Abstract
To characterize the temporal evolution of ultrashort X-ray pulses emitted by laser plasmas using a pump-probe method, a magnetic bottle time-of-flight electron spectrometer is constructed. The design is determined by numerical calculations of a mirror magnetic field and of the electron trajectory in a flight tube. The performance of the spectrometer is characterized by measuring the electron spectra of xenon atoms irradiated with a laser-driven plasma X-ray pulse. In addition, two-color above-threshold ionization (ATI) experiment is conducted for measurement of the X-ray laser pulse duration, in which xenon atoms are simultaneously irradiated with an X-ray laser pump and an IR laser probe. The correlation in the intensity of the sideband spectra of the 4d inner-shell photoelectrons and in the time delay of the two laser pulses yields an X-ray pulse width of 5.7 ps, in good agreement with the value obtained using an X-ray streak camera.
Highlights
Laser-produced plasmas (LPPs) are expected to be a compact and bright light source in the vacuum ultraviolet (VUV) and soft X-ray regime.[1,2] Even hard X-rays up to 20 keV caused by energetic electrons in an LPP can be obtained by irradiating a bulk target with intense laser pulses.[3]
Two-color above-threshold ionization (ATI) experiment is conducted for measurement of the X-ray laser pulse duration, in which xenon atoms are simultaneously irradiated with an X-ray laser pump and an IR laser probe
In order to characterize the magnetic bottle spectrometer, we measure the electron energy spectra of Xe atoms subjected to the laser-driven plasma soft X-ray laser at the Japan Atomic Energy Agency (JAEA).[20]
Summary
Laser-produced plasmas (LPPs) are expected to be a compact and bright light source in the vacuum ultraviolet (VUV) and soft X-ray regime.[1,2] Even hard X-rays up to 20 keV (gold Kα) caused by energetic electrons in an LPP can be obtained by irradiating a bulk target with intense laser pulses.[3]. In order to evaluate the temporal characteristics of the X-rays in the subpicosecond domain, Woerkom et al.[12] and Schins et al.[13] adopted a cross-correlation technique as pump-probe spectroscopy. In this method, first, an X-ray pump pulse ionizes the inner- and outer-shell electrons. The method has been demonstrated for a single attosecond laser pulse by Hentschel et al..[16] In that study, the cross correlation of high-order harmonics in the XUV regime with a few-cycle probe pulse was measured to evaluate the temporal characteristics of an XUV pulse. The full width at half maximum (FWHM) of the laser pulse is found to be 5.7 ps, in agreement with the temporal profile measured by an X-ray streak camera
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