Heavy Ion Fusion-a Future Perspective E. Michael Campbell PPPL, June 7, 2004

Presentation Outline Present Fusion landscape Why HIF Challenges Opportunities Path Forward

Fusion Facts No Administration commitment to rapid development of Fusion energy –Budget deficit is increasing problem (approaching % of GDP seen in late 1980’s) and no “cold war windfall” –War, Homeland security are priorities –Energy Priorities are “nearer term” solutions Hydrogen (Hydrogen already at ~11 Mtons/year and annual growth is ~10%) Fission –Viewed as Science Program with energy S&T deferred to “after Burning plasmas or Scientific feasibility” demonstrated NGNP at INL

Fusion Facts (cont’d) ITER and not IFE initiative will be OFES focus for next decade –IFE not supported (“we can’t afford two approaches today”) by DOE, OFES or OMB –OFES and OS view is ICF/IFE is NNSA (NNSA$>>OS$) responsibility –OFES priority after ITER is to better exploit existing facilities (present run time on 3 major OFES facilities is ~14 weeks) –Some OS interest in High Energy Density Physics

ICF S&T advances, funding and controversy are made possible by its Multiple Missions: HIF lies in the Energy and S&T plane Stockpile Stewardship National Security Science/technology Energy( National Security) ICF

An IFE initiative should be catalyzed by Ignition and High Performance Implosion Results Ignition will catalyze IFE interest and may lead to broad support for an IFE initiative –ICF/IFE community must maintain ignition focus on NIF (~2010) Implosion Experiments will have an impact if successful –Cryogenic, low , DT Direct drive implosions on Omega (~2006) –Integral Fast Ignition experiments on FIREXI and Omega-EP (ZR and PW?) –Implosions on Z And HIF………………………………….

The Motivation for HIF has not changed HIF accelerators have attractive efficiency, rep- rate and durability for IFE –Large accelerator community experience that is relevant Focusing optics are more robust to fusion chamber environment (radiation/debris) than lasers < 4  illumination for targets allows for neutronically thick liquid walls NNSA indirect target physics program (and FI research (OFES & NNSA)) BUT…………………………

HIF Development faces significant challenges Development path is costly and has not been viewed as symbiotic with other ICF/IFE programs Little/no target experiments Advantages are “too far off” to motivate IFE support today Competition from HEDP facilities

What Would Marshall say?

Innovation and a broad program approach will position HIF for a future IFE initiative Accelerator –Increase modularity (reduce “unit size”) –Beam manipulations in space and time (like lasers!) Lasers : – temporal pulse shaping –CPA (extreme temporal compression ) –Phase plates and deformable mirrors Pulse Power developing analogous capabilities –Develop “average power” experiments Target design and fabrication –Advanced simulations –Targets to compensate for driver limitations –Fast Ignition –Develop “average power experiments”

Innovation and a broad program approach will position HIF for a future IFE initiative Utilize existing facilities –Implosions to exploit HIF relevant concepts Symmetry control (Shims) Low temperature ablators ( Be:Cu) –Rad-Hydro with foams –Ions from short pulse lasers Ion-plasma interaction Neutralization physics (?) Source development required! Synergistic Engineering Physics and technology with Pulse Power –Neutronically thick liquid walls –Reactor concepts –Driver technology There is time to innovate…………….

IFE requires: Drivers Z-R OMEGA EP & Nike,Trident,.. NIF Simulations Target S&T 3D rad.-hydro Simulation of igniting target Double shell target

Accelerators Accelerators

Pulse Shaping for Robust HIF Point Design (Indirect Drive) 120 beams, 7MJ Laser Pulse Shaping (Direct Drive) ~60 beams ~2 MJ Improved HIF Beam Manipulations are required !

Innovations Beam Production Accel-decel injector + compression Transport Solenoid transport of large- perveance heavy-ion beams Longitudinal Compression Transverse Focusing Neutralized drift compression Plasma lens, Plasma channel pinch transport

(cm) Axial compression 120 X Radial compression to 1/e focal spot radius < 1 mm Beam intensity on target increases by 50,000 X. R(cm) Ramped keV K + ion beam injected into a 1.4-m long plasma column. Background plasma at 10 times beam density (not shown). 3.9T solenoid LSP simulations of neutralized drift and focusing show significant spatial and temporal compression Z(cm) Experiments are essential to validate concept!

Targets Targets

Graded Cu dopant In Be shell A small fill tube IFE has benefited from Innovation in Drivers, Physics, and Target Fabrication: Target design and fabrication(graded Be:Cu ablators and fill tubes) Increased Hydro stability

HIF can benefit from Innovation in Target Design and Fabrication : (Shims to control symmetry) Target design and Fabrication can compensate for Driver Limitations (3D Rad-Hydro Codes are required!!!) Shims Experiments are underway at Z to validate conceptsExperiments are underway at Z to validate concepts Future Experiments on Omega and NIFFuture Experiments on Omega and NIF HIFZ

Fast Ignition Concepts for HIF and Z are similar HIF FI Concept (120 ev radiation Implosion) Ignitor Beam Pulse Power FI Concept Final Shell position Initial shell Position

Polar Direct Drive on NIF is an example of non- spherical “initial conditions” that may lead to ignition/gain imploded fuel assemblies) Baseline Approach: Move the Beams! New Approach: Re-point the Beams! Multi-Dimensional Calculations and 192 beams make this possible!

Ions From UUL Ions From UUL

Protons and ions are accelerated in relativistic laser-solid interactions by three principal mechanisms III. Target Normal Sheath Acceleration E i ~ 10 x T e Electrons penetrate target & form dense sheath on rear, non- irradiated surface Strong electrostatic sheath field ionizes surface layer (E o ~ kT / e d ~ MV/  m) Rapid (~ps) acceleration in expanding sheath produces very laminar ion beam II. Front-surface charge separation Static limit: T i ~ T e II. III CD 2 I. Incident laser I. Thermal expansion T i ~ 5-10 x T e Surface Layer (e.g., CaF 2 ) F 7+ ion Bulk Target (e.g., CD 2 ) e-e- D + ion

Laser-Ion diodes have very interesting characteristics but need development 50  m W + 1  m CaF 2 (900 O C) 4% conversion of laser energy to F 7+ ion beam observed !! 20 J, 350 fs  m Transverse emittance: <  mm-mrad ( Longitudinal emittance: < keV-ns (velocity correlated) Energy spread:100% Bunch charge:10 11 – protons/ions Source diameter:~50  m (fwhm) Charge state purity:>80% He-like Particle current:>100 kA (at source) Rep-rate:determined by laser driver Laser-ion efficiency:> 1% (4-20% observed Neutralization ~100% Laser-ion diodes

PW IONs can be focused 50  m 200  m >400  m Streak images of visible Planckian emission

Al has been heated to ~23 ev by a focused laser produced proton beam Electron heating Focused proton beam Planar proton beam P K Patel et al Laser to Proton conversion efficiencies ~10% were observed at Nova PW   Next generation of PW (2-3 kJ) may lead to ~100ev via ion heating T ~23 ev (7 x 10 5 j/g) (~0.2 joules from 10 joule laser)

Laser-Ion acceleration should be explored in conjunction with Heavy-ion Inertial Fusion program and Fast Ignitor Proton-driven fast Ignition Roth, Cowan, Key et al. PRL 86, 436 (2001) Heavy-Ion Beam Driven Hohlraum High particle-current density neutral beam transport physics ballistic focusing (FI) beam self-heating at focus (FI, HIF) High energy density beam-target interaction physics (FI & HIF) Isochoic heating to ~60 ev has been demonstrated Beam Focusing has been demonstrated Novel Ion Sources for Induction Accelerators

Chambers Chambers

HIF and Z pinch employ thick liquid walls enabled by < 4  target illumination Flibe Jets Xray driven targets Z pinch IFE HIF “Reactor Physics” collaboration should be key element of Z and HIF IFE research

Multiple reactor chambers are a feature of Pulse Power IFE Z-Pinch IFE DEMO study used 12 chambers, Symbiosis with HIF?

Innovation and a broad program approach will position HIF for a future IFE initiative Accelerators Target design and fabrication Exploit existing Facilities Partner with Pulse power for reactor design and Engineering Become Champion of “average power” experiments Always keep sight of the end goal !