Speaker
Description
This contribution presents the Radio Neutrino Observatory in Greenland (RNO-G), designed to measure cosmic neutrinos in the EeV range through an array of radio antennas detecting nano-second-long radio flashes. The RNO-G electronic system is outlined, illustrating how signals are measured from the antennas to the recorded pulses. New instrumentation developments are presented, focusing on electric melters to install LPDA antennas into the Greenlandic ice sheet. The new system will simplify deployment and reduce positioning uncertainty to ±2cm (x/y) and ±1 degree (rotational). We report on field tests from the RNO-G site at Summit Station.
Summary (500 words)
Ultra-high-energy cosmic neutrinos can help us understand some of the most violent events in the universe, such as AGNs and gamma-ray bursts. To detect them, RNO-G has instrumented the Greenlandic ice sheet with several autonomous stations (8 built so far, 35 when completed) spaced 1.25 km apart. Each of these stations has an effective detector volume of ~1km^3 of glacial ice. When a neutrino with an energy in the EeV range interacts with a nucleus in the ice, the resulting particle shower emits coherent radio pulses on the Cherenkov cone due to a time-dependent charge imbalance. To record these pulses, the RNO-G stations consist of 3, 100m deep holes instrumented with 15 RX antennas as well as 8 LPDA antennas close to the surface. After an amplification stage, the pulses are digitized, and several trigger algorithms (based on amplitude or integrated power) decide what pulses to record and write to disc. This step reduces a continuous data stream with a sampling rate of 2.4 GHz to a per-station trigger rate of ~1Hz. We present the initial design and performance of the first 7 RNO-G stations as documented here [1].
The phased nature of the RNO-G construction allows for continuous improvement of instrumentation methods and hardware. One current improvement is the development of electrical melters for the deployment of LPDA antennas. Currently, the best method to deploy LPDA antennas is by digging 1.5 m deep trenches by hand into the glacier, to put 8 antennas per station just below the snow surface. This method comes with several problems apart from the high physical effort: The antennas can be easily damaged, the properties of the surrounding snow are not well understood, and positional and orientational uncertainty is high due to the broad width of the trenches. The electrical melter we developed solves these issues by melting a precise slot of 4cm width and 155cm length into the glacial ice sheet, perfectly suited to fit LPDA antennas. Two designs were developed, one to melt a horizontal slot for upward facing LPDA antennas to measure cosmic rays and one to melt a wedge shaped slot for downward facing LPDA antennas to measure neutrino interactions in the ice. Preliminary tests of the electrical melters were conducted, and a full deployment test is planned for July 2026 in Greenland. The tests include power consumption, melting speed, and accuracy of the declination angle. Due to the high elevation of the detector above 3000m, the nominal power produced by a generator is reduced, leading to a drop in efficiency, which was measured as well. Furthermore, as this method allows for deploying LPDA antennas several meters below the surface, it has the potential to increase the initial effective volume of the LPDA-trigger by up to 10%.
[1] S. Agarwal et al 2025 JINST 20 P04015