S. Dittmeier

Overview of HVCMOS pixel sensors

High voltage CMOS (HVCMOS) sensors are presently considered for the use in Mu3e experiment, ATLAS and CLIC. These sensors can be implemented in commercial HVCMOS processes. HVCMOS sensors feature fast charge collection by drift and high radiation tolerance. The sensor element is an n-well/p-type diode. This proceeding-paper gives an overview of HVCMOS projects and the recent results.

The MuPix Telescope: A Thin, High-Rate Tracking Telescope

The MuPix Telescope is a particle tracking telescope, optimized for tracking low momentum particles at high rates. It is based on the novel High-Voltage Monolithic Active Pixel Sensors (HV-MAPS), designed for the Mu3e tracking detector. The telescope represents a first application of the HV-MAPS technology and also serves as test bed of the Mu3e readout chain. The telescope consists of up to eight layers of the newest prototypes, the MuPix7 sensors, which send self-triggered data via fast serial links to FPGAs, where the data is time-ordered and sent to the PC. A particle hit rate of 1 MHz per layer could be processed. Online tracking is performed with a subset of the incoming data. The general concept of the telescope, chip architecture, readout concept and online reconstruction are described. The performance of the sensor and of the telescope during test beam measurements are presented.

Ultra-low material pixel layers for the Mu3e experiment

The upcoming Mu3e experiment will search for the charged lepton flavour violating decay of a muon at rest into three electrons. The maximal energy of the electrons is 53 MeV, hence a low material budget is a key performance requirement for the tracking detector. In this paper we summarize our approach to meet the requirement of about 0.1 % of a radiation length per pixel detector layer. This includes the choice of thinned active monolithic pixel sensors in HV-CMOS technology, ultra-thin flexible printed circuits, and helium gas cooling.

MuPix7—A fast monolithic HV-CMOS pixel chip for Mu3e

The MuPix7 chip is a monolithic HV-CMOS pixel chip, thinned down to 50 \mu m. It provides continuous self-triggered, non-shuttered readout at rates up to 30 Mhits/chip of 3x3 mm^2 active area and a pixel size of 103x80 \mu m^2. The hit efficiency depends on the chosen working point. Settings with a power consumption of 300 mW/cm^2 allow for a hit efficiency >99.5%. A time resolution of 14.2 ns (Gaussian sigma) is achieved. Latest results from 2016 test beam campaigns are shown.

Towards Multi-Gigabit readout at 60 GHz for the ATLAS silicon microstrip detector

In this paper we present the status of s feasibility study for a wireless readout of the Silicon inner-tracker for the ATLAS silicon strip detector with use of the 60 GHz band, also known as the Millimeter wave band due to its wavelength of 5 mm. The 60 GHz band is very suitable for high data rate and short distance applications, which can provide wireless Multi Gigabit per second radial data transmission inside the ATLAS silicon strip detector, making a first level track trigger processing all hit data feasible. A first prototype of the 60 GHz wireless multigigabit data transfer topology is currently under development at the University of Heidelberg using the 130 nm SiGe HBT BiCMOS 8HP technology. The wireless transceiver consists of a transmitter and a receiver. The transmitter includes an On-Off-Keying scheme (OOK) modulator, a Local Oscillator (LO), a Power Amplifier (PA) and a BandPass Filter (BPF). The receiver part is composed of a BPF, a Low Noise Amplifier (LNA), a double balanced down convert Gilbert mixer, a LO, BPF to remove the mixer introduced noise, a Intermediate Frequency (IF) amplifier and a OOK Demodulator that converts the signal back to its original form. The first prototype will be designed to handle a data rate of 3.5 Gbps over a link distance of 1 m. The required distance for the ATLAS silicon strip detector is about 10 cm. First simulations of the LNA show that a Noise Figure (NF) of 5 dB, a power gain of 21 dB at 60 GHz with a 3dB bandwidth of more than 20 GHz with a power consumption of 11 mW are achieved. A mixer with a NF of 9.3 dB, a conversion gain of 8.5 dB with a input power PLO of -2 dBm and RF power of -30 dBm@60 GHz with a power consumption of 7 mW is here achieved. Simulations of the PA show an output referred compression point P1dB of 19.7 dB at 60 GHz.

60 GHz wireless data transfer for tracker readout systems—first studies and results

To allow highly granular trackers to contribute to first level trigger decisions or event filtering, a fast readout system with very high bandwidth is required. Space, power and material constraints, however, pose severe limitations on the maximum available bandwidth of electrical or optical data transfers. A new approach for the implementation of a fast readout system is the application of a wireless data transfer at a carrier frequency of 60 GHz. The available bandwidth of several GHz allows for data rates of multiple Gbps per link. 60 GHz transceiver chips can be produced with a small form factor and a high integration level. A prototype transceiver currently under development at the University of Heidelberg is briefly described in this paper. To allow easy and fast future testing of the chips functionality, a bit error rate test has been developed with a commercially available transceiver. Crosstalk might be a big issue for a wireless readout system with many links in a tracking detector. Direct crosstalk can be avoided by using directive antennas, linearly polarized waves and frequency channeling. Reflections from tracking modules can be reduced by applying an absorbing material like graphite foam. Properties of different materials typically used in tracking detectors and graphite foam in the 60 GHz frequency range are presented. For data transmission tests, links using commercially available 60 GHz transmitters and receivers are used. Studies regarding crosstalk and the applicability of graphite foam, Kapton horn antennas and polarized waves are shown.

Readout Electronics for the First Large HV-MAPS Chip for Mu3e

Mu3e is an upcoming experiment searching for charged lepton flavour violation in the rare decay μ+->e+e-e+. A silicon pixel tracker based on 50 μm thin High-Voltage Monolithic Active Pixel Sensors in a 1T magnetic field will deliver precise vertex and momentum information. The MuPix High-Voltage Monolithic Active Pixel Sensor combines pixel sensor cells with integrated analogue electronics and a complete digital readout. For the characterization of the first large MuPix system-on-chip a dedicated readout system was developed. The readout chain and the first results from the characterization of the large scale MuPix8 prototype are presented.

Readout via Flexprints for the Mu3e Experiment

The Mu3e experiment at PSI aims to search for the charged lepton flavor violating decay µ + → e +e −e + with a sensitivity to a branching ratio of 10−16. To achieve this, a high intensity muon beam with a rate of 108 - 109 muons per second is stopped on a target. The decay electrons are detected with a silicon pixel tracking detector using High Voltage Monolithic Active Pixel Sensors (HV-MAPS) and timing detectors consisting of scintillating fibres and tiles. Instead of a triggered readout, the experiment uses online event filtering. This requires the readout of all hits detected in the pixel sensors. Hence, data from the sensors is transferred using fast serial LVDS links with data rates of 1.25 Gb/s over flex-print cables made of polyimide and aluminium foil. The flex-prints also provide power and control signals. In total, about 1000 sensors have to be powered and read out with one to three fast serial data links each. Studies of the serial data transmitted from the current pixel sensor prototype MUPIX7 at 1.25 Gb/s have been performed. Flex-print cables produced in-house have been tested regarding impedance, quality of service, and bandwidth. An outlook on the flex-print design to connect the next generation of MUPIX sensors and build first detector modules is given.