TwinGrid: A wafer post-processed multistage Micro Patterned Gaseous Detector

This paper presents a new multistage Micro Patterned Gaseous Detector (MPGD) made by wafer post-processing. The device consists of a double metal grid supported by SU-8 structures on top of a Timepix chip. The detector has been operated with He/iC4H10 and Ar/iC4H10 gas mixtures. Cosmic rays as well as 55Fe decay events have been recorded using the Timepix chip in 2D and 3D readout modes. The detector can be operated like a Micromegas (high field close to the chip) or like a GEM (amplification stage followed by a low extraction field). This approach for manufacturing GEM-like radiation imaging detectors allows for precise dimensional control and considerable geometrical design freedom.