Berlin 2001 – wissenschaftliches Programm
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K: Kurzzeitphysik
K 2: High power laser plasmas
K 2.1: Fachvortrag
Dienstag, 3. April 2001, 16:35–17:05, EB107
Ultrashort x-ray pulses in the keV-range from laser generated plasmas — •U. Andiel1, K. Eidmann1, I. Uschmann2, E. Förster2, and K. Witte1 — 1Max-Planck-Insitut für Quantenoptik, 85748 Garching — 2Institut für Optik und Quantenelektronik, 07743 Jena
We focused ultra-short (790nm or 395nm, 70-150mJ, 150fs) laser pulses at oblique incidence on the surface of flat solid targets. Focal intensities in the range of 1018W/cm2 are generated at 10Hz repetition rate. Preplasma formation is strongly suppressed by a high contrast ratio of 1010 achieved with frequency doubling. From spectral analysis of aluminum K-shell emission electron temperatures of (200-400)eV and electron densities of (0.5−1)· 1024cm−3 close to solid density are determined[1].
For investigation of time resolved aluminum K-shell spectra in the range of (7-8.5)Å, we coupled a conical crystal spectrometer to an ultra fast streak camera. We installed an Auston switch system, for accumulation of a high number of laser shots at a total time resolution of 0.9ps. The observed aluminum K-shell spectra show time resolved line broadening and shifting. We measured FWHM durations in the range of (1-2)ps for cold Kα emission, as well as for Lyα and Heα lines and their satellites. Experimental data are well reproduced by hydro code simulations, post processed with an atomic kinetics code. K-shell spectra generated with high contrast frequency doubled and medium contrast fundamental laser pulses are compared.
Finally, we investigated time resolved Kα emission from copper targets. X-ray pulse durations in the range of (1-3)ps were measured using fundamental and frequency doubled laser pulses with s- and p-polarization.
[1] A. Saemann, K. Eidmann, I.E. Golovkin, R.C. Mancini, E. Andersson, E. Förster, and K. Witte, Phys. Rev. Lett., vol.82, 4843 (1999)