The Verticalix test bench

Monday, Oct 12, 2020

The Verticalix test bench is a cryostat designed to measure very low dark currents. The dark current is the current that is thermally generated inside a semi-conductor detector in the absence of light, and is therefore strongly dependent on the temperature of the detector. Opposite to standard cryostats, Verticalix has no entrance window to let light entering the cryostat. Moreover, the inside of the cryostat is very cold: the environment of the detectors inside their housing is typically around 10 K, corresponding to a level of thermal radiation so small that it cannot be detected in the wavelength range of interest to ASTEROID (near infrared up to 2.1 µm). In this configuration, very low dark currents (« 1 e-/s/pixel) can be measured. The temperature of the detector can be set within a very wide range (typically 40 to 160 K), with a stability over days of about 1.5 mK. Some measurements under photon flux can also be performed with this test bench, using a small cryogenic black body. This is useful to quickly measure the response of the detector, or its linearity.