By Paul van der Hulst

In order to operate properly, the sensitive Transition Edge Sensors (TES) of the X-IFU X-ray instrument in Athena must be cooled down to around 100mK. The signals of multiple pixels on the image sensor are therefore transmitted over a single wire pair, which reduces the heat load on the refrigerators and wiring complexity. Unfortunately, fabrication tolerances in the lithographic filters that isolate the signals cause changes in the signal magnitude and signal pulse duration. This compromises the energy resolution of the detector by up to a few eV when no precautions are taken.

The paper describes a control method that compensates for the filter tolerances and restores the signal pulse shape. It re-uses already available hardware to compensate for the off-resonance series impedance of the filters. It requires only a minimal increase in calibration effort since most parameters are non-critical. Experiments show that the controller allows the preservation of single-pixel performance in multiplexed operation.

Access to the manuscript in ADS.