  An antihydrogen detector consisting of a thin BGO disk and a surrounding
plastic scintillator hodoscope has been developed. We have characterized the
two-dimensional positions sensitivity of the thin BGO disk and energy
deposition into the BGO was calibrated using cosmic rays by comparing
experimental data with Monte-Carlo simulations. The particle tracks were
defined by connecting BGO hit positions and hits on the surrounding hodoscope
scintillator bars. The event rate was investigated as a function of the angles
between the tracks and the energy deposition in the BGO for simulated
antiproton events, and for measured and simulated cosmic ray events.
Identification of the antihydrogen Monte Carlo events was performed using the
energy deposited in the BGO and the particle tracks. The cosmic ray background
was limited to 12 mHz with a detection efficiency of 81 %. The signal-to-noise
ratio was improved from 0.22 s^{-1/2} obtained with the detector in 2012 to
0.26 s^{-1/2} in this work.
