M. Deveaux

CMOS monolithic active pixel sensors for minimum ionizing particle tracking using non-epitaxial silicon substrate

Nonepitaxial, high resistivity silicon has been used as a substrate for implementation of CMOS monolithic active pixel sensors (MAPS) designed for high precision minimum ionizing particle tracking. The readout electronics circuitry is integrated directly on top of such a substrate using a standard commercial CMOS process. In this paper, measurements of these devices using a high-energy particle beam are presented. Efficient and performing MIP tracking is demonstrated for both small (20 /spl mu/m) and large (40 /spl mu/m) pixel readout pitch. Radiation hardness that satisfies many future particle physics applications is also proven. These results show that the use of epitaxial substrate for MAPS fabrication is not mandatory, opening a much larger choice of possible CMOS processes in the future.

Optimization of Tracking Performance of CMOS Monolithic Active Pixel Sensors

CMOS Monolithic Active Pixel Sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. In these devices, a thin, moderately doped, undepleted silicon layer is used as the active detector volume with the readout electronics implemented on top of it. Recently, a new MAPS prototype was fabricated using the AMS 0.35 mum OPTO process, featuring a thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particle beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry was also fabricated and tested. Each pixel circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode, followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration independently of full frame readout time and strongly reduces the pixel-to-pixel output signal dispersion. First measurements using this structure are also presented

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.

Optimization of tracking performance of CMOS monolithic active pixel sensors

CMOS monolithic active pixel sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. A thin, moderately doped, undepleted silicon layer is used in these devices as a detector active volume with the readout electronics implemented on top of it. A new MAPS prototype has been fabricated using recently available AMS 0.35 /spl mu/ OPTO process, featuring thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particles beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry is included in the design. The circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode and followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration time independently of full frame readout and reducing pixel-to-pixel output signal dispersion. First measurements using this structure are presented.

Radiation tolerance of CMOS monolithic active pixel sensors with self-biased pixels

CMOS monolithic active pixel sensors (MAPS) are proposed as a technology for various vertex detectors in nuclear and particle physics. We discuss the mechanisms of ionizing radiation damage on MAPS hosting the dead time free, so-called self bias pixel. Moreover, we introduce radiation hardened sensor designs which allow operating detectors after exposing them to irradiation doses above 1 Mrad.

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.

Prototyping the read-out chain of the CBM Microvertex Detector

The Compressed Baryonic Matter (CBM) Experiment at the future FAIR (Darmstadt/Germany) will study the phase diagram of hadronic matter in the regime of highest net-baryon densities. The fixed target experiment will explore the nuclear fireballs created in violent heavy ion reactions with a rich number of probes. To reconstruct the decay topologies of open-charm particles as well as to track low-momentum particles, an ultra-light and precise Microvertex Detector (MVD) is required. The necessary performance in terms of spatial resolution, material budget and rate capability will be reached by equipping the MVD with highly granular, radiation-hard CMOS Monolithic Active Pixel Sensors (CPS) developped at IPHC Strasbourg, which are operated in the target vacuum of the experiment. This contribution introduces the concept of the MVD and puts a focus on the latest results obtained from the R&D of the electronics and read-out chain of the device. Moreover, we briefly introduce the PRESTO project, which realises a prototype of a full size quadrant of an MVD detector station.

Radiation hardness improved CMOS sensors as particle detectors in high energy physics and medical applications

The use of CMOS Monolithic Active Pixel Sensors for high precision minimum ionizing particle tracking has been proven to be a viable and powerful novel experimental technique. In this approach a lightly doped thin and partially depleted silicon epitaxial layer is used as a radiation sensitive detector volume. The readout electronics circuitry is integrated directly on top of epitaxy using standard commercial CMOS process. For the pixel pitch of 20/spl mu/m particle tracking precision of below 2/spl mu/m and full efficiency have been measured in the past. In this work measurements with CMOS MAPS fabricated on non-epitaxial, high resistivity substrate are presented. Efficient and performing MIP tracking is demonstrated, also for a large 40/spl mu/m pixel readout pitch. These results proves that the use of epitaxial substrate for MAPS fabrication is not mandatory, opening much larger choice of possible CMOS processes in the future.

Status of the vertex detector program of the CBM experiment at FAIR

Abstract The Compressed Baryonic Matter Experiment (CBM) is one of the core experiments of the future FAIR facility (Darmstadt/Germany). The fixed-target experiment will explore the phase diagram of strongly interacting matter in the regime of high net baryon densities with numerous rare probes. The Micro Vertex Detector (MVD) will determine the secondary decay vertex of open charm particles with ∼ 50 μ m precision, contribute to the background rejection in dielectron spectroscopy, and help to reconstruct neutral decay products of strange particles by means of missing mass identification. The MVD comprises four stations with 0.3 and 0 . 5 % x ∕ X 0 , which are placed between 5 and 20 cm downstream the target and inside vacuum. It will host highly-granular, next-generation Monolithic Active Pixel Sensors, with a spatial precision of 5 μ m , a time resolution of 5 μ s , and a peak rate capability of ∼ 700 kHz ∕ mm 2 . Moreover, a tolerance to 3 ⋅ 1 0 13 n e q ∕ cm 2 and ≳ 3 Mrad are required. In this document, we summarize the status of sensor development, station prototyping, and the detector slow control.

A prototype for the data acquisition of the CBM Micro Vertex Detector

The Compressed Baryonic Matter Experiment (CBM) will be installed at the SIS-100/SIS-300 heavy ion synchrotrons of the FAIR facility, which is currently under construction at Darmstadt, Germany. Its purpose is the study of hadronic matter in the region of highest net baryonic densities with rare probes, e.g. open charm particles. To reconstruct those particles, an ultra light Micro-Vertex Detector (MVD) with a spatial resolution of few micrometers and a material budget of 0.3% X0 is required. Moreover, this MVD needs to handle an ambitioned collision rate of ∼ 105 Au+Au collision with up to 35AGeV beam energy.