The first results were obtained at the νGeN experimental facility aimed at the search for coherent neutrino scattering and other interactions. Alexey Lubashevskiy, the Head of Sector No. 1 of the Experimental Department of Nuclear Spectroscopy and Radiochemistry of the Laboratory of Nuclear Problems JINR, comments on the νGeN experiment, the status of work, and acquired results.

At present, coherent elastic neutrino−nucleus scattering is an intriguing task for modern physics. This process has not been detected for reactor neutrinos yet. After detection, it will open the way to the search for New Physics by searching for nonstandard neutrino interactions, the search for sterile neutrinos, and other investigations. Moreover, it will open up the possibility of applied research like reactor monitoring and remote control.

Measurements with the first detector of the νGeN spectrometer have shown the absence of considerable differences in the spectra in low energy fields at the reactor, both operating and shutdown.

The νGeN experimental setup is located under Reactor Unit #3 of the Kalinin nuclear power plant (KNPP) at a distance of about 10 m from the centre of the reactor core. This gives a possibility for operating an enormous neutrino flux greater than 5⋅10¹³ neutrinos/ (cm²⋅sec). The location is indicated in the figure.

Figure 1. Location of the experimental room at KNPP

Structural materials of the reactor provide good shielding against cosmic radiation equal to 50 m water equivalent. Specially developed high-purity low-threshold germanium detectors are used to record neutrino signals. The detectors at the KNPP are surrounded by a system of passive and active shielding reducing the external background in the region of interest.

Figure 2. Left: Basic diagram of facility shielding. Right: Facility installation

In 2021, works on equipment optimisation were completed and the planned measurements started. The detector energy resolution reached at the KNPP is 101.6(5) eV (FWHM). The signal detection efficiency is above 80% for signals with energies above 250 eV.

Figure 3. Low-energy regions of experimental spectra taken from the reactor in operation and during its shutdown

More details are available in the report “First Results of the νGeN Experiment on Coherent Neutrino Scattering” by A. V. Lubashevskiy made on 29.09.2021 at the seminar.

Alexey Lubashevskiy,
Head of Sector No 1 of the Experimental Department of Nuclear Spectroscopy and Radiochemistry,
on behalf of the νGeN collaboration
Figures and photos by the author