The readout electronics and data acquisition system of the MINOS vertex tracker

The MINOS (MagIc Numbers Off Stability) collaboration has developed a compact vertex tracker for in-beam gamma spectroscopy of very exotic nuclei. It comprises a cylindrical time projection chamber with a Micromegas amplification plane, a cylindrical tracker based on a curved Micromegas, and two off-the-shelf silicon detectors. In total, MINOS comprises ~5000 channels. Besides performance goals, the readout electronics system was designed to be versatile and upgradable with minimal effort. The hardware part consists of three types of custom-made cards. The Feminos is a small digital board that can read out a front-end card equipped with AFTER chips (originally developed for the T2K neutrino experiment), or AGET chips, a pin-compatible evolution designed by the GET collaboration. Multiple Feminos are synchronized by a board called the trigger clock module, and are connected to a data acquisition PC through a Gigabit Ethernet switch. System configuration, monitoring and data acquisition rely on a generic object-oriented framework based on the ICE middleware, a free software infrastructure for distributed computing. After a brief description of the detectors of MINOS, we present the design and performance of the readout and data acquisition system of this instrument, and show some of the results obtained during their validation in an in-beam test recently performed at HIMAC, Chiba, Japan.