47 Matching Results

Search Results

Advanced search parameters have been applied.

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

Design of precision mounts for optimizing the conversion efficiency of KDP crystals for the National Ignition Facility

Description: A key design challenge for the National Ignition Facility (NIF), being constructed at Lawrence Livermore National Laboratory (LLNL), [Hibbard, R L , 1998], is the frequency converter consisting of two KDP crystals and a focusing lens Frequency conversion is a critical performance factor for NIF and the optical mount design for this plays a key role in meeting design specifications The frequency converter is a monolithic cell that mounts the optics and is the point on the beamline where the frequency conversion crystals are optimally aligned and the cell is focused on target The lasing medium is neodymium in phosphate glass with a fundamental frequency (1{omega}) of 1 053 {micro}m Sum frequency generation in a pair of conversion crystals (KDP/KD*P) produces 1 8 MJ of the third harmonic light (3{omega} or {lambda}=O 35 pm). The phase-matching scheme on NIF is type I second harmonic generation followed by type II sum-frequency-mixing of the residual fundamental and the second harmonic light This laser unlike previous laser system designs, must achieve high conversion efficiency, 85%, which is close to the 90 8% theoretical maximum As a result, this design is very sensitive to angular variations in beam propagation and in the crystal axes orientation. Factors that influence the phase matching angle include crystal inhomogeneity, residual and induced stress in the crystals, the crystals` natural and mounted surface figure, mounting imperfections and gravity sag These angular variations need to be controlled within a 40 {micro}rad error budget. The optical mount contributions to the angular error budget are 20 {micro}rad and are what make the frequency converter in the Final Optics Cell (FOC) such a challenging precision design. The premise of using full edge support in the FOC design is primarily driven by the spherical target chamber design that has optics mounted at multiple longitudinal ...
Date: March 30, 1998
Creator: Hibbard, R. L.
Partner: UNT Libraries Government Documents Department

Frequency converter design and manufacturing considerations for the National Ignition Facility

Description: The National Ignition Facility (NIF), being constructed at Lawrence Livermore National Laboratory (LLNL), comprises 192 laser beams, Figure 1. The lasing medium is neodymium in phosphate glass with a fundamental frequency (1{omega}) of 1.053 {micro}m. Sum frequency generation in a pair of conversion crystals (KDP/KD*P) produces 1.8 Mj of the third harmonic light (3{omega} or {lambda}=0.35). On NIF the frequency conversion crystals are part of the Final Optics Assembly (FOA), whose two principal functions are to convert the laser light to 3{omega} and focus it on target. In addition, the FOA provides a vacuum window to the target chamber, smoothes the on- target irradiance profile, moves the unconverted light away from the target, and provides signals for alignment and diagnostics. The FOA has four Integrated Optics Modules (IOM), Figure 4, each of which contains two 41 cm square crystals are mounted with the full edge support to micro radian angular and micron flatness tolerances. This paper is intended to be an overview of the important factors that affect frequency conversion on NIF. Chief among these are angular errors arising from crystal growth, finishing, and mounting. The general nature of these errors and how they affect frequency conversion, and finally the importance of a frequency conversion metrology tool in assessing converter performance before opto-mechanical assemblies are installed on NIF will be discussed.
Date: March 25, 1998
Creator: Hibbard, R.L.; English, R.E., Jr.; De Yoreo, J.J. & Montesanti, R.C.
Partner: UNT Libraries Government Documents Department

Frequency conversion of high-intensity, femtosecond laser pulses

Description: Almost since the invention of the laser, frequency conversion of optical pulses via non- linear processes has been an area of active interest. However, third harmonic generation using ~(~1 (THG) in solids is an area that has not received much attention because of ma- terial damage limits. Recently, the short, high-intensity pulses possible with chirped-pulse amplification (CPA) laser systems allow the use of intensities on the order of 1 TW/cm2 in thin solids without damage. As a light source to examine single-crystal THG in solids and other high field inter- actions, the design and construction of a Ti:sapphire-based CPA laser system capable of ultimately producing peak powers of 100 TW is presented. Of special interest is a novel, all-reflective pulse stretcher design which can stretch a pulse temporally by a factor of 20,000. The stretcher design can also compensate for the added material dispersion due to propagation through the amplifier chain and produce transform-limited 45 fs pulses upon compression. A series of laser-pumped amplifiers brings the peak power up to the terawatt level at 10 Hz, and the design calls for additional amplifiers to bring the power level to the 100 TW level for single shot operation. The theory for frequency conversion of these short pulses is presented, focusing on conversion to the third harmonic in single crystals of BBO, KD*P, and d-LAP (deuterated I-arginine phosphate). Conversion efficiencies of up to 6% are obtained with 500 fs pulses at 1053 nm in a 3 mm thick BBO crystal at 200 GW/cm 2. Contributions to this process by unphasematched, cascaded second harmonic generation and sum frequency generation are shown to be very significant. The angular relationship between the two orders is used to measure the tensor elements of C = xt3)/4 with Crs = -1.8 x 1O-23 m2/V2 and .15Cri + ...
Date: June 1, 1997
Creator: Banks, P S
Partner: UNT Libraries Government Documents Department

Use of alternating-Z doubling in high-dynamic-range tripling: design and evaluation of an optimized prototype tripler

Description: We designed and tested an alternating-Z tripler that consisted of two detuned, Type-1, potassium dihydrogen phosphate (KD*P) doublers and one KD*P mixer. The crystal thicknesses were, respectively, 13, 10 and 10 mm, and the detunings of the doublers were +420 and -520 µrad. All three crystals were fabricated from 80% deuterated KDP. Conversion efficiency was measured and calculated for input 1053- nm pulses with approximately rectangular waveforms and durations of either 1 or 6 ns, and for 20-ns pulses that exhibited intensity variation by a factor of 10. The measured peak conversion efficiency was more than 80%, and energy conversion efficiencies ranged from 62-80% depending on the waveform of the input pulse. The expected large dynamic range in input intensity, 9-10, was observed, and the measured and calculated efficiencies were in excellent agreement.
Date: July 27, 1998
Creator: Auerbach, J. M.; Barker, C.; Eimerl, D.; Milan, D. & Milonni, P. W.
Partner: UNT Libraries Government Documents Department

Frequency converter development for the National Ignition Facility

Description: The design of the National Ignition Facility (NIF) incorporates a type I/type II third harmonic generator to convert the 1.053-{micro}m fundamental wavelength of the laser amplifier to a wavelength of 0.351 {micro}m for target irradiation. To understand and control the tolerances in the converter design, we have developed a comprehensive error budget that accounts for effects that are known to influence conversion efficiency, including variations in amplitude and phase of the incident laser pulse, temporal bandwidth of the incident laser pulse, crystal surface figure and bulk non-uniformities, angular alignment errors, Fresnel losses, polarization errors and crystal temperature variations. The error budget provides specifications for the detailed design of the NIF final optics assembly (FOA) and the fabrication of optical components. Validation is accomplished through both modeling and measurement, including full-scale Beamlet tests of a 37-cm aperture frequency converter in a NIF prototype final optics cell. The prototype cell incorporates full-perimeter clamping to support the crystals, and resides in a vacuum environment as per the NIF design.
Date: October 30, 1998
Creator: Auerbach, J M; Barker, C E; Burkhart, S C; Couture, S A; DeYoreo, J J; Hackel, L A et al.
Partner: UNT Libraries Government Documents Department

Frequency up-conversion and trapping of ultrashort laser pulses in semiconductor plasmas

Description: It is shown that the interaction of ultrashort laser pulses with nonstationary semiconductor plasmas can, under appropriate conditions, lead to a variety of interesting phenomena including controlled upshifting of the laser frequency leading to the possibility of tunable lasers in a wide range of frequencies, and trapping (nonpropagation) of a substantial part of the incident pulse.
Date: July 1, 1998
Creator: Berezhiani, V.I.; Mahajan, S.M. & Miklaszewski, R.
Partner: UNT Libraries Government Documents Department

Superradiant pulse compression using free-carrier plasma

Description: Free-carrier plasma can be used as an effective nonlinear medium for pulse compression. In the backward Raman amplifier geometry, the lower-frequency seed can extract most of the long pump energy through the mechanism of nonlinear superradiance. Filamentation is avoided due to strong dependence of the Raman instability growth rate on the wavenumber.
Date: July 21, 2000
Creator: Shvets, G.; Fisch, N. J.; Pukhov, A. & Meyer-ter-Vehn, J.
Partner: UNT Libraries Government Documents Department

Development of a metrology instrument for mapping the crystallographic axis in large optics

Description: A metrology instrument has been developed to scan crystals and map the peak tuning angles for frequency conversion from the infrared to the ultra violet over large apertures. The need for such a device emerged from the National Ignition Facility (NIF) program where frequency conversion crystals have been found to have significant crystallographic axis wander at the large NIF aperture size of 4 1 cm square. With only limited access to a large aperture laser system capable of testing these crystals, scientists have been unable to determine which crystal life-cycle components most affect these angular anomalies. A system that can scan crystals with a small diameter probe laser beam and deliver microradian accuracy and repeatability from probe point to probe point is needed. The Crystal Alignment Verification Equipment (CAVE) is the instrument designed to meet these needs and fit into the budget and time constraints of the ongoing NIF development. In order to measure NIF crystals, the CAVE has a workspace of 50 x 50 cm and an angular measurement accuracy of 10 {micro}radians. Other precision requirements are probe beam energy measurement to 2% of peak, thermal control to 20 0. 1°C around the crystal, crystal mounting surface flatness of 1 {micro}m over 40 cm square, and clean operations to Class 100 standards. Crystals are measured in a vertical position in a kinematic mount capable of tuning the crystal to 1 {micro}radian. The mirrors steering the probe beam can be aligned to the same precision. Making tip/tilt mounts with microradian level adjustment is relatively commonplace. The real precision engineering challenge of the CAVE system is maintaining the angular alignment accuracy of the probe laser relative to the crystal for each spatial position to be measured. The design team determined that a precision XY stage with the required workspace and angular ...
Date: October 21, 1998
Creator: Hibbard, R L; Liou, L W; Michie, R B & Summers, M D
Partner: UNT Libraries Government Documents Department

Pulse compression in plasma: Generation of femtosecond pulses without CPA

Description: Laser pulses can be efficiently compressed to femtosecond duration when a smaller-frequency short pulse collides with high frequency long pulse in rare plasma, absorbing most of its energy. The mechanism of short pulse amplification is nonlinear superradiance.
Date: July 20, 2000
Creator: Shvets, G.; Fisch, N. J.; Pukhov, A. & Meyer-ter-Vehn, J.
Partner: UNT Libraries Government Documents Department

Perturbation theory for frequency doubling and tripling of electric field amplitude and phase ripples

Description: A perturbation theory has been developed to calculate the transfer of electric field amplitude and phase ripples from the first harmonic to either the second harmonic or the third harmonic. The theory is restricted to steady-state conversion processes. In the case of small phase gradients, the real and imaginary parts of the output harmonic ripple are related to the real and imaginary parts of the input perturbation by a 2 {times} 2 matrix. To confirm the validity of the perturbation theory, we have performed an initial set of experiments on the Optical Sciences Laser to investigate the transfer of a weak ripple from the first harmonic to the second harmonic.
Date: June 27, 1995
Creator: Auerbach, J.M.; Eimerl, D.; Hunt, J.T.; Milam, D.; Trenholme, J.B. & Milonni, P.W.
Partner: UNT Libraries Government Documents Department

High-energy Picosecond Laser Pulse Recirculation for Compton Scattering

Description: Frequency upconversion of laser-generated photons by inverse Compton scattering for applications such as nuclear spectroscopy and gamma-gamma collider concepts on the future ILC would benefit from an increase of average source brightness. The primary obstacle to higher average brightness is the relatively small Thomson scattering cross section. It has been proposed that this limitation can be partially overcome by use of laser pulse recirculation. The traditional approach to laser recirculation entails resonant coupling of low-energy pulse train to a cavity through a partially reflective mirror. Here we present an alternative, passive approach that is akin to 'burst-mode' operation and does not require interferometric alignment accuracy. Injection of a short and energetic laser pulse is achieved by placing a thin frequency converter, such as a nonlinear optical crystal, into the cavity in the path of the incident laser pulse. This method leads to the increase of x-ray/gamma-ray energy proportional to the increase in photon energy in frequency conversion. Furthermore, frequency tunability can be achieved by utilizing parametric amplifier in place of the frequency converter.
Date: June 12, 2007
Creator: Jovanovic, I; Anderson, S G; Betts, S M; Brown, C; Gibson, D J; Hartemann, F V et al.
Partner: UNT Libraries Government Documents Department

Group velocity effects in broadband frequency conversion on OMEGA. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

Description: The powerful lasers needed for ICF can only produce light in the infrared wavelengths. However, the one micron wavelength produced by the neodymium glass that powers OMEGA and other lasers used for fusion research does not efficiently compress the fuel pellet. This happens because the infrared light is not well absorbed by the target, and because of the creation of suprathermal electrons. These suprathermal electrons preheat the fuel, adding extra resistance to compression. To eliminate these problems associated with longer wavelengths of light, the process of frequency converting the laser beam was invented. This process efficiently converts the initial beam to a beam which has three times the frequency and one third the wavelength. The third-harmonic beam, in the UV range, has a better absorption rate. The PV-WAVE computer program that the author has written has shown that increasing the frequency of SSD (Smoothing by Spectral Dispersion) on OMEGA to approximately 10 GHz as planned will not hurt the third harmonic generation conversion efficiency significantly. The increased bandwidth and increased frequency of SSD will make the laser beams that strike the target on OMEGA much smoother and more uniform than ever before. Therefore it is both safe and advisable to add a second tripler crystal to the OMEGA system and decrease the SSD time cycle to around 100 picoseconds. Since the conversion efficiency remains high up to approximately 30 GHz, more experiments on OMEGA may be carried out with even higher modulation frequencies. These modifications to the existing OMEGA laser should make target irradiation more uniform, leading to more uniform compression and hopefully, a higher energy yield.
Date: March 1, 1999
Creator: Grossman, P.
Partner: UNT Libraries Government Documents Department

Multi-wavelength injection seeded mid-infrared optical parametric oscillator for DIAL

Description: We have constructed and fielded a multi-wavelength injection seeded mid-IR OPO source for DIAL. This OPO system was built for ground based remote sensing measurements of species with both broad (300 cm{sup -1}) and narrow absorption bandwidths (0.07 cm{sup -1} FWHM). The OPO utilizes a single frequency tunable diode laser for the injection seeded signal wavelength in the region from 6400 to 6700 cm{sup -1} and an angle phase-matched 5 cm LiNbO3 crystal to provide large tuning excursions on a slow time scale. The pump was a diode pumped Nd:YAG MOPA (9398 cm{sup -1}) running at 180 Hz. This pump source was repeatedly injection seeded with a different wavelength on each of film sequential shots forming a set of three pulses having wavelength separations on the order of 0.4 cm{sup -1} at a three color set repetition rate of 60 Hz. This combination of OPO signal and pump source produced a set of three time staggered idler wavelengths separated by 0.4 cm{sup -1} with the center wavelength tunable from 2700 to 3000 cm{sup -1}. This OPO system was used in field test experiments to detect the release of chemicals from a standoff distance of 3.3 Km. We present key OPO design criteria, performance data, and numerical simulations that agree with our observations of pump induced spectral impurities in the OPO output.
Date: January 27, 1996
Creator: Webb, M.S.; Stanion, K.B. & Deane, D.J.
Partner: UNT Libraries Government Documents Department

An adaptive optics system for solid-state laser systems used in inertial confinement fusion

Description: Using adaptive optics the authors have obtained nearly diffraction-limited 5 kJ, 3 nsec output pulses at 1.053 {micro}m from the Beamlet demonstration system for the National Ignition Facility (NIF). The peak Strehl ratio was improved from 0.009 to 0.50, as estimated from measured wavefront errors. They have also measured the relaxation of the thermally induced aberrations in the main beam line over a period of 4.5 hours. Peak-to-valley aberrations range from 6.8 waves at 1.053 {micro}m within 30 minutes after a full system shot to 3.9 waves after 4.5 hours. The adaptive optics system must have enough range to correct accumulated thermal aberrations from several shots in addition to the immediate shot-induced error. Accumulated wavefront errors in the beam line will affect both the design of the adaptive optics system for NIF and the performance of that system.
Date: September 17, 1995
Creator: Salmon, J.T.; Bliss, E.S.; Byrd, J.L.; Feldman, M.; Kartz, M.A.; Toeppen, J.S. et al.
Partner: UNT Libraries Government Documents Department

Frequency doubling in poled polymers using anomalous dispersion phase-matching

Description: The authors report on a second harmonic generation in a poled polymer waveguide using anomalous dispersion phase-matching. Blue light ({lambda} = 407 nm) was produced by phase-matching the lowest order fundamental and harmonic modes over a distance of 32 {micro}m. The experimental conversion efficiency was {eta} = 1.2 {times} 10{sup {minus}4}, in agreement with theory. Additionally, they discuss a method of enhancing the conversion efficiency for second harmonic generation using anomalous dispersion phase-matching to optimize Cerenkov second harmonic generation. The modeling shows that a combination of phase-matching techniques creates larger conversion efficiencies and reduces critical fabrication requirements of the individual phase-matching techniques.
Date: October 1, 1995
Creator: Kowalczyk, T.C.; Singer, K.D. & Cahill, P.A.
Partner: UNT Libraries Government Documents Department

Investigation of laser-induced damage in DKDP under multi-color irradiation

Description: Laser-induced initiation of bulk damage sites in DKDP crystals is investigated under simultaneous exposure to 532- and 355-nm nanosecond laser pulses in order to simulate the operational conditions during harmonic conversion as well as probe the damage mechanisms. The results demonstrate synergetic damage effects under the dual-wavelength excitation. Furthermore, the damage performance is directly related to and can be predicted from the damage performance at each wavelength separately. The measured relative effective absorption coefficients at the two wavelengths are found to depend on the laser fluence. Laser-induced damage sites initiated within the bulk of optical components is a key limiting factor in the development of high power laser systems. Potassium dihydrogen phosphate (KH{sub 2}PO{sub 4} or KDP) and its deuterated analog (KD{sub 2-x}H{sub x}PO{sub 4} or DKDP) have been widely used for over three decades as Pockels cells and frequency converters and are still the only nonlinear materials suitable for large-aperture laser systems [1,2]. Damage thresholds in these materials have increased over time, primarily due to purer raw materials and improvement in growth processes, though localized damage sites still arise from laser intensities far below that necessary for intrinsic dielectric breakdown [3]. The damage precursors and their absorption mechanism leading to damage initiation are still unknown despite more than four decades of research [4,5]. In the case of KDP and DKDP crystals, recent work has highlighted the importance of synergetic effects between the second and third harmonics in Nd:glass lasers present during harmonic conversion to the observed damage density [6]. In this work, we quantitatively assess the damage performance of KDP/DKDP crystals under simultaneous exposure to the second and third harmonics of a nanosecond Nd:YAG laser system in order to (a) probe the underlying mechanism of damage initiation and (b) simulate the conditions taking place during harmonic conversion towards developing ...
Date: August 21, 2006
Creator: DeMange, P; Negres, R A; Rubenchik, A M; Radousky, H B; Feit, M D & Demos, S G
Partner: UNT Libraries Government Documents Department

Cryogenic loss monitors with FPGA TDC signal processing

Description: Radiation hard helium gas ionization chambers capable of operating in vacuum at temperatures ranging from 5K to 350K have been designed, fabricated and tested and will be used inside the cryostats at Fermilab's Superconducting Radiofrequency beam test facility. The chamber vessels are made of stainless steel and all materials used including seals are known to be radiation hard and suitable for operation at 5K. The chambers are designed to measure radiation up to 30 kRad/hr with sensitivity of approximately 1.9 pA/(Rad/hr). The signal current is measured with a recycling integrator current-to-frequency converter to achieve a required measurement capability for low current and a wide dynamic range. A novel scheme of using an FPGA-based time-to-digital converter (TDC) to measure time intervals between pulses output from the recycling integrator is employed to ensure a fast beam loss response along with a current measurement resolution better than 10-bit. This paper will describe the results obtained and highlight the processing techniques used.
Date: September 1, 2011
Creator: Warner, A. & Wu, J.
Partner: UNT Libraries Government Documents Department

CAVE: the design of a precision metrology instrument for studying performance of KDP crystals

Description: A device has been developed to measure the frequency conversion performance of large aperture potassium dihydrogen phosphate (KDP) crystals. Third harmonic generation using ICDP is critical to the function of the National Ignition Facility (NIF) laser. The crystals in the converter can be angularly or thermally tuned but are subject to larger aperture inhomogeneities that are functions of growth manufacturing and - mounting. The CAVE (Crystal Alignment Verification Equipment) instrument scans the crystals in a thermally and mechanically controlled environment to determine the local peak tuning angles. The CAVE can then estimate the optimum tuning angle and conversion efficiency over the entire aperture. Coupled with other metrology techniques, the CAVE will help determine which crystal life-cycle components most affect harmonic conversion.
Date: March 30, 1998
Creator: Hibbard, R.L., LLNL
Partner: UNT Libraries Government Documents Department

Measurement of SBS physics parameters. Final report

Description: SBS characteristics of the KD{sup *}P crystals were determined by the method of SBS generation excitation in the transverse resonator. Fused silica was utilized as the test medium. Experimental oscillograms of Stokes pulses were processed by the method of pulse form approximation using the four-parametric function of time. The obtained SBS characteristics for these materials are in good agreement with the published literary data and the available theoretical presentation data.
Date: December 31, 1995
Partner: UNT Libraries Government Documents Department

Inertial confinement fusion quarterly report: October--December 1995. Volume 6, Number 1

Description: This issue presents recent results from the ICF program at Lawrence Livermore National Laboratory in areas ranging from cryogenics to plasma instabilities. The article ``Metastable Crystal Structures of Solid Hydrogen`` describes primarily Raman spectroscopy studies of H{sub 2} and D{sub 2} films deposited at various rates and temperatures. All ignition target designs for ICF require a cryogenic deuterium-tritium (DT) fuel layer of uniform thickness and acceptable roughness. Solid DT layers, in particular, are easier to support in the presence of gravity and self-symmetrize due to self heating from the beta decay of tritium. The roughness of these films is closely related to their crystal structure, so it is important to understand film morphology under different deposition conditions. Three articles present different approaches to the study of plasma instabilities that lead to stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). In ``Modeling of Self-Focusing Experiments by Beam Propagation Codes,`` the authors describe the use of computer codes to model nonlinear effects during the propagation of laser beams through optical elements. Such codes have played a key role in the design of high-power lasers for ICF, both historically and for the NIF. The article ``Optical Scatter--A Diagnostic Tool to Investigate Laser Damage in KDP and DKDP`` examines the important problem of characterizing single crystals of KH{sub 2}PO{sub 4} (KDP) and deuterated KDP. These materials are used as optical switches, for frequency conversion in the Nova laser, and will be required for the NIF. The use of soft x-rays as a plasma probe is the topic of ``Soft X-Ray Interferometry.`` Interferometry of laser-produced plasmas presents a significant challenge, especially at electron densities exceeding 10{sup 20} cm{sup {minus}3}. The authors compare x-ray and optical interferometry of plasmas and show experimental results from a soft x-ray Mach-Zehnder interferometer.
Date: July 1, 1996
Creator: McEachern, R.L.; Carpenter, J.; Miguel, A.; Murphy, P.; Perez, J. & Schleich, D.
Partner: UNT Libraries Government Documents Department

Numerical thermal stability studies of the National Ignition Facility final optics assembly

Description: The National Ignition Facility (NIF), the world`s most powerful laser system, is being built at Lawrence Livermore National Laboratory (LLNL) to study inertial fusion and high-energy-density science. This billion-dollar facility consists of 192 beams focusing 1.8 MJ on a fusion target. The Final Optics Assembly (FOA), the last mechanical apparatus before the target chamber, converts the light from an incoming frequency of 1 {omega} to a target-ready 3 {omega}, and focuses the laser beam. The performance of the frequency conversion crystals is very sensitive to temperature changes; crystal temperature must be maintained within a 0.1 C of a nominal temperature prior to a laser shot. To ensure system availability, it is important to have an estimate of the thermal recovery time to operating temperature of the FOA after thermal disturbances caused by normal and maintenance operations. This paper presents Computational fluids Dynamics (CFD) fluid and thermal design calculations for both normal and maintenance operations of the NIF FOA.
Date: December 1, 1998
Creator: Parietti, L. & Martin, R.A.
Partner: UNT Libraries Government Documents Department

Transient radiation effects in D.O.I. optical materials: KD{sup *}P

Description: Department of Energy and Defense Programs systems are becoming increasingly reliant on the use of optical technologies that must perform under a range of ionizing radiation environments. In particular, the radiation response of materials under consideration for applications in direct optical initiation (D.O.I.) schemes must be well characterized. In this report, transient radiation effects observed in a KD*P crystal are characterized. Under gamma exposure with 2 MeV photons in a 20--30 nsec pulse, the authors observe induced absorption at 1.06 {micro}m that causes a peak decrease in overall sample transmittance of only 10%. This induced loss is seen to recover fully within the first 30 {micro}sec.
Date: July 1, 1998
Creator: Simmons-Potter, K.
Partner: UNT Libraries Government Documents Department