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Laser aperture diagnostics system for gain and wavefront measurements on NIF/LMJ amplifiers

Description: We are in the midst of constructing an amplifier laboratory (Arnplab) that will be the physics and engineering proving ground for fill sized segmented glass amplifiers of designs that will outfit the National Ignition Facility (NIF) and Laser Megajoule (LMJ) projects. Amplab will demonstrate the cornerstone mechanical, electrical and optical concepts that support the NW and LMJ amplifier schemes. Here we address the optical diagnostics that will be used to characterize optical performance of the amplifiers. We describe, the apparatus that will be used in pulsed measurements of gain distribution and wave-front distortions. The large aperture diagnostic system or LADS, is now being built through a collaborative effort between CEL-V and LLNL. The LADS will provide measurements of gain and wave front distortions over the fill extracting aperture of the NIF and LMJ prototype amplifiers. The LADS will be able to address each of eight apertures via motorized stages and following semi-automated alignment, take data on the aperture of interest. The LADS should be operational in mid-1997 at LLNL and will be used to characterize the optical performance of the very first fill scale prototype 4 x 2 NIF and LMJ amplifiers. It will be transported to Bordeaux, France to make similar measurements during activation of the first 8-aperture LMJ-like facility (LIL) that is planned to start in the near future.
Date: December 17, 1996
Creator: Zapata, L. E., LLNL
Partner: UNT Libraries Government Documents Department

Performance measurements of sealed-tube electron beam windows

Description: This paper describes the performance of the thin-film windows used in a new sealed-tube electron gun. Measurements include beam current, power, and power density along with window transmission, temperature, electron scattering and window life tests. A number of novel beam diagnostic tools were developed as part of this effort. Results are compared to Monte Carlo computer predictions and show good agreement. Transmitted beam powers in excess of 200 watts have been achieved, with current densities exceeding 30 milliamperes per square centimeter at sixty kilovolts beam energy. Predicted window wearout time exceeds several thousand hours at a current density of two milliamperes per square centimeter and a beam accelerating voltage of 60 kilovolts. This work was carried out under a Cooperative Research and Development Agreement (CRADA) between Lawrence Livermore National Laboratory and American International Technologies, Inc.
Date: February 23, 1996
Creator: Myers, B.R.; Chen, H.L.; Meyer, G. & Wakalopulos, G.
Partner: UNT Libraries Government Documents Department

Calculations of radiation damage in target, container and window materials for spallation neutron sources

Description: Radiation damage in target, container, and window materials for spallation neutron sources is am important factor in the design of target stations for accelerator-driver transmutation technologies. Calculations are described that use the LAHET and SPECTER codes to obtain displacement and helium production rates in tungsten, 316 stainless steel, and Inconel 718, which are major target, container, and window materials, respectively. Results are compared for the three materials, based on neutron spectra for NSNS and ATW spallation neutron sources, where the neutron fluxes are normalized to give the same flux of neutrons of all energies.
Date: July 1, 1996
Creator: Wechsler, M.S.; Ferguson, P.D.; Sommer, W.F. & Mansur, L.K.
Partner: UNT Libraries Government Documents Department

Design, manufacture, and calibration of infrared radiometric blackbody sources

Description: A Radiometric Calibration Station (RCS) is being assembled at the Los Alamos National Laboratories (LANL) which will allow for calibration of sensors with detector arrays having spectral capability from about 0.4-15 {mu}m. The configuration of the LANL RCS. Two blackbody sources have been designed to cover the spectral range from about 3-15 {mu}m, operating at temperatures ranging from about 180-350 K within a vacuum environment. The sources are designed to present a uniform spectral radiance over a large area to the sensor unit under test. The thermal uniformity requirement of the blackbody cavities has been one of the key factors of the design, requiring less than 50 mK variation over the entire blackbody surface to attain effective emissivity values of about 0.999. Once the two units are built and verified to the level of about 100 mK at LANL, they will be sent to the National Institute of Standards and Technology (NIST), where at least a factor of two improvement will be calibrated into the blackbody control system. The physical size of these assemblies will require modifications of the existing NIST Low Background Infrared (LBIR) Facility. LANL has constructed a bolt-on addition to the LBIR facility that will allow calibration of our large aperture sources. Methodology for attaining the two blackbody sources at calibrated levels of performance equivalent to present state of the art will be explained in the following.
Date: April 1, 1996
Creator: Byrd, D.A.; Michaud, F.D. & Bender, S.C.
Partner: UNT Libraries Government Documents Department

Technical evaluation of two 6-kW mono-Si photovoltaic systems at the National Renewable Energy Laboratory

Description: This paper presents an analysis of performance data on the two 6-kW{sub ac} grid-connected photovoltaic systems at the National Renewable Energy Laboratory (NREL). The performance parameters analyzed include dc and ac power, aperture efficiency, energy, capacity factor and performance index which are compared to plane-of-array irradiance, ambient temperature, and back-of-module temperature as a function of time, either daily or monthly. Power ratings of the systems were also obtained for data corresponding to different test conditions. This study has shown, in addition to expected seasonal trends, that system monitoring is a valuable tool in assessing performance and detecting faulty equipment. In addition, methods applied for this study may be used to evaluate and compare systems employing different cell technologies.
Date: May 1, 1996
Creator: Dyk, E.E. van; Strand, T. & Hansen, R.
Partner: UNT Libraries Government Documents Department

Energy stability in recirculating, energy-recovering linacs in the presence of a FEL

Description: Recirculating, energy-recovering linacs can be used as driver accelerators for high power FELs (free electron lasers). Instabilities which arise from fluctuations of the cavity fields are investigated. Energy changes can cause beam loss on apertures, or, when coupled to M{sub 56}, phase oscillations. Both effects change the beam induced voltage in the cavities and can lead to unstable variations of the accelerating field. An analytical model which includes amplitude and phase feedback, has been developed to study the stability of the system for small perturbations from equilibrium. The interaction of the electron beam with the FEL is a major perturbation which affects both the stability of the system and development of startup and recovery scenarios. To simulate the system's response to such large parameter variations, a numerical model of the beam-cavity interaction has been developed which includes low level rf feedback, phase oscillations and beam loss instabilities and the FEL interaction. Agreement between the numerical model and the linear theory has been demonstrated in the limit of small perturbations. In addition, the model has been benchmarked against experimental data obtained during CEBAF's high current operation. Numerical simulations have been performed for the high power IR DEMO approved for construction at CEBAF.
Date: July 1, 1996
Creator: Merminga, L.; Bisognano, J. & Delayen, J.R.
Partner: UNT Libraries Government Documents Department

CIS photovoltaic technology. Annual technical report, January 12, 1995--January 11, 1996

Description: EPV`s overall strategy in developing CIGS photovoltaic technology has been to define and construct a flexible set of large area vacuum deposition equipment and to explore CIGS formation recipes that can be implemented on this equipment. This is the inverse of the conventional approach in which manufacturing techniques are sought that can reproduce a high efficiency laboratory scale process over large areas. A feature of this equipment is the use of proprietary linear sources capable of downwards evaporation. Using recipes generated within this program, CIGS cells with efficiencies up to 13.9% were prepared by EPV under a separate CRADA with NREL. Entirely within this program, an aperture area efficiency of 9.6% was achieved for a laminated submodule of area 135.2 cm{sup 2}. Considerable effort has gone into the preparation and characterization of CIGS prepared on substrates measuring 96.5 cm x 44.5 cm, and good compositional uniformity has been achieved along both the short and long directions of the plate. Despite this, the material has not yet achieved the efficiency levels demonstrated in smaller scale equipment, and recipe development is ongoing. As part of a program to eliminate, if possible, the use of CdS, alternative buffer layers such as InSe, In{sub x}S{sub y}, and ZnSe have been explored, and, to gain insight into junction formation, CdSe. Of these compounds, ZnSe has shown the most promise, and further experiments are being conducted to optimize material and device properties.
Date: June 1, 1996
Creator: Delahoy, A.E.; Britt, J.S. & Gabor, A.M.
Partner: UNT Libraries Government Documents Department

Stress level evaluation of thin films under thermal loading from a brazing process

Description: X-ray front end beamline windows are made of thin beryllium foil that is commonly brazed or diffusion bonded onto a copper frame. In the brazing process, due to differences in the thermal expansion coefficient of the beryllium and copper materials, the beryllium film ends up in a state of very high level compression stress after cooling from 700{degrees}C (the brazing temperature) to room temperature. This makes the thin Be foil deform into a dome-shaped structure due to the usual asymmetrical geometry of the window. This paper studies the brazing process using a finite element method and explains the reason for such phenomena. Recommendations are offered for possible improvement in the bonding process of beryllium to the window block.
Date: June 1, 1996
Creator: Wang, Z. & Kuzay, T.M.
Partner: UNT Libraries Government Documents Department

3-D electromagnetic modeling of wakefields in accelerator components

Description: We discuss the use of 3-D finite-difference time-domain (FDTD) electromagnetic codes for modeling accelerator components. Computational modeling of cylindrically symmetric structures such as induction accelerator cells has been very successful in predicting the wake potential and wake impedances of these structures, but full 3-D modeling of complex structures has been limited due to substantial computer resources required for a full 3-D model. New massively parallel 3-D time domain electromagnetic codes now under development using conforming unstructured meshes allow a substantial increase in the geometric fidelity of the structures being modeled. Development of these new codes are discussed in context of applicability to accelerator problems. Various 3-D structures are tested with an existing cubical cell FDTD code and wake impedances compared with simple analytic models for the structures; results will be used as benchmarks for testing the new time time domain codes. Structures under consideration include a stripline beam position monitor as well as circular and elliptical apertures in circular waveguides. Excellent agreement for monopole and dipole impedances with models were found for these structures below the cutoff frequency of the beam line.
Date: September 18, 1996
Creator: Poole, B.R.; Caporaso, G.J.; Ng, Wang C.; Shang, C.C. & Steich, D.
Partner: UNT Libraries Government Documents Department

Beryllium window for synchrotron light sources

Description: As part of an on-going upgrade program at the National Synchrotron Light Source, a parametric study of rectangular flat and curved beryllium windows of varying thickness and heights and under varying thermal loading was undertaken. The study consisted of a series of 2D and 3D thermal stress finite element analyses to determine the relative benefit of various combinations of parameters with respect to the windows` ability to withstand thermal loads. This study includes evaluation of fixed versus flexible mounting of flat and curved beryllium windows. Buckling analyses for both types of mountings are also included.
Date: October 1, 1996
Creator: Lynch, D.R.; Berman, L.; Montanez, P.; Pjerov, S.; Stefan, P. & Woodle, M.
Partner: UNT Libraries Government Documents Department

Design analysis of a composite L5-80 slit for x-ray beamlines at the Advanced Photon Source

Description: White-beam slits are precision high-heat-load devices used on beamlines of the Advanced Photon Source (APS) to trim and shape the incoming x-rays beam before the beam is transmitted to other optical components. At the APS, the insertion devices that generate the x-ray are very powerful. For example, the heat flux associated with an x- ray beam generated by Undulator A will be on the order of 207 W/mm{sup 2} at the L5-80 slit location (about 27.5 m away from the insertion device) at normal incidence. The total power is about 5.3 kW. The optical slits with micron-level precision are very challenging to design under such heat flux and total power considerations. A novel three-metal composite slit has been designed to meet the diverse thermal, structural, and precision requirements. A closed form solution, and a commercial code, ANSYS, have been used for the analysis of the optimized design for the slit set.
Date: December 31, 1996
Creator: Nian, H.L.T.; Kuzay, T.M. & Shu, D.
Partner: UNT Libraries Government Documents Department

Model calibration and symmetry restoration of the advanced light source

Description: The symmetry of the ALS magnetic lattice is crucial in suppressing nonlinear structural resonances. Breaking the symmetry of the lattice can lead to a reduction in the dynamic aperture. The degree of symmetry breaking can be determined by fitting a magnetic lattice model to the measured orbit response matrix. This reveals a large beating of the vertical beta-function caused mainly by gradient errors in the QD quadrupole magnets. When the quadrupole field strengths are adjusted to compensate for the gradient errors, the symmetry of the lattice is restored. The new lattice has a larger dynamic aperture and an improved injection efficiency.
Date: June 10, 1996
Creator: Robin, D.; Portmann, G.; Nishimura, H. & Safranek, J.
Partner: UNT Libraries Government Documents Department

IBM, Endicott second year annual report. Executive summary

Description: PMSP (Polymer Metal Solvent Paste) material must be deposited on a five inch wafer with 100% bump survival. The target geometry is 0.010{double_prime} diameter, and 0.004{double_prime} high with a flat surface. Accomplishments: The photobumping process has been refined to yield bumps that are 0.010{double_prime} in diameter and greater than 0.0035{double_prime} high. The surface is flat and bonding results in a strong bond with no air entrapment between the chip bump and card pad. Initial work with photobumping yielded a bump surface that was concave. In photobumping, 0.004{double_prime} thick photoresist is imaged to create apertures. These apertures are filled with PMSP in two passes with a solvent drying process that occurs between the first and the second pass After the first pass filling, solvent from the PM SP interacted with the photoresist and caused the top surface, at the circumference of the aperture, to shrink. On the second pass filling, this slightly depressed surface fills up with PM SP. We call this blooming because the diameter of the bump is extended at the surface. When the photoresist is stripped, the thin surface extension of the bump diameter is folded over on top of the bump. This fold created a ridge at the circumference of the bump that would make initial contact with the card surface during bonding. The result was a high probability of air entrapment at the joint interface. The blooming problem was corrected by changing from an aqueous to a semiaqueous photorcsist that was more solvent resistant. Flat surface bumps are made with 100% yield on five inch wafers. Double layers of 0.002{double_prime} photoresist are used to define the nearly 0.004{double_prime} high bumps. Work is in progress to use single layers of 0.003{double_prime} and 0.004{double_prime} photoresist. A single layer should eliminate perturbations from a straight side wall profile that ...
Date: November 1, 1996
Creator: Gaynes, M.A.
Partner: UNT Libraries Government Documents Department

Spatial filter issues

Description: Experiments and calculations indicate that the threshold pressure in spatial filters for distortion of a transmitted pulse scales approximately as I{sup O.2} and (F{number_sign}){sup 2} over the intensity range from 10{sup 14} to 2xlO{sup 15} W/CM{sup 2} . We also demonstrated an interferometric diagnostic that will be used to measure the scaling relationships governing pinhole closure in spatial filters.
Date: December 9, 1996
Creator: Murray, J.E.; Estabrook, K.G.; Milam, D.; Sell, W.D.; Van Wonterghem, R.M.; Feil, M.D. et al.
Partner: UNT Libraries Government Documents Department

Time-frequency analysis of synthetic aperture radar signals

Description: Synthetic aperture radar (SAR) has become an important tool for remote sensing of the environment. SAR is a set of digital signal processing algorithms that are used to focus the signal returned to the radar because radar systems in themselves cannot produce the high resolution images required in remote sensing applications. To reconstruct an image, several parameters must be estimated and the quality of output image depends on the degree of accuracy of these parameters. In this thesis, we derive the fundamental SAR algorithms and concentrate on the estimation of one of its critical parameters. We show that the common technique for estimating this particular parameter can sometimes lead to erroneous results and reduced quality images. We also employ time-frequency analysis techniques to examine variations in the radar signals caused by platform motion and show how these results can be used to improve output image quality.
Date: August 1, 1996
Creator: Johnston, B.
Partner: UNT Libraries Government Documents Department

Design, performance and production of the Fermilab TESLA RF input couplers

Description: The TeV Energy Superconducting Linear Accelerator (TESLA) requires as one of its technical components a radiofrequency (rf) input coupler that transfers 1.3 GHz rf energy from the rf distribution system to a nine-cell superconducting accelerating cavity operating at a temperature of 1.8 K. The input coupler design is driven by numerous design criteria, which result in a rather complicated implementation. The production of twelve input couplers for the TESLA Test Facility (TTF) is underway at Fermilab, with the first two couplers having been delivered late in 1995. This paper discusses the Fermilab TESLA rf input coupler design, recent test results, and production issues.
Date: October 1, 1996
Creator: Champion, M.
Partner: UNT Libraries Government Documents Department