Study of the signal response of the MONCH 25[mu]m pitch hybrid pixel detector at different photon absorption depths

MONCH is a 25 [mu]m pitch hybrid silicon pixel detector with a charge integrating analog read-out front-end in each pixel. The small pixel size brings new challenges in bump-bonding, power consumption and chip design. The MONCH02 prototype ASIC, manufactured in UMC 110 nm technology with a field of view of 4x4 mm super(2) and 160x160 pixels, has been characterized in the single photon regime, i.e. with less than one photon acquired per frame on average on a 3x3 pixel cluster. The low noise and small pixel size allow spatial interpolation with high resolution. Understanding charge sharing as a function of the photon absorption depth and sensor bias is a key for optimal processing of single photon data for high resolution imaging. To characterize the charge collection of the detector, the sensor was illuminated with a 20 ke V photon beam in edge-on configuration at the SYRMEP beamline of Elettra. By slicing the beam by means of a 5 [mu]m slit and scanning through the 320 [mu]m silicon sensor depth, the charge collection is characterized as a function of the photon absorption depth for different sensor bias voltages.