Abstract
We propose a scheme that can generate attosecond x-ray pulses through an angular dispersion enhanced self-amplified spontaneous emission (ESASE) free electron laser (FEL). In this scheme, an angular dispersion section is implemented into a conventional ESASE set-up, together with a few cycle laser pulse to manipulate the electron beam effectively. During the procedure, the transverse-longitudinal phase space coupling is introduced into the electron beam in addition to the energy modulation and momentum compaction processes. As a result, the peak current of the electron beam will be strengthened significantly within a narrow width of the electron bunch, which can be used to generate ultrashort FEL pulses. Comparing to a conventional ESASE scheme, the proposed scheme can reduce the required modulation laser power by at least one order of magnitude. The signal-to-noise ratio of the final FEL radiation pulses can also be improved. In addition, we discuss the possibility of using this scheme to generate two-pulse two-color x-ray FEL with tunable central wavelengths and time delays for a conceivable x-ray pump/x-ray probe experiment.
Highlights
The pump-probe technique is widely used to investigate the fast dynamic phenomena within chemical, physical, and biological reactions, in which the pump laser initiates the excitation of the sample and the probe laser with a certain time delay characterizes the changes [1,2,3,4]
In order to generate attosecond radiation pulses, the external few-cycle laser power used in a conventional enhanced self-amplified spontaneous emission (ESASE) scheme needs to be as high as tens of GW, which is quite difficult to be supplied and becomes rather impractical when it comes to high rep-rate free electron laser (FEL) facilities
It is worth noting that the modulation processes of the electron beam before entering the radiator section are done with a three-dimensional algorithm dealing with the dynamics of electrons [26]
Summary
The pump-probe technique is widely used to investigate the fast dynamic phenomena within chemical, physical, and biological reactions, in which the pump laser initiates the excitation of the sample and the probe laser with a certain time delay characterizes the changes [1,2,3,4]. The advanced short-wavelength x-ray lasers open up a new world of the atomic inner-shell electronic transitions Given these circumstances, the generation of attosecond x-ray pump and x-ray probe laser pulses is of great interests in the scientific community. In order to generate attosecond radiation pulses, the external few-cycle laser power used in a conventional ESASE scheme needs to be as high as tens of GW, which is quite difficult to be supplied and becomes rather impractical when it comes to high rep-rate FEL facilities. We discuss the possibility of using this scheme to generate two-pulse two-color x-ray FEL with tunable central wavelengths and time delays for a conceivable x-ray pump/x-ray probe experiment
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