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Penetrating radiation impact on NIF final optic components

Description: Goal of the National Ignition Facility (NIF) is to achieve thermonuclear ignition in a laboratory environment in inertial confinement fusion (ICF). This will enable NIF to service the DOE stockpile stewardship management program, inertial fusion energy goals, and advance scientific frontiers. All of these applications will make use of the extreme conditions that the facility will create in the target chamber. In the case of a prospected 20 MJ yield scenario, NIF will produce 10{sup 19} neutrons with DT fusion 14 MeV energy per neutron. There will also be high-energy x rays as well as solid, liquid, and gaseous target debris produced either directly or indirectly by the inertial confinement fusion process. A critical design issue is the protection of the final optical components as well as sophisticated target diagnostics in such a harsh environment.
Date: October 15, 1996
Creator: Marshall, C.D.; Speth, J.A.; DeLoach, L.D. & Payne, S.A.
Partner: UNT Libraries Government Documents Department

Conduction band states and the 5d-4f laser transition of rare earth ion dopants

Description: We discuss how the interactions of the 5d orbital with the conduction band of the host medium play a crucial role in determining whether rare earth containing materials can serve as useful laser materials, based on their 5d-4f transition. To explore this issue, we examine the pump-probe spectra of Sm[sup 2+], Eu[sup 2+], and Ce[sup 3+] dopants in various fluoride and chloride crystals. In addition we suggest that the luminescence properties are also profoundly impacted by this interaction. The outstanding UV laser performance achieved by the Ce:LiSrAlF[sub 6] crystal is rationalized in terms of the reduced overlap of conduction band states with the cerium ions.
Date: December 31, 1996
Creator: Payne, S.A.; Marshall, C.D.; Bayramian, A. & Lawson, J.K.
Partner: UNT Libraries Government Documents Department

Next-generation laser for Inertial Confinement Fusion

Description: We report on the progress in developing and building the Mercury laser system as the first in a series of a new generation of diode- pumped solid-state Inertial Confinement Fusion (ICF) lasers at Lawrence Livermore National Laboratory (LLNL). Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1 omega energies of 100 J and with 2 omega/3 omega frequency conversion.
Date: September 29, 1997
Creator: Marshall, C.D.; Deach, R.J. & Bibeau, C.
Partner: UNT Libraries Government Documents Department

Next generation laser for Inertial Confinement Fusion

Description: We are in the process of developing and building the ``Mercury`` laser system as the first in a series of a new generation of diode-pumped solid-state Inertial Confinement Fusion (ICF) lasers at LLNL. Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1{omega} energies of 100 J and with 2{omega}/3{omega} frequency conversion.
Date: July 18, 1997
Creator: Marshall, C.D.; Beach, J. & Bibeau, C.
Partner: UNT Libraries Government Documents Department

Neutron and gamma irradiated optical property changes for the final optics of the National Ignition Facility

Description: Based on studies the authors have performed with several radiation sources such as pulsed nuclear reactors, they have been able to construct a physical picture and measure quantitative parameters necessary to model the radiation-induced losses expected for fused silica and fused quartz National Ignition Facility (NIF) target area. It is important to note that these surrogate radiation sources do not have identical temporal and spectral characteristics to NIF, therefore caution is in order since the results obtained to date must be extrapolated somewhat to predict NIF performance.
Date: July 17, 1995
Creator: Marshall, C.D.; Speth, J.A.; DeLoach, L.D. & Payne, S.A.
Partner: UNT Libraries Government Documents Department

Diode-pumped Yb:Sr{sub 5}(PO{sub 4}){sub 3}F laser performance

Description: The performance of the first diode-pumped Yb{sup 3+}-doped Sr{sub 5}(PO{sub 4}){sub 3}F (Yb:S-FAP) laser is discussed. We found the pumping dynamics and extraction cross-sections of Yb:S-FAP crystals to be similar to those previously inferred by purely spectroscopic techniques. The saturation fluence for pumping was measured to be 2.2 J/cm{sup 2} using three different methods based on either the spatial, temporal, or energy transmission properties of a Yb:S-FAP rod. The small signal gain implies an emission cross section of 6.0 x 10{sup -20} cm{sup 2} that falls within error bars of the previously reported value of 7.3 x 10{sup -20} cm{sup 2}, obtained from spectroscopic techniques. Up to 1.7 J/cm{sup 3} of stored energy density was achieved in a 6 x 6 x 44 mm Yb:S-FAP amplifier rod. An InGaAs diode array has been fabricated that has suitable specifications for pumping a 3 x 3 x 30 mm Yb:S-FAP rod. In a free running configuration diode-pumped slope efficiencies up to 43% were observed with output energies up to {approximately}0.5 J per 1 ms pulse. When the rod was mounted in a copper block for cooling, 13 W of average power was produced with power supply limited operation at 70 Hz and 500 {mu}s pulses.
Date: March 17, 1995
Creator: Marshall, C.D.; Payne, S.A. & Smith, L.K.
Partner: UNT Libraries Government Documents Department

Analysis of Sr{sub 5{minus}x}Ba{sub x}(PO{sub 4}){sub 3}F:Yb{sup 3+} crystals for improved laser performance with diode-pumping

Description: Crystals of Yb{sup 3+}:Sr{sub 1-x}Ba{sub x}(PO{sub 4}){sub 3}F (0 < x < 5) have been investigated as a means to obtain broader absorption bands than are currently available with Yb{sup 3+}:S-FAP [Yb{sup 3+}: Sr{sub 5}(PO{sub 4}){sub 3}F], thereby improving diode-pumping efficiency for high peak power applications. Large diode-arrays have a FWHM pump band of >5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr{sub 5-x}Ba{sub x}-FAP crystals indicates that adding barium to the lattice increases the pump band to 13-16 run which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Filchtbauer-Ladenburg method, and small signal gain. Overall, Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while having a broader absorption band to better accommodate diode pumping.
Date: February 19, 1997
Creator: Schaffers, K.I.; Bayramian, A.J.; Marshall, C.D.; Tassano, J.B. & Payne, S.A.
Partner: UNT Libraries Government Documents Department

Laser properties of an improved average-power Nd-doped phosphate glass

Description: The Nd-doped phosphate laser glass described herein can withstand 2.3 times greater thermal loading without fracture, compared to APG-1 (commercially-available average-power glass from Schott Glass Technologies). The enhanced thermal loading capability is established on the basis of the intrinsic thermomechanical properties (expansion, conduction, fracture toughness, and Young`s modulus), and by direct thermally-induced fracture experiments using Ar-ion laser heating of the samples. This Nd-doped phosphate glass (referred to as APG-t) is found to be characterized by a 29% lower gain cross section and a 25% longer low-concentration emission lifetime.
Date: March 15, 1995
Creator: Payne, S.A.; Marshall, C.D. & Bayramian, A.J.
Partner: UNT Libraries Government Documents Department

New tunable lasers for potential use in LIDAR systems

Description: We discuss the optical and laser properties of two new tunable laser crystals, Ce:LiSrAlF{sub 6} and Cr:ZnSe. These crystals are unique in that they provide a practical alternative to optical parametric oscillators as a means of generating tunable radiation in the near ultraviolet and mid-infrared regions (their tuning ranges are at least 285-315 nm and 2.2-2.8 microns, respectively). While these crystals are relatively untested in field deployment, they are promising and likely to be useful in the near future.
Date: June 1996
Creator: Payne, S. A.; Page, R. H.; Marshall, C. D.; Schaffers, K. I.; Bayramian, A. J. & Krupke, W. F.
Partner: UNT Libraries Government Documents Department

Diode-pumped solid-state laser driver experiments for inertial fusion energy applications

Description: Although solid-state lasers have been the primary means by which the physics of inertial confinement fusion (ICF) have been investigated, it was previously thought that solid-state laser technology could not offer adequate efficiencies for an inertial fusion energy (IFE) power plant. Orth and co-workers have recently designed a conceptual IFE power plant, however, with a high efficiency diode-pumped solid-state laser (DPSSL) driver that utilized several recent innovations in laser technology. It was concluded that DPSSLs could offer adequate performance for IFE with reasonable assumptions. This system was based on a novel diode pumped Yb-doped Sr{sub 5}(PO{sub 4}){sub 3}F (Yb:S-FAP) amplifier. Because this is a relatively new gain medium, a project was established to experimentally validate the diode-pumping and extraction dynamics of this system at the smallest reasonable scale. This paper reports on the initial experimental results of this study. We found the pumping dynamics and extraction cross-sections of Yb:S-FAP crystals to be similar to those previously inferred by purely spectroscopic techniques. The saturation fluence for pumping was measured to be 2.2 J/cm{sup 2} using three different methods based on either the spatial, temporal, or energy transmission properties of a Yb:S-FAP rod. The small signal gain implies an emission cross section of 6.0{times}10{sup {minus}20} cm{sup 2}. Up to 1.7 J/cm{sup 3} of stored energy density was achieved in a 6{times}6{times}44 mm{sup 3} Yb:S-FAP amplifier rod. In a free running configuration diode-pumped slope efficiencies up to 43% were observed with output energies up to {approximately}0.5 J per 1 ms pulse from a 3{times}3{times}30 mm{sup 3} rod. When the rod was mounted in a copper block for cooling, 13 W of average power was produced with power supply limited operation at 70 Hz with 500 {mu}s pulses.
Date: July 11, 1995
Creator: Marshall, C.D.; Payne, S.A.; Emanuel, M.E.; Smith, L.K.; Powell, H.T. & Krupke, W.F.
Partner: UNT Libraries Government Documents Department

Properties of a new average power Nd-doped phosphate laser glass

Description: The Nd-doped phosphate laser glass described herein can withstand 2.3 times greater thermal loading without fracture, compared to APG-1 (commercially-available average-power glass from Schott Glass Technologies). The enhanced thermal loading capability is established on the basis of the intrinsic thermomechanical properties and by direct thermally-induced fracture experiments using Ar-ion laser heating of the samples. This Nd-doped phosphate glass (referred to as APG-t) is found to be characterized by a 29% lower gain cross section and a 25% longer low-concentration emission lifetime.
Date: March 9, 1995
Creator: Payne, S. A.; Marshall, C. D.; Bayramian, A. J.; Wilke, G. D. & Hayden, J. S.
Partner: UNT Libraries Government Documents Department

Scalable diode-pumped solid state laser architecture for inertial fusion energy

Description: A study of diode-pumped solid state lasers for fusion, energy is presented, including performance of a subscale laser oscillator and amplifier, radiation-hardness of the final optic, and a system-level modeling exercise.
Date: February 16, 1995
Creator: Payne, S.A.; Marshall, C.D.; Emanuel, M.A.; Beach, R.J.; Orth, C.D.; Powell, H.T. et al.
Partner: UNT Libraries Government Documents Department

Diode-pumped solid-state lasers: next generation drivers for inertial fusion energy and high energy density plasma physics

Description: We are in the process of developing and building a laser system as the first in a series of a new generation of diode-pumped solid-state Inertial Confinement Fusion (ICF) lasers at LLNL (see Fig. 1 below). This laser system named �Mercury� will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1- 10 ns pulse with lo energies of 100 J and with 2(omega)J/3(omega) frequency conversion.
Date: August 3, 1998
Creator: Beach, R. J.; Bibeau, C.; Ebbers, C. A.; Emanuel, M. A.; Honea, E. C.; Krupke, W. F. et al.
Partner: UNT Libraries Government Documents Department

Shot Automation for the National Ignition Facility

Description: A shot automation framework has been developed and deployed during the past year to automate shots performed on the National Ignition Facility (NIF) using the Integrated Computer Control System This framework automates a 4-8 hour shot sequence, that includes inputting shot goals from a physics model, set up of the laser and diagnostics, automatic alignment of laser beams and verification of status. This sequence consists of set of preparatory verification shots, leading to amplified system shots using a 4-minute countdown, triggering during the last 2 seconds using a high-precision timing system, followed by post-shot analysis and archiving. The framework provides for a flexible, model-based execution driven of scriptable automation called macro steps. The framework is driven by high-level shot director software that provides a restricted set of shot life cycle state transitions to 25 collaboration supervisors that automate 8-laser beams (bundles) and a common set of shared resources. Each collaboration supervisor commands approximately 10 subsystem shot supervisors that perform automated control and status verification. Collaboration supervisors translate shot life cycle state commands from the shot director into sequences of ''macro steps'' to be distributed to each of its shot supervisors. Each Shot supervisor maintains order of macro steps for each subsystem and supports collaboration between macro steps. They also manage failure, restarts and rejoining into the shot cycle (if necessary) and manage auto/manual macro step execution and collaborations between other collaboration supervisors. Shot supervisors execute macro step shot functions commanded by collaboration supervisors. Each macro step has database-driven verification phases and a scripted perform phase. This provides for a highly flexible methodology for performing a variety of NIF shot types. Database tables define the order of work and dependencies (workflow) of macro steps to be performed for a shot. A graphical model editor facilitates the definition and viewing of an ...
Date: September 21, 2005
Creator: Lagin, L J; Bettenhausen, R C; Beeler, R G; Bowers, G A; Carey, R; Casavant, D D et al.
Partner: UNT Libraries Government Documents Department

Status of the National Ignition Facility Integrated Computer Control System (ICCS) on the Path to Ignition

Description: The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is a stadium-sized facility under construction that will contain a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for multiple experimental diagnostics. NIF is the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion (ICF) and matter at extreme energy densities and pressures. NIF's laser beams are designed to compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. NIF is comprised of 24 independent bundles of 8 beams each using laser hardware that is modularized into more than 6,000 line replaceable units such as optical assemblies, laser amplifiers, and multifunction sensor packages containing 60,000 control and diagnostic points. NIF is operated by the large-scale Integrated Computer Control System (ICCS) in an architecture partitioned by bundle and distributed among over 800 front-end processors and 50 supervisory servers. NIF's automated control subsystems are built from a common object-oriented software framework based on CORBA distribution that deploys the software across the computer network and achieves interoperation between different languages and target architectures. A shot automation framework has been deployed during the past year to orchestrate and automate shots performed at the NIF using the ICCS. In December 2006, a full cluster of 48 beams of NIF was fired simultaneously, demonstrating that the independent bundle control system will scale to full scale of 192 beams. At present, 72 beams have been commissioned and have demonstrated 1.4-Megajoule capability of infrared light. During the next two years, the control system will be expanded to include automation of target area systems including final optics, target positioners and diagnostics, in preparation for project completion in 2009. Additional capabilities to support fusion ignition ...
Date: September 11, 2007
Creator: Lagin, L. J.; Bettenhauasen, R. C.; Bowers, G. A.; Carey, R. W.; Edwards, O. D.; Estes, C. M. et al.
Partner: UNT Libraries Government Documents Department