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Growth of large KDP crystals in the form of plates

Description: This paper suggests a new technique of growth-oriented KDP crystals in the form of plates. The technique includes: using small oriented seeds spaced between two parallel platforms with a rapid growth of crystals between these two platforms, in a tank containing a KDP solution. As a result, crystals in the form of plates can be obtained. The thickness of the crystal plate depends on the distance between platforms. The horizontal dimensions of the plate depend on the volume of solution and the diameter of the platforms. The orientation of the plates are defined by the orientation of the seed. KDP crystals in the form of plates of two orientations are grown. The peculiarities of morphology and some characteristics of crystals are discussed.
Date: May 1, 1998
Creator: Beriot, E & Tatartchenko, V
Partner: UNT Libraries Government Documents Department

Effect of pH on the growth of KDP

Description: The acidity of KDP salt solution is one of the important parameters. This parameter determines a lot of properties of solution, crystallization processes in solution, properties of grown crystals. An alteration of the KDP salt solution acidity changes it`s properties such as KDP salt volubility, stability of the KDP solution, solution density, solution viscosity, solution heat capacity, etc. It also changes state of impurities in the solution and characteristics of interaction between growing faces of the crystal and solution impurities. As a result kinetics of crystallization changes, habit and physical properties of the grown crystal change too. It should be mentioned that investigations in were done for low rate processes of crystal growth. Here we report the results of our investigations which have been done for high rate crystal growth processes (R{sub Z} {approx} 20 mm/day).
Date: March 20, 1998
Creator: Rashkovich, L. N.
Partner: UNT Libraries Government Documents Department

Laser conditioning study of KDP on the optical sciences laser using large area beams

Description: Considerable attention has been paid over the years to the problem of growing high purity KDP and KD*P to meet threshold requirements on succeeding generations of inertial confinement fusion lasers at LLNL. While damage thresholds for these materials have increased over time, the current National Ignition Facility (NIF) maximum fluence requirement (redline) for KD*P frequency triplers of 14.3 J/cm{sup 2} at 351 nm, 3 ns has not been reached without laser (pre)conditioning. It is reasonable to assume that, despite the rapid increase in damage thresholds for rapidly grown crystals, -a program of large scale conditioning of the 192 NIF triplers will be required. Small area ramp (R/1) tests on single sites indicate that KDP damage thresholds can be raised on average up to 1.5X the unconditioned values. Unpublished LLNL 3{omega} raster conditioning studies on KDP, however, have not conclusively shown that off-line conditioning is feasible for KD*P. Consequently, investigating the feasibility of on-line conditioning of NIF triplers at 3{omega} has become a high priority for the KDP damage group at LLNL. To investigate the feasibility of on-line conditioning we performed a series of experiments using the Optical Sciences Laser (OSL) on numerous samples of conventional and rapid growth KDP and KD*P. The experiment entailed exposing sites on each sample to a range of ramped shot (N/l) sequences starting at average fluences of -2 J/cm{sup 2} (in a 7 mm ``top hat`` beam @ 351 nm, 3 ns) up to peak fluences of approximately 13 J/cm{sup 2}. Test results indicated that the most effective conditioning procedure entailed a 7-8 shot ramp starting at 2 J/cm{sup 2} and ending at 12-13 J/cm{sup 2}. The pinpoint onset fluence for the 8/1 tests was 1.4 times that of the unconditioned site. Damage evolution appears to be exponential as a function of increasing fluence. When ...
Date: December 20, 1997
Creator: Runkel, M.; DeYoreo, J.; Sell, W. & Milam, D.
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 ┬Árad. 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

Investigation of damage in KDP using scattering techniques

Description: Interest in producing high damage threshold KH{sub 2}PO{sub 4} (KDP) and (D{sub x}H{sub 1-x}){sub 2}PO{sub 4} (DKDP)(also called KD*P) for frequency conversion and optical switching applications is driven by the requirements of the National Ignition Facility (NIF). Presently only the best crystals meet the NIF system requirements at the third harmonic (351 nm) and only after a laser conditioning process. Neither the mechanism for damage in bulk KDP nor the mechanism for conditioning is understood. As part of a development effort to increase the damage thresholds of KDP and DKDP, we have been developing techniques to pinpoint the locations where damage will initiate in the bulk material. After we find these locations we will use other measurement techniques to determine how these locations differ from the other surrounding material and why they cause damage. This will allow crystal growers to focus their efforts to improve damage thresholds. Historically damage thresholds have increased it is believed as a consequence of increased purity of the growth solution and through the use of constant filtration during the growth process. As a result we believe that damage is caused by defects in the crystals and have conducted a series of experiments using light scatter to locate these defects and to determine when and where damage occurs. In this paper we present results which show a low correlation between light scatter from bulk defects in KDP and the initiation sites for damage. We have also studied the effects of thermal conditioning on light scatter, strain induced birefringence and damage threshold. We have seen evidence that regions of high strain also exhibit lower damage threshold than the surrounding lower strain material. When thermally conditioned, these crystals show a decrease in some of the strong linear scattering features and a decrease in the strain birefringence while the ...
Date: February 12, 1997
Creator: Woods, B.; Runkel, M.; Yan, M.; Staggs, M.; Zaitseva, N.; Kozlowski, M. et al.
Partner: UNT Libraries Government Documents Department

Investigation of steady-state and transient defect populations in KH2PO4 subsequent to high fluence laser irradiation

Description: Microscopic fluorescence imaging and time-resolved Raman scattering are employed to investigate the effect of high power 355 nm laser irradiation on preexisting and transient defect populations in KH 2 PO 4 . Defect clusters in the bulk of KDP crystals are imaged with 1 micron spatial resolution using their NIR emission. The intensity of the emission clusters varies widely within the image field. The exposure of the crystal at high power 355 nm, 3 ns laser irradiation leads to a reduction of the number of observed optically active centers. In addition, time resolved Raman scattering was employed to study the transient generation of defects during high power 355 nm laser irradiation.
Date: January 26, 1999
Creator: De Yoreo, J. J.; Demos, S. G.; Radousky, H. B. & Staggs, M.
Partner: UNT Libraries Government Documents Department

Photothermal mapping of defects in the study of builk damage in KDP

Description: Interest in producing high-damage-threshold KH{sub 2}PO{sub 4} (KDP) and (D{sub x}H{sub 1-x}){sub 2}PO{sub 4} (DKDP) for frequency conversion and optical switching applications is driven by the requirements of the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL). At present only the best crystals meet the NIF system requirements at the third harmonic (351 nm) and only after a laser conditioning process. Neither the mechanism for damage in bulk KDP nor the mechanism for conditioning is understood. As part of a development effort to increase the damage thresholds of KDP and DKDP, we have been developing a diagnostic tool that will find these locations, we will use other measurement techniques to determine how these locations differ from the surrounding material and why they cause damage. This will allow crystal growers to focus their efforts during the growth process in improving damage thresholds.
Date: December 20, 1997
Creator: Woods, B.; Yan, M.; DeYoreo, J.; Kozlowski, M.; Radouski, H. & Wu, Z.
Partner: UNT Libraries Government Documents Department

Sources of strain in rapidly grown crystals of KH{sub 2}PO{sub 4}

Description: The objective of this paper is to describe the results of x-ray topographic studies on potassium di-hydro phosphate (KDP) crystals grown from solutions at high supersaturation which produces growth rates of ten to fifty times those of conventional methods. Strain in the crystals is discussed.
Date: February 1, 1995
Creator: De Yoreo, J.; Zaitseva, N. & Woods, B.
Partner: UNT Libraries Government Documents Department

A procedure for diamond turning KDP crystals

Description: A procedure and the equipment necessary for single-point diamond flycutting (loosely referred to as diamond turning) potassium di-hydrogen phosphate (KDP) crystals are described. It is based on current KDP diamond turning activities at the Lawrence Livermore National Laboratory (LLNL), drawing upon knowledge from the Nova crystal finishing development during the 1980`s and incorporating refinements from our efforts during 1995. In addition to describing a step-by-step process for diamond turning KDP, specific discussions are included on the necessary diamond tool geometry and edge sharpness, cutting fluid, and crystal preparation, handling, cleaning, and inspection. The authors presuppose that the reader is already familiar with diamond turning practices.
Date: July 7, 1995
Creator: Montesanti, R.C. & Thompson, S.L.
Partner: UNT Libraries Government Documents Department

Predicting laser-induced bulk damage and conditioning for deuterated potassium di-hydrogen phosphate crystals using ADM (absorption distribution model)

Description: We present an empirical model that describes the experimentally observed laser-induced bulk damage and conditioning behavior in deuterated Potassium dihydrogen Phosphate (DKDP) crystals in a self-consistent way. The model expands on an existing nanoabsorber precursor model and the multi-step absorption mechanism to include two populations of absorbing defects, one with linear absorption and another with nonlinear absorption. We show that this model connects previously uncorrelated small-beam damage initiation probability data to large-beam damage density measurements over a range of ns pulse widths relevant to ICF lasers such as the National Ignition Facility (NIF). In addition, this work predicts the damage behavior of laser-conditioned DKDP and explains the upper limit to the laser conditioning effect. The ADM model has been successfully used during the commissioning and early operation of the NIF.
Date: February 26, 2010
Creator: Liao, Z M; Spaeth, M L; Manes, K; Adams, J J & Carr, C W
Partner: UNT Libraries Government Documents Department

MAGNESIUM MONO POTASSIUM PHOSPHATE GROUT FOR P-REACTOR VESSEL IN-SITU DECOMISSIONING

Description: The objective of this report is to document laboratory testing of magnesium mono potassium phosphate grouts for P-Reactor vessel in-situ decommissioning. Magnesium mono potassium phosphate cement-based grout was identified as candidate material for filling (physically stabilizing) the 105-P Reactor vessel (RV) because it is less alkaline than portland cement-based grout (pH of about 12.4). A less alkaline material ({<=} 10.5) was desired to address a potential materials compatibility issue caused by corrosion of aluminum metal in highly alkaline environments such as that encountered in portland cement grouts. Information concerning access points into the P-Reactor vessel and amount of aluminum metal in the vessel is provided elsewhere. Fresh and cured properties were measured for: (1) commercially blended magnesium mono potassium phosphate packaged grouts, (2) commercially available binders blended with inert fillers at SRNL, (3) grouts prepared from technical grade MgO and KH{sub 2}PO{sub 4} and inert fillers (quartz sands, Class F fly ash), and (4) Ceramicrete{reg_sign} magnesium mono potassium phosphate-based grouts prepared at Argonne National Laboratory. Boric acid was evaluated as a set retarder in the magnesium mono potassium phosphate mixes.
Date: January 5, 2011
Creator: Langton, C. & Stefanko, D.
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

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

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

Sources of optical distortion in rapidly grown crystals of KH{sub 2}PO{sub 4}

Description: We report results of x-ray topographic and optical measurements on KH{sub 2}PO{sub 4} crystals grown at rates of 5 to 30mm/day. We show that optical distortion in these crystals is caused primarily by 3 sources: dislocations, differences in composition between adjacent growth sectors of the crystal, and differences in composition between adjacent sectors of vicinal growth hillocks within a single growth sector of the crystal. We find that the compositional heterogeneities cause spatial variations in the refractive index and induced distortion of the transmitted wave front while large groups of dislocations are responsible for strain induced birefringence which leads to beam depolarization.
Date: March 20, 1995
Creator: De Yoreo, J.J.; Zaitseva, N.P.; Woods, B.W.; Land, T.A. & Rek, Z.U.
Partner: UNT Libraries Government Documents Department

Rapid growth of large-scale (40-55 cm) KDP crystals

Description: KDP (KH{sub 2}PO{sub 4}) single crystals up to 47 cm in size have been grown by the rapid growth technique on the point seed in glass recrystallizers of 1000 L in volume at growth rates of 10 to 25 mm/day in both the [001] and [100] directions. Measurements of the optical quality of 41 x 41 cm single crystal plates are presented.
Date: February 13, 1997
Creator: Zaitseva, N.P.; DeYoreo, J.J.; Dehaven, M.R.; Vital, R.L.; Carman, L.M. & Spears, H.R.
Partner: UNT Libraries Government Documents Department

Impurity and laser-induced damage in the growth sectors of rapidly grown DKP crystals

Description: We report the experimental results of impurity contamination and laser-induced damage investigations on rapidly grown potassium dihydrogen phosphate (KDP) crystals. Using absorption spectroscopy and chemical analysis, we determined the impurity distribution in the different growing sectors of KDP single crystals. The level of impurity was dependent on starting materials and growth rate. We also studied influence of impurities on laser-induced damage in fast grown KDP. The laser damage threshold (LDT) in the impurity-rich prismatic sector is same as in the high purity pyramidal sector within experimental error. Meanwhile, the LDT at the boundary of the prismatic and pyramidal sectors is less than half of that in the bulk. Furthermore, we found that the thermal annealing of the crystal eliminated the weakness of this sector boundary and increased its LDT to the same level as in the bulk of the crystal. Result suggests that the laser damage occurred in the vicinity of a high; localized strain field.
Date: February 13, 1997
Creator: Yan, M.; Torres, R.; Runkel, M.; Woods, B.; Hutcheon, I.; Zaitseva, N. et al.
Partner: UNT Libraries Government Documents Department

Recent results in a search for inorganic scintillators for x- and gamma-ray detection

Description: We present recent results from an ongoing search for inorganic scintillators for gamma ray detection in which we measure the scintillation properties (luminous efficiency, decay time, and emission wavelength) of powdered samples excited by brief x-ray pulses. Recent promising candidates include cerium doped lutetium borate (LuBO{sub 3}) and the lutetium double phosphates K{sub 3}Lu(PO{sub 4}){sub 2} and Rb{sub 3}Lu(PO{sub 4}){sub 2}, which have luminous intensities above 25,000 photons/MeV. In order to find scintillators that are compatible with silicon photodetectors, we have tested over 1,100 samples using a photomultiplier tube with a GaAs:Cs photocathode, which is sensitive to emissions from 200-950 nm. While many samples exhibited strong emissions in the 600-900 nm range, all had decay times that were larger than 10 {mu}s.
Date: October 1997
Creator: Moses, W. W.; Weber, M. J.; Derenzo, S. E.; Perry, D. & Berahl, P.
Partner: UNT Libraries Government Documents Department

Effect of impurities and stress on the damage distributions of rapidly grown KDP crystals

Description: Development of high damage threshold, 50 cm, rapidly grown KF*P frequency triplers for operation of the National Ignition Facility (NIF) in the 14 J/cm2, 351 nm, 3 ns regime requires a thorough understanding of how the crystal growth parameters and technologies affect laser induced damage. Of particular importance is determining the effect of ionic impurities (e.g. Cr3+, Fe3+, Al3+) which may be introduced in widely varying concentrations via starting salts. In addition, organic particulates can contaminate the solution as leachants from growth platforms or via mechanical ablation. Mechanical stresses in the crystals may also play a strong role in the laser-induced damage distribution (LIDD), particularly in the cases of large boules where hydrodynamic forces in the growth tank may be quite high. WE have developed a dedicated, automated damage test system with diagnostic capabilities specifically designed for measured time resolved bulk damage onset and evolution. The data obtained make it possible to construct characteristic damage threshold distributions for each sample. Test results obtained for a variety of KDP samples grown from high purity starting salts and individually doped with Lucite and Teflon, iron, chromium, and aluminium show that the LIDD drops with increasing contamination content. The results also show that solution filtration leads to increased damage performance for undoped crystals but is not solely responsibility for producing the high LIDDs required by the NIF. The highest LIDD measured on a rapidly grown sample indicate that it is possible to produce high damage threshold material using ultrahigh purity, recrystallized starting salts, continuous filtration and a platform designed to minimize internal stress during growth.
Date: December 20, 1997
Creator: Runkel, M.; Tan, M.; De Yoreo, J. & Zaitseva, N.
Partner: UNT Libraries Government Documents Department

Measurement of point defect energetics in potassium dihydrogen phosphate (KDP). Final report

Description: Potassium dihydrogen phosphate (KDP) in the normal and deuterated form (KD*P) exhibits excellent electrooptical and nonlinear optical properties and is commonly used in frequency conversion applications. Frequency doubling (2 {omega}) of Nd:YAG or Nd:YLF laser fundamental output at 1.06 {micro}m produces visible radiation at 532 nm with relatively good conversion efficiency. Frequency tripling (3{omega}) and quadrupling (4{omega}) are also utilized for production of ultraviolet (uv) radiation at 355 and 266 nm, respectively. However in the latter case the conversion efficiency is relatively low, especially at high incident fluences ({approximately}2 GW/cm{sup 2}). A fundamental problem associated with high peak-power laser excitation of KDP is the production of transient optical absorption that inhibits conversion efficiency. The role of point defects on frequency conversion efficiency and optoelectronic device performance in KDP and its isomorphs is not fully understood. However, it is evident from the extant data that their existence, even in pure specimens, affects the overall performance of these technologically important materials, and that further research is required to elucidate their role. Accordingly, they have investigated the temperature-dependent optical absorption and radioluminescence (RL) of pure KDP as well as doped specimens: KDP:Fe, KDP:Cr, and KDP:Al.
Date: October 1, 1997
Creator: Cooke, D.W.; Muenchausen, R.E. & Bennett, B.L.
Partner: UNT Libraries Government Documents Department

Erosion of magnesium potassium phosphate ceramic waste forms.

Description: Phosphate-based chemically bonded ceramics were formed from magnesium potassium phosphate (MKP) binder and either industrial fly ash or steel slag. The resulting ceramics were subjected to solid-particle erosion by a stream of either angular Al{sub 2}O{sub 3} particles or rounded SiO{sub 2} sand. Particle impact angles were 30 or 90{degree} and the impact velocity was 50 m/s. Steady-state erosion rates, measured as mass lost from a specimen per mass of impacting particle, were dependent on impact angle and on erodent particle size and shape. Material was lost by a combination of fracture mechanisms. Evolution of H{sub 2}O from the MKP phase appeared to contribute significantly to the material loss.
Date: November 20, 1998
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Producing KDP and DKDP crystals for the NIF laser

Description: The cost and physics requirements of the NIF have established two important roles for potassium dihydrogen phosphate (KDP) crystals. 1. To extract more laser energy per unit of flashlamp light and laser glass, the NIF has adopted a multipass architecture as shown in Figure 1. Light is injected in the transport spatial filter, first traverses the power amplifiers, and then is directed to main amplifiers, where it makes four passes before being redirected through the power amplifiers towards the target. To enable the multipass of the main amplifiers, a KDP-containing Pockels cell rotates the polarization of the beam to make it either transmit through or reflect off a polarizer held at Brewster's angle within the main laser cavity. If transmitted, the light reflects off a mirror and makes another pass through the cavity. If reflected, it proceeds through the power amplifier to the target. the original seed crystal as the pyramid faces grow. Unfortunately, this pyramidal growth is very slow, and it takes about two years to grow a crystal to NIF size. To provide more programmatic flexibility and reduce costs in the long run, we have developed an alternative technology commonly called rapid growth. Through a combination of higher temperatures and higher supersaturation of the growth solution, a NIF-size boule can be grown in 1 to 2 months from a small ''point'' seed. However, growing boules of adequate size is not sufficient. Care must be taken to prevent inclusions of growth solution and incorporation of atomically substituted 2. Implosions for ICF work far better at shorter wavelengths due to less generation of hot electrons, which preheat the fuel and make it harder to compress. Compromising between optic lifetime and implosion efficiency, both Nova and the NIF operate at a tripled frequency of the 1053-nm fundamental frequency of a neodymium ...
Date: September 2, 1999
Creator: Atherton, L J; Burnham, A K; Combs, R C; Couture, S A; De Yoreo, J J; Hawley-Fedder, R A et al.
Partner: UNT Libraries Government Documents Department

Experimental Investigation of the Thermal Upset and Recovery of the National Ignition Facility's Optics Module

Description: The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is being constructed as the latest in a series of high-power laser facilities to study inertial confinement fusion. In particular, the NIF will generate and amplify 192 laser beams and focus them onto a fusion fuel capsule the size of a BB. The energy deposited by the laser beams will raise the core temperature of the target to 100,OOO,OOO C, which will ignite the fusion fuel and produce a fusion energy output that is several times greater than the energy input. The ability to generate, condition, and focus 192 laser beams onto a target the size of a BB, requires precision optical hardware and instrumentation. One of the most critical pieces of optical hardware within the NIF is the Optics Module (OM), a mechanical apparatus which is responsible for optical focusing and frequency conversion of the laser beam to optimize the energy deposition at the fusion target. The OM contains two potassium dihydrogen phosphate (KDP), frequency conversion crystals and a focusing lens. The functionality of the KDP crystals is extremely temperature sensitive. Small temperature changes on the order of 0.1 C can significantly alter the performance of these components. Consequently, to maximize NIF system availability and minimize beam conditioning problems, accurate temperature control of the OM optical components was deemed a necessity. In this study, an experimental OM prototype, containing mock frequency conversion crystals and a focusing lens, was used determine the thermal stability provided by a prototype water temperature control system. More importantly, the OM prototype was used to identify and characterize potential thermal upsets and corresponding recovery times of the KDP crystals. The results of this study indicate that the water temperature control system is adequate in maintaining uniform steady-state temperatures within the OM. Vacuum pump-down and venting ...
Date: May 1, 1999
Creator: Bernardin, J. D.
Partner: UNT Libraries Government Documents Department