Abstracts Brochure - CERN

THPCH — Poster Session 29-Jun-06 16:00 - 18:00
a room-temperature, high-Q 400 ns delay line; it is then extracted out of the line in a short time using the switch.
The pulse compression system has achieved a gain of 11, which is the ratio between output and input power. Power
handling capability of the switch is estimated at the level of 10MW.
Double-pulse Generation with the VUV-FEL Injector Laser for Pump/Probe Experiments
The injector laser of the VUV-FEL at DESY,
Hamburg, was modified to allow the gener- O. Grimm, K. Karsten, S. Schreiber (DESY)
ation of double-pulses, separated by a few
cycles of the 1.3 GHz radio-frequency. Such double pulses are needed for driving the planned infrared/VUV pump/
probe facility. Construction constraints of the facility will result in an optical path length about 80 cm longer for
the infrared. Although the VUV can be delayed using normal-incidence multilayer mirrors at selected wavelengths,
a fully flexible scheme is achieved by accelerating two electron bunches separated by more than the path length
difference and then combine the infrared radiation from the first with the VUV from the second. This paper explains
schemes for the generation of double-pulses with the laser system. It summarizes experimental studies of the effect
on the operation of diagnostic instrumentation and on the tunability of the machine. Of special concern is the effect
of wakefields on the quality of the second bunch, critical for achieving lasing.
Commissioning of the Laser System for SPARC Photoinjector
In this paper we report the commissioning
of the SPARC photoinjector laser system. In
the high brightness photoinjector the quality
of the electron beam is directly related to the
C. Vicario, G. Gatti, A. Ghigo (INFN/LNF) P. Musumeci, M. Petrarca
(INFN-Roma)
features of the laser pulse. In fact the temporal pulse shape, the temporization and the transverse distribution of
the electron beam is determined by the incoming laser pulse. The SPARC laser system is based on an amplified
Ti:Sapphire active medium and the pulse shape is imposed by a programmable acousto-optics dispersive filter. The
transfer-line has been designed to reduce the angular jitter and to preserve to the cathode the temporal and spatial
features of the laser pulse. The laser system has been integrated with the accelerator apparatus. The diagnostics and
the control system has been completed. We present the measured performances and the simulations we carried out
for the next research activities.
Temporal Quantum Efficiency of a Micro-structured Cathode
In this work the experimental and simulation
results of photoemission studies for photoelectrons
are presented*. The cathode used
was a Zn disc having the emitting surface
V. Nassisi, F. Belloni, G. Caretto, D. Doria, A. Lorusso, M.V. Siciliano
(INFN-Lecce)
morphologically modified. Two different excimer lasers were employed like energy source to apply the photoelectron
process: XeCl (308nm, 10ns) and KrF (248nm, 20ns). Experimental parameters were the laser fluence (up to 70
mJ/cm2) and the anode-cathode voltage (up to 20 kV). The output current was detected by a resistive shunt with
the same value of the characteristic impedance of the sistem, about 100 ?. In this way, our device was able to record
fast current signals. The best values of global quantum efficiency were approximately 5x 10 -6 for XeCl and 1x 10 -4
for KrF laser, while the peaks of the temporal quantum efficiency were 8x 10 -6 and 1.4x10-4, respectively. The higher
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