Enhancing Bubble Nucleation Analysis in Scintillating Bubble Chambers Through Ultrasonic Ping and Echo Signal Processing

At Northwestern University's Physics and Astronomy Department, the Scintillating Bubble Chamber (SBC) team collaborates with Fermilab to detect dark matter using superheated noble liquids. Bubbles in these chambers emit acoustic chirps, often before they visibly form. Experimenters analyze these signals' frequency and intensity to help identify bubble nucleation from dark matter interactions. Instead of relying solely on bubble-generated pulses, we aim to ultrasonically “ping” bubbles and analyze their echoes, distinguishing them from background noise to refine dark matter detection. Using a Red Pitaya with piezo drivers and piezoelectrics for emission and reception, we generated and recorded arbitrary sinusoidal waveforms or chirps to capture echoes from bubbles. A high-voltage pulse from an ultrasonic emitter strikes the bubbles, producing echoes influenced by acoustic impedance differences. An ultrasonic sensor detects these weak signals, then pre-amplifies and filters to reduce noise. Although many range finders include built-in amplifiers, we added an external ultrasonic driver to boost performance. The Red Pitaya digitizes the amplified echoes for analysis, enhancing our understanding of how echo characteristics vary with environmental conditions—mirroring the bubble nucleation observed in the SBC’s chamber and representing potential dark matter interactions.