magneto-inertial fusion & magnetized hed...

Magneto-Inertial Fusion& Magnetized HED Physics

Bruno S. Bauer, UNR& Magneto-Inertial Fusion Community

Workshop on Scientific Opportunitiesin High Energy Density Plasma Physics

Washington, DCAugust 25-27, 2008

The mainline path to fusion energy is basedon the established fact that magnetic fieldssignificantly improve the insulation ofthermonuclear fuel from its surroundings.Can the same insulation improve theperformance of inertially confined systems?A body of theoretical literature suggeststhat it can. Magnetized high energy densityphysics experiments are now helping to testand develop this idea, while significantlyadvancing a vital fundamental frontier ofHED science.

Abstract

BSB 8/24/08

Magneto-Inertial Fusion (MIF)& Magnetized HED Physics

1. Can magnetic field benefit inertial fusion?

2. Does MIF research advance fundamental HED science? Is it important to other fields? Are the ingredients for significant progress available?

BSB 8/24/08

Fermi recognized intense pulsed Bcould reduce thermal conduction

Enrico Fermi, "Super Lecture No. 5--Thermal Conduction as Affectedby a Magnetic Field," Los Alamos Report 344, Sept. 17, 1945.

"A possible method of cutting down the conduction to the walls wouldbe the application of a strong magnetic field, H. This tends to makethe electrons go in circles between collisions, so impedes theirmobility. Actually, it makes them go in spirals, and does not reducethe conductivity parallel to H but only to the other two dimensions,so one would probably want to design the container elongated in thedirection of H, or even toroidal... with the lines of force never leavingthe deuterium... rather large fields will be required... thus a field inexcess of 20,000 gausses would help reduce conduction loss. Whileit would not be possible to produce such fields in a large volume in asteady state,the technical problem of making the field is much aidedby the fact that the time during which the field is needed is muchshorter than the usual relaxation time of magnetic fields, so it needbe applied only instantaneously."

FSC

A strong magnetic field can relax the conditions for hot-spot ignition …

Bhsrhs

Bhs~ 10 MG: Bhs~100 MG:

β≈4•104 κ⊥≈0.2κ|| for ωceτe≈1.2

β≈4•102 κ⊥≈0.01κ|| for ωceτe≈12

rα=270 µm rα/rhs > 5 rα=27 µm α-particles trapped: rα/rhs ≈ 0.5, ωcατα≈0.1

*P. W. McKenty, et al., Phys. Plasmas 8, 2315 (2001)

Considering NIF 1.5 MJ, direct-drive point design* ρhs ≈ 30g/cc, Ths ≈ 7keV (before ignition), rhs ≈ 50µm.

Tens of MG magnetic field is needed for effective reduction of thehot-spot thermal losses through magnetic insulation.

Effective confinement of the alpha particles (relaxation of the hot-spot ρR requirement), requires Bhs~100 MG.

α

O.V. Gotchev, N.W. Jang, J.P. Knauer, M.D. Barbero, D.D. Meyerhofer & R. Betti, UR-LLER.D. Petrasso & C.K. Li, MIT Plasma Science and Fusion Center BSB 8/24/08

FSC

A laser-driven implosion of magnetized cylindrical plasma examines magnetic insulation in ICF

Current driven in coilInitial B ~ 0.1 MG

Implode with40 OMEGA beams 1-ns 14-kJ pulse

Preliminary results B ~ 60 MG10× more neutrons than with B=0

CH shell target20-µm thick

8-atm D2 fill gas

RES, BSB 8/24/08

FSC

Magnetic fields are measured via deflection of the D3He backlighter protons traversing the target area

Cylindrical implosion target860 μm diam.,1.5 mm long

Target stalkBacklighter target stalk

MIFEDS coil4 mm diam. 1200 μm wide

Cylindrical implosion target860 μm diam. and 1.5 mm long

Target stalk Backlighter target stalk

MIFEDS coil4 mm diam. 1200 μm wide

Proton maps at T0+2.9 ns(shot 51069)

Data analysis combined with GEANT4 particle transport code simulations suggest B up to about 60 MG has been observed

RES 8/24/08

FSC

Modeling shows magnetic field gives higher T-- still to be confirmed experimentally

Stagnation phase

LILAC MHD simulations show shock heating ionizes and preheats plasma; then adiabatic compression gives keV ion temperature

Plasma β ~ 50% on axis; about β ~ 12 at 10 µm RES , BSB 8/24/08

One concept for MIF

RES, BSB 4/22/07

• E.g., Al can driven by I > 1 MA, Bθ ~ 100 T

Magneto-inertial fusion:Dense fuel + magnetic insulation

Particle EnergyConfinement Confinement

ICF Inertial InertialMIF Inertial MagneticMFE Magnetic Magnetic

DT fuel:100 gm/cm3

e- thermalconduction:τE ~ 10 ps

j x B = ∇p10-9 gm/cm3

τE ~ 1 s

Eg, 0.1 gm/cm3

τE ~ 100 ns

RES, BSB 4/22/07

Cylindrical compact-torus plasma

Initial FRC~ 20-30 kG~ 200 eV~ 1017 cm-3

Cylindrical liner implosion

LANL-AFRL liner-on-plasma compression seeks to examine MIF physics in fusion regime

Final FRC~ 1019 cm-3

~ 2-4 MG~ 1-5 keV

Shiva Star: 16MA, 9MJ

FRX-L: The Field Reversed Configuration (FRC) Plasma Injector for MTF

Field Reversed Configurationhigh-β self-organized plasma

• <β> ~ 1

• compact torus like spheromak

• Can translate into liner

The LANL FRC has parameters orders of magnitude different than previous FRCs.How will FRC behave under compression? How will liner interact with FRC?

Large current compresses liner=> large kinetic energy (MJ) => Mbar pressure

107 amps< 10 μs

Bθ ~ 100 tesla (40,000 atm)

“Liner” = thin-walled aluminumcylinder the size of a beer can

RES, BSB 8/24/08

AFRL radiographs of liner implosiondemonstrate good liner performance

Stationary 6-mm probe jacket

Elastic-plastic deformed 7-mm thick liner at 12:1 radial compression

Flash x-rayradiographs

Side-on viewof liner moving4 mm/μs

Initial 1-mm thickAluminum liner

RES, BSB 4/22/07

Courtesy of J. Degnan, AFRL

Glide planes interfere with FRC injection

AFRL success with shaped linerRadiograph plus simulation Radiograph alone

Glide planes eliminated

Enhanced magnetic mirror centers FRC

U N C L A S S I F I E D

Operated by the Los Alamos National Security, LLC for the DOE/NNSA

The liner-FRC compression experiment will enable the study of many MIF physics issues

Can multi-keV temperatures be obtained by compression of a magnetically confined plasma to megabar pressures using a solid metal liner?

What limits liner compression and dwell time? How do nearby boundaries (walls) driven by intense magnetic and radiation fields turn into plasmas? How are hydrodynamic instabilities at boundaries changed in the presence of a thermonuclear (fusing) plasma? How can we minimize impurity influx?

Do we have the right material conductivity and transport models (for both walls and plasma)? What effects do velocity shear, initial density profile, finite Larmor radius, and other conditions have on particle and energy transport at MHEDLP conditions?

Visit http://fusionenergy.lanl.gov/mhedlp-wp.pdf for community white paper on Magnetized HEDLP (April 20, 2007) for many more questions!

http://fusionenergy.lanl.gov/mhedlp-wp.pdf

The liner-FRC compression experiment will enable the study of many MIF physics issues

Idealized imploded liner

Idealized compressed FRC(interferogram)

Rayleigh-Taylor growth;Wall plasma interactions

High-β, collisional MHD;rotational instability

Impurities; energy losses;fusion reaction rate

MIF could have advantagesLow ρ → bigger, cheaper targets High To → reduced radial convergence (e.g., 10)Low v → less power, intensity → more & cheaper energy possibleLow v, Bo → adiabatic compression → no pulse shaping, no shocksBig targets, low v → massive pushers → long dwell, burn timesB → rB, not ρr, for alpha deposition

MIF could be profitableCost-effective capacitor bank driverEfficiently heated G~10 hot spotOverall fusion gain could reach G~50 with edge fueling (by cool fuel at wall or jets)Non-cryogenic, macroscopic, simple targetDriver stand off via recyclable transmission lines or plasma jets10 GJ output ~ $50 of heat per shot

•Recycled tin flibe-insulatedtransmission lines

•Flibe primarycoolant at 550 oC(Tmelt = 459 oC)

• Tin Tmelt = 232 oC inserted short time

•Studied by P. Peterson, UC Berkeley

MoltenFlibe

SolidFlibe

Steel

FusionBurst

Tin

IM-1 01-0659 (4/01)

Structural insulator

MIF might use Flibe working fluid

Note – no line of sight needed; electricity goes around corners

Miniature plasma jets from capillary discharges merge to form a plasma ring (Witherspoon, 2007)

Imploding plasma liners can be an inexpensive path to forming cm & µs-scale HED plasmas

Forming a plasma liner with an array of dense plasma jets using pulsed power technology: Plasma gun development at HyperV:

Many potential applicationsFundamental studies of HEDLP, including laser-plasma interactions* and diagnostic development

Laboratory astrophysics and materials science* studies

Experimental validation of rad-hydro simulations

High flux pulsed neutron sources & ultimately MIF

For MIF only

Significant development of high-Mach-number Plasma Jets by HyperV Technologies

x

y

0 0.05 0.1 0.150

0.1

0.2

0.3

0.4

ro2.3E-042.1E-041.8E-041.6E-041.4E-041.1E-049.1E-056.9E-054.6E-052.3E-050.0E+00

t = 7.20013E-06

Density

ro_max=2.29E-004

DW, YCFT, BSB 8/24/08

Plasma liners could be advantageous

Standoff delivery of imploding momentumInexpensive liner fabricationRepetitive operationFast compressionPossible remote current drive by lasersor particle beamsDiagnostics could view both the liner andthe target plasmaAdditional fuel for fusion

YCFT, BSB 4/22/07

Magneto-Inertial Fusion& Magnetized HED Physics

1. A) Magnetic thermal insulation coulddecrease the cost of a G~10 hot spot

B) Alpha trapping can heat fuel with small ρrC) Simple driver & target could yield enough

energy per shot to be profitable

2. Does MIF research advance fundamental HED science? Is it important to other fields? Are the ingredients for significant progress available?

BSB 8/24/08

MIF science priorities have much incommon with ICF, but with B≠0

Explore, illuminate, and understand Stability and transport in dense plasmas with high magnetic fields, especially for collisional, beta>1 plasma

Interaction of magnetized HED plasma with cold, dense matter

Pressure amplification & instability growth in convergent flows

Radiation-MHD phenomena (e.g., radiative collapse, ablation)

Energy deposition of energetic particles & radiation in magnetized material, from solid state to warm dense matter to HED plasma

Continuously apply this developing knowledge to the exploration & illumination of MIF configuration space, with attention to characteristics such as gain-efficiency product, and to the influences on such characteristics in various domains

BSB 8/24/08

A vast scientific wildernesslies beyond B = 0

BB=0

B=0

75% of Maxwell’s equations involve B

Marshakwave

Rayleigh-Taylor

instability

Shockwave

Uncertainty jumps 100xwhen B ≠ 0

BSB 8/24/08

Liner compression of MIF plasma involves many processes at metal-plasma interface

Plasma

O2 impurities

H impurities

radiation

Skin depth

vapors

melts

gas

Hyper-velocity

metallic wall compresses

interior magnetized

plasma

Convectivetransfer

Thermal conduction

Alpha particles

Ohmicheating

X

X B

X

X

Zebra experiment: 1 MA in 100 ns through mm-diameter Al rod, designed to increase the likelihood of success of radiation-MHD modeling

How does radiation-MHD modeling compare with experimental data?

Experiment & modeling: Effect of MG field on aluminum surface (1 MA on 1-mm rod)

Compressed partially ionized metal

Heated surface metal plasma

MHD instability

Anode

Cathode

RES, BSB 8/18/08

I

Experiment on 1-MA Zebra (UNR) studies plasma formed by multi-MG field on aluminum

BSB, NLG 4/22/08

The ‘hourglass’ load is designed to avoid spurious plasma formation

1-mm-diameter central wire is shielded from AK contactsSF, BSB 6/21/07

Results of different MHD codes & tables are being compared with experiment

MHRDR -- UNR: MHD, Eulerian, single materialRAVEN -- LANL, UNR: MHD + strength, Lagrangian, multi-material w/ strengthMACH2 -- NumerEx: ALE, multi-materialUP -- VNIIEF(Russia) : Lagrangian, multi-materialMHD code, IPR (India), Chaturvedi: Lagrangian, multi-material*ALEGRA -- SNL: ALE*LASNEX – LANL: Lagrangian*

* Results not included in this presentation

VM, BSB 8/19/08

Electron temperature profiles calculated at 140 ns

MHRDR

ALE, Mach2

UP, Garanin

EUL, Mach2

Raven, UNR

Raven, LANL

Garanin’s TEmax=35 eV

VM, BSB 6/21/07

Many diagnostics examine transformation of rod into plasma

V-dot and B-dot probesOptical, VUV, EUV, x-ray photodiodes; PMTsTime-resolved optical & EUV spectroscopyStreak camera & time-gated imagingLaser diagnostics (Shadowgraphy, Schlieren, Interferometry, Faraday rotation)

A comprehensive set of fundamental data is being collected & compared with rad-MHD modeling;

Vital data for engineering MIF, MITL, & other systemsdr/dt ~ 2-4 mm/μs for dB/dt = 2000-8000 T/μs; Bthr ~ 200-300 T

TA, BSB 8/24/08

Plasma formation from conductors driven by intense current is of broad interest

Fundamental radiation-MHD (and beyond):Challenging interplay of magnetic diffusion, hydrodynamics, and radiative energy transfer

• Wire-array z-pinches• Magnetically accelerated flier plates• Liner acceleration by magnetic field• Ultrahigh magnetic field generators• Magneto-inertial fusion• High-current fuses• Magnetically insulated transmission lines• Astrophysics

TA, BSB 8/18/08

Galactic and extragalactic jets are among most spectacular astrophysical phenomena

DDR, BSB 8/24/08

J. Wiseman, J. Biretta. “What can we learn about extragalactic jets from galactic jets?” New Astronomy Reviews, 46, 411, 2002

Jet from quasar: length 160 kiloparsecs (5.2x105 light-years)

Protostellar jet: length 0.5 parsecs (1.6 light-years)

Differentially rotating accretion disc is thought to be a key player in the formation

of both galactic and extragalactic jets

Differential rotation creates a strong toroidal magnetic field which pushes the material in the vicinity of the “central engine” up and down with respect to the plane of the disc.

A current pattern is formed, in which the current flows along the axis and returns over a much larger surface (a “cocoon” structure).

DDR, BSB 8/24/08

Illustration from http://www.aoc.nrao.edu/pr/m87.collimation.html

An array of plasma jets could form a differentially rotating disc that amplifies

and transforms magnetic field

Side view, with weak cusp B to see creation of

toroidal B

DDR, BSB 8/24/08

Derived parameters for 12 Witherspoon-gun jets forming a 20-cm diameter disc:

Plasma kinematic viscosity ν~2⋅105 cm2/sReynolds number Re≡rvrot/ν~250Magnetic Reynolds number Rem≡rvrot/Dmagn~500

Top view

D.D. Ryutov, “Using plasma jets to simulate galactic outflows,” presented at Plasma Jet Workshop, Los Alamos, January 24-25, 2008

Magneto-Inertial Fusion (MIF)& Magnetized HED Physics

1. A) Magnetic thermal insulation coulddecrease the cost of a G~10 hot spot

B) Alpha trapping can heat fuel with small ρrC) Simple driver & target could yield enough

energy per shot to be profitable

2. MIF magnetized HEDP is a vital fundamental frontier of HED science, important to many fields, that can be significantly advanced with existing facilities

BSB 8/24/08

Thank you!



Slide 44

• Recently I led/wrote (with ~30 contributors) a community white paper on Magnetized HEDLP. (April 20, 2007)

• Copies are available at


• Merging OFES panel recommendations with Davidson reports

• Basically, adding a new research thrust: dense plasmas in ultrahigh magnetic fields, or MHEDLP

Overarching Question: Can fusion-relevant thermonuclear temperatures be obtained when plasma is compressed with megagauss fields?

Dense Plasmas in Ultrahigh Magnetic Fields




Liner-FRC compression physics (continued)

What happens when the liner stagnates on the plasma target pressure? What is the realistic energy partition between liner ablation consequent generated plasma, radiation and ion flux? How does the sheath at the liner- plasma boundary behave? To what extent do the liner and plasma mix?

Do the FRC scaling laws hold as expected for strong boundary compression? Can strong elongation increase MTF fusion yield? Can an elongated liner remain stable as it is compressed?

Can we take advantage of ultra high magnetic fields and high density to enable plasma diagnostics that are not possible in more conventional regimes?



Slide 46

MIF/MTF approach has many common features with IFE

• Pulsed, rep-rated systems, storage and switching of driver energy

• Achieving driver stand-off under rep-rated conditions (but the problem typically takes a different form)

• Designing a chamber to take the intense energy and particle loads

• Chamber clearing

• Isotope and chemical separations at the back end for DT and blanket materials

There are also some significant differences:•Target physics/gain•Target manufacture/formation•Electrical connections•Symmetry needs•Driver power levels

The input energy & power required for hot spot gain G are set by the fuel pressure & β

T = 10 keV; p, β n = p/(2kT)τE = G[nτE]L / n (Lawson)B = (2nkT/β)½

Thermal diffusivity χ = f(n,T,B)e.g., χBohm = kT/(16eB) ~ 1 m2/s

R = (χτE)½ & e.g., Volume ∝ R3 ∝ τE1½ ∝ p-1½

Energy = 3nkT*Volume ∝ p-½

Power = Energy/τE ∝ p½

RS, BSB 4/22/07

Thermal diffusion determines DT hot spot mass & energy

103

Density (gram/cm3)

1

10-3

10-6

10-9 10-6 10-3 1

Fuel

Mas

s (g

ram

s)

Diffusion-limitZero magneticfield

NIF

ApproximateUpper-limit “Bohm”βpoloidal = 1

Advanced concepts

ITER

Diffusion-limit“classical” magnetic confinementβpoloidal = 1

IM-1/0476 03/01

MTF

Fuel

Ene

rgy

(joul

es)

106

109

103

106103 109Pressure (atm.)RS, BSB 4/22/07

LANL has demonstrated high-density FRC formation

•Integrated liner-on-plasma experiments in next two years

•Goal to determine if liner flux compression can generate thermonuclear temperatures



High pressure FRC plasmas are produced in FRX-L

FRC parameters in FRX-L, following installation of improved high-current crowbar system. The plasma pressure is 2-3 MegaPascals, (20-30 bars); higher than even the highest field tokamak plasmas. An n=2 rotational instability develops by t=20 µsec, terminating the plasma.



An FRC compression experiment is being developed at Shiva Star (AFRL)

Shiva Star Capacitor Bank, up to 9 MJ of stored energy

• 80 to 90 kV, 1300 uF, 25 to 45 nH

• 11 to 16 MA, J x B force implodes 10 cm diameter, 1 mm thick, 4 to 30 cm long Al liner in 15 to 24 μsec

• e.g., 4.4 MJ energy storage gives 1.5 MJ in liner kinetic energy

GW, BSB 8/24/08

Implosions of high Mach number plasma jets has additional potential for fusion applications

• An approximately spherical distribution of jets are launched towards a common center

• The jets merge to form a spheroidal shell (liner), imploding towards the center

Plasma jet

Arrows indicate flow direction

Plasma gun

Magnetized target plasma

Plasma liner

Supersonic Plasma Jets and Precursor Flows in Wire-Array Z-Pinch

J. P. Chittenden, et. al., “Indirect-Drive ICF using Supersonic, Radiatively Cooled, Plasma Slugs,” PRL, 88 (23), 2002

Cylindrically converging precursor plasma flow in wire-array Z-pinch Experiments.S. C. Bott, et. al, Phys Rev E, 74, 2006.

Low-cost electric pulsed power can apply plenty of pressure, energy, & power

Superconducting magnets (constant)B < 15 Teslap < βB2/2μ0 ~ 100 atm

Liner technology (pulsed 107J / 10-5s ~ 1012 W)B ~ 103 Teslap ~ βB2/2μ0 ~ 106 atm

Laser compression (pulsed)p ~ 1011 atm

RS, BSB 4/22/07

MIF seeks minimum-cost trade-off between input energy & power

Generic MIFQ ~ 1 cost$1*E(J)

+ $10*P(MW)

RS, BSB 4/22/07

MTF power plant concept

Confinement chamber

Cassette loader

Person

The “kopeck” problem• Jim Tuck was one of the fusion energy

pioneers at Los Alamos• When first informed of laser fusion he

scoffed• He noted that the likely value of the

energy pulse generated would best bereckoned in kopecks (= 0.01 Soviet Rubles)rather than dollars

• Not only must energy be produced, but thevalue of that energy must be more than thecost to produce it

MIF typically seeks B > 1 MG

• An established method of generating MG fields is with metal liner implosions, often aluminum.

• Seed field is introduced into a cylindrical enclosure, which is then imploded by z pinch or theta pinch compression.

• Megagauss conferences have documented this possibility for more than 30 years

Theory of FRC behavior is incomplete

Hoffman and Slough, Nuc. Fus. 33, 27(1993)

Experiments show slow decay MHD theory predicts fast decay

Recent theory suggests elongated shape can be stable (D. C. Barnes, Phys. Plasmas, 2002)

Magnetic confinement: j x B = ∇p

In each case one investigates thermal diffusivity χ because τE = (size)2/ χ

Tokamaks

RFP FRC

Stellarator

Externally controlled

Spheromak

Self organized

RS, BSB 9/20/03

Possible MTF plasma targets

Russian MAGO

Field-Reversed Configuration

RS, BSB 9/20/03

Zebra pulses MG field on mm-diam rods

Vacuum chamber

LoadSpark gaps Water switches

Gas switch

Marx bank Intermediate storage Pulse forming line

Typical operation:Marx charged to 85 kV Load current 0.9 – 1 MAStored energy 150 kJ Rise-time 70 ns (10%-90%)PFL voltage 2.2 MV Current rise 1013 A/s (10 kA/ns)

TA, BSB 6/2107

Density profiles at 140 ns calculated by different codes for Zebra expt

MHRDR

ALE, Mach2

UP, Garanin

EUL, Mach2

Raven, LANL

Raven, UNR

VM, BSB 6/21/07

Electrical conductivity varies by tableSesame Format Material Viewer V.1

VM, BSB 1/01/08

Plasma formation is still uncertain in computer simulations, but is clear in experiment

Plasma forms for ≤1.25-mm diameter rods:Optical photodiodes indicate T > 10 eVVUV photodiodes show plenty of 16-73 eV photonsEUV photodiodes observe many >70 eV photonsEUV spectra display emission lines from multiply ionized aluminum, mainly Al3+ and Al4+

Laser shadowgrams show z-pinch instability growth

Vapor cloud forms for 2.0-mm diameter rods:Optical photodiodes indicate T < 0.5 eVNo signal observed on VUV & EUV photodiodesLaser shadowgrams show stable expansion

BSB 6/22/08

IFE power plant with stand-off driver

Shiva Star at AFRL (Alb.)

Atlas can implode liners @ NTS

RS, BSB 9/20/03

Liner radius vs time

“Magnetic tower jets” were studied using the MAGPIE Z-pinch (Imperial College, London, UK)

S.V. Lebedev, A. Ciardi, D.J. Ampleford, et al. “Magnetic tower outflows from a radial wire array Z-pinch.” Monthly Notices of the Royal Astronomical Society, 361, 97, 2005.

DDR, BSB 8/24/08

Streaked self-emission & laser shadowgrams show consistent plasma expansion

Tim e [ns]250 300 350 400 450 500Ze

rba

Cur

rent

[MA

], R

adiu

s [m

m],

Stre

ak &

PD

Sig

nals

[a.u

.]

0 .0

0.5

1.0

1.5

2.0

2.5

3.01s-r(t) 2s-r(t) 3f-r(t) 3i-r(t) 3s-r(t) 1ds-r(t) 2ds-r(t) Zebra Current [M A]Integrated Streak [a.u.]Photo D iode [a.u.]Photom ultip lier [a.u.]

SF, BSB 2/09/07

Future possibility: Proton radiography of a liner implosion on Zebra

Laser Target

Shield

Liner

Cathode

Anode

SF, BSB 7/22/07

BB=0

B=0

A vast scientific wildernesslies beyond B=0

75% of Maxwell’s equations involve B

Marshakwave

Rayleigh-Taylor

instability

Shockwave

Uncertainty jumps 100xwhen B ≠ 0

BSB 8/24/08

magneto-inertial fusion & magnetized hed...

Documents