Characterization of VUV pulses from the short-pulse facility at DELTA and steps towards pump-probe experiments
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Date
2015
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Abstract
The short-pulse facility at the 1.5-GeV synchrotron light source DELTA, operated by the TU
Dortmund University, generates coherent VUV radiation by Coherent Harmonic Generation
(CHG) as well as coherent THz pulses. The goal is to provide femtosecond coherent VUVradiation
pulses for time-resolved pump-probe experiments. CHG is based on the interaction
of ultrashort laser pulses with electrons in an undulator to generate synchrotron radiation
pulses of similar length, but at coherent harmonics of the laser wavelength. The goals of
this PhD thesis were the characterization of the CHG pulses and the preparation of the first
pump-probe experiments with the new light source. The CHG pulses were characterized
using different methods which are applied either at a diagnostics beamline in air (for long
wavelengths of 200 nm and above) or at an evacuated VUV beamline (for 200 nm and below).
The characterization includes studying the transverse and longitudinal coherence properties
of the CHG pulses, the intensity of the radiation, its angular and spectral distribution,
estimate of the energy modulation, and the dependence of these properties on different
parameters. In order to perform pump-probe experiments, an evacuated laser beamline
of 53 m length was constructed and commissioned to guide some part of the laser pulses
to the experimental station at the VUV beamline. This included optimizing and focusing
the laser beam, realizing the temporal and transverse overlap between pump and probe
pulses, controlling and monitoring the beam position with motorized in-vacuum mirrors
and diagnostics screens, and stabilizing the angle and position of the beam using an optical
feedback system.
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Keywords
VUV pulses, Short-pulse facility, DELTA, Pump probe experiments