Speaker
Description
CONUS+ has recently achieved the first detection of coherent elastic neutrino-nucleus scattering (CEνNS) of reactor antineutrinos on germanium nuclei in the fully coherent regime, and is now entering a precision phase. The dominant uncertainty in the first measurement was the energy scale, contributing 14% to the signal prediction uncertainty, motivating a dedicated sub-keV calibration campaign.
A neutron activation campaign was performed at the MPIK Low Level Laboratory, where one of the new 2.4 kg CONUS+ HPGe detectors was irradiated with a strong ²⁴¹AmBe source to produce ⁷¹Ge via neutron capture. The subsequent decay of ⁷¹Ge via electron capture populates atomic vacancy states, emitting characteristic K-, L-, and M-shell X-ray lines that serve as precision energy calibration points down to the detector threshold. For the first time, the ⁷¹Ge M-shell X-ray line was clearly resolved at (158.7±1.4) eVee, validating the CONUS+ energy reconstruction at the detection threshold level. This comprehensive validation covers the energy scale, energy resolution, trigger efficiency, and the separation of physical from noise events, demonstrating that a contribution below 4% to the signal prediction uncertainty is achievable.
In this poster I will present the analysis of the K-, L-, and M-shell X-ray lines from the activation campaign, the detector characterization results, and their implications for the CONUS+ energy calibration strategy, paving the way for precision CEνNS and beyond Standard Model physics measurements.