Figure 3
From: Extremely Low Loss Phonon-Trapping Cryogenic Acoustic Cavities for Future Physical Experiments

Measured impedance (absolute value and phase) of the 5th OT of the longitudinal mode (15.7 MHz) at 3.75 K for the cavity number 3.
From: Extremely Low Loss Phonon-Trapping Cryogenic Acoustic Cavities for Future Physical Experiments

Measured impedance (absolute value and phase) of the 5th OT of the longitudinal mode (15.7 MHz) at 3.75 K for the cavity number 3.