Toward a Monolithic Pixel Sensor for Heavy Ion Spectroscopy - Pixel Structure Design and Optimization

Detection and classification of cosmic particles is essential for many scientific and engineering applications. Currently available heavy ion detectors necessitate an external readout integrated circuit when conducting both measurements of particle energy deposition and particle incident position. In this paper, we propose an innovative monolithic pixel detector topology capable of distinguishing between particles in a predefined LET range. The analog and digital readout circuitry are incorporated into the pixel region while maintaining almost an 100% detection fill factor over the entire pixel array. We present comprehensive CAD 3D simulations of the device to verify the applicability of the detector for galactic cosmic rays with the specified LET levels and induced charge distribution. We evaluate the charge collection performance under heavy-ion hit conditions and provide an assessment of the impact on charge collection from the particle impinging position, particle LET, angle of penetration and circuit bias. The results indicate a linear relationship between particle LET and collected charge, regardless of the ion hit position and almost independent of the circuit voltage bias. The simulation results for various particle incident angles show correlations between charge collection and particle trajectory length. We propose an implementation which makes it possible to determine the particle angle of penetration and particle LET attributes. The radiation tolerance of the sensor was estimated. Its applicability to the non-ionizing radiation environment was shown to be adequate for low Earth orbits.