Speaker
Jason Bessuille
(MIT)
Description
Traditionally, 2D readout schemes for GEM detectors have used a chemical etching process to expose lines on an underlying layer while still preserving an orthogonal set of lines on the top layer. Due to the thickness of the substrate the area of copper on the lower level must be much greater than on the top to achieve equal charge sharing. As an alternative we have produced 2D readout boards using standard circuit board manufacturing techniques. This method employs pads between the lines on the top layer. The pads are then connected by tiny vias to traces on the lower layer running in a different direction to the top lines achieving a 2D readout scheme. The area of copper for the lines and pads are comparable and better controlled than with the chemical etching approach. Also, since the lines and pads are at the same level, the charge sharing is easily fixed during the design process. This approach allows readout designs other that orthogonal to be developed and tailored to the physics needs. We have studied a variety of different designs from various orthogonal designs to R-Phi designs used in the STAR FGT project, to stereo designs used in the OLYMPUS GEM tracker. XUV designs are also possible with the added benefit of redundancy to resolve multi-hit events. Depending on the feature sizes such 2D readout boards can be produced by a wide range of vendors. We will present our experience producing such boards and show some results from STAR and OLYMPUS.
