A dump leakage calorimeter to measure the flux of high-energy electrons and photons

We developed a novel apparatus based on a lead glass calorimeter that can measure the flux of high-energy electrons or photons. Our detector uses the electromagnetic shower leakage from the beam dump, where the particles are disposed of at the beamline's end. A prototype of such a calorimeter was set up at the FLASHForward experiment at DESY. We show that it can measure the electron bunch charge with precision and accuracy at the 10% and 3% level, respectively. Additionally, it is capable of determining the beam's position with a precision on the order of tens of micrometers. Finally, we show the applicability to the measurement of high-energy photons.