Abstracts Brochure - CERN

THPLS — Poster Session 29-Jun-06 16:00 - 18:00
undulator, two in-vacuum undulators have been installed in the long straight sections at the improvement. New
variably polarized undulator will be also installed in summer 2006. Improvement of booster synchrotron will be
also performed in summer 2006 with aiming to top-up operation in the future. Now UVSOR-II has been operated in
750MeV with the emittance of 27nm-rad in daily users runs. Not only the development of high quality SR beams but
also basic investigations for new light source have been performed; development of storage ring FEL and investigation
of intense THz burst SR. Bunch slicing experiment with a Ti:Sa laser (800nm) has also been started since 2005, and
experiments for coherent harmonic generation and coherent SR generation with the laser-beam interaction have been
performed.
Observation of Intense THz Synchrotron Radiation by Bunch Slicing with Femto-second
Pulse Laser in UVSOR-II Electron Storage Ring
We have performed electron bunch slicing
experiments using a femto-second high
power pulse laser in the UVSOR-II electron
storage ring. As the pulse laser system we
have used a Ti:Sa laser whose wavelength is
M. Katoh, M. Hosaka, K. Kimura, A. Mochihashi, M. Shimada
(UVSOR) T. Hara (RIKEN Spring-8 Harima) T. Takahashi (KURRI)
Y. Takashima (Nagoya University)
800 nm, typical pulse duration is 100 fs, pulse repetition is 1 kHz and typical average power is 2W. The laser is
operated in mode-locked condition and synchronized with the electron beam revolution. The laser pulse is injected
into an undulator section and it goes along with the electron bunch. By adjusting the radiation wavelength of the
undulator to the laser wavelength, the electron beam energy can be partially modulated in the electron bunch. We
have observed THz synchrotron radiation (SR) light from a bending magnet that is downstream of the interaction
region. The SR light contains extremely intense THz pulse radiation that is synchronized with the laser injection. The
extremely high intensity strongly suggests that the THz pulses are coherent synchrotron radiation from the electron
bunch with a hole because of the laser-beam interaction.
Observation of THz Synchrotron Radiation Burst in UVSOR-II Electron Storage Ring
Very intense THz synchrotron radiation
bursts have been observed in single-bunch
operation in the UVSOR-II electron storage
ring*. The observation was performed in an
A. Mochihashi, M. Hosaka, M. Katoh, K. Kimura, M. Shimada
(UVSOR) T. Takahashi (KURRI) Y. Takashima (Nagoya University)
infrared beam line in UVSOR-II by using a liquid-He-cooled In-Sb hot-electron bolometer that has a good response
time of several microseconds. Thanks both to the beam line and the detector, it is clearly observed that the intense
bursts have typical macroscopic and microscopic temporal structure. Macroscopically, it is clearly observed that the
bursts tend to be generated with quasi-periodic structure in which the period tends to depend on the beam intensity.
From a microscopic point of view, each burst has also quasi-periodic structure in itself, and the period almost corresponds
to the half value of the inverse of the synchrotron oscillation frequency. The peak intensity of the bursts was
about 10000 times larger than that of ordinary synchrotron radiation in the same wavelength region. The extremely
high intensity strongly suggests that the bursts are coherent synchrotron radiation, although the radiation wavelength
was much shorter than the electron bunch length.
*Y. Takashima et al., Jpn. J. Appl. Phys. 44, No.35 (2005) L1131.
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