Thomson backscattering diagnostic set-up for the study of nanosecond electron bunches in high space-charge regime

A Thomson backscattering diagnostic apparatus was set up in the ELTRAP (ELectron TRAP) device for the measurement of density as well as longitudinal energy and energy spread of nanosecond electron bunches traveling through a longitudinal magnetic field in a dynamical regime where space-charge effects play a significant role. We discuss the main features of the apparatus as well as the challenging technical issues of the backscattering experiment. In particular, we detail the technical solutions and the characterization of both bunch and laser injection in the vacuum chamber, photon detection, space and time coincidence of electron and laser pulses. Then we summarize the results with an estimate of the minimum sensitivity of the set-up.