Epitaxial hybrid pixel with triggerless readout in 130 nm Cmos technology for the Micro Vertex Detector of the Panda experiment

摘要

The Micro Vertex Detector (MVD) is the innermost one of the Panda experiment, sitting around the beam pipe. The sensors are arranged in a barrel section with two pixel and two strip layers, and 6 forward disks with mixed pixel and microstrip sensors. For the pixel detector part, a hybrid solution with thinned epitaxial sensors was chosen. The main requirements for the readout include: a pixel size of 100·100 μm~2, an input charge measurement with 12 b that implies an amplitude resolution of 1 part out of 4096, a working frequency of 155.5 MHz, and a triggerless acquisition. The readout of the pixel detector is based on a front end chip, named Topix, that is under development. The Asic will provide the time position with a resolution of 6.43 ns and a charge measurement with a Time Over Threshold (TOT) technique; it features a matrix of 116·110 pixel cell channels and 311 Mb/s serializers as output ports. A 130 nm Cmos technology has been used to reduce the circuit size and to provide tolerance for the total dose, besides techniques against single event upset have been implemented. A Topix prototype with the full cell has been completely tested for radiation damage before and after irradiation, and a new release has been submitted to build an hybrid assembly. The stringent requirements in terms of space for the MVD lead to an architecture based on optical links. The GigaBit Transceiver (GBT) from CERN has been chosen as the baseline solution for the interface to the data acquisition. Low mass cables based on aluminium on polyimide are under development for the interconnections.