  MIRC-X is an upgrade of the six-telescope infrared beam combiner at the CHARA
telescope array, the world's largest baseline interferometer in the
optical/infrared, located at the Mount Wilson Observatory in Los Angeles. The
upgraded instrument features an ultra-low noise and fast frame rate infrared
camera (SAPHIRA detector) based on e-APD technology. We report the MIRC-X
sensitivity upgrade work and first light results in detail focusing on the
detector characteristics and software architecture.
