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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

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

Development of an actively modelocked and Q-switched oscillator for laser fusion program at LLL

Description: A method was developed that allows the mode-locking process to go to its steady state condition before the laser is Q-switched. This is done by pumping the laser quasi-cw for about 5 ms. During this time, the loss in the Q-switch is such that the laser will just slightly go above threshold. The active modulator is on during this time, and the laser oscillates quasi-cw for a period long enough to obtain stable transform-limited short pulses. At the end of this prelase period, the laser is Q-switched, and a train of stable, short pulses is obtained.
Date: July 19, 1978
Creator: Kuizenga, D.J.
Partner: UNT Libraries Government Documents Department

Metal vapor excimer laser. Quarterly progress report, August 1, 1978--October 31, 1978

Description: Progress in the metal vapor excimer program was slowed in the quarter as a result of a fire which occurred in the apparatus. As this period closed, the fire related damage had largely been repaired; in spite of the setback there will be sufficient time to generate data for the mid-December workshop meeting. Initial design considerations for the foil and foil support of a high temperature, transverse e-beam discharge device have been generated. In addition, foil material testing has been performed.
Date: December 1, 1978
Creator: Kovacs, M.A. & Jacob, J.H.
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

Research on frequency shifting of ultraviolet lasers. Final report, June 23, 1977--May 23, 1978

Description: The four-wave mixing interaction proposed for uv frequency shifting cannot be phase matched with known techniques. One related process that avoids phase matching problems is stimulated Raman scattering (SRS). The same wavelength generated by four-wave mixing (2821 A) could also be generated by SRS using the uv pump source alone. In this case, the uv pump power must be high enough to exceed the oscillation threshold. SRS was observed in liquid CO pumped by the doubled Nd:YAG laser at 5320 A. The quadrupled Nd:YAG pump power at 2660 A was insufficient to attain SRS threshold. Although high-efficiency SRS should be attainable in the uv with more pump power, it is unlikely that this process can compete with frequency shifting of a KrF laser by SRS in hydrogen. The materials examined for Raman shifting of 10 ..mu..m lasers show promise for efficient energy conversion to the 16..mu..m region. However, a more quantitative evaluation must await further data on Raman cross section and linewidth. In the case of fibers, some further materials development work is also required.
Date: January 1, 1979
Creator: Klein, M B
Partner: UNT Libraries Government Documents Department

Janus neodymium glass laser operations manual

Description: A manual, prepared to guide personnel in operating and maintaining the Janus glass laser system, is presented. System components are described in detail. Step-by-step procedures are presented for firing the laser and for performing routine maintenance and calibration procedures.
Date: September 29, 1978
Creator: Auerbach, J.M.; Holmes, N.C. & Trainor, R.J.
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

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

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

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

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