OMEGA and OMEGA EP Will Provide Key Physics Data for Laser IFE. J. M. Soures University of Rochester Laboratory for Laser Energetics

Transcription

1 OMEGA and OMEGA EP Will Provide Key Physics Data for Laser IFE J. M. Soures University of Rochester Laboratory for Laser Energetics 2005 US-Japan Workshop on Laser IFE San Diego, CA March 2005

2 Summary OMEGA and OMEGA EP will provide key physics data for laser IFE The OMEGA 60-beam UV laser is conducting direct-drive cryogenic capsule implosion experiments leading towards direct-drive ignition on the NIF. Fast-ignition core assembly experiments are being conducted on OMEGA. The OMEGA EP laser, under construction (completion in 2007), will provide a unique capability to couple high-intensity petawatt heating beams to a symmetric direct-drive implosion facility. I1593

3 OMEGA Cryogenic Capsules The life cycle of a cryogenic target is an engineering tour de force Shadowgraph X-ray pinhole camera 1 m MCTC C-mount Shroud retractor Existing tritium equipment Tritium Facility DT compressor Permeation cryostat Characterization station Target chamber Moving cryostat transfer cart (MCTC) E12062d Target positioning accuracy is more challenging with cryogenic targets.

4 The best layer to date is 1.2-μm rms (all modes) with the best regions below 1.0-μm rms 24 shadowgraphic views of x and y Radius (pixels) Unwrapped Image X (pixels) Spectrum (μm 2 ) X (pixels) Primary bright band Multiple secondary bright bands Inner 0.8-μm rms Outer 0.3-μm rms Angle ( ) Mode l 10 2 T1905f

5 Key parameters of cryogenic implosions are measured and compared to simulations Absorption Drive Core size Fusion reaction history Fuel ρr n Fuel temperature I1592

6 In cryogenic D 2 implosions, the total ρr n is inferred from the energy loss of secondary D 3 He protons Typically, 4 to 6 measurements per implosion CPS1 KO1 TIM4 CPS2 TIM2 TIM1 = Magnet-based CPS s = WRF spectrometers TIM5 KO3 KO2 TIM6 TIM3 Incident protons Yield/MeV ( 10 6 ) Shot ρr ~ 110 mg/cm Proton energy (MeV) Al wedge filter t CR-39 CR-39 Top view of WRF spectrometer Front view of etched CR-39 E13490

7 A 2-D hydrodynamic simulation demonstrates good agreement in predicting target performance for shot (α ~ 4) R (μm) TC6465f 15μm offset, 4.1 μm ice rms DRACO 2-D density near peak burn, shot α ~ 4, 17.5 kj 25 0 Z (μm) Density (g/cm3) D 2-D Expt Y 1n Y 2n <ρr> (mg/cm2) T ion (kev) ρr(mg/cm 2 ) D DRACO polar lineout of the total ρr Range of measured ρr s (4 LOS) Azimuth (degrees) 180

8 Scaled ignition performance on OMEGA is approaching the predicted equivalence of high gain on the NIF Normalized yield α = 6 α = 4 DRACO OMEGA data σ (μm) 1-THz, 2-D SSD with PS, 1-μm-rms ice roughness, 840-Å outer-surface roughness, 2% rms power imbalance E13398 Target offset and ice quality presently limit access to low σ for α = 4 campaign

9 OMEGA EP: Fast Ignition A complementary approach to hot-spot ignition, namely fast ignition is an active research area at LLE Conventional ICF Fast Ignitor* Temperature Hot spot Burn wave Mass density Radius Low-density central spot ignites a high-density cold shell ρt hot ρt cold (isobaric) Fast injection of heat Temperature Burn wave Mass density Radius Fast-heated side spot ignites a high-density fuel ball ρ hot ρ cold (isochoric) E12526d Key physics issues hot electron production transport to the core core formation * M. Tabak et al., Phys. Plasmas 1, 1626 (1994).

10 Ignition could be achieved at lower drive energies with fast ignition Direct-drive FI at the NIF Target gain g/cc, 92 kj, g/cc, 200 kj, Fast ignition NIF point designs 150 g/cc, 330 kj, v = 4x NIF v = 3x Driver energy (MJ) 1000-MJ yield Direct drive 100-MJ yield Indirect drive 10-MJ yield E12527b

11 Fast ignition with cryogenic fuel will be conducted on OMEGA with the high energy petawatt OMEGA EP Channeling Concept* Cone-Focused Concept** Hole boring Ignition Light pressure bores hole in coronal plasma. 10 ps ~1-MeV electrons heat DT fuel to ~10 kev, ~300 mg/cm 2. Au cone e Single ignitor beam: 10 ps Key physics issues hot electron production transport to the core core formation E11710g * M. Tabak et al., Phys. Plasmas 1, 1626 (1994). ** R. Kodama, Nature 418, 933 (2002).

12 Gas-tight fast-ignition targets were developed for fuel-assembly experiments 870-μm OD shell 24-μm wall ~10 atm D 2 or D 3 He fill 35 half-angle gold cone Backlighting 35 beams, 12 kj, 1 ns on target 15 beams, 6 kj, 1 ns on backlighter Areal-density measurements 55 beams, 22 kj, 1 ns on target 870 μm E12573b

13 The backlit framing-camera images show the core assembly and cone reaction in great detail 1.73 ns 1.85 ns 2.04 ns 2.15 ns Cone Shell 2.23 ns 2.54 ns 2.65 ns 2.77 ns E12558d Shot 32381, V backlighter, D 2 fill, yield = , ρr ~ 60 mg/cm 2 (D 3 He proton de/dx) 200 μm

14 OMEGA EP To enhance the Nation s high-energy-density science capabilities, LLE is building a multipetawatt laser Power (PW) OMEGA EP short-pulse capability ( Wcm 2 ) 10 fs 100 fs 1 ps Extreme field science Hot dense matter physics Wcm Wcm 2 OMEGA EP with long-pulse capability Energy (kj) Wcm 2 Fast ignition Wcm 2 > 1-keV hohlraum sources 20- to 100-keV radiography 10 ps 100 ps 1 ns E11703f

15 OMEGA EP: ICF Program OMEGA EP will be used to backlight cryogenic implosions and study fast ignition OMEGA target chamber OMEGA EP target chamber Main amplifiers OMEGA Laser Bay Compression chamber Short-pulse performance Short-pulse beam 1 Short-pulse beam 2 G5546r Short pulse (IR) IR energy on-target (kj) Intensity (W/cm 2 ) 1 to 100 ps to 100 ps 2.6 ~ OMEGA EP Laser Bay OMEGA EP will be completed in FY07.

16 The OMEGA EP building was completed in February 2005 OMEGA EP Laser Bay April 2004 Mechanical room OMEGA Laser bay Target Bay Capacitor bay January 2005 Laser bay slab, 1 m E13574a

17 Both OMEGA EP compressors contain four tiled grating units OMEGA (or) OMEGA EP target chamber Beam entry ports (2) Beamline 2 Beamline 1 E12412b 1 3 tiled grating set

18 The grating compressor chamber is currently under construction 5.5 m 23 m 4.2 m Diagnostics or to OMEGA EP chamber To OMEGA chamber Input beams G5601f Beam combiner DM s

19 Short pulses will be delivered to OMEGA through vacuum tubes and focused by an f/2 parabola OMEGA target chamber G5567b Parabola in retracted position

20 OMEGA EP is designed to perform integrated fast-ignition experiments with cryogenic implosions Co-propagating OMEGA EP ignitor and channeling beams test both concepts. Channeling beam: I > W/cm 2 E ~ 0.5 to 2.6 kj in 100 ps r focus ~ 15 μm shot cycle time < 2 h Ignitor beam: I > W/cm 2 E ~ 0.5 to 2.6 kj in <10 ps r focus < 10 μm shot cycle time < 2 h These experiments will validate hot-electron transport and core-heating physics. Cryo target lower pylon OMEGA target chamber Cryo shot cycle < 2 h E11715

21 In the next few years, OMEGA EP and FIREX will come online; allowing integrated experiments at near-ignition conditions G = 1 on OMEGA Neutron yield Cryogenic DT implosions on OMEGA EP and FIREX; multi-kj petawatt beams coupled to tens of kj compression systems 10 6 CD cone implosions on Gekko Kodama. et al. E Heating laser power (PW) 10.0

22 Summary/Conclusions OMEGA and OMEGA EP will provide key physics data for laser IFE The OMEGA 60-beam UV laser is conducting direct-drive cryogenic capsule implosion experiments leading towards direct-drive ignition on the NIF. Fast-ignition core assembly experiments are being conducted on OMEGA. The OMEGA EP laser, under construction (completion in 2007), will provide a unique capability to couple high-intensity petawatt heating beams to a symmetric direct-drive implosion facility. I1593