34 research outputs found
Laser and rf synchronization measurements at SPARC
The SPARC project consists in a 150 MeV S-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been recently completed. During year 2006 a first experimental phase aimed at characterizing the beam emittance in the first 2 m drift downstream the RF gun has been carried out. The low level RF control electronics to monitor and synchronize the RF phase in the gun and the laser shot on the photocathode has been commissioned and extensively tested during the emittance measurement campaign. The laser synchronization has been monitored by measuring the phase of the free oscillation of an RF cavity impulsively excited by the signal of a fast photodiode illuminated by the laser shot. Phase stability measurements are reported, both with and without feedback correction of the slow drifts. A fast intra-pulse phase feedback system to reduce the phase noise produced by the RF power station has been also positively tested
Design of high gradient, high repetition rate damped C-band rf structures
The gamma beam system of the European Extreme Light Infrastructure–Nuclear Physics project
foresees the use of a multibunch train colliding with a high intensity recirculated laser pulse. The linac
energy booster is composed of 12 traveling wave C-band structures, 1.8 m long with a field phase
advance per cell of 2Ď€=3 and a repetition rate of 100 Hz. Because of the multibunch operation, the
structures have been designed with a dipole higher order mode (HOM) damping system to avoid beam
breakup (BBU). They are quasiconstant gradient structures with symmetric input couplers and a very
effective damping of the HOMs in each cell based on silicon carbide (SiC) rf absorbers coupled to each
cell through waveguides. An optimization of the electromagnetic and mechanical design has been done to
simplify the fabrication and to reduce the cost of the structures. In the paper, after a review of the beam
dynamics issues related to the BBU effects, we discuss the electromagnetic and thermomechanic design
criteria of the structures. We also illustrate the criteria to compensate the beam loading and the rf
measurements that show the effectiveness of the HOM damping
RF Design of the X-band Linac for the EuPRAXIA@SPARC_LAB Project
We illustrate the RF design of the X-band linac for the upgrade of the SPARC_LAB facility at INFN-LNF (EuPRAXIA@SPARC_LAB). The structures are travelling wave (TW) cavities, working on the 2Ď€/3 mode, fed by klystrons with pulse compressor systems. The tapering of the cells along the structure and the cell profiles have been optimized to maximize the effective shunt impedance keeping under control the maximum value of the modified Poynting vector, while the couplers have been designed to have a symmetric feeding and a reduced pulsed heating. In the paper we also present the RF power distribution layout of the accelerating module and a preliminary mechanical design
Intense terahertz pulses from SPARC-LAB coherent radiation source
The linac-based Terahertz source at the SPARC_LAB test facility is able to gene
rate highly intense Terahertz broadband
pulses
via
coherent transition radiation (CTR) from high brightness electron beams. The THz pulse duration is typically
down to 100 fs RMS and can be tuned through the electron bunch duration and shaping. The measured stored energy in a
single THz pulse has reached 40
ÎĽ
J, which corresponds to a peak
electric field of 1.6 MV/cm at the THz focus. Here we
present the main features, in particular spatial and sp
ectral distributions and energy
characterizations of the
SPARC_LAB THz source, which is very competitive for investigations in Condensed Matter, as well as a valid tool for
electron beam longitudinal diagnostics
Design, realization and test of C-band accelerating structures for the SPARC_LAB linac energy upgrade
Realization and high power tests of damped C-band accelerating structures for the ELI-NP linac
Design, realization, and high power test of high gradient, high repetition rate brazing-free S -band photogun
In this paper, we address the energy spread and slice energy spread of an externally injected electron beam in plasma wakefield accelerators operating in the linear or quasilinear regime. The energy spread is first derived taking into account the phase dependence of the wakefield along the finite-length bunch together with the dephasing during acceleration and found to be strongly dependent on the bunch length. This could be compensated by the beam loading effect, the energy spread from which is then derived and found to be nearly independent of the bunch length. However, the transverse dependence of the beam loading effect also makes the particles at the same longitudinal position experience different accelerating fields, introducing a significant slice energy spread. To estimate the slice energy spread, a theoretical analysis was conducted by taking the transverse betatron motion into account. As a study case, 3D simulations for the 5 GeV laser-plasma acceleration stage of the European Plasma Research Accelerator with eXcellence in Applications project have been performed. Careful optimization of the parameters allows one to obtain an energy spread of ≤1% and a slice energy spread of ≤0.1%, with good agreement between theories and simulations