Office of Fusion Energy Sciences, under LANS Contract No. DE-AC52-06NA25396

Outline - Page 3

Outline • Magneto Inertial Fusion: MIF – A hybrid (magnetic + inertial) approach to fusion – High risk – high payoff – Example: Magnetized Target Fusion: MTF • FRCHX (AFRL) - Implosion to MegaBar pressure • FRXL (LANL) formation • MIF reactor issues • Platform for science – Compressed plasma = High Energy Density – Initial plasma = Field Reversed Configuration

Magneto–inertial fusion - Page 4

Magneto–inertial fusion • MIF regime lies between magnetic and inertial fusion approaches • access to 1-100 Megabar pressures and multi-Megagauss magnetic fields • Compared to ICF • Embedded magnetic field improves confinement • macro scale plasmas (µm → cm) • Lower velocity implosion drivers (≈ 0.5cm/µsec) • Lower compression ratio (≈ 10:1) • National Academy of Science IFE Review documents available at: http://fire.pppl.gov/icf_nas_review_2010.html • Scientific American, May 26, 2011 • Popular Science

Wide Range of Driver/Target Combinations - Page 5

Wide Range of Driver/Target Combinations

• U. Rochester LLE: Direct drive laser implosion of cylinders — shock pre-heating, high implosion velocity [Gotchev et al., Rev. Sci. Instr. 80, 043504 (2009)] • Los Alamos / HyperV Plasma Liner Experiment: Merging plasma jets for remote standoff [A. G. Lynn, et al, Rev. Sci. Instr. 81, 10E115 (2010)] • Los Alamos / AFRL Field Reversed Configuration: Shiva Star FRCHX, ~20 µs, 0.5 cm/µs liner implosion [Taccetti, Intrator, Wurden et al., Rev. Sci, Instr. 74, 4314 (2003); Degnan et al., IEEE Trans. Plas. Sci. 36, 80 (2008); Intrator et al Phys Plas 11(5), 2580 (2004)] • Sandia National Laboratories Magnetized Liner Inertial Fusion: Laser preheated magnetized fuel, LASNEX simulations indicate interesting yields [S. A. Slutz, et al., Phys. Plasmas 17, 056303 (2010)]

MIF could be a low cost alternative - Page 6

MIF could be a low cost alternative

Facility US$ cost: plasma energy EPLAS heating power PHEAT Bohm loss rate

Cost = c1 EPLAS + c2 PHEAT ≈ $10 B E P L A S / E I T E R +$ 3B PHEAT / PNIF Where EITER = 320 MegaJoule PNIF = 1.1x10^14 Watt

MIF < $100M

From Fig. 7: Lindemuth & Siemon, Amer Journ Phys, 77(5), 407, (2009)

MIF operates at reduced ρR - Page 7

MIF operates at reduced ρR Lindl-Widner plot [Basko, NF2000] • Compression r0/r ≈ 10-15 • B ≈ 3-6 MG • BR ≈ 0.6 MG-cm • P ≈ Mbar

FRXL • nD0 ≈ 5x10^16 cm^-3 • ρD0 ≈ 1 ngm/cm^3 compressed: • ρDcR ≈ 20 ngm/cm^2 • Fuel mass ≈ 1 µgm

Next: FRC cannon (inductive acceleration) • nD0 ≈ 10^18 cm^-3 • ρD0 ≈ 3 µgm/cm^3 Compressed: ρDcR ≈ 0.2 mgm/cm^2, Fuel mass ≈ 3 mgm

Outline - Page 8

Outline • Magneto Inertial Fusion: MIF – Example: Magnetized Target Fusion: MTF • FRCHX (AFRL) - Implosion to MegaBar pressure • FRXL (LANL) formation • MIF reactor issues • Platform for science

MIF collaborations - Page 9

MIF collaborations • Air Force Research Laboratory - Kirtland Albuquerque: first solid liner on plasma experiment • LANL: plasma target development, translation physics • Univ Nevada-Reno: Z pinch plasma surface interactions

MTF: subset of MIF - Page 10

MTF: subset of MIF • Formation: LANL (cusp mirror coils, segmented theta-pinch coil, separatrix, quartz tube, open magnetic field lines, closed poloidal magnetic field line, toroidal plasma current) • Translation • Compression (LANL: design, test; AFRL: Shiva-FRC) • Target: Field Reversed Configuration • High plasma/magnetic pressure: β • Natural divertor isolates walls, impurities

Bz(z) profile design point - Page 11

Bz(z) profile design point • Intrator et al, Journ Fusn Energy (2008) • Shows FRXL coilset (4 deg cone) Bz (Tesla) vs z wrt east cusp (m), showing theta coil, entrance mirror, translation, and mock liner.

FRC formation & launch after liner t0 - Page 12

FRC formation & launch after liner t0 • Time sequence of liner current initiation and FRC formation, translation. • Experimentally measured inside radius r(t) of aluminum liner implosion onto vacuum B field • Intrator et al, Adiabatic model and design of a translating Field Reversed Configuration, Physics of Plasmas. 2008;15: 042505. • Intrator et al, Experimental measurements of a converging flux conserver suitable for compressing a field reversed configuration for magnetized target fusion. Nuclear Fusion. 2002;42: 211-22.

Shiva Star: Air Force pulsed power - Page 13

Shiva Star: Air Force pulsed power Shiva Star (photo left) can store 9 MJ of energy with 1.3 mF of capacitors, at up to 120kV. More typically, at 4.5 MJ, it delivers 12 MA of current to crush a 30-cm tall, 10 cm diameter, 1 mm thick, 300 gm Aluminum cylindrical liner load in FRCHX, which is located under the center of Shiva Star (photo right).

FRCHX progress - Page 14

FRCHX progress • 2010 April – Translation observed and capture inferred in non implosion data • 2010 April 16 – First FRC engineering test: formation & compression – no neutron or SXR signatures – FRC lifetime did not last through compression time • 2011 – Working on methods to increase FRC lifetime – Plasma gun injection, deeper mirror well, RF preionization, trigger timing, inductive FRC acceleration – Waiting for Chicago to release DOE funds

Mach2 model guides next shots (Numerex) - Page 15

Mach2 model guides next shots (Numerex) • 30 cm liner with standard bias field in liner: Part of FRC doesn’t make it in (t = 5.0e-006) • 30 cm liner with modified bias field in liner: Deeper trough, better capture (t = 5.0e-006)

Outline - Page 16

MTF experiments - Page 17

MTF experiments A small size experiment ….. [Images showing experimental setup and hardware for plasma target generation and diagnostics]

FRXL translation & capture data - Page 18

FRXL translation & capture data Data 2.6° θ coil • Magnetics: Bdot and flux loops at the chamber wall • total light emission from the plasma at several axial locations • The FRC translates then rebounds then is trapped in mirror region (shorter than FRC!). • decay ≈ 10 µs from coming to rest

Outline - Page 19

Outline • Magneto Inertial Fusion: MIF – A hybrid (magnetic + inertial) approach to fusion • MIF reactor issues • Platform for science

MIF + reactor issues - Page 20

MIF + reactor issues • MIF could benefit from o Higher density => alpha energy deposition in fuel o Liquid walls could absorb neutrons, shock, heat o Increase dwell time to ≈ radiation loss time • Compared with ICF: o Lower (than ICF) rep rate to clear debris and walls o ICF style target tracking is not necessary • problems are very different from MFE o Less materials development necessary o Need pulsed power switching development o Need recyclable transmission line and/or driver standoff

Outline - Page 21

Outline • Magneto Inertial Fusion: MIF • MIF reactor issues • Platform for science – Compressed plasma = High Energy Density – Initial plasma = Field Reversed Configuration

HED physics platform - Page 22

HED physics platform • Dramatically relax technical hurdles for inexpensive access to HED regimes (≈ Mbar) • Distribute power and energy over large spatial and temporal scales: Inductive acceleration • High momentum flyer plasma meets its own reflection and is compressed • Repetitive FRCs can increase dwell time

FRC physics experiments - Page 23

FRC physics experiments Field Reversed Configuration (a) Configuration diagram: segmented theta-pinch coil, cusp/mirror coils, separatrix, open magnetic field lines, closed poloidal magnetic field line, toroidal plasma current, quartz tube. (b) 3D topology showing poloidal field Bp and toroidal field Bθ.

Emerging reconnection paradigm - Page 24

Emerging reconnection paradigm FRCs are collisionless and large, and can probe reconnection physics • Diagrams showing plasma inflow, advected magnetic field, B reconnection, O-point formation, and plasmoid development across reconnection layer length 2L • Can internal structure differ from the outside?

MHD physics: reconnection - Page 25

MHD physics: reconnection FRC worldwide database extended by FRXL spans a huge range of collisionality, system size • S = LvA / (η/µ0) • number of plasmoids Np = (S/Scrit)^α • Plot of log10(S) vs log10(LSP/ρi) displaying collisional SP regime, collisionless regime, plasmoid transition (α = 0.38, α = 0.80), and collisional MHD + plasmoids.

Other MIF talks - Page 26

Other MIF talks • Lindemuth: Fusion parameter space from first principles - SO4A-5 (Thurs, 11:45AM) • Hsu: Plasma liner experiments - IO4A-5 (Tues 4:15PM) • Degnan, Grabowski: Magnetized Target Fusion - IP1B-14 (Mon morning) • VanDevender: Z Pinch power stack – SO4B-4 (Thur 11:05AM) CC24A

Summary - Page 27

Summary • MIF: hybrid fusion approach between inertial and magnetic fusion • High risk – high payoff route • MTF: first attempts at experiments = AFRL-LANL collaboration • Reactor issues for MIF • Physics platform: HED and MHD