Data reduction for a calorimetrically measured 163Ho spectrum of the ECHo-1k experiment

The electron capture in 163 Ho experiment (ECHo) is designed to directly measure the effective electron neutrino mass by analysing the endpoint region of the 163 Ho electron capture spectrum. We present a data reduction scheme for the analysis of high statistics data acquired with the first phase of the ECHo experiment, ECHo-1k, to reliably infer the energy of 163 Ho events and discard triggered noise or pile-up events. On a first level, the raw data is filtered purely based on the trigger time information of the acquired signals. On a second level, the time profile of each triggered event is analysed to identify the signals corresponding to a single energy deposition in the detector. We demonstrate that events not belonging to this category are discarded with an efficiency above 99.8%, with a minimal loss of 163 Ho events of about 0.7%. While the filter using the trigger time information is completely energy independent, a slight energy dependence of the filter based on the time profile is precisely characterised. This data reduction protocol will be important to minimise systematic errors in the analysis of the 163 Ho spectrum for the determination of the effective electron neutrino mass.