Micromegas with resistive anode

We report results of small prototype micromegas chambers with stainless steel mesh affixed on the surface of the resistive sheet that is glued to the readout PCB board. Two types of resistive sheets are studied: thin plastic sheet extruded from a special acetal copolymer with volume resistivity on the order of 10¹² ¿-cm and bakelite sheets with resistivity in the range of 10¹⁰ to 10¹⁰ ¿ cm. Our tests show that resistive sheets can significantly extend the gas gain of standard micromegas without the resistive layer while providing good protection against sparks. The additional thickness of high resistive layer on top of readout anodes can help to spread micromegas signals laterally. This feature allows wider readout elements for precision tracking and using 2D strips etched on double sided PCBs for 2D position measurements.