We have started the development of a gamma ray observation device for making astronomical observations.
The device is planned to be employed in an astronomical observation experiment using an a scientific balloon that is being planned by Nagoya University and Kavli IPMU.
The observation device will be carried to an altitude of 40 km using the balloon of JAXA, to observe celestial objects.
In 2022, the observation device was completed, and the achievements were presented and published at the SPIE International Conference (please see the link).

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/12181/1218172/Balloon-borne-narrow-field-of-view-semiconductor-Compton-telescope-concept/10.1117/12.2628199.short?SSO=1