The development of instrumentation is one of the most important and exciting parts of experimental sciences. To some extent, making experiments is developing instruments. I had the fortune to start my scientific career learning from a great hardware specialist, a leader in the field of gaseous particle detectors. Although my studies were focused on data analysis, I was practically immersed in detector physics since my MS degree thesis.
When I arrived in Trento, in 2016, I started a project for developing Monolithic Active Pixel Sensors (MAPS) for space applications. Most of image sensors we use today (e.g. the cameras of our mobile phones) are APS, fabricated with the CMOS process for light detection. MAPS were proposed in early 90s as detectors for particle physics experiments. Just like in APS, where front-end electronics is near to the photodiode in the pixel itself, the idea is to equip the pixel with a continuously active preamplifier, a signal-shaper, a discriminator and possibly multiple event buffers, alongside the region of charge collection. But collecting charges from ionisation is somewhat more difficult than detecting visible light. The region where ionisation electrons are collected has to be suitably shielded to allow embedding the electronics. This is the reason why MAPS for charged particles took longer to be ready than APS for light detection.
With respect to the standard hybrid silicon microstrip or pixel technology, MAPS profit from the uninterrupted progress of CMOS technology, they do not need wire-or bump- bonding, they are more precise, more robust, easier to control and readout, cheaper and less invasive. All desirable features for a space technology. On the other hand, they are still relatively small-sized and power-demanding.
In Trento, I started two lines of development of MAPS for space application. On one side, we are adapting the ALPIDE sensor, developed for the ALICE experiment at the LHC, to be the building block of the HEPD-02 tracker. This project is currently the main laboratory effort of Trento’s APP group, as the launch of HEPD-02 is scheduled by 2022.
Furthermore, we lead the Work-Package 6 of the INFN ARCADIA project, aiming at developing low-power monolithic sensors specifically designed for space applications. ARCADIA is developing a platform for fully depleted CMOS sensors, with flexible readout systems and adjustable geometries. The fabrication of the first demonstrator is almost finished and the test campaign is about to start.