Abstracts Brochure - CERN

MOPCH044
MOPCH045
MOPCH046
26-Jun-06 16:00 - 18:00 MOPCH — Poster Session
Peculiarities of the Doppler Effect for Moving Radiative Particles in Dispersive Medium
at Extreme Conditions
M.V. Vysotskyy, V.I. Vysotskii (National Taras Shevchenko University
of Kyiv, Radiophysical Faculty)
58
The features of Doppler effect for fast moving
radiating particles with discrete energy
levels spectrum (e.g. radiation at channeling)
at parameters close or equal to extreme
condition of Cherenkov effect are studied. The formal usage of Cherenkov condition leads in this case to incorrect
and unphysical results. The main task of this work was to find maximal radiation frequency and its dependence
from the system parameters. This finite frequency was found. It was shown that at correct use of conservation laws
the dependence of radiation and absorption frequencies on deviation from exact Cherenkov condition contains one
discontinuity. The value of these frequencies on two sides of this discontinuity is different by 2.5 times. It was shown
that the positions of these discontinuities depend on deviation value and corresponds to the condition of normal
Doppler effect transformation into abnormal. Conditions that correspond to maximal radiation and absorption frequencies
are different and are shifted in different directions form the exact Cherenkov condition (in relation to the
velocity and dielectric permittivity).
A Source of Coherent Soft X-ray Radiation Based on High-order Harmonic Generation and
Free Electron Lasers
We examine a scheme for a Free Electron
M. Gullans (UCB) G. Penn, A. Zholents (LBNL)
Laser (FEL) harmonic amplifier seeded by a
∼30-nm wavelength signal produced using a
process of High-order Harmonic Generation (HHG). The seed is first amplified in an optical klystron from ∼100 kW
to ∼30 MW using a 1 GeV electron beam and then is used for an energy modulation of electrons in the downstream
undulator. Subsequently, a 100-MW level of radiation at shorter wavelengths down to 4 nm is obtained by bunching
the energy modulated electrons and passing the bunched beam through an undulator tuned to the desired harmonic
of 30 nm. We also compare this scheme to a more familiar harmonic cascade FEL by replacing the HHG with an
additional stage of harmonic generation.
Modeling Fermi@Elettra Linac with the Electron Beam Dynamics Code Impact
We report modeling of the electron beam dy-
I.V. Pogorelov, J. Qiang, A. Zholents (LBNL)
namics in the Fermi@Elettra linac using the
particle tracking code Impact. The new version
of this code icludes realistic RF fields, short-range tranverse and longitudinal wakefields, space charge, and
coherent synchrotron radiation. Parallel capabilities of Impact allow fast tracking with a large number of macroparticles
needed to gain understanding of the onset of microbunching instability. Recent simulation results are presented.