D. Doering

Radiation tolerance of a column parallel CMOS sensor with high resistivity epitaxial layer

CMOS Monolithic Active Pixel Sensors (MAPS) demonstrate excellent performances in the field of charged particle tracking. A single point resolution of 1–2 μm and a detection efficiency close to 100% were routinely observed with various MAPS designs featuring up to 106 pixels on active areas as large as 4 cm2[1]. Those features make MAPS an interesting technology for vertex detectors in particle and heavy ion physics. In order to adapt the sensors to the high particle fluxes expected in this application, we designed a sensor with fast column parallel readout and partially depleted active volume. The latter feature was expected to increase the tolerance of the sensors to non-ionizing radiation by one order of magnitude with respect to the standard technology. This paper discusses the novel sensor and presents the results on its radiation tolerance.

Random Telegraph Signal in Monolithic Active Pixel Sensors

CMOS Monolithic Active Pixel Sensors (MAPS) technology allows integrating very small sensing elements with a pixel pitch of ∼ 10 μm together with analogue and digital signal processing circuits into a monolithic chip, which may be thinned down to a thickness of ∼ 50 μm. These features make MAPS an interesting technology for a broad range of applications in charged particle tracking. Intense R&D was performed in the last years in order reach the necessary radiation hardness. In the context of these studies, radiation induced Random Telegraph Signal (RTS) was found to introduce a substantial amount of accidental (noise) hits. In this work, we present a first systematic investigation of the rate of these fake hits as function of environmental conditions like accumulated radiation dose and temperature. Moreover, strategies to reduce the impact of RTS are studied.

A data parallel digitizer for a time-based simulation of CMOS Monolithic Active Pixel Sensors with FairRoot

CMOS Monolithic Active Pixel Sensors (MAPS) demonstrated excellent performances in the field of charged particle tracking. They feature an excellent single point resolution of few μm, a light material budget of 0.05% Xo in combination with a good radiation tolerance and time resolution. This makes the sensors a valuable technology for micro vertex detectors (MVD) of various experiments in heavy ion and particle physics like STAR and CBM. State of the art MAPS are equipped with a rolling shutter readout. Therefore, the data of one individual event is typically found in more than one data train generated by the sensor. This paper presents a concept to introduce this feature in both simulation and data analysis, taking profit of the sensor topology of the MVD. This topology allows to use for massive parallel data streaming and handling strategies within the FairRoot framework.

Noise performance and ionizing radiation tolerance of CMOS Monolithic Active Pixel Sensors using the 0.18μm CMOS process

CMOS Monolithic Active Pixel Sensors (MAPS) have demonstrated excellent performance as tracking detectors for charged particles. They provide an outstanding spatial resolution (a few μm), a detection efficiency of 99.9%, very low material budget (0.05% X0) and good radiation tolerance ( 1 Mrad, 1014 neq/cm2) [1]. This recommends them as an interesting technology for various applications in heavy ion and particle physics. For the vertex detectors of CBM and ALICE, we are aiming at developing large scale sensors with an integration time of 30μs. Reaching this goal is eased by features available in CMOS-processes with 0.18μm feature size. To exploit this option, some sensor designs have been migrated from the previously used 0.35μm processes to this novel process. We report about our first findings with the devices obtained with a focus on noise and the tolerance to ionizing radiation.

Status of the micro vertex detector of the compressed baryonic matter experiment

The CBM experiment will investigate heavy-ion collisions at beam energies from 8 to 45 AGeV at the future accelerator facility FAIR. The goal of the experiment is to study the QCD phase diagram in the vincinity of the QCD critical point. To do so, CBM aims at measuring rare probes among them open charm. In order to identify those rare and short lived particles despite the rich combinatorial background generated in heavy ion collisions, a micro vertex detector (MVD) providing an unprecedented combination of high rate capability and radiation hardness, very light material budget and excellent granularity is required. In this work, we will discuss the concept of this detector and summarize the status of the R&D.