29 Matching Results

Search Results

Advanced search parameters have been applied.

The Mercury Laser System-A scaleable average-power laser for fusion and beyond

Description: Nestled in a valley between the whitecaps of the Pacific and the snowcapped crests of the Sierra Nevada, Lawrence Livermore National Laboratory (LLNL) is home to the nearly complete National Ignition Facility (NIF). The purpose of NIF is to create a miniature star-on demand. An enormous amount of laser light energy (1.8 MJ in a pulse that is 20 ns in duration) will be focused into a small gold cylinder approximately the size of a pencil eraser. Centered in the gold cylinder (or hohlraum) will be a nearly perfect sphere filled with a complex mixture of hydrogen gas isotopes that is similar to the atmosphere of our Sun. During experiments, the laser light will hit the inside of the gold cylinder, heating the metal until it emits X-rays (similar to how your electric stove coil emits visible red light when heated). The X-rays will be used to compress the hydrogen-like gas with such pressure that the gas atoms will combine or 'fuse' together, producing the next heavier element (helium) and releasing energy in the form of energetic particles. 2010 will mark the first credible attempt at this world-changing event: the achievement of fusion energy 'break-even' on Earth using NIF, the world's largest laser! NIF is anticipated to eventually perform this immense technological accomplishment once per week, with the capability of firing up to six shots per day - eliminating the need for continued underground testing of our nation's nuclear stockpile, in addition to opening up new realms of science. But what about the day after NIF achieves ignition? Although NIF will achieve fusion energy break-even and gain, the facility is not designed to harness the enormous potential of fusion for energy generation. A fusion power plant, as opposed to a world-class engineering research facility, would require that the laser deliver ...
Date: March 26, 2008
Creator: Ebbers, C A & Moses, E I
Partner: UNT Libraries Government Documents Department

Optical and thermo-optical characterization of KTP and its isomorphs for 1.06 {micro}m pumped OPO`s

Description: The need to protect personnel from inadvertent eye trauma from fielded laser sources dictates that the highest externally accessible fluences produced by these systems be kept below the maximum permissible exposure (MPE) for intra-beam viewing. The large MPE value for a typical Q-switched (10 ns pulsewidth) source is 1 J/cm{sup 2} for wavelengths in the range of 1.5--1.8 microns, while the MPE for a similar pulsewidth Nd:YAG source is 5 {micro}J/cm{sup 2}. This 5 order of magnitude difference in the MPE is one reason for the trend towards shifting the output of near infrared sources used for remote sensing or ranging to the eyesafe wavelength region, even at the expense of overall system efficiency. There are 5 nonlinear optical crystals available with apertures of at least 10 x 10 mm{sup 2} which are also highly transparent in the 1.5 micron region; LiNbO{sub 3}, KNbO{sub 3}, KTP, KTA, and RTA. All 5 crystals are capable of 1,555 nm generation in an orientation with a favorable nonlinear optical coupling. However, KTP, KTA, or RTA are preferred materials, given that the generated signal of the OPO should remain at a fixed wavelength, insensitive to angular or thermal variations. The authors have characterized the phasematching angle, linewidth, thermal conductivity, and d{lambda}/dT for KTP, KTA, and RTA optical parametric oscillators.
Date: February 17, 1996
Creator: Ebbers, C.A. & Velsko, S.P.
Partner: UNT Libraries Government Documents Department

The Mercury Laser Advances Laser Technology for Power Generation

Description: The National Ignition Facility (NIF) at Lawrence Livermore Laboratory is on target to demonstrate 'breakeven' - creating as much fusion-energy output as laser-energy input. NIF will compress a tiny sphere of hydrogen isotopes with 1.8 MJ of laser light in a 20-ns pulse, packing the isotopes so tightly that they fuse together, producing helium nuclei and releasing energy in the form of energetic particles. The achievement of breakeven will culminate an enormous effort by thousands of scientists and engineers, not only at Livermore but around the world, during the past several decades. But what about the day after NIF achieves breakeven? NIF is a world-class engineering research facility, but if laser fusion is ever to generate power for civilian consumption, the laser will have to deliver pulses nearly 100,000 times faster than NIF - a rate of perhaps 10 shots per second as opposed to NIF's several shots a day. The Mercury laser (named after the Roman messenger god) is intended to lead the way to a 10-shots-per-second, electrically-efficient, driver laser for commercial laser fusion. While the Mercury laser will generate only a small fraction of the peak power of NIF (1/30,000), Mercury operates at higher average power. The design of Mercury takes full advantage of the technology advances manifest in its behemoth cousin (Table 1). One significant difference is that, unlike the flashlamp-pumped NIF, Mercury is pumped by highly efficient laser diodes. Mercury is a prototype laser capable of scaling in aperture and energy to a NIF-like beamline, with greater electrical efficiency, while still running at a repetition rate 100,000 times greater.
Date: January 21, 2009
Creator: Ebbers, C A; Caird, J & Moses, E
Partner: UNT Libraries Government Documents Department

Yb{sup 3+}:BaCaBO{sub 3}F: A potential new self-frequency-doubling laser material

Description: Yb:BaCaBO{sub 3}F (Yb:BCBF) has been investigated as a new laser crystal with potential for self-frequency-doubling. An YB:BCBF laser has been pumped at 912 mm, and a measured slope efficiency of 38% has been obtained for the fundamental laser output at 1034 nm. Single crystal powders of BCBF have been compared with K*P for a relative measure of the second harmonic generating potential, yielding d{sub eff}[BCBF]= (0-66)d{sub eff}[K*P]. The growth, spectroscopy, laser performance, and linear and nonlinear optical properties of YB:BCBF are reported here.
Date: March 9, 1995
Creator: Schaffers, K.I.; DeLoach, L.D.; Ebbers, C.A. & Payne, S.A.
Partner: UNT Libraries Government Documents Department

A high average power electro-optic switch using KTP

Description: High damage threshold, high thermal conductivity, and small thermo-optic coefficients make KTiOPO{sub 4} (KTP) an attractive material for use in a high average power Q-switch. However, electro-chromic damage and refractive index homogeneity have prevented the utilization of KTP in such a device in the past. This work shows that electro-chromic damage is effectively suppressed using capacitive coupling, and a KTP crystal can be Q-switched for 1.5 {times} 10{sup 9} shots without any detectable electro-chromic damage. In addition, KTP with the high uniformity and large aperture size needed for a KTP electro-optic Q-switch can be obtained from flux crystals grown at constant temperature. A thermally compensated, dual crystal KTP Q-switch, which successfully produced 50 mJ pulses with a pulse width of 8 ns (FWHM), has been constructed. In addition, in off-line testing the Q-switch showed less than 7% depolarization at an average power loading of 3.2 kW/cm{sup 2}.
Date: April 1, 1994
Creator: Ebbers, C. A.; Cook, W. M. & Velsko, S. P.
Partner: UNT Libraries Government Documents Department

Double-passed, high-energy quasi-phase-matched optical parametric chirped-pulse amplifier

Description: Quasi-phase-matched (QPM) optical parametric chirped-pulse amplification (OPCPA) in periodically poled materials such as periodically poled LiNbO{sub 3} (PPLN) and periodically poled KTiOPO{sub 4} (PPKTP) has been shown to exhibit advantages over the OPCPA in bulk nonlinear crystals. [GHH98, RPN02] The use of the maximum material nonlinear coefficient results in ultra-high gain with low pump peak power. Furthermore, propagation of signal, pump, and idler beams along one of the crystal principal axes eliminates the birefringent walk-off, reduces angular sensitivity, and improves beam quality. Relatively high level of parasitic parametric fluorescence (PF) in QPM OPCPA represents an impediment for simple, single-stage, high-gain amplification of optical pulses from nJ to mJ energies. PF in QPM is increased when compared to PF in critical phase matching in bulk crystals as a result of broader angular acceptance of the nonlinear conversion process. PF reduces prepulse contrast and conversion efficiency by competition with the signal pulse for pump pulse energy. Previous experiments with QPM OPCPA have thus resulted in pulse energies limited to tens of {mu}J. [JSE03] Optical parametric amplification of a narrowband signal pulse in PPKTP utilizing two pump beams has been demonstrated at a mJ-level, [FPK03] but the conversion efficiency has been limited by low energy extraction of pump pulse in the first pass of amplification. Additionally, narrow spectral bandwidth was the result of operation far from signal-idler degeneracy. Here we present a novel double-pass, broad-bandwidth QPM OPCPA. 1.2 mJ of amplified signal energy is produced in a single PPKTP crystal utilizing a single 24-mJ pump pulse from a commercial pump laser. [JFE05] To our knowledge, this is the highest energy demonstrated in QPM OPCPA. Double-passed QPM OPCPA exhibits high gain (> 3 x 10{sup 6}), high prepulse contrast (> 3 x 10{sup 7}), high energy stability (3% rms), and excellent beam quality. We ...
Date: September 19, 2005
Creator: Jovanovic, I; Forget, N; Brown, C G; Ebbers, C A; Blanc, C L & Barty, C J
Partner: UNT Libraries Government Documents Department

250 watt average power electro-quality Q-switched diode pumped power oscillator

Description: We describe an electro-optically Q-switched, diode-pumped ND:YAG slab laser oscillator operating at an average power of greater than 250 watts. More than 100 watts of frequency doubled light has been demonstrated.
Date: April 1, 1994
Creator: Velsko, S. P.; Ebbers, C. A.; Comaskey, B.; Albrecht, G. F. & Mitchell, S. C.
Partner: UNT Libraries Government Documents Department

Removal of Lattice Imperfections that Impact the Optical Quality of Ti:Sapphire using Advanced Magnetorheological Finishing Techniques

Description: Advanced magnetorheological finishing (MRF) techniques have been applied to Ti:sapphire crystals to compensate for sub-millimeter lattice distortions that occur during the crystal growing process. Precise optical corrections are made by imprinting topographical structure onto the crystal surfaces to cancel out the effects of the lattice distortion in the transmitted wavefront. This novel technique significantly improves the optical quality for crystals of this type and sets the stage for increasing the availability of high-quality large-aperture sapphire and Ti:sapphire optics in critical applications.
Date: February 26, 2008
Creator: Menapace, J A; Schaffers, K I; Bayramian, A J; Davis, P J; Ebbers, C A; Wolfe, J E et al.
Partner: UNT Libraries Government Documents Department

Yttrium Calcium Oxyborate for high average power frequency doubling and OPCPA

Description: Significant progress has been achieved recently in the growth of Yttrium Calcium Oxyborate (YCOB) crystals. Boules have been grown capable of producing large aperture nonlinear crystal plates suitable for high average power frequency conversion or optical parametric chirped pulse amplification (OPCPA). With a large aperture (5.5 cm x 8.5 cm) YCOB crystal we have demonstrated a record 227 W of 523.5nm light (22.7 J/pulse, 10 Hz, 14 ns). We have also demonstrated the applicability of YCOB for 1053 nm OPCPA.
Date: June 20, 2006
Creator: Liao, Z M; Jovanovic, I; Ebbers, C A; Bayramian, A; Schaffers, K; Caird, J et al.
Partner: UNT Libraries Government Documents Department

A Laser Technology Test Facility for Laser Inertial Fusion Energy (LIFE)

Description: A LIFE laser driver needs to be designed and operated which meets the rigorous requirements of the NIF laser system while operating at high average power, and operate for a lifetime of >30 years. Ignition on NIF will serve to demonstrate laser driver functionality, operation of the Mercury laser system at LLNL demonstrates the ability of a diode-pumped solid-state laser to run at high average power, but the operational lifetime >30 yrs remains to be proven. A Laser Technology test Facility (LTF) has been designed to specifically address this issue. The LTF is a 100-Hz diode-pumped solid-state laser system intended for accelerated testing of the diodes, gain media, optics, frequency converters and final optics, providing system statistics for billion shot class tests. These statistics will be utilized for material and technology development as well as economic and reliability models for LIFE laser drivers.
Date: October 6, 2009
Creator: Bayramian, A J; Campbell, R W; Ebbers, C A; Freitas, B L; Latkowski, J; Molander, W A et al.
Partner: UNT Libraries Government Documents Department

High-average-power diode-end-pumped intracavity-doubled Nd:YAG laser

Description: A compact diode-pumped ND:YAG laser was frequency-doubled to 0.532 {mu}m with an intracavity KTP or LBO crystal using a `V` cavity configuration. Two acousto-optic Q-switches were employed at repetition rates of 10-30 kHz. Dichroic fold and end mirrors were used to output two beams with up to 140 W of 0.532 {mu}m power using KTP and 116 W using LBO as the frequency doubling crystal. This corresponds to 66% of the maximum output power at 1.064 {mu}m obtained with an optimized output coupler reflectivity. The minimum output pulse duration varied with repetition rate from 90 to 130 ns. The multimode output beam had a smooth profile and a beam quality of M{sup 2} = 5 1.
Date: February 12, 1998
Creator: Honea, E.C.; Ebbers, C.A.; Beach, R.J.; Speth, J.A.; Emanuel, M.S>; Skidmore, J.A. et al.
Partner: UNT Libraries Government Documents Department

Highly Efficient Tabletop Optical Parametric Chirped Pulse Amplifier at 1 (micron)m

Description: Optical parametric chirped pulse amplification (OPCPA) is a scalable technology, for ultrashort pulse amplification. Its major advantages include design simplicity, broad bandwidth, tunability, low B-integral, high contrast, and high beam quality. OPCPA is suitable both for scaling to high peak power as well as high average power. We describe the amplification of stretched 100 fs oscillator pulses in a three-stage OPCPA system pumped by a commercial, single-longitudinal-mode, Q-switched Nd:YAG laser. The stretched pulses were centered around 1054 nm with a FWHM bandwidth of 16.5 nm and had an energy of 0.5 nJ. Using our OPCPA system, we obtained an amplified pulse energy of up to 31 mJ at a 10 Hz repetition rate. The overall conversion efficiency from pump to signal is 6%, which is the highest efficiency obtained With a commercial tabletop pump laser to date. The overall conversion efficiency is limited due to the finite temporal overlap of the seed (3 ns) with respect to the duration of the pump (8.5 ns). Within the temporal window of the seed pulse the pump to signal conversion efficiency exceeds 20%. Recompression of the amplified signal was demonstrated to 310 fs, limited by the aberrations initially present in the low energy seed imparted by the pulse stretcher. The maximum gain in our OPCPA system is 6 x 10{sup 7}, obtained through single passing of 40 mm of beta-barium borate. We present data on the beam quality obtained from our system (M{sup 2}=1.1). This relatively simple system replaces a significantly more complex Ti:sapphire regenerative amplifier based CPA system used in the front end of a high energy short pulse laser. Future improvement will include obtaining shorter amplified pulses and higher average power.
Date: December 4, 2001
Creator: Jovanovic, I.; Ebbers, C.A.; Comaskey, B.J.; Bonner, R.A. & Morse, E.C.
Partner: UNT Libraries Government Documents Department

Inertial Fusion Energy's Role in Developing the Market for High Power Laser Diodes

Description: Production-cost models for high-power laser-diodes indicate systems of 10GW peak power coupled with facilitization of semi-conductor manufacturing capacity could yield costs below $0.02/Watt. This is sufficient to make IFE competitive with other nuclear power technologies.
Date: November 29, 2007
Creator: Ladran, A L; Ault, E R; Beach, R J; Campbell, J H; Erlandson, A C; Felker, A J et al.
Partner: UNT Libraries Government Documents Department

Removal of Lattice Imperfections that Impact the Optical Quality of Ti:Sapphire using Advanced Magnetorheological Finishing Techniques

Description: Ti:sapphire has become the premier lasing medium material for use in solid-state femtosecond high-peak power laser systems because of its wide wavelength tuning range. With a tuneable range from 680 to 1100 nm, peaking at 800 nm, Ti:sapphire lasing crystals can easily be tuned to the required pump wavelength and provide very high pump brightness due to their good beam quality and high output power of typically several watts. Femtosecond lasers are used for precision cutting and machining of materials ranging from steel to tooth enamel to delicate heart tissue and high explosives. These ultra-short pulses are too brief to transfer heat or shock to the material being cut, which means that cutting, drilling, and machining occur with virtually no damage to surrounding material. Furthermore, these lasers can cut with high precision, making hairline cuts of less than 100 microns in thick materials along a computer-generated path. Extension of laser output to higher energies is limited by the size of the amplification medium. Yields of high quality large diameter crystals have been constrained by lattice distortions that may appear in the boule limiting the usable area from which high quality optics can be harvested. Lattice distortions affect the transmitted wavefront of these optics which ultimately limits the high-end power output and efficiency of the laser system, particularly when operated in multi-pass mode. To make matters even more complicated, Ti:sapphire is extremely hard (Mohs hardness of 9 with diamond being 10) which makes it extremely difficult to accurately polish using conventional methods without subsurface damage or significant wavefront error. In this presentation, we demonstrate for the first time that Magnetorheological finishing (MRF) can be used to compensate for the lattice distortions in Ti:sapphire by perturbing the transmitted wavefront. The advanced MRF techniques developed allow for precise polishing of the optical inverse ...
Date: October 9, 2007
Creator: Menapace, J A; Schaffers, K I; Bayramian, A J; Davis, P J; Ebbers, C A; Wolfe, J E et al.
Partner: UNT Libraries Government Documents Department


Description: In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test stand is being developed to investigate accelerator optimization for future upgrades. This test stand will enable work to explore the science and technology paths required to boost the current 10 Hz monoenergetic gamma-ray (MEGa-Ray) technology to an effective repetition rate exceeding 1 kHz, potentially increasing the average gamma-ray brightness by two orders of magnitude. Multiple bunches must be of exceedingly high quality to produce narrow-bandwidth gamma-rays. Modeling efforts will be presented, along with plans for a multi-bunch test stand at LLNL. The test stand will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. The photoinjector will be a high gradient standing wave structure, featuring a dual feed racetrack coupler. The accelerator will increase the electron energy so that the emittance can be measured using quadrupole scanning techniques. Multi-bunch diagnostics will be developed so that the beam quality can be measured and compared with theory. Design will be presented with modeling simulations, and layout plans.
Date: May 12, 2010
Creator: Marsh, R A; Anderson, S G; Barty, C P; Chu, T S; Ebbers, C A; Gibson, D J et al.
Partner: UNT Libraries Government Documents Department


Description: In support of X-band photoinjector development efforts at LLNL, a 50 MW test station is being constructed to investigate structure and photocathode optimization for future upgrades. A SLAC XL-4 klystron capable of generating 50 MW, 1.5 microsecond pulses will be the high power RF source for the system. Timing of the laser pulse on the photocathode with the applied RF field places very stringent requirements on phase jitter and drift. To achieve these requirements, the klystron will be powered by a state of the art, solid-state, high voltage modulator. The 50 MW will be divided between the photoinjector and a traveling wave accelerator section. A high power phase shifter is located between the photoinjector and accelerator section to adjust the phasing of the electron bunches with respect to the accelerating field. A variable attenuator is included on the input of the photoinjector. The distribution system including the various x-band components is being designed and constructed. In this paper, we will present the design, layout, and status of the RF system.
Date: March 11, 2011
Creator: Marsh, R A; Anderson, S G; Barty, C J; Beer, G K; Cross, R R; Ebbers, C A et al.
Partner: UNT Libraries Government Documents Department

Mercury and Beyond: Diode-Pumped Solid-State Lasers for Inertial Fusion Energy

Description: We have begun building the ''Mercury'' laser system as the first in a series of new generation diode-pumped solid-state lasers for inertial fusion research. Mercury will integrate three key technologies: diodes, crystals, and gas cooling, within a unique laser architecture that is scalable to kilojoule and megajoule energy levels for fusion energy applications. The primary near-term performance goals include 10% electrical efficiencies at 10 Hz and 1005 with a 2-10 ns pulse length at 1.047 {micro}m wavelength. When completed, Mercury will allow rep-rated target experiments with multiple chambers for high energy density physics research.
Date: December 1, 1999
Creator: Bibeau, C.; Bayramian, A.; Beach, R.J.; Chanteloup, J.C.; Ebbers, C.A.; Emanuel, M.A. et al.
Partner: UNT Libraries Government Documents Department