Top: receiver noise temperature in the Q band derived from two absorbers at ambient and liquid N₂ temperatures. Middle: system temperature (receiver + background cold load) when different elements of the system are inserted in the beam path of the receiver: free path (black), chamber (red), chamber plus RF coil (blue), and chamber plus RF coild plus Teflon^TM windows (violet). The inset shows a zoom-in on frequency with the receiver temperature (top panel; free path) shifted by 10 K in cyan. Bottom: temperature difference between background (BCL) and internal (ICL) cold loads. Colours correspond to the same conditions as those indicated in the top panel. The receiver noise, system temperature, and the cold load temperature differences are in K.