Development of a Reconfigurable Monolithic Active Pixel Sensor in Radiation-hard Technology for Outer Tracking and Digital Electromagnetic Calorimetry

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As particle physics progresses, the demands in terms of detector technologies always push toward needing fine segmentation, faster read-out and greater radiation tolerance; all at lower cost. To find particles too massive to have been seen already, particle colliders have to continuously push towards higher energies. However, as collision energies increase, the rates for events containing potential evidence for such new physics decreases as a fraction of the total, making it important at high energies to also have very high interaction rates. Also, as energies increase, the numbers of particles produced per collision increase and the mean energies of the produced particles of interest increase. The latter means that charged particles become harder to bend in the detector magnetic field and so better spatial precision (hence smaller sense elements) is needed leading to the need for much greater granularity (number of pixels per unit area). At higher energies, particle showers tend to also be much more collimated, making track separation also harder without many more read-out cells per unit area. Finally, at hadron colliders, high rates require many collisions per beam crossing so the interesting interactions are typically buried in 200 uninteresting ones produced at the same time. Unpicking the tracks from the interesting collision also requires very precise measurements. Finally, billions of collisions per second lead to radiation levels over years of operation that go way beyond the capabilities of normal electronics requiring specialist designs to work after the expected doses.Particle physics sensors are not able to exploit the development of ultra-cheap mega-pixel cameras in many commercial devices because these neither have the speed or radiation hardness needed but they easily meet the requirements in terms of granularity. Therefore, if fast, radiation-hard versions could be designed, these would be a game-changer in terms of sensor affordability. Recent work has shown that there are commercial CMOS technologies available that can support radiation-hard designs and this proposal seeks to exploit these to demonstrate devices that could allow very large areas of experiments to be equipped with such detectors affordably. Aspects of the design that makes the sensors radiation hard also make them faster which is an added advantage for these applications. Nevertheless, proving small sensors with the required properties is a first step towards final arrays requiring thousands of square metres of sensors and much development time is needed before a very large array could be envisaged. Therefore, even though the possible applications are quite a long way off, the amount of time to develop new technologies to the required maturity to be exploited in such large arrays means that this R&D is very timely. The UK has a lead in a number of the technology aspects for this but there are many other groups internationally pursuing the same goals and so this proposal is also important if current leadership, much of it developed through work for ATLAS and CMS upgrades and for the International Linear Colldier, is not to be lost.