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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

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

Preliminary examination of the Linear Free-Electron Laser

Description: The Linear Free Electron Laser is numerically analyzed in the one dimensional limit by following an average (resonant) particle. Several different wiggler schemes are presented, and electron beam current density requirements are discussed. A variable phase angle buncher is also proposed.
Date: February 5, 1979
Creator: Prosnitz, D. & Szoke, 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

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

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

Damage history of Argus, a 4TW Nd-glass system

Description: Argus is a twin beam, 20 cm output aperture, Nd:glass laser system that has delivered 4TW to a laser fusion target. This performance is based on the concepts that multiple spatial filtering can prevent beam fill factors. Damage to optics due to self focusing and filamentation does not occur on Argus. The only form of damage is induced by broadband radiation from xenon flashlamps interacting with contaminants on or in the Nd:glass. The severity of damage is measured by the fraction of the beam obscured by the damage sites. This averages 0.1% per surface or 0.75% per arm. The amount of damage does not appear to be strongly related to the number of amplifier firings and generally occurs during the first few firings.
Date: December 6, 1977
Creator: Stowers, I.F. & Patton, H.G.
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

Far infrared chemical lasers. Technical progress report No. 5, September 1, 1978-August 31, 1979

Description: The intention to use the optically-pumped water vapor laser to study energy absorption and transfer in this triatomic molecule was not realized. The system at this moment is not well-enough understood to be as useful as was originally anticipated. What is known is that laser action in the far infrared is the result of flash-pumping, through suprasil, water vapor in the 10-100 mtorr pressure range, in a large resonator. About ten lines at about 100-200 cm/sup -1/ have been found. Four of them very definitely can be assigned to transitions that evolve from the feeding of the level (001)6/sub 42/. The other lines are of dubious assignment or completely unassignable. All of the hundred or so lines of well-known water discharge laser have been assigned to places in the level scheme where the bend-stretch wave functions are mixed.
Date: January 1, 1979
Creator: Robinson, D. W.
Partner: UNT Libraries Government Documents Department

Additive enhancement of short pulse flashlamps

Description: A key factor in the development of iodine photodisassociation lasers is the improvement of pump lamp efficiency in the 250 to 300 nm pump band at pulsewidths of about 10 ..mu..s. Previous work by Gusinow showed that certain metal additives appeared to enhance pump lamp output in the 250 to 300 nm region by as much as a factor of three. This had been determined by comparing microdensitometer traces of spectrograms of doped and undoped lamps. The principal problems noted with these lamps were a shot-to-shot variability of more than 30% and an effective life of only 20 shots (a result of migration of the dopants from between the electrodes to the colder regions behind the electrodes).
Date: April 1, 1977
Creator: Shaw, J. F.; Maynard, R. & Lovoi, P.
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

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

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

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

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

Overvoltage protection by point-plane spark gaps

Description: In electron-beam-controlled discharge CO/sup 2/ lasers, such as those used in the Antares and Helios laser-fusion drivers at the Los Alamos Scientific Laboratory (LASL), protection needs to be provided against possible damage due to overvoltage. A passive (self-breakdown) point-plane spark gap has been developed and successfully used in the Helios power amplifiers which operate at voltages up to 300 kV. A gap of similar design is planned for use in the Antares power amplifiers which operate at 550 kV. These gaps must reliably hold off the normal discharge voltage, but break down with short delay if overvoltaged, diverting the discharge energy to a resistor. A prototype of the Antares gap has been built and is undergoing tests. Parameters being investigated include voltage polarity, gap spacing, gas composition, and gas pressure. Results of these measurements and the operational experience of the Helios gaps will be presented.
Date: January 1, 1979
Creator: Scarlett, W.R. & Riepe, K.B.
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

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

Investigation of efficiency optimization in free electron lasers

Description: The dynamics of trapped particles in the presence of the wiggler magnetic field and the electromagnetic radiation field in free electron lasers were investigated. From the results of computer simulations, it was found that, for a given set of parameters, the efficiency of energy extraction from the electron beam maximizes at a particular intensity of the electromagnetic radiation. Based on the physical argument of the dynamics of the trapped particles, a criterion which predicts accurately the optimum intensity of the electromagnetic radiation was obtained. (TFD)
Date: January 1, 1979
Creator: Kwan, T.J.T.
Partner: UNT Libraries Government Documents Department

Metal vapor excimer laser. Quarterly progress report, May 1, 1978--July 31, 1978

Description: The discharge tube and circuitry has been assembled and tested and awaits the addition of metal vapor for the first discharge and gain tests. Further problems with the discharge tube as a result of high voltage arcing were encountered and finally overcome. Materials testing with cadmium has demonstrated that stainless steel and Inconel are suitable for fabrication materials while Monel is not. An investigation of scaling considerations of a single pulse metal vapor laser system was initiated and some preliminary assessments are detailed below. Inverse Bremsstrahlung pumping of a metal vapor system is discussed as a possible alternate to a conventional e-beam stabilized discharge.
Date: October 1, 1978
Creator: Kovacs, M.A. & Jacob, J.H.
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

Bibliography of GRASER research. Informal report

Description: The bibliography contains 161 references to literature on the problem of developing gamma-ray lasers or of observing stimulated emission or coherent spontaneous emission of nuclear gamma radiation, together with a number of references that deal with phenomena that are expected to be central to their realization. The period covered is 1917 through 1979.
Date: April 1, 1979
Creator: Baldwin, G.C.
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

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