Abstract
A magnetic chicane bunch compressor for a new compact accelerator-based terahertz (THz) radiation source at the Institute of Advanced Energy, Kyoto University, was completely installed in March 2016. The chicane is employed to compress an electron bunch with an energy of 4.6 MeV generated by a 1.6-cell photocathode radio frequency (RF)-gun. The compressed bunch is injected into a short planar undulator for THz generation by coherent undulator radiation (CUR). The characteristics of the bunch compressor and the compressed bunch were investigated by observing the coherent transition radiation (CTR). The CTR spectra, which were analyzed by using a Michelson interferometer, and the compressed bunch length were also estimated. The results were that the chicane could compress the electron bunch at a laser injection phase less than 45 degrees, and the maximum CTR intensity was observed at a laser injection phase around 24 degrees. The optimum value of the first momentum compaction factor was around −45 mm, which provided an estimated rms bunch length less than 1 ps.
Highlights
Small-scale electron accelerator systems have been proven to have the potential to produce a high power and tunable radiation in the range of far-infrared and terahertz (THz) regimes. These features are significantly beneficial to THz science and fulfill the lack of a high-power THz radiation source [1]. This kind of source injects a radio frequency (RF)-modulated electron beam whose bunch length is comparable to the radiation wavelength of an undulator
The energy chirp of the bunch depends on the energy modulation by the accelerating electric field E(φ) inside the RF gun and can be changed by adjusting the timing of the laser pulse relative to the phase of E(φ)
The measurement was performed at a laser pulse energy of 133 μJ and 4 pulses per macropulse
Summary
Small-scale electron accelerator systems have been proven to have the potential to produce a high power and tunable radiation in the range of far-infrared and terahertz (THz) regimes. These features are significantly beneficial to THz science and fulfill the lack of a high-power THz radiation source [1]. In the first step of development, THz radiation is generated via CUR from a low-energy short bunch electron injected into a 10-period planar undulator. The bunch length of the compressed bunch was estimated from the spectra analyzed by an in-air Michelson interferometer
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