High Voltage Monolithic Active Pixel Sensors for the MOLLER experiment

The MOLLER experiment [1] aims to measure the parity-violating asymmetry ( A P V ) in electron–electron scattering at 11 GeV, and thus determine the weak charge of the electron to a high precision (2.4%). Two of the key sub-systems in the experimental apparatus are the main detector array, consisting of 224 fused silica detector modules and an electron beam Compton polarimeter. The main detector array can be operated in either pulsed mode for particle tracking, or integration mode for the asymmetry measurement at high rate detection. A subset of these detector modules will be equipped with an array of High Voltage Monolithic Active Pixel Sensors (HVMAPS), to be used in particle tracking and allowing for real-time monitoring of the event profile in the main Møller region. HVMAPS are also used for the Compton polarimeter, consisting of four-plane planes of HVMAPS chips, housed in a vacuum chamber upstream of the interaction point. An overview of the implementation of the HVMAPS for the main detectors and Compton polarimeter is provided.