ATHENA’s first detection of cold antihydrogen atoms relied on their annihilation signatures in a sophisticated particle detector. We will review the features of the ATHENA detector and its applications in trap physics. The detector for a new experiment ALPHA will have considerable challenges due to increased material thickness in the trap apparatus as well as field non‐uniformity. Our studies indicate that annihilation vertex imaging should be still possible despite these challenges. An alternative method for trapped antihydrogen, via electron impact ionization, will be also discussed.