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Abstracts Brochure - CERN

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MOPCH044<br />

MOPCH045<br />

MOPCH046<br />

26-Jun-06 16:00 - 18:00 MOPCH — Poster Session<br />

Peculiarities of the Doppler Effect for Moving Radiative Particles in Dispersive Medium<br />

at Extreme Conditions<br />

M.V. Vysotskyy, V.I. Vysotskii (National Taras Shevchenko University<br />

of Kyiv, Radiophysical Faculty)<br />

58<br />

The features of Doppler effect for fast moving<br />

radiating particles with discrete energy<br />

levels spectrum (e.g. radiation at channeling)<br />

at parameters close or equal to extreme<br />

condition of Cherenkov effect are studied. The formal usage of Cherenkov condition leads in this case to incorrect<br />

and unphysical results. The main task of this work was to find maximal radiation frequency and its dependence<br />

from the system parameters. This finite frequency was found. It was shown that at correct use of conservation laws<br />

the dependence of radiation and absorption frequencies on deviation from exact Cherenkov condition contains one<br />

discontinuity. The value of these frequencies on two sides of this discontinuity is different by 2.5 times. It was shown<br />

that the positions of these discontinuities depend on deviation value and corresponds to the condition of normal<br />

Doppler effect transformation into abnormal. Conditions that correspond to maximal radiation and absorption frequencies<br />

are different and are shifted in different directions form the exact Cherenkov condition (in relation to the<br />

velocity and dielectric permittivity).<br />

A Source of Coherent Soft X-ray Radiation Based on High-order Harmonic Generation and<br />

Free Electron Lasers<br />

We examine a scheme for a Free Electron<br />

M. Gullans (UCB) G. Penn, A. Zholents (LBNL)<br />

Laser (FEL) harmonic amplifier seeded by a<br />

∼30-nm wavelength signal produced using a<br />

process of High-order Harmonic Generation (HHG). The seed is first amplified in an optical klystron from ∼100 kW<br />

to ∼30 MW using a 1 GeV electron beam and then is used for an energy modulation of electrons in the downstream<br />

undulator. Subsequently, a 100-MW level of radiation at shorter wavelengths down to 4 nm is obtained by bunching<br />

the energy modulated electrons and passing the bunched beam through an undulator tuned to the desired harmonic<br />

of 30 nm. We also compare this scheme to a more familiar harmonic cascade FEL by replacing the HHG with an<br />

additional stage of harmonic generation.<br />

Modeling Fermi@Elettra Linac with the Electron Beam Dynamics Code Impact<br />

We report modeling of the electron beam dy-<br />

I.V. Pogorelov, J. Qiang, A. Zholents (LBNL)<br />

namics in the Fermi@Elettra linac using the<br />

particle tracking code Impact. The new version<br />

of this code icludes realistic RF fields, short-range tranverse and longitudinal wakefields, space charge, and<br />

coherent synchrotron radiation. Parallel capabilities of Impact allow fast tracking with a large number of macroparticles<br />

needed to gain understanding of the onset of microbunching instability. Recent simulation results are presented.

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