Rare Events Detected with a Bulk Acoustic Wave High Frequency Gravitational Wave Antenna

TL;DR

This paper reports the operation of a cryogenic Bulk Acoustic Wave gravitational wave detector over 153 days, observing rare transient events potentially linked to gravitational waves, with detailed analysis of their characteristics and environmental correlations.

Contribution

First demonstration of a high frequency BAW gravitational wave detector monitoring for rare events over extended periods, with analysis of observed transients and environmental factors.

Findings

Detected two transient events during 153 days of operation.

Events correlated with acoustic modes and environmental data.

Potential implications for high frequency gravitational wave detection.

Abstract

This work describes the operation of a High Frequency Gravitational Wave detector based on a cryogenic Bulk Acoustic Wave (BAW) cavity and reports observation of rare events during 153 days of operation over two seperate experimental runs (Run 1 and Run 2). In both Run 1 and Run 2 two modes were simultaneously monitored. Across both runs, the 3rd overtone of the fast shear mode (3B) operating at 5.506 MHz was monitored, while in Run 1 the second mode was chosen to be the 5th OT of the slow shear mode (5C) operating at 8.392 MHz. However, in Run 2 the second mode was selected to be closer in frequency to the first mode, and chosen to be the 3rd overtone of the slow shear mode (3C) operating at 4.993 MHz. Two strong events were observed as transients responding to energy deposition within acoustic modes of the cavity. The first event occurred during Run 1 on the 12/05/2019 (UTC), and was observed in the 5.506 MHz mode, while the second mode at 8.392 MHz observed no event. During Run 2, a second event occurred on the 27/11/2019(UTC) and was observed by both modes. Timing of the events were checked against available environmental observations as well as data from other detectors. Various possibilities explaining the origins of the events are discussed.