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Comparison of amplified spontaneous emission pulse cleaners for use in chirped pulse amplification front end lasers

Description: We compare various schemes for removing amplified spontaneous emission from seed laser pulses. We focus on compact schemes that are compatible with fiber laser front end systems with pulse energies in the 10nJ-1{micro}J range and pulse widths in the 100fs-10ps range. Pre-pulse contrast ratios greater than 10{sup 9} have been measured.
Date: July 2, 2007
Creator: Dawson, J.; Siders, C.; Phan, H.; Kanz, V. & Barty, C.
Partner: UNT Libraries Government Documents Department

A pilot application of risk-informed methods to establish inservice inspection priorities for nuclear components at Surry Unit 1 Nuclear Power Station. Revision 1

Description: As part of the Nondestructive Evaluation Reliability Program sponsored by the US Nuclear Regulatory Commission, the Pacific Northwest National Laboratory has developed risk-informed approaches for inservice inspection plans of nuclear power plants. This method uses probabilistic risk assessment (PRA) results to identify and prioritize the most risk-important components for inspection. The Surry Nuclear Power Station Unit 1 was selected for pilot application of this methodology. This report, which incorporates more recent plant-specific information and improved risk-informed methodology and tools, is Revision 1 of the earlier report (NUREG/CR-6181). The methodology discussed in the original report is no longer current and a preferred methodology is presented in this Revision. This report, NUREG/CR-6181, Rev. 1, therefore supersedes the earlier NUREG/CR-6181 published in August 1994. The specific systems addressed in this report are the auxiliary feedwater, the low-pressure injection, and the reactor coolant systems. The results provide a risk-informed ranking of components within these systems.
Date: February 1, 1997
Creator: Vo, T.V.; Phan, H.K.; Gore, B.F.; Simonen, F.A. & Doctor, S.R.
Partner: UNT Libraries Government Documents Department

Data collection and analysis in support of risk assessment for hydroelectric stations

Description: This project is to provide the U.S. Army Corps of Engineers with a risk analysis that evaluates the non-routine closure of water flow through the turbines of powerhouses along the Columbia and Snake Rivers. The project is divided into four phases. Phase 1 efforts collected and analyzed relevant plant failure data for hydroelectric generating stations in the United States and Canada. Results from the Phase 1 efforts will be used to assess the risk (probability times consequences) associated with non-routine shut down of hydroelectric stations, which will be performed in the remaining phases of the project. Results of this project may be used to provide policy recommendations regarding operation and maintenance of hydroelectric stations. The methodology used to complete the Phase 1 of the project is composed of data collection and analysis activities. Data collection included performing site visits, conducting a data survey of hydroelectric stations, conducting an expert panel workshop, and reviewing and tabulating failure data from generic sources. Data analysis included estimating failure rates obtained from the survey data, expert judgment elicitation process, generic data, and combining these failure rates to produce final failure rate parameters. This paper summarizes the data collection analysis, results and discussions for the Phase 1 efforts.
Date: October 1, 1995
Creator: Vo, T.V.; Mitts, T.M.; Phan, H.K.; Blackburn, T.R. & Casazza, L.O.
Partner: UNT Libraries Government Documents Department

Fiber laser front end for high energy petawatt laser systems

Description: We are developing a fiber laser front end suitable for high energy petawatt laser systems on large glass lasers such as NIF. The front end includes generation of the pulses in a fiber mode-locked oscillator, amplification and pulse cleaning, stretching of the pulses to >3ns, dispersion trimming, timing, fiber transport of the pulses to the main laser bay and amplification of the pulses to an injection energy of 150 {micro}J. We will discuss current status of our work including data from packaged components. Design detail such as how the system addresses pulse contrast, dispersion trimming and pulse width adjustment and impact of B-integral on the pulse amplification will be discussed. A schematic of the fiber laser system we are constructing is shown in figure 1 below. A 40MHz packaged mode-locked fiber oscillator produces {approx}1nJ pulses which are phase locked to a 10MHz reference clock. These pulses are down selected to 100kHz and then amplified while still compressed. The amplified compressed pulses are sent through a non-linear polarization rotation based pulse cleaner to remove background amplified spontaneous emission (ASE). The pulses are then stretched by a chirped fiber Bragg grating (CFBG) and then sent through a splitter. The splitter splits the signal into two beams. (From this point we follow only one beam as the other follows an identical path.) The pulses are sent through a pulse tweaker that trims dispersion imbalances between the final large optics compressor and the CFBG. The pulse tweaker also permits the dispersion of the system to be adjusted for the purpose of controlling the final pulse width. Fine scale timing between the two beam lines can also be adjusted in the tweaker. A large mode area photonic crystal single polarization fiber is used to transport the pulses from the master oscillator room to the main ...
Date: June 15, 2006
Creator: Dawson, J W; Messerly, M J; Phan, H; Mitchell, S; Drobshoff, A; Beach, R J et al.
Partner: UNT Libraries Government Documents Department

Value impact analysis of Generic Issue 143, Availability of Heating, Ventilation, Air Conditioning (HVAC) and Chilled Water Systems

Description: This study evaluates the values (benefits) and impacts (costs) associated with potential resolutions to Generic Issue 143, ``Availability of HVAC and Chilled Water Systems.`` The study identifies vulnerabilities related to failures of HVAC, chilled water, and room cooling systems; develops estimates of room heatup rates and safety-related equipment vulnerabilities following losses of HVAC/room cooler systems; develops estimates of the core damage frequencies and public risks associated with failures of these systems; develops three proposed resolution strategies to this generic issue; and performs a value/impact analysis of the proposed resolutions. Existing probabilistic risk assessments for four representative plants, including one plant from each vendor, form the basis for the core damage frequency and public risk calculations. Both internal and external events were considered. It was concluded that all three proposed resolution strategies exceed the $1,000/person-rem cost-effectiveness ratio. Additional evaluations were performed to develop ``generic`` insights on potential design-related and configuration-related vulnerabilities and potential high-frequency ({approximately}1E-04/RY) accident sequences that involve failures of HVAC/room cooling functions. It was concluded that, although high-frequency accident sequences may exist at some plants, these high-frequency sequences are plant-specific in nature or have been resolved through hardware and/or operational changes. The plant-specific Individual Plant Examinations are an effective vehicle for identification and resolution of these plant-specific anomalies and hardware configurations.
Date: November 1, 1993
Creator: Daling, P. M.; Marler, J. E.; Vo, T. V.; Phan, H. & Friley, J. R.
Partner: UNT Libraries Government Documents Department

Design and Operation of a tunable MeV-level Compton-scattering-based (gamma-ray) source

Description: A mono-energetic gamma-ray (MEGa-ray) source based on Compton-scattering, targeting nuclear physics applications such as nuclear resonance fluorescence, has been constructed and commissioned at Lawrence Livermore National Laboratory. In this paper, the overall architecture of the system, as well as some of the critical design decisions made in the development of the source, are discussed. The performances of the two laser systems (one for electron production, one for scattering), the electron photoinjector, and the linear accelerator are also detailed, and initial {gamma}-ray results are presented.
Date: July 7, 2009
Creator: Gibson, D J; Albert, F; Anderson, S G; Betts, S M; Messerly, M J; Phan, H H et al.
Partner: UNT Libraries Government Documents Department

Ultrabright Laser-based MeV-class Light Source

Description: We report first light from a novel, new source of 10-ps 0.776-MeV gamma-ray pulses known as T-REX (Thomson-Radiated Extreme X-rays). The MeV-class radiation produced by TREX is unique in the world with respect to its brightness, spectral purity, tunability, pulse duration and laser-like beam character. With T-REX, one can use photons to efficiently probe and excite the isotope-dependent resonant structure of atomic nucleus. This ability will be enabling to an entirely new class of isotope-specific, high resolution imaging and detection capabilities.
Date: April 2, 2008
Creator: Albert, F; Anderson, G; Anderson, S; Bayramian, A; Berry, B; Betts, S et al.
Partner: UNT Libraries Government Documents Department

LASER TECHNOLOGY FOR PRECISION MONOENERGETIC GAMMA-RAY SOURCE R&D AT LLNL

Description: Generation of mono-energetic, high brightness gamma-rays requires state of the art lasers to both produce a low emittance electron beam in the linac and high intensity, narrow linewidth laser photons for scattering with the relativistic electrons. Here, we overview the laser systems for the 3rd generation Monoenergetic Gamma-ray Source (MEGa-ray) currently under construction at Lawrence Livermore National Lab (LLNL). We also describe a method for increasing the efficiency of laser Compton scattering through laser pulse recirculation. The fiber-based photoinjector laser will produce 50 {micro}J temporally and spatially shaped UV pulses at 120 Hz to generate a low emittance electron beam in the X-band RF photoinjector. The interaction laser generates high intensity photons that focus into the interaction region and scatter off the accelerated electrons. This system utilizes chirped pulse amplification and commercial diode pumped solid state Nd:YAG amplifiers to produce 0.5 J, 10 ps, 120 Hz pulses at 1064 nm and up to 0.2 J after frequency doubling. A single passively mode-locked Ytterbium fiber oscillator seeds both laser systems and provides a timing synch with the linac.
Date: April 20, 2010
Creator: Shverdin, M Y; Bayramian, A; Albert, F; Anderson, S G; Betts, S M; Chu, T S et al.
Partner: UNT Libraries Government Documents Department