Longitudinal bunch profil monitoring via electro-optic single shot diagnostic with linear response

A new approach of electro-optic (EO) spectral encoding allows for the non-invasive characterization of the longitudinal electron bunch distribution at the ELYSE laser triggered ps pulse radiolysis facility: the transverse electric field of the relativistic bunch is encoded to the temporally dispersed spectrum of a supercontinuum whose wavelength dependent polarisation state is then analyzed with balanced detection. This method combines the spectral bandwidth of the probe (Fourier transform limit < 5 fs) with a direct signal response of the detection scheme. As a result, the field amplitude within the EO crystal can be determined in an absolute, undistorted manner with a time window several times longer than the electron pulse. The diagnostic allows bunch monitoring at the 100 pC level even for low beam energy and brightness. The influence of the accelerator conditions on the bunch profile and its stability has been studied for the 4 - 8 MeV bunches at ELYSE with a 500 μm thick ZnTe crystal at a distance of 4 mm to the e^--beam centre.