Abstracts Brochure - CERN

MOPCH — Poster Session 26-Jun-06 16:00 - 18:00
A Compact Dual RF Photo-injector to Compress Ellipsoidal Electron Bunches
It was recently shown that uniformly filled
ellipsoidal ’waterbag’ electron bunches can
be created in practice, by transverse shaping
of a femtosecond photo-excitation laser in a
S.B. van der Geer, O.J. Luiten, W.P.E.M. Op ’t Root, M.J. Van der
Wiel, M.J. de Loos, T. van Oudheusden, S.B. van der Geer (TUE)
sufficiently high acceleration field*. In standard rf photoguns the electron bunch loses orders of magnitude in
average brightness during acceleration due to non-linear space-charge forces. Waterbag bunches have linear selffields
in all coordinates and therefore do not suffer from these deteriorating effects. This allows waterbag bunches
to be ballistically compressed at sub or mildly relativistic energies, a regime that formally needed to be avoided.
Detailed GPT simulations of a new type of rf-photogun based on this concept are presented. We show that using
established radio-frequency accelerator technology, 100 fs electron bunches with kA peak currents and sub-micron
rms normalized emittances are attainable.
*O. J. Luiten et al. Phys. Rev. Lett. 93, 094802 (2004).
Possibilities of Experimental Study of Wakefield Undulator Radiation
The wakefield undulator (WFU) radiation
mechanism first proposed in Ref.* points A. Opanasenko, Z.V. Zhiglo (NSC/KIPT)
to new opportunities for generating high
brightness ultra-short wavelength light, Ref.**. It consists in photon emission by a short bunch of relativistic charged
particles undulating in the nonsynchronous harmonics of wakefields, which are induced as the bunch moves through
a periodic corrugated waveguide. In this connection, there is interest in carrying out experiments on detecting the
WFU radiation. This work is devoted to development of experimental methods on viewing WFU radiation in visual
range. We consider possibilities of applying short-pulsed ampere range electron beams with energy 100 MeV accelerated
in an rf linac operating in energy stored mode. The periodic structure as a WF undulator was calculated. We
analyze possible sources of background radiation such as: thermal radiation of a hot cathode; inelastic scattering of
beam electrons on a residual gas; bremsstrahlung radiation of beam electrons on nucleus of a residual gas; bendingmagnet
and diffraction radiation. The ways of suppression of the background radiation are considered.
*A. Opanasenko, Proc. of MMET’02, Kiev, Ukraine, p.642; http://arxiv.org/abs/physics/0209100. **A. Opanasenko,
Proc. of RUPAC’04, Dubna, Russia.
Centroid and Emittance of a Beam Slice in a Kicked Bunch
A transversely kicked bunch will decohere
due to, among other things, chromatic- and C.-x. Wang, W. Guo (ANL)
amplitude-dependent tune shifts. The chromatic
tune shift leads to correlation between transverse and longitudinal phase space. Such a correlation can be
used for compressing the synchrotron radiation of the bunch with adequate optics. In this report, we revise the
decoherence calculation to derive the centroid and second moments of a beam slice in a kicked bunch, taking into
account chromatic and nonlinear decoherence, but neglecting wakefield and radiation damping, etc.
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MOPCH061
MOPCH062