HVCMOS Active Pixel Sensors for Measuring GCR and SEP

The development of depleted monolithic active pixel sensors to be used for the measurement of the tracks and the energy depositions of galactic cosmic ray and solar energetic particles is presented. Simulations and preliminary measurements verify the design choices. The chip comprises of the pixel array, an embedded controller, ADC, and bias circuits. In normal operation mode only hit pixels are readout. The technology used permits the placement of the CMOS devices in shallow n and p wells which are separated from the deep n-well by a buffer p-substrate. The sensing diode consists of a high resistivity p-type substrate biased at a negative voltage and the segmented deep n-well on its top. The dynamic range of energy depositions and of count rates to be handled spans many orders of magnitude. For this reason, two designs have been performed one with low gain tailored to high energy depositions and one with high gain for the low energy depositions.