Abstracts Brochure - CERN

MOPCH006
MOPCH007
MOPCH008
26-Jun-06 16:00 - 18:00 MOPCH — Poster Session
Beam Adaptation at the Infrared FEL, CLIO
J.P. Berthet, F. Glotin, J.-M. Ortega (CLIO/ELYSE/LCP) W. Salah
(The Hashemite University)
46
The infrared free-electron laser CLIO is tunable
from 3 to 150 5m by operating its driver
RF linear accelerator between 50 and 12
MeV. This is the largest spectral range ever
obtained with a single optical cavity. We have studied the electron beam transverse adaptation in the FEL undulator
throughout the spectral and energy range. Each beam dimension is measured by a moving wire whose temperature
dependant resistivity is monitored. The results are compared with simulations computed with the TRANSPORT
code.
Undulators for a Seeded HGHG-FEL at MAX-lab
J. Bahrdt, W.F. Frentrup, A. Gaupp, M. Scheer (BESSY GmbH) S.
Werin (MAX-lab)
Undulators for a Seeded HGHG-FEL at
MAX-lab Within the European FEL Design
Study a seeded HGHG-FEL will be set up at
MAX-lab. In the modulator, a planar pure
permanent magnet undulator, the 3rd harmonic of a Ti:Sapphire laser (267nm) interacts with the electron beam. In
the following dispersive section the energy modulation is converted into a spatial modulation. The radiator emits
at the third harmonic (89nm). The radiator has an APPLE II type magnetic structure providing full polarization
control. The undulators and the dispersive section are currently built at BESSY. The electron beam height at MAX-lab
of 400mm requires a specific design of the undulator carriages. The magnetic and mechanical design of the HGHG
stage will be presented.
Double Pulse Lasing from the BESSY-FEL
BESSY proposes a linac-based High-Gain
K. Goldammer, B.C. Kuske, A. Meseck (BESSY GmbH)
Harmonic-Generation (HGHG) free electron
laser (FEL) facility with three independent
FEL lines. Two to four HGHG stages downconvert the initial seed wavelength (230nm to 460nm) to the desired
radiation range (1.24nm to 51nm). High FEL gain is ensured as the seed radiation interacts only with unperturbed
parts of the electron bunch in every HGHG-stage. This so-called fresh-bunch-technique relies on dipole chicanes that
delay the electron bunches relative to the radiation. Fresh-bunch chicanes are incorporated prior to each modulator
in the BESSY-FEL allowing the bunch to completely travel through all undulators. However, simulations show that
bunch parts that have previously lased generate a noticeable radiation power level in the final amplifiers. This motivated
simulation studies on the significance and applicability of such inherent additional pulses. It is revealed that
the BESSY-FEL provides the opportunity to deliver double pulses at the FEL exit being of high interest to the user
community. Temporal seperation and intensity levels can be controlled by carefully optimising the properties of the
magnetic chicanes.