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Phase control and measurement of ultrashort optical pulses

Description: We have used the Direct Optical Spectral Phase Measurement (DOSPM) technique to characterize the cubic phase tuning ability of our pulse stretcher. We have compared the measured phase to the phase determined from cross-correlation measurements.
Date: February 10, 1995
Creator: Sullivan, A.; White, W.E.; Chu, K.C. & Heritage, J.P.
Partner: UNT Libraries Government Documents Department

Study of supra-thermal electrons and K-{alpha} x-rays from high intensity 500 fs laser-produced plasmas

Description: We describe recent laser-solid interaction experiments using the 500 fs Janus Nd:glass (1053 nm) laser presently at 1.5 TW power level. The laser beam path is enclosed in vacuum from the compressor to the target and is focused using an off-axis paraboloid. Optical diagnostics monitor the near field pattern, focal spot, spectrum, temporal shape and pre-pulse level. A 12 {mu}m diameter (FWHM) focal spot is achieved (2.5 {times} diffraction limit) corresponding to a peak irradiance of 8 {times} 1017 W cm{sup {minus}2} on target. A suite of x-ray diagnostics characterize the x-ray emission from the plasma. We present results for normal incidence irradiation of high-Z (Zn, Ge, Mo, Sn) solid targets. The supra-thermal electrons produced in the short scale length plasma have temperature T{sub H} > 100 keV and can efficiently fluoresce the cold K-{alpha} lines in the 8--30 keV energy range.
Date: July 1, 1995
Creator: Dunn, J.; Young, B.K.F.; Hankla, A.K.; Conder, A.D.; White, W.E. & Stewart, R.E.
Partner: UNT Libraries Government Documents Department

Table-top transient collisional excitation x-ray laser research at LLNL

Description: We describe recent experiments at the Lawrence Livermore National Laboratory (LLNL) to produce a table-top x-ray laser. Using a combination of long 800 ps and short {approximately}1 ps high power laser pulses with {approximately} 6 J in each beam, a transient collisionally excited Ne-like ion x-ray laser scheme has been investigated. We present results of high x-ray laser gain for the Ne- like Ti 3p-3s J=O-l transition at 326 {Angstrom} and have achieved gL product of 15 for target lengths up to 1 cm. We have extended the transient collisional scheme to shorter wavelengths using the Ni-like analog, specifically the 4d-4p J=O-l of Ni-like Pd at 147 {Angstrom}.
Date: October 6, 1997
Creator: Dunn, J.; Osterheld, A. L.; Shepherd, R.; White, W. E.; Shlyaptsev, V. N.; Bullock, A. B. et al.
Partner: UNT Libraries Government Documents Department

In-Situ Cleaning of Metal Photo-Cathodes in rf Guns

Description: Metal cathodes installed in rf guns typically exhibit much lower quantum efficiency than the theoretical limit. Experimenters often use some sort of in situ technique to ''clean'' the cathode to improve the QE. The most common technique is laser cleaning where the laser is focused to a small spot and scanned across the cathode surface. However, since the laser is operated near the damage threshold, it can also damage the cathode and increase the dark current. The QE also degrades over days and must be cleaned regularly. We are searching for a more robust cleaning technique that cleans the entire cathode surface simultaneously. In this paper we describe initial results using multiple techniques such as several keV ion beams, glow discharge cleaning and back bombarding electrons. Results are quantified in terms of the change in QE and dark current.
Date: January 3, 2007
Creator: Schmerge, J.F.; Castro, J.M.; Clendenin, J.E.; Colby, E.R.; Dowel, D.H.; Gierman, S.M. et al.
Partner: UNT Libraries Government Documents Department

Matter in Extreme Conditions Instrument - Conceptual Design Report

Description: The SLAC National Accelerator Laboratory (SLAC), in collaboration with Argonne National Laboratory (ANL), Lawrence Livermore National Laboratory (LLNL), and the University of California at Los Angeles (UCLA), is constructing a Free-Electron Laser (FEL) research facility. The FEL has already met its performance goals in the wavelength range 1.5 nm - 0.15 nm. This facility, the Linac Coherent Light Source (LCLS), utilizes the SLAC 2-Mile Linear Accelerator (linac) and will produce sub-picosecond pulses of short wavelength X-rays with very high peak brightness and almost complete transverse coherence. The final one-third of the SLAC linac is used as the source of electrons for the LCLS. The high energy electrons are transported across the SLAC Research Yard, into a tunnel which houses a long undulator. In passing through the undulator, the electrons are bunched by the force of their own synchrotron radiation and produce an intense, monochromatic, spatially coherent beam of X-rays. By varying the electron energy, the FEL X-ray wavelength is tunable from 1.5 nm to 0.15 nm. The LCLS includes two experimental halls as well as X-ray optics and infrastructure necessary to create a facility that can be developed for research in a variety of disciplines such as atomic physics, materials science, plasma physics and biosciences. This Conceptual Design Report, the authors believe, confirms the feasibility of designing and constructing an X-ray instrument in order to exploit the unique scientific capability of LCLS by creating extreme conditions and study the behavior of plasma under those controlled conditions. This instrument will address the Office of Science, Fusion Energy Sciences, mission objective related to study of Plasma and Warm Dense Matter as described in the report titled LCLS, the First Experiments, prepared by the LCLS Scientific Advisory Committee (SAC) in September 2000. The technical objective of the LCLS Matter in Extreme Conditions (MEC) ...
Date: December 9, 2009
Creator: Boyce, R.F.; Boyce, R.M.; Haller, G.; Hastings, J.B.; Hays, G.; Lee, H.J. et al.
Partner: UNT Libraries Government Documents Department

X-band photoinjector for a chirped-pulse FEL

Description: The phase noise and jitter characteristics of the laser and rf systems of a high gradient X-band photoinjector have been measured experimentally. When > 100 coherently phased 5 MeV electron bunches are produced in bursts, the photoinjector should be an ideal electron source for a pulsed, pre-bunched free-electron laser (FEL) operating at 100 GHz. The laser oscillator is a self-modelocked Titanium:Sapphire system operating at the 108th subharmonic of the rf gun. The X-band signal is produced from the laser by a phase-locked dielectric resonance oscillator, and amplified by a pulsed TWT and klystron. A comparison between the klystron and TWT amplifier phase noise and the fields excited in the rf gun demonstrates the filtering effect of the high Q structure, thus indicating that the rf gun can be used as a master oscillator, and could be energized by either a rf oscillator such as a magnetron or a compact source such as a cross-field amplifier. In particular, the rf gun can play the role of a pulsed rf clock to synchronize the photocathode laser system: direct drive of a synchronously mode-locked AlGaAs quantum well laser has been achieved using the X0-band gun rf fields. This novel, GHz repetition rate, sub-picosecond laser system is being developed to replace the more conventional femtosecond Ti: Al<sub>2</sub>O<sub>3</sub> system. Some advantages include pumping this laser with a stabilized current source instead of a costly, low efficiency pump laser. Finally, dark current measurements and initial photoelectron measurements are reported.
Date: December 15, 1998
Creator: Luhmann, Jr., N. C.; Alvis, R. M.; Baldis, H. A.; Hartemann, F. V; Heritage, J. P.; Ho, C. H. et al.
Partner: UNT Libraries Government Documents Department