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An electro-optical timing diagnostic for pump-probe experiments at the free-electron laser in Hamburg FLASH

Abstract

Femtosecond pump-probe experiments have extensively been used to follow atomic and molecular motion in time. The very intense extreme ultraviolet XUV light of the Free electron LASer in Hamburg FLASH facility allows to investigate fundamental processes such as direct one or few photon inner shell ionizations. A supplementary Ti:Sapphire near infrared femtosecond laser system allows to perform two-color pump-probe experiments with FLASH involving intense laser fields of hugely different photon energies. Within this work a bunch arrival measurement system has been built, which assists these two-color pump-probe experiments to reduce the temporal jitter of FLASH and to increase the temporal resolution. The diagnostic is based upon an electro-optical detection scheme and measures the relative arrival time between the Ti:Sapphire femtosecond pulse and the electron bunch, which generates the self-amplified by stimulated emission SASE XUV pulse in the undulator section of FLASH. Key feature of the diagnostic is a 150 m long glass fiber pulse transport line, which inflicts non-linear dispersion. A dispersion control system to compensate for this higher order dispersion has been developed including the control and programming of a spatial light phase modulator. It was possible to transport a 90 fs FWHM short near infrared femtosecond laser pulse  More>>
Authors:
Publication Date:
Jul 15, 2009
Product Type:
Thesis/Dissertation
Report Number:
DESY-THESIS-2009-027
Resource Relation:
Other Information: TH: Diss. (Dr.rer.nat.)
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; FREE ELECTRON LASERS; CONTROL SYSTEMS; BEAM MONITORING; TIME RESOLUTION; OPTICAL PUMPING; BEAM BUNCHING; ELECTRON BEAMS; OPTICAL DISPERSION; OPTICAL FIBERS; NEAR INFRARED RADIATION; LASER RADIATION; OPTIMIZATION; PULSE TECHNIQUES; TIMING CIRCUITS
OSTI ID:
21219805
Research Organizations:
Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamburg Univ. (Germany). Fakultaet fuer Mathematik, Informatik und Naturwissenschaften
Country of Origin:
Germany
Language:
English
Other Identifying Numbers:
Other: ISSN 1435-8085; TRN: DE09FA094
Availability:
Commercial reproduction prohibited; INIS; OSTI as DE21219805
Submitting Site:
DEN
Size:
152 pages
Announcement Date:
Oct 06, 2009

Citation Formats

Azima, Armin. An electro-optical timing diagnostic for pump-probe experiments at the free-electron laser in Hamburg FLASH. Germany: N. p., 2009. Web.
Azima, Armin. An electro-optical timing diagnostic for pump-probe experiments at the free-electron laser in Hamburg FLASH. Germany.
Azima, Armin. 2009. "An electro-optical timing diagnostic for pump-probe experiments at the free-electron laser in Hamburg FLASH." Germany.
@misc{etde_21219805,
title = {An electro-optical timing diagnostic for pump-probe experiments at the free-electron laser in Hamburg FLASH}
author = {Azima, Armin}
abstractNote = {Femtosecond pump-probe experiments have extensively been used to follow atomic and molecular motion in time. The very intense extreme ultraviolet XUV light of the Free electron LASer in Hamburg FLASH facility allows to investigate fundamental processes such as direct one or few photon inner shell ionizations. A supplementary Ti:Sapphire near infrared femtosecond laser system allows to perform two-color pump-probe experiments with FLASH involving intense laser fields of hugely different photon energies. Within this work a bunch arrival measurement system has been built, which assists these two-color pump-probe experiments to reduce the temporal jitter of FLASH and to increase the temporal resolution. The diagnostic is based upon an electro-optical detection scheme and measures the relative arrival time between the Ti:Sapphire femtosecond pulse and the electron bunch, which generates the self-amplified by stimulated emission SASE XUV pulse in the undulator section of FLASH. Key feature of the diagnostic is a 150 m long glass fiber pulse transport line, which inflicts non-linear dispersion. A dispersion control system to compensate for this higher order dispersion has been developed including the control and programming of a spatial light phase modulator. It was possible to transport a 90 fs FWHM short near infrared femtosecond laser pulse Fourier limited by the dispersion compensated glass fiber. The electro-optical signal induced by the FLASH electron bunch was generated, characterized and optimized. The signal features beside the designated bunch arrival timing capability the additional possibility to measure the longitudinal electron bunch density distribution of an arbitrary bunch of FLASH in a single shot with a temporal resolution of below 100 fs RMS. Timing and bunch analysis capabilities of the developed diagnostic have been cross-checked with other comparable diagnostics at FLASH like the transversal deflecting cavity structure named LOLA. Finally, the timing diagnostic was part of a series of two-color near-infrared/XUV pump-probe experiments. It was used to correct the measurement delay times of the experiments a posteriori and thus compensate for the temporal jitter of FLASH. By this means the temporal resolution of two-color pump-probe experiments at FLASH was improved by more than a factor 4 from 250 fs RMS or worse to just 60 fs RMS. A pump-probe experiment performed on a Gallium-Arsenide waver using the FLASH XUV pulse as pump pulse revealed an optical light reflectivity modulation induced by FLASH. The temporal dynamics of this process was investigated in detail due to the jitter corrections of the timing diagnostic. The improved temporal resolution lead to a high degree in the understanding and interpretation of the underlying physical processes of the observed reflectivity modulation. Meanwhile the timing diagnostic advanced to a standard diagnostic, which is regularly utilized by pump-probe experimental groups of the FLASH user facility. (orig.)}
place = {Germany}
year = {2009}
month = {Jul}
}