Microwave amplification chain calibration in an axion haloscope via cavity-emitted radiation

In an axion haloscope, the weak photon signal, theoretically converted from axions, is captured by a detection cavity. The amplification chain assists the signal receiver to read the signal from the cavity and requires accurate calibration. Typically, the readout line is calibrated using the Y-factor method, involving a switch that directs the signal from either the detection line or the calibration line. However, this switch introduces several disadvantages. In response, we propose a calibration method that eliminates the need for a switch. In this approach, the cavity temperature is decoupled to its incoming noise source and can be controlled, resulting in excess or deficiency of the noise spectrum near its resonance frequency. The experimental result shows that the amplification chain can be calibrated directly using the temperature-varied cavity-emitted radiation.