We conducted the first cooling test of the NINJA cryostat. In this test, only the optical bench and the thermal shields were installed inside the cryostat. Using a mechanical cooler, we confirmed that the entire optical bench could be cooled to below 50 K (β220Β°C), and that it could be maintained at the planned operating temperature of 75 K (β198Β°C) through temperature control using heaters.
