Around the Lab
2002 Year in Review
January, 2003As our staff looks back on 2002, we can see it has been a year of many technological and scientific accomplishments. From the cryogenic target research to our annual Summer High School Student Program, all areas of LLE have seen advancement. Our staff can take pride in these accomplishments as well as look forward to 2003.
Listed below are just a few of LLE’s accomplishments from 2002.
Cryogenic Target Implosions
In a September OMEGA experiment, the fusion neutron yield from a D2-filled, high-adiabat cryogenic target implosion was near 100% of the 1-D LILAC hydrodynamic code prediction. The time-integrated x-ray images shown here were used to assess the implosion symmetry and placement precision of the cryogenic targets.
ICF Ablator Burnthrough Data
The first ICF ablator burnthrough data in halfraums were obtained in joint SNL/LANL/LLNL/LLE experiments this year. The achievement of indirect-drive ignition of a NIF capsule requires precise capsule shock timing and prediction of ablator burn-through timing to within a few percent. These experiments are the first attempts to time resolve the coalescence of two shocks (at pressures of ~10 and 60 Mbar, respectively) in Be+0.9% Cu wedge ablator samples (supplied by the Target Fabrication Group at LANL). DOE Progress Report, February 2002
2-D Performance of a Low-Adibat Cryogenic Implosion
A new low-adiabat drive pulse (α ~ 4) has been developed specifically for the 5-μm-CH, 100-μm-thick cryogenic D2 capsules routinely imploded on OMEGA. The shell stability with this pulse is considerably improved compared to the nominal α ~ 3 design that is, in turn, scaled from the baseline direct-drive-ignition pulse shape for the NIF. Therefore, these implosions are less sensitive to the current levels of laser system nonuniformity on OMEGA. Above is a shadowgraph of the target used on shot 28969, the first experiment with this new configuration. DOE Progress Report, November 2002
2ω/Green Beam Activation on OMEGA
A 2ω probe laser was activated on OMEGA to characterize underdense plasmas and to investigate 2ω laser-plasma interactions. This project is a collaboration between LLNL’s target physicists and engineers and LLE’s target and laser scientists and engineers. The project redirects the 2ω laser light of an existing beam to a specified port using a kinematic mirror. Beam pointing, focusing, energy diagnostics, and a dedicated 2ω distributed phase plate have been successfully activated. The first target physics experiments using the new probe have provided high-quality data for backscattering in laser-scale-length plasmas. DOE Progress Report, July 2002
Planar Cryogenic Target Positioner on OMEGA
A new planar cryogenic target positioner has been deployed on OMEGA to measure the properties of condensed gasses at cryogenic temperatures. It uses a closed-loop cooling system that is fully compatible with the infrastructure developed for spherical cryogenic targets. This photograph was taken the instant a shot occurred utilizing this new system. “Around the Laboratory,” November 2002
Simulated Backlit OMEGA Cryogenic Implosion
Work in support of future experiments employing OMEGA EP investigated the use of soft (2.0-keV) x-ray backlighting to capture areal density images of stagnated OMEGA cryogenic implosions. The image shown to the right was generated with the SPECT3D software analyzing a 2-D DRACO radiation hydrodynamic simulation of a perturbed OMEGA cryogenic implosion.
New OMEGA Diode-Pumped Regenerative Amplifier
A new highly stable, diode-pumped Nd:YLF regenerative amplifier (ODR) was installed in the OMEGA SSD driver line. This amplifier produces shaped optical pulses of up to 7-ns duration at an energy level of ~ 1 mJ with an output energy fluctuation of only ~0.9% rms. The ODR output is designed to drive the OMEGA power amplifiers and routinely demonstrates high beam roundness with an ellipticity of <1%; this is an important characteristic to ensure optimum OMEGA beamline performance. Improved temporal-pulse-shape stability, beam quality, reliability, and compactness are the principal advantages of the ODR in comparison to previous designs. The image above shows an overview of the major components. DOE Progress Report, October 2002
Determination of Imploded Core Temperature and Density Gradients
A team lead by Roberto Mancini of the University of Nevada, Reno and Jeffrey Koch of LLNL is conducting NLUF experiments to spectroscopically determine 1-D temperature and density gradients in the cores of indirect-drive capsules imploded on OMEGA. The method is based on a novel self-consistent analysis for data from simultaneous x-ray line spectra and x-ray monochromatic images. An array of implosion core images recorded with the MMI-2 diagnostic in OMEGA shot 26787 is shown above. DOE Progress Report, August 2002
High-Performance, Direct-Drive Target Designs
Continuing development for the “wetted-foam” direct-drive target design has resulted in a substantial increase in target gain and an extension of the designs to the higher laser energies that might be of interest for fusion energy production. This plot demonstrates calculated target gain (thermonuclear energy out/laser energy on target) as a function of the laser energy in MJ for several wetted-foam direct-drive capsule designs with different implosion velocities compared to the baseline “all-DT” NIF direct-drive capsule design. The colored lines are the results of a simple scaling model while the solid symbols represent full 1-D hydrocode simulations. DOE Progress Report, June 2002.
Optical Parametric Chirped-Pulse Amplification (OPCPA)
A key element of future ultrahigh-intensity lasers is a stable, high-efficiency laser source capable of generating broad-bandwidth pulses that can be amplified by a high-power amplifier system. Optical parametric chirped-pulse amplification (OPCPA) is a novel laser concept that is well-suited for this application. LLE demonstrated one of the higher-efficiency OPCPA systems. The OPCPA concept is based in part on an LLE-invented concept: chirped-pulse amplification (CPA). The CPA idea created a revolution in laser technology by enabling the development of ultrahigh-intensity lasers. DOE Progress Report, September 2002
Deformable Mirrors
The assembly of deformable mirrors at LLE is a joint project with LLNL. The assembly technology was transferred from LLNL to LLE, who is currently producing mirrors to be used on the NIF. LLE’s Optical Manufacturing Group has optimized a low-stress, high-reflectance coating process for the deformable mirror faceplate and has developed an aluminum coating that protects the epoxied post and transducer joint from flash-lamp radiation. This photograph shows a completed deformable mirror. “Around the Laboratory,” September 2002
Physics of Supernova Explosions
A wide range of experiments performed through the NLUF Program on the OMEGA laser are exploring the physics of supernova explosions.
X-Ray Thomson Scattering
The first demonstration of x-ray Thomson scattering as a high-density temperature and density diagnostic occurred at LLE. The target configuration shown in this illustration used x-ray radiation from a Ti plasma as a probe. DOE Progress Report, September 2002
Summer High School Research Program
This year LLE hosted 15 local high school students in its research program. Each student is assigned a mentor and a research project. At the end of the program each student is required to present the results of their research. In conjunction with the research presentations the 2002 William D. Ryan Inspirational Teacher Award was presented to James Keefer of Brockport High School. Recipients of the award are nominated by past and present participants of the Summer High School Research Program.
For current information on LLE’s accomplishments, read our quarterly publication, the LLE Review, and the monthly DOE Progress Report. Current and past issues are available through the publications section of this web site.