The IBEX background monitor

The IBEX Background Monitor (IBaM) provides a small and lightweight method for independently measuring IBEX’s high-energy proton background by integrating the flux of >∼14 keV protons over a ∼7° conical FOV. The IBaM is part of the IBEX-Hi sensor and has a co-aligned look direction. This paper describes the principle of the IBaM and details its design and responses. In particular, we show the response of major components to both ions and ultraviolet (UV) light background. We also provide the geometric factor and calculate expected count rates.