High rate performance of small-pad resistive Micromegas. Results of different resistive protection concepts

We present the development of resistive micromegas aiming at precision tracking in high rate environment without efficiency loss up to several MHz/cm$^2$. To achieve this goal, the optimisation of the spark protection resistive layer and the miniaturisation of the readout elements, are key elements of the project. Several small-pad micromegas detectors have been built with a anode plane matrix of 48x16 readout pads, rectangular in shape, with dimensions 0.8x2.8 mm$^2$. With this anode/readout layout, different concepts of the spark protection resistive layers have been implemented. Characterisation and performance studies of the detectors have been carried out by means of radioactive sources, X-Rays, and test beam. A comparison of the performance obtained with the different resistive layout is presented, in particular focusing on the response under high irradiation and high rate exposure.