Beamline setup

Optical probe:

As an alternative to the FEL probing, the TG can be probed by an ultrafast optical pulse at wavelength λlaser=785, 393 or 261 nm (see sketch); the installation of OPA and/or NOPA devices for probe pulses tunable in the UV-visible range, as well as a white-light supercontinuum source (450-720 nm) can be provided upon user request . The optical pulse can be a normal incidence, i.e. at the bisector of the crossed FEL beams (opt. 1), or can be tuned in the ~40o-70o range (opt. 2, NOTE: in this case 2θ-values of 79o and 105.4o are not available), with variable angles possible upon request. A breadboard with a quite large space (~0.5 m2) is installed near the end-station to host optical setups requested by users
The optically probed transient grating diffracted signal is detected by an in-vacuum CCD (link detectors). A Faraday rotation setup is aditionally available for the optical probe in transmission at normal incidence. 

Important note

Using the optical laser as a probe, the phase matching for TG (Bragg diffraction) is forbidden for FEL wavelenghts shorter than ~45 nm, even exploiting the smallest value of 2 (18.4°) and the larger incident angle / shorter wavelength θB~ 70° / λlaser~260 nm) of the probing laser. This limits the maximum grating wavevector to k~0.05 nm-1. This limitation is relaxed using the mini-TIMER setup at DiProI, which allows the fulfilment of the phase matching basically in the whole range of FERMI (i.e. down to λFEL~4 nm), while keeping the grating vector lower than k~0.05 nm-1

SLU parameters:

Seed Laser for Users (SLU)

Laser typeTi:Sapphire
Central Wavelength/Energy795 [nm]
Wavelength fluctuations1 * 10-3 [%]
Spectral Bandwidth FWHM18 [nm]
Tunability1 [%]
Beam shapeGaussian
Other beam shapeM2<1.5
Pulse duration FWHM65 [fs]
PolarisationLinear Horizontal, Linear Vertical, Circular
Other polarisationAll linear and circular polarizations available
Pulse repetition rate50 [Hz]
Maximum pulse energy1.5 * 10-3 [J]
Pulse energy fluctuations5 * 10-3 [sigma]
Peak power20 * 109 [W]
Peak fluence on target10 [J/cm2]
Special modes2nd and 3rd harmonics (~390 and ~260 nm) available

Last Updated on Thursday, 12 March 2020 12:28