Monitoring Individual Ion Bunches: The Ionoacoustic Approach

Ionoacoustics refers to the measurement of acoustic waves excited by ions as they slow down in matter. Detecting these acoustic signals with ultrasonic transducers enables the reconstruction of the longitudinal and transversal beam parameters with remarkable precision in an extensive range of beam intensities. Being radiation hard and straightforward to use, ionoacoustics complements the existing suite of particle detectors, especially for radiation sources with high particle fluxes. Experimental campaigns at various RF-based accelerators, i.e., a synchrotron, a clinical synchrocyclotron and a tandem accelerator, could demonstrate the sub-mm localisation of the Bragg peak with protons and heavier ions. Further, ionoacoustics was demonstrated to reveal lateral beam parameters and the beam intensity in transmission mode, i.e., without the particles stopping in the detector volume. One particularly interesting application case depicts laser-ion sources that benefit from the electromagnetic pulse resistance of ionoacoustic detector designs. Despite the extremely high fluxes, the ionoacoustic method was proven to be sensitive to the absolute particle number, which might become interesting for applications in the context of the Flash effect.