Capacitively coupled hybrid pixel assemblies for the CLIC vertex detector

The vertex detector at the proposed CLIC multi-TeV linear e+e− collider must have minimal material content and high spatial resolution, combined with accurate time-stamping to cope with the expected high rate of beam-induced backgrounds. One of the options being considered is the use of active sensors implemented in a commercial high-voltage CMOS process, capacitively coupled to hybrid pixel ASICs. A prototype of such an assembly, using two custom designed chips (CCPDv3 as active sensor glued to a CLICpix readout chip), has been characterised both in the lab and in beam tests at the CERN SPS using 120 GeV/c positively charged hadrons. Results of these characterisation studies are presented both for single and dual amplification stages in the active sensor, where efficiencies of greater than 99% have been achieved at −60 V substrate bias, with a single hit resolution of 6.1μm. Pixel cross-coupling results are also presented, showing the sensitivity to placement precision and planarity of the glue layer.