Novel silicon and GaAs sensors for compact sampling calorimeters

Abstract Two samples of silicon pad sensors and two samples of GaAs sensors are studied in an electron beam with 5 GeV energy from the DESY-II test-beam facility. The sizes of the silicon and GaAs sensors are about 9 $$\times $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>×</mml:mo> </mml:math> 9 $$\hbox {cm}^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>cm</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:math> and 5 $$\times $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>×</mml:mo> </mml:math> 8 $$\hbox {cm}^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>cm</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:math> , respectively. The thickness is 500 µm for both the silicon and GaAs sensors. The pad size is about 5 $$\times $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>×</mml:mo> </mml:math> 5 $$\hbox {mm}^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>mm</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:math> . The sensors are foreseen to be used in a compact electromagnetic sampling calorimeter. The readout of the pads is done via traces connected to the pads and the front-end ASICs at the edges of the sensors. For the silicon sensors, copper traces on a Kapton foil are connected to the sensor pads with conducting glue. The pads of the GaAs sensors are connected to bond-pads via aluminium traces on the sensor substrate. The readout is based on a dedicated front-end ASIC, called FLAME. Pre-processing of the raw data and deconvolution is performed with FPGAs. The whole system is orchestrated by a Trigger Logic Unit. Results are shown for the signal-to-noise ratio, the homogeneity of the response, edge effects on pads, cross talk and wrongly assigned signals due to the readout traces.