Sampling elements for Digital Hadron Calorimeters

Digital sampling calorimetry is a new concept proposed for future colliders. Sampling the jet with moderate-resolution imaging detectors, and analyzing it with a dedicated pattern-recognition algorithm, is predicted to yield very good jet-energy resolution. Large area, thin (5-7mm), robust detectors, based on single-Thick Gas Electron Multipliers (THGEM), are currently developed, in collaboration with Shikma Bressler group and with scientists from Aveiro and Coimbra universities (Portugal). They are designed to fit into the very narrow gaps between the Hadron-calorimeter iron slabs. Followingh extensive R&D, at the laboratory and at CERN-SPS accelerator on THGEM, WELL, resistive WELL (RWELL), segmented resistive WELL (SRWELL), present candidate sampling elements are Resistive Plate WELL (RPWELL) detectors with pad readout. They consist of a single-faced THGEM electrode, coupled to a segmented readout anode, via a resistive sheet. Beam tests have resulted in close to 100% efficiency and pad mulipicity values of ~1.2 in a discharge-free operation mode, in Ne/CH4, Ar/CH4 and Ar/CO2. The operation stability results from avalanche quenching and discharge damping by the resistive plate. Large-area RPWELL detector protypes (50x50cm2) are under assembly.