Performance Of Small-Pad Resistive Micromegas For Operation Under High Particle Flow

Motivated mainly by future upgrades at high-luminosity LHC (HL-LHC) and detectors at future accelerators, most of the HEP R&D collaborations are focusing on the design of new particle detectors for operation under high particle flow. In the field of Micro-Pattern-Gaseous-Detectors, were designed the small-pad resistive Micromegas prototypes, to overcome the limitations of current resistive strip Micromegas chambers. In these new prototypes, pads with 1x3 mm(2) area replace the readout strips to reduce the occupancy. The spark protection resistive layer has been redesigned and optimized with different techniques to permit a safe behavior of the detector, at rates of the order of tens MHz/cm(2) over large surfaces without efficiency loss. The firstly-developed design exploits a pad-patterned embedded resistor layout made by screen-printing, while the most recent technique involves uniform sputtered DLC (Diamond Like Carbon structure) layers, where the charge evacuates through the several vias connected to the ground. Comparative studies have been conducted on the performance of the detectors with two resistive layouts, and between two DLC prototypes with different pitch of vias and surface resistivity. The results of the tests performed with high intensity X-rays and with high-energy charged particle beams will be presented.