for Preperations Integrated Cryogenic Fast-Ignition Experiments on OMEGA/OMEGA EP
b-layered DT Cryogenic Target
OMEGA EP
David D. Meyerhofer Director, Experimental Division Laboratory for Laser Energetics ME and Physics Departments University of Rochester
9th International Fast Ignition Workshop Cambridge, MA 35 November 2006
Summary
Preparations for fast-ignition experiments on OMEGA and OMEGA EP are progressing well
OMEGA EP construction is progressing well Most technical risks have been overcome 17 of 27 gratings delivered Completion in April 2008 Cryogenic target capabilities show continued progress <1-nm-rms ice-roughness targets have been imploded on OMEGA Areal densities in excess of 100 mg/cm2 have been observed New capabilities are being developed for OMEGA EP in response to user input Simultaneous side- and backlighting is now baseline A 4~ probe beam will be installed Contrast diagnostics are under development OMEGA/OMEGA EP will begin integrated experiments in FY09
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Short-pulse OMEGA EP beams can be directed either to OMEGA or new OMEGA EP target chamber
Short pulse combined IR energy (kJ) Pulse duration at full energy (ps) Focusing (diam) Intensity (W/cm2)
Beam 1 2.6 10 to 100 >80% in 20 nm 3 1020
Beam 2 2.6 80 to 100 >80% in 40 nm 2 1018
Each beam duration can be as short as 1 ps at reduced energy (grating damage and B-integral)
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Beam 2 can produce 2.6 kJ in 10 ps when propagating on a separate path
OMEGA EP will have a variety of stand-alone configurations
OMEGA EP target chamber Orthogonal TIMS! (TIM is a vacuum diagnostic inserter) TIM
TIM
OMEGA EP sidelighter 2.6 kJ, 10 ps
Up to four longpulse UV beams, 10 ns, 6.5 kJ
23
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OMEGA EP backlighter, 2.6 kJ, 10 ps Simultaneous sidelighting and backlighting will be possibletwo long-pulse UV beams still available
OMEGA EP construction is progressing well
Major technical risks have been overcome 17 of 27 gratingsmeeting damage threshold and wavefronthave been delivered, Grating tiling requirements demonstrated with full-size optics, Double-pulse plasma-electrode Pockels cell has been demonstrated. Two laser front ends are operational. A >1-J, 1-ps, prototype laser (MTW) is operational Laser-diagnostic development Target shots for diagnostic development. The remaining schedule risk is the delivery of vacuum-compatible tables for the grating-compression chamber Commercial tables have too much outgassing and damage gratings. OMEGA EP will be completed in April 2008
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Integrated cryogenic DD FI experiments will validate/compare both channeling and cone concepts on a single facility
CryoNTD
High throughput Proven diagnostics Proven cryogenics
Neutronics
D
t
X-ray imaging Petawatt beam - OMEGA EP
7705 mm
12949 mm
4660 mm 26.57 Alignment station
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Cone targets
Direct-drive DD and DT cryo capsules
Image recording system
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Neutron imaging
The ultimate fast-ignition integrated experiments will require cryogenic targets
Understanding of direct-drive, cryogenic-target production and fielding continues to progress Both cryogenic D2 and DT targets have demonstrated <2-nm-rms inner-ice roughness. Ice quality is maintained through the target shot. A test stand for cryogenic cone-in-shell target development is being assembled. Both optical shadowgraphy and x-ray phase contrast imaging will be available.
While fast ignition reduces the target-uniformity requirements, the highest areal densities will be achieved with high-quality targets.
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We have produced DT (45:55) ice layers with an ice roughness less than 1-nm rms for all modes
n
n
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n
The neutron averaged areal density tRn is greater than 100 mg/cm2 for cryogenic D2 implosions
1. D + D 3He (0.7 MeV) + p 2. 3He + D p (12.517.4 MeV) + 4He
t
dE/dx corresponds to tRn ~ 100 to 110 mg/cm2 over several lines-of-sight Low-energy tail suggests peak tR approaches 200 mg/cm2 Further analysis is underway to infer a tR(t) by convolving the neutron emission rate with the measured proton spectrum*
t
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*V. A. Smalyuk et al., Rev. Phys. Lett. 90, 135002 (2003).
The core x-ray continuum is measured with a pinhole-array spectrometer
~200 monochromatic images with 50-nm pinholes Array tilt spreads images along energy axis
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Core emission is well separated from ablationregion emission and background
The peak areal density tRpeak may be inferred by using core self emission to backlight the fuel shell
Emitted x-ray spectrum is the product of a source term and an attenuation term 1-D simulations can be used to estimate t and suggest the tRpeak could be as high as 180 to 190 mg/cm2
I
t
&~ Spect = (eE/kThot) (entRshell), where n is the mass attenuation coefficient and is proportional to t The fuelshell attenuation is proportional to t2R
2-D simulations are expected shortly to confirm fuel density estimates
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Experimental capabilities for OMEGA EP beyond the baseline are under development
The OMEGA EP user workshop in January 2006 identified a number of desired capabilities. A contrast measurement is the primary missing laser diagnostic Front-end contrast has been measured Contrast diagnostic is under development Desired experimental capabilities include Simultaneous side- and backlighting (now baseline) 4~ probe beam (under development) Other target diagnostics are being developed on MTW (>1 J, 1 ps) - TIM-based, 2-ps, x-ray streak camera - High-resolution optical transition radiation - Modular electron spectrometer A follow-up workshop to begin detailed experimental planning will be held in Spring 2008
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Improved diagnostics of the laser-focal conditioning are under development
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A suite of complimentary diagnostics are needed to cover OMEGA EPs range of operating conditions
Single-shot autocorrelator Pulse mixing in nonlinear medium 0.5 to 12 ps No No No Yes No
Property
Streak camera EO imaging of temporal pulse 8 to 300 ps Yes No Yes No Yes
EO-SPIDER Spectral phase interferometry 0.5 to 30 ps Yes Yes Yes No Yes
Measurement technique Pulse-width range Complete intensity characterization Complete field characterization High sensitivity Insensitive to trigger jitter Insensitive to beam quality
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The on-target irradiance is calculated from calibrated near-field measurements of a sample beam
Pre-shot calibration of sample beam measure transfer wavefront from main to sample beam using two probe sources On-shot measurement measure sample beam wavefront and amplitude Post-shot calculation Calculate ...