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Review of long-pulse laser development

Description: A brief review of some present techniques to obtain long-pulse laser action in excimer discharge devices will be presented. An attempt will be made to point out the strengths and weaknesses of these techniques. 18 refs., 15 figs.
Date: January 1, 1989
Creator: Sze, R.C.
Partner: UNT Libraries Government Documents Department

The Los Alamos Photoinjector Program

Description: Free-electron lasers (FELS) require electron beams of high peak brightness. In this presentation, we describe the design of a compact high-brightness electron source for driving short-wavelength FELs. The experiment uses a laser-illuminated Cs/sub 3/Sb photoemitter located in the first rf cavity of an injector linac. The photocathode source and associated hardware are described. The doubled YAG laser (532 nm), which is used to drive the photocathode, produces 75-ps micropulses at 108-MHz repetition rate and peak powers of approximately 300 kW. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a 4-ps resolution streak camera. Present experiments give the following results: micropulse current amplitude of 100 mA to 400 A, beam emittances ranging from 10 n.mm.mrad to 40 n.mm.mrad, an energy spread of +-3%, and peak current densities of 600 A/cm/sup 2/. A brief discussion on the possible applications of this very bright and compact electron source is presented. 16 refs., 5 figs., 1 tab.
Date: September 1, 1987
Creator: Sheffield, R.L.; Gray, E.R. & Fraser, J.S.
Partner: UNT Libraries Government Documents Department

Nova pulse power design and operational experience

Description: Nova is a 100 TW Nd/sup + +/ solid state laser designed for experiments with laser fusion at Lawrence Livermore National Laboratory (LLNL). The pulsed power for Nova includes a 58 MJ capacitor bank driving 5336 flashlamps with millisecond pulses and subnanosecond high voltages for electro optics. This paper summarizes the pulsed power designs and the operational experience to date.
Date: January 1, 1987
Creator: Whitham, K.; Larson, D.; Merritt, B. & Christie, D.
Partner: UNT Libraries Government Documents Department

Multi-megajoule Nd: glass fusion laser design

Description: New technologies make multi-megajoule glass lasers economically feasible. Laser architectures using harmonic switchout, target plane holographic injection, phase conjugation, continuous apodization and higher amplifier efficiencies have been devised. A plan for a multi-megajoule laser which can be built for an acceptable cost relies on manufacturing economies of scale and the demonstration of the new technologies presented here. These include continuous pour glass production, rapid harmonic crystal growth, switching of large blocks of power using larger capcaitors packed more economically and by using large identical parts counts.
Date: April 4, 1986
Creator: Manes, K.R.
Partner: UNT Libraries Government Documents Department

Transverse correlations in start-up of a free electron laser from noise

Description: Linearized Vlasov-Maxwell equations are used to derive a partial differential equation determining the 3-dimensional slowly varying envelope function of the radiated electric field. The equation is solved analytically. From the correlation function <E(z,r,t) E*(z',r',t)> of the electric field averaged over the stochastic ansemble describing the initial shot noise in the beam, we compute the longitudinal and transverse correlation lengths sigma/sub L/ and sigma/sub T/. The radiated power S per unit cross-sectional area of the the electron beam is determined. Our analysis is applicable for wiggler length L = N/sub w/lambda/sub w/ long enough for the exponential regime to be researched, but short enough so that L sigma/sub theta/ less than or equal to a, the electron beam radius. 6 refs.
Date: March 1, 1986
Creator: Yu, L.H. & Krinsky, S.
Partner: UNT Libraries Government Documents Department

Evolution of free-electron laser development

Description: Recent experimental demonstrations of free-electron laser oscillators and amplifiers have verified the feasibility of these broadly tunable photon sources. We review the current status and their continuing evolution toward ever higher output power and shorter wavelengths. 46 refs.
Date: January 1, 1986
Creator: Newman, B.E.
Partner: UNT Libraries Government Documents Department

Layered target burnthrough experiments using 50 nsec KrF laser pulses

Description: Experiments have been performed on two types of planar layered targets using the Sprite KrF laser. The targets lused were: (1) 0.25 to 3.0 microns of Al deposited on an SiO/sub 2/ substrate and (2) 0.25 to 3.0 microns of CH (parylene-N) deposited on 0.20 microns of Al on an SiO/sub 2/ substrate. The laser was characterized by a pulse length of 50 nsec FWHM, an intensity of 2 x 10/sup 10/ watts/cm/sup 2/ and a wavelength of 248.5 nm. A filtered photoiodide and a streak camera, each operating in the visible, viewed the rear of the target. We measured the time from the beginning of the laser pulse to the onset of the visible light signal as seen by the photoiodide at the rear of the initially opaque target. This time is referred to as the burnthrough time. We obtain an estimate of the mass ablation by plotting the mass ablation depth (mass density times target thickness in ..mu..gm/cm/sup 2/) versus the burnthrough time. These results are consistent with earlier mass loss measurements and with analytic and hydro-code calculations (LASNEX). The streak camera data shows emission at target positions larger than the laser focal spot, and thus are consistent with 1-D and 2-D calculations which show target surface ablation to be primarily driven by reradiated photons from the hot laser produced plasma.
Date: January 1, 1986
Creator: Kephart, J.F.; Dingus, R.S.; Gitomer, S.J.; Kopp, R.A. & Shaw, M.J.
Partner: UNT Libraries Government Documents Department

Narrow band tuning with small long pulse excimer lasers

Description: We discuss frequency narrowing and tuning with simple dispersion elements with small long-pulse excimer lasers. The improved performance over short-pulse lasers is discussed and attributed to the increased number of round trips. A physical model of the dynamics of line narrowing is presented.
Date: December 1, 1985
Creator: Sze, R.C.; Kurnit, N.; Watkins, D. & Bigio, I.
Partner: UNT Libraries Government Documents Department

Potential for efficient frequency conversion at high average power using solid state nonlinear optical materials

Description: High-average-power frequency conversion using solid state nonlinear materials is discussed. Recent laboratory experience and new developments in design concepts show that current technology, a few tens of watts, may be extended by several orders of magnitude. For example, using KD*P, efficient doubling (>70%) of Nd:YAG at average powers approaching 100 KW is possible; and for doubling to the blue or ultraviolet regions, the average power may approach 1 MW. Configurations using segmented apertures permit essentially unlimited scaling of average power. High average power is achieved by configuring the nonlinear material as a set of thin plates with a large ratio of surface area to volume and by cooling the exposed surfaces with a flowing gas. The design and material fabrication of such a harmonic generator are well within current technology.
Date: October 28, 1985
Creator: Eimerl, D.
Partner: UNT Libraries Government Documents Department

Steady-state FEL: particle dynamics in the FEL portion of a two-beam accelerator

Description: Motivated by its use in a Two-Beam Accelerator, we have studied a ''steady-state'' FEL; i.e., a periodic but very long structure in which the electron beam energy is replenished once a period with a short induction acceleration unit. We have studied longitudinal particle motion in such a device using a 1-D simulation code. We show that after an initial start-up section, particle detrapping from the pondermotive wave is minimal in a steady-state FEL of several kilometers. A simple linear model of particle diffusion is shown to describe the numerical results quite well.
Date: September 1, 1985
Creator: Sternbach, E. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

Specific heat loading in Nd:glass lasers

Description: The specific thermal load parameter, chi, for xenon flashlamp-pumped Nd:glass gain media is written as a function of neodymium concentration, pump pulse duration, and energy extraction efficiency. The currently available data on radiative and nonradiative decay probabilities of several commercial Nd:glasses are used to calculate and graph specific thermal load parameter values. By factoring these results into performance scaling relationships for zig-zag and disk lasers, specific Nd:glasses can be selected for optimized laser performance.
Date: August 7, 1985
Creator: Krupke, W.F.
Partner: UNT Libraries Government Documents Department

Status of the Los Alamos Free-Electron Laser

Description: Since the initial oscillator experiments were completed last year, the Los Alamos FEL has undergone some major modifications and additions in preparation for the next set of experiments. The laser performance is projected to be substantially enhanced, the rf energy-recovery technique will be demonstrated, and FEL physics measurements will be expanded. The accelerator is now being tuned with very promising performance. The above experiments will be completed during the next year.
Date: January 1, 1985
Creator: Watson, J.M.
Partner: UNT Libraries Government Documents Department

Evaluation of bidirectionally conducting thyratrons for pulsed excimer lasers

Description: In the last few years many new applications have been found for excimer lasers in industry and defense programs. Many of these programs have very stringent requirements of lifetime, reliability, and power that are not available commercially. Power conditioning systems capable of driving excimers with reliable lifetimes of 5 billion pulses have been built with off-the-shelf components. In this paper we will discuss the requirements and life test performance of three types of thyratrons designed specifically for driving excimer lasers and also the life of associated components.
Date: January 1, 1984
Creator: McDuff, G.; Rust, K.; Menown, H. & Neale, C.
Partner: UNT Libraries Government Documents Department

Progress toward free-electron lasers for applications

Description: Using an electron beam in a magnetic field as the gain medium, free-electron lasers offer a powerful new source of tunable, coherent radiation. Results are just becoming available from several new experiments, but they are confirming the theoretical promise of these devices. Backed up by a strong base of accelerator technology, free-electron lasers are expected to become important in applications requiring wavelengths from the far infrared part of the spectrum to the vacuum ultraviolet.
Date: January 1, 1984
Creator: Brau, C.A.
Partner: UNT Libraries Government Documents Department

First operation of the Los Alamos free-electron laser oscillator

Description: An FEL oscillator has been operated at wavelengths between 9 and 11 ..mu..m with a peak intracavity power of about 20 MW and an average output power of 1 kW in 70- ..mu..s pulses. We present the design parameters and operating characteristics. We report measurements of spontaneous emission, start-up of oscillations, and signal growth through approx. 9 orders of magnitude to saturation. The dependence of gain and saturation on cavity length, alignment, beam parameters, and other critical variables are discussed and compared with theory. 7 references.
Date: January 1, 1983
Creator: Warren, R.W.; Newnam, B.E.; Stein, W.E.; Winston, J.G.; Sheffield, R.L.; Lynch, M.T. et al.
Partner: UNT Libraries Government Documents Department

Halide laser glasses

Description: Energy storage and energy extraction are of prime importance for efficient laser action and are affected by the line strengths and linewidths of optical transitions, excited-state lifetimes, nonradiative decay processes, spectroscopic inhomogeneities, nonlinear refractive index, and damage threshold. These properties are all host dependent. To illustrate this, the spectroscopic properties of Nd/sup 3 +/ have been measured in numerous oxide, oxyhalide, and halide glasses. A table summarizes the reported ranges of stimulated emission cross sections, peak wavelengths, linewidths, and radiative lifetimes associated with the /sup 4/F/sub 3/2/ ..-->.. /sup 4/I/sub 11/2/ lasing transition.
Date: January 14, 1982
Creator: Weber, M.J.
Partner: UNT Libraries Government Documents Department

Reinjection laser oscillator and method

Description: A uv preionized CO/sub 2/ oscillator with integral four-pass amplifier capable of providing 1 to 5 GW laser pulses with pulse widths from 0.1 to 0.5 ns full width at half-maximum (FWHM) is described. The apparatus is operated at any pressure from 1 atm to 10 atm without the necessity of complex high voltage electronics. The reinjection technique employed gives rise to a compact, efficient system that is particularly immune to alignment instabilities with a minimal amount of hardware and complexity.
Date: August 20, 1981
Creator: McLellan, E.J.
Partner: UNT Libraries Government Documents Department

Laser-based instrumentation for detection of chemical-warfare agents

Description: Several laser-based techniques are being developed for remote, point, and surface contamination detection of chemical warfare agents. These techniques include optoacoustic spectroscopy, laser-induced breakdown spectroscopy, and synchronous detection of laser-induced fluorescence. Detection limits in the part-per-million to part-per-billion regime have been demonstrated.
Date: January 1, 1981
Creator: Quigley, G.P.; Radziemski, L.J.; Sander, R.K. & Hartford, A. Jr.
Partner: UNT Libraries Government Documents Department

Small-signal-gain spectrum of an 1800 Torr CO/sub 2/ amplifier

Description: Prominent hot-band effects have been observed in the 9.4 and 10.6 ..mu..m gain spectrum of an 1800 Torr electron-beam-controlled-discharge CO/sub 2/ laser amplifier. The data are in good agreement with theoretical calculations at 53 different frequencies.
Date: January 1, 1981
Creator: Goldstein, J.C.; Haglund, R.F. Jr. & Comly, J.C. Jr.
Partner: UNT Libraries Government Documents Department

Status of the free-electron laser experiment at Los Alamos

Description: Main design parameters are presented for the accelerator, the laser, and the wiggler. Four sections are presented that discuss unusual or different features in the design, construction, alignment, and diagnostic parts of the experiment. Up-to-date performance characteristics of the components are described. (MOW)
Date: January 1, 1981
Creator: Warren, R.W.; Brau, C.A.; Newnam, B.E.; Stein, W.E.; Winston, J.G. & Young, L.M.
Partner: UNT Libraries Government Documents Department

Free electron lasers

Description: A review of experimental and theoretical concepts of a free electron laser is given. The possibilities of scaling these lasers to high powers are discussed. (MOW)
Date: January 1, 1980
Creator: Brau, C.A.
Partner: UNT Libraries Government Documents Department

Laser materials: July 1, 1977-July 31, 1978

Description: Fluoride materials display specific properties applicable for use as active and passive optical elements for advanced laser programs. Generally, these materials exhibit low values of n/sub 2/ and high ultraviolet transmission. Nd:YLF is a very promising laser fusion oscillator element operating in conjunction with phosphate and fluoroberyllate systems. New materials possessing high concentrations of terbium and cerium - KTb/sub 3/F/sub 10/, RbTb/sub 3/F/sub 10/ and potassium cerium compounds, display high magneto-optical rotatory power, high Verdet's constant, for use as Faraday rotators. Nd:YLF, operating at 1.047 ..mu..m or 1.053 ..mu..m has been identified as the most promising oscillator material for phosphate and fluoroberyllate systems. The new materials investigation included crystal growth and phase study of KTb/sub 3/F/sub 10/. KTb/sub 3/F/sub 10/ displays one of the highest figures of merit of any known material. Preliminary growth studies of other potential rotator materials included the RbF-Tb/sub 3/F/sub 10/ and the KF-CeF/sub 3/ systems. Compounds of both systems are expected to display high Verdet's constants.
Date: August 8, 1979
Creator: Folweiler, R.C.
Partner: UNT Libraries Government Documents Department