HARDROC: Readout chip for CALICE/EUDET Digital Hadronic Calorimeter

HARDROC (HAdronic Rpc Detector Read Out Chip) is the very front end chip designed for the readout of the RPC or Micromegas foreseen for the Digital HAdronic CALorimeter (DHCAL) of the future International Linear Collider and designed within the CALICE collaboration. The very fine granularity of the ILC hadronic calorimeters (1cm
²
pads) implies a huge number of electronics channels (4 10
⁵
/m
³
) which is a new feature of “imaging” calorimetry. Moreover, for compactness, the chips must be embedded inside the detector making crucial the reduction of the power consumption to 10 μWatt per channel. This is achieved using power pulsing, made possible by the ILC bunch pattern (1 ms of acquisition data for 199 ms of dead time). HARDROC readout is a semi-digital readout with three thresholds which allows both good tracking and coarse energy measurement, and also integrates on chip data storage. The overall performance of HARDROC will be described with detailed measurements of all the characteristics. Hundreds of chips have indeed been produced and tested before being mounted on printed boards developed for the readout of large scale (1m
²
) RPC and Micromegas prototypes. These prototypes have been tested with cosmics and also in testbeam at CERN between 2008 and 2010 to evaluate the performance of different kinds of GRPCs and to validate the semi-digital electronics readout system in beam conditions. A production of 10 000 chips has been launched in March 2010 to equip 40 GRPC planes (400 000 channels) of a 1 cubic meter detector that will be tested in 2011.