Abstract
An x-ray Hanbury Brown-Twiss interferometry to diagnose a temporal profile of a femtosecond electron bunch (e-bunch) is presented. We show that intensity interference of spontaneous x-ray radiation from the e-bunch reflects the e-bunch profile. Based on this relationship, a temporal profile of the 8.1-GeV e-bunch at SPring-8 Angstrom Compact free-electron LAser (SACLA) that generates x-ray free-electron laser (XFEL) light is characterized through the intensity interference measurement. Combining this e-bunch profile with a numerical simulation, the XFEL pulse duration generated by the e-bunch is estimated to be less than 10 fs.
Highlights
Optical pulses and particle beams with ultrashort temporal duration, such as femtosecond electron pulses from a photocathode electron gun, attosecond laser light from high harmonic generation [1], and femtosecond synchrotron radiation produced by a laser-slicing technique [2], have been powerful probes for capturing ultrafast processes, which have provided new insights in various fields ranging in materials science, chemistry, and biology
A temporal profile of the 8.1-GeV e-bunch at SPring-8 Angstrom Compact free-electron LAser (SACLA) that generates x-ray free-electron laser (XFEL) light is characterized through the intensity interference measurement
The ultrafast XFEL pulses are generated from the electron bunches (e-bunches) that are accelerated to a relativistic speed with strong compression to a femtosecond regime
Summary
Optical pulses and particle beams with ultrashort temporal duration, such as femtosecond electron pulses from a photocathode electron gun, attosecond laser light from high harmonic generation [1], and femtosecond synchrotron radiation produced by a laser-slicing technique [2], have been powerful probes for capturing ultrafast processes, which have provided new insights in various fields ranging in materials science, chemistry, and biology. XFEL light sources are capable of generating sub-10 fs XFEL pulses [21,24] In such cases, the e-bunch duration is comparable to or shorter than the time resolution of the e-bunch diagnostic schemes that are presently available. The HBT interferometry was extended to synchrotron x-ray radiation 20 years ago [31,32], and the transverse coherence properties and the x-ray pulse duration were evaluated with this technique [33–35]. Spatial profiles of the spontaneous x-ray beam generated by the e-bunch are measured in a shot-by-shot manner while changing the bandwidths using x-ray monochromators, and evaluate the degree of intensity interference via second-order intensity correlation functions. Since the coherence time can be changed from picosecond to attosecond by using x-ray monochromators, the x-ray HBT interferometry enables us to evaluate temporal profiles of the femtosecond or even attosecond e-bunches
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