Luminosity is a key parameter of each collider. Its precise and fast measurement is essential for the physics program.

The Tel Aviv University (TAU) team is part of the FCAL collaboration, which develops technologies of compact and fast calorimeters with low average power consumption to measure the integrated luminosity with high precision, using small angle Bhabha scattering (LumiCal), and the bunch-by-bunch luminosity, using beamstrahlung pairs (BeamCal). For the LumiCal, a silicon-tungsten ‘sandwich’ calorimeter is used. For the BeamCal, radiation hard and very fast sensors, like GaAs or single crystal sapphire, are considered. A small Moliere radius is required for the measurement of Bhabha events in the presence of background and it also allows the detection of single high energy electrons on top of the widely spread beamstrahlung in the BeamCal.

Two multi-plane prototypes of a luminometer were studied in beams of electrons and muons with momenta around 5 GeV at CERN and at DESY. The results for the longitudinal and the transverse shower profiles are compared to Geant4 simulation of the setups and used to

determine the effective Moliere radius of the prototypes. The ultra-thin detector planes developed at TAU demonstrate a very small effective Moliere radius approaching the inherent limit in tungsten. The final results of the 2014 CERN testbeam, as well as preliminary results from the 2016 DESY testbeam will be presented.