Implementation Of GEANT4 And Its Applications To The Analysis Of Space Radiation Effects

Studies of space energetic proton radiation effects on devices are the main concerns of spacecraft safety, this paper presents simulations of shielding effects of spacecraft Al shell and radiation damage effects on semiconductor devices based on Monte Carlo codes Geant4.The various space radiation sources models are reviewed in the paper. Irradiation-induced macroscopic detector properties changes and the underlying proton-material atoms interaction mechanisms are investigated in details: both TID/SEE by ionizing processes and displacement damage of primary recoils produced by elastic/inelastic interaction between protons and atoms will result in device electronics property changes.An introduction of Geant4 running environment, software framework and functionalities is presented in the paper, and its applications to shielding and radiation damage effects are implementated. A simulation of mono-energetic protons indicates that the transversing ratio is above 100% as a result of nuclear reactions and becomes bigger as the incident proton energy increases with the spacecraft Al shell as the first shielding layer, secondary heavy-Z nucleus produced in Al layer all deposite with almost all neutrons,γ-rays and a part of protons, electrons transmitting out. For SPE spectrum, 'shifting effects' occurs with only higher part of incident proton spectrum transversing through Al shielding layer, the average proton energy increases drasmatically below 4mm of Al layer above which only linearly, and the transversing ratio decreases quickly below 10mm above which convergents to some about 10%.Finally, ionization effects of incident protons in various materials (Al, Si, H₂O ,SiO₂) are simulated andcompared with NIST reference data, including LET value and range. Energy deposited of Bragg curve in the incident direction is presented with its peak value and plateau stope as a function of incident proton energy and the physics process, such as with or without non-elastic interactions, energy deposited distribution in horizontal direction is also given and most of the energy deposit around proton trajectory with the radius less than a few millimeters, and it becomes bigger as the incident proton energy increases. For displacement damage in semiconductor material Si, information of primary recoil atoms are given by using D.H. Wright space electronics physics package, including the recoil types, production ratio, spectrum, average recoil energy and spatial distribution, the calculation uncovered the facts that primary recoils are nuclei from He to P as point distribution with most of which distribute along the proton trajectory, and their concentrations decrease in gradient manner. Lindhard-Robinson-Akkerman partitioning functions are applied to NIEL calculation based on previous primary recoils simulation as a function of incident proton enegy, with the results compared to reference data of Summers and Jun.