Injection of a short electron bunch into THz radiation section with an undulator and strong guiding magnetic fields

Terahertz (THz) radiation from a plasma cylinder with embedded radial electric and axial magnetic fields is investigated. The plasma density and the electric and magnetic fields are such that the electron plasma frequency is near the electron cyclotron frequency and in the THz regime. Two-dimensional particle-in-cell simulations show that the plasma electrons oscillate not only in the azimuthal direction but also in the radial direction. Spectral analysis shows that the resulting oscillating current pattern has a clearly defined characteristic frequency near the electron cyclotron frequency, suggesting resonance between the cyclotron and plasma oscillations. The resulting far-field THz radiation in the axial direction is also discussed.

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Dynamical effects on superradiant THz emission from an undulator

Journal of Synchrotron Radiation ◽

10.1107/s1600577519002509 ◽

2019 ◽

Vol 26 (3) ◽

pp. 737-749 ◽

Cited By ~ 1

Author(s):

Gianluca Geloni ◽

Takanori Tanikawa ◽

Sergey Tomin

Keyword(s):

Magnetic Field ◽

Phase Space ◽

Electron Bunch ◽

Field Amplitude ◽

Thz Radiation ◽

Frequency Range ◽

Output Intensity ◽

Electron Bunches ◽

The Impact ◽

Longitudinal Phase

Superradiant emission occurs when ultra-relativistic electron bunches are compressed to a duration shorter than the wavelength of the light emitted by them. In this case the different electron contributions to the emitted field sum up in phase and the output intensity scales as the square of the number of electrons in the bunch. In this work the particular case of superradiant emission from an undulator in the THz frequency range is considered. An electron bunch at the entrance of a THz undulator setup has typically an energy chirp because of the necessity to compress it in magnetic chicanes. Then, the chirped electron bunch evolves passing through a highly dispersive THz undulator with a large magnetic field amplitude, and the shape of its longitudinal phase space changes. Here the impact of this evolution on the emission of superradiant THz radiation is studied, both by means of an analytical model and by simulations.

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Investigation of Bunch Compressor and Compressed Electron Beam Characteristics by Coherent Transition Radiation

Particles ◽

10.3390/particles2010003 ◽

2018 ◽

Vol 2 (1) ◽

pp. 32-43

Author(s):

Sikharin Suphakul ◽

Heishun Zen ◽

Toshiteru Kii ◽

Hideaki Ohgaki

Keyword(s):

Electron Bunch ◽

Transition Radiation ◽

Michelson Interferometer ◽

Bunch Length ◽

Thz Radiation ◽

Compaction Factor ◽

Rf Gun ◽

Coherent Transition Radiation ◽

Beam Characteristics ◽

Injection Phase

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.

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UV pulse trains by α-BBO crystal stacking for the production of THz-rap-rate electron bunches

Journal of Plasma Physics ◽

10.1017/s0022377812000281 ◽

2012 ◽

Vol 78 (4) ◽

pp. 429-431 ◽

Cited By ~ 11

Author(s):

LI-XIN YAN ◽

JIAN-FEI HUA ◽

YING-CHAO DU ◽

YUAN-FANG HUANG ◽

YAN YOU ◽

...

Keyword(s):

High Power ◽

Pulse Shaping ◽

Electron Bunch ◽

Difference Frequency Generation ◽

Thz Radiation ◽

Radiation Mechanisms ◽

Pulse Trains ◽

Wake Field ◽

Birefringent Crystal ◽

Set Up

AbstractUltrashort electron bunch trains can be used for plasma wake field acceleration (PWFA) to overcome the limit of transformer ratio of a single electron bunch, or high-power terahertz (Thz) radiation production by various radiation mechanisms. Basic facility for high-power THz radiation development based on ultrashort electron beam has been set up at accelerator lab of TUB. Using birefringent crystal serials, ultraviolet (UV) pulse shaping for photocathode radio frequency gun to produce THz-repetition-rate pulse train was realized. Driven by such pulses, ultrashort electron bunch train with picosecond (ps) spacing was obtained for THz production. Measurement of the stacked UV pulse trains was done by difference frequency generation (DFG), and the measured group velocity mismatch of α-BBO crystal at 266.7-nm wavelength was 0.8 ps/mm. This method may also be applied to form ramped electron bunch trains for PWFA.

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