BUNCH LENGTH MEASUREMENTS FROM THE INCOHERENT SYNCHROTRON RADIATION FLUCTUATION AT SOLEIL

Bunch length measurements can be made by analysing the pulse to pulse intensity fluctuation of the incoherent synchrotron radiation as it has been reported at the ALS [1]. Such a method has been tested at SOLEIL for picosecond bunch durations, at several wavelengths and bandwidths in the visible range, using an avalanche photodiode. Thanks to the low- optics, the lengths of 15 µA bunches as short as a few ps have been measured in good agreement with the streak camera results. We first used the radiation from a bending magnet, and then from a HU640 undulator that enhances the photon flux. Using the radiation from an undulator also shows that the method is still valid when the number of spikes emitted by an electron bunch is reduced to one thousand. We intend to use this result to measure the very short bunch length of the femto-slicing operation foreseen at SOLEIL.