Test beam studies of prototype sensor planes of very forward calorimeters

Special calorimeters are currently under development for the forward region of the future electron-positron collider. In the current detector concepts, two calorimeters are foreseen - the Luminosity Calorimeter (LumiCal) for precise luminosity measurement, and the Beam Calorimeter (BeamCal) for luminosity optimization. Both are designed as sensor-tungsten sandwich calorimeters. For each calorimeter prototypes of a sensor plane were prepared with silicon sensors for LumiCal and GaAs sensors for BeamCal. For each calorimeter, the first prototypes of sensor sectors have been prepared and assembled, with the sensor pad bonded to a fan-out on one side and to FE-ASICs developed by UST Cracow on the other. The fully assembled system was then tested in a 4 GeV electron beam at DESY II accelerator. The trajectory of beam particles was measured using a silicon strip detector telescope. The track reconstruction algorithm was adopted from telescope software and the impact points of electrons on the sensor were predicted. Results of the test beam data analysis on the performance of the system are reported.