Bulk Micromegas detectors for large TPC applications

A large volume TPC will be used in the near future for a variety of experiments, including T2K and possibly the Linear Collider detector. The bulk Micromegas detector is a novel construction technique suited for building compact and robust low mass detectors. The ability to pave a large surface with a simple mechanical solution and negligible dead space between modules is of particular interest for these applications, offering a simple and low cost alternative to wire chambers. We have built and tested two large bulk detectors ( 26 × 27 cm 2 with 8 × 8 mm 2 pads) in the former HARP field cage setup at CERN, with cosmic ray data in a magnetic field up to 0.4 T. We present the excellent detector performances, with gains in excess of 10 4 , space point resolution of 700 μ m at 1 m drift, and d E / d x resolution of 12 % . Improvement on the point resolution with the use of a resistive anode is also discussed.