The EUDET high resolution beam telescope — The final digital readout

A high resolution (?<3 ?m) beam telescope based on monolithic active pixel sensors (MAPS) has been built within the EUDET collaboration. EUDET is a coordinated detector R&D programme for a future linear collider providing test beam infrastructure to detector R&D groups. The telescope consists of six sensor planes with a pixel pitch of either 10 or 30 ?m for the demonstrator, or 18.4 ?m for the final telescope. These are located on two arms, between which a device-under-test may be positioned. A general purpose cooling and positioning infrastructure is available, along with a custom-made trigger logic unit, a flexible data acquisition system based on dedicated VME readout boards, a platform-independent, lightweight DAQ framework, and a data analysis tool based on the standard ILC software framework. Since the first installation of a demonstrator telescope in 2007, the DAQ system has been continuously improved and adapted to new sensor types, and has been used by a total of more than ten groups over the summers of 2008 and 2009 as a reference system for tests at DESY and the high energy hadron test beam facility at CERN. In 2008 the sensors were upgraded to the high-resolution Mimosa18 chips, providing the user with the option of enhanced resolution, at the expense of readout speed. In parallel with the 2009 test beam campaign, the final Mimosa26 sensors were installed in the demonstrator telescope as a DUT, and the readout system was adapted to the new sensors. Soon afterwards the six planes of the telescope were replaced with Mimosa26 sensors and the final telescope was commissioned. After an overview of the pixel telescope, its data acquisition system and its performance, the commissioning of the final telescope will be presented. The main feature is the Mimosa26 sensor chip that includes on-sensor data sparsification and digital readout, allowing greatly enhanced readout speed, while maintaining good resolution.