Modelling instrument background for CCD x-ray spectrometers in space

The European Space Agency (ESA) X-ray Evolving Universe Spectroscopy (XEUS) mission is designed as a follow-on to the ESA X-ray Multi Mirror (XMM-Newton) mission and may contain charge-coupled device (CCD) based instrumentation. Low instrument background is essential for the mission to maximise sensitivity. Results from XMM-Newton and the Japanese Space Agency Suzaku mission show that both the detector design and the orbit (LEO vs. HEO) have major impacts on the instrument background. This gives implications for the optimal instrument configuration for XEUS and other future missions. Here we use a Monte Carlo simulation technique, utilising the Geant4 toolkit, to model the instrument background for CCDs in-orbit. The model will be initially verified by simulating the background from the XMM-Newton and Suzaku missions and comparing this to real data obtained in-orbit. The simulated data will then be analysed to gain a better understanding of the cause of the background. Suggestions for minimizing the instrument background in future missions based on the results found here are included.