Abstract A feasibility study is presented on a newly developed microdosimetry system named Octobox, for its application in low dose rate, mixed radiation environments. A full characterization of the device was performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan, out-of-field of various heavy ion radiation fields — 290 MeV/u C, 230 MeV/u and 490 MeV/u Si and 400 MeV/u Ne ions, as well as a low dose rate Rn environment at the Australian Nuclear Sciences and Technology Organization (ANSTO). The device was shown to collect adequate statistics in a short period of time whe...