PSI, Villigen
IAP Univ. Bern, Bern
The knowledge and control of electron bunch lengths is one of the key diagnostics in XFEL accelerators to reach the desired peak current in the electron beam. A compact electro-optical monitor was designed and build for bunch length measurements at the Swiss FEL. It is based on a mode locked ytterbium fiber laser probing the field-induced birefringence in an electro-optically active crystal (GaP) with a chirped laser pulse. The setup allows the direct time resolved single-shot measurement of the Coulomb field (THz-radiation) of the electron beam -and therefore the bunch length- with an accuracy as good as 200fs. Simulations of the signals expected at the SwissFEL and the results of first test at the SLS linac will be presented.
PSI, Villigen
IAP Univ. Bern, Bern
Pulsed Yb fiber lasers emit at 1030 nm which provides a better phase matching in standard EO crystals (GaP, ZnTe) than Ti:Sa lasers (800nm). We present a mode locked ytterbium fiber laser which is phase locked to the RF. A subsequent fiber amplifier is used to boost the power and to broaden the spectrum due to nonlinear effects. The produced pulses have a spectral width of up to 100 nm and are therefore suitable for EO bunch length measurements, especially for spectral decoding. The laser delivers a chirped pulse of some ps, the fourier limited pulse duration of ~30 fs can be almost reached by an additional shaper setup with a spatial light modulator in the Fourier plane.
PSI, Villigen
A screen monitor containing OTR foils and scintillator crystals has been designed to measure the transverse profile of electron bunches in the PSI-XFEL. In conjunction with quadrupole magnets in FODO cells and a transverse deflecting structure, the screen monitors will be used to measure transverse and longitudinal phase space projections of the electron pulses in the 250 MeV Injector. Tomographic methods will be used to reconstruct the phase space distributions.
PSI, Villigen
In this paper, we describe four very different operating modes of the SwissFEL facility, the requirements of the challenging beam diagnostics and ultra-stable RF systems needed for two special operating modes with 10 pC, and the present status of developing beam diagnostics and RF systems for the PSI 250 MeV injector test facility, which is under construction.
