N. Stoffle University of Houston Simulation of Van Allen Belt and Galactic Cosmic Ray Ionized Particle Tracks in a Si Timepix Detector N. Stoffle University of Houston

Collaborators Lawrence Pinsky - University of Houston Anton Empl - University of Arkansas at Little Rock Son Hoang - University of Houston Stanislav Pospisil - IEAP Jan Jakubek - IEAP Daniel Turecek - IEAP Zdenek Vykydal - IEAP

Timepix Detector Hybrid Pixel Detector Track Imaging 256 x 256 pixel grid 14mm square 300 µm Si Track Imaging Charge sharing impacts Calibration: ToT to Energy

LEO Radiation Environment Trapped Radiation Galactic Cosmic Rays Geomagnetic shielding and cusp regions

Simulation Method Overview Produce Input data for Monte Carlo routines Generate LEO Orbital track data Gather Particle and Energy data from models for each point in the orbital track Simulate interaction and energy deposition physics in the Timepix detector Model charge movement within Silicon layer Process data and produce track images

Orbital Track Generation SPENVIS Orbit Generator One minute data Latitude Longitude Altitude B L Image generated using SPENVIS

Trapped Radiation Data AE8/AP8 data on a one-minute cadence Each point has spectral data associated Both electron and protons Energy Bin Data Integral Flux Differential Flux Image generated using SPENVIS

Galactic Cosmic Ray Data SPENVIS limited to 1/10th orbit for GCR spectra Average spectra used for high/low shielded regions Images generated using SPENVIS

Data Sampling Generate source data for use in Monte Carlo code ROOT data structures and tools used Assume random isotropic field Impose total flux limits from data sets Generate a list of particle hits Orbit location, Species, Energy, Time, Position, and Angle

Monte Carlo Simulation Simplified Detector Geometry Source data propagated through material Energy deposition and location (depth/pixel) Secondaries included Raw data output requires further processing Charge collection Post Processing

Charge Movement Drift and diffusion processes within the Silicon layer impact measurements Bouchami et al (2011) proposed model for Medipix2 technology Apply this model to produce modified track pixel mapping

Post Processing Combine tracks within the same acquisition time window into a single frame Produce results that can mimic hardware acquisition settings Output files in preferred structure for direct use within Pixelman

Current Results Trapped Proton frames Electrons below 10MeV assumed screened by vehicle shielding Track structures and frame data sets visible in Pixelman 1 second time window 60 second frame separation

Forward Work Incorporate and Verify charge collection model using heavy ion accelerator measurements Implement methods for direct estimation of GCR spectra instead of averaged data Utilize rigidity at given orbital point

Summary Robust and flexible track simulation method has been developed Source input data can be modified as needed Highly applicable to space radiation dosimetry

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