Supersonic gas curtain-based in-vivo transverse beam profile monitoring for medical accelerators

To ensure patient safety, treatment effectiveness, and facility efficiency, each ion beam therapy facility requires a complete online characterization of the charged particle beam. Existing dosimetry methods are either limited in the information they provide or invasive to the beam, highlighting the need for new in-vivo dosimetry solutions. Since 2015, the QUASAR Group at the Cockcroft Institute, UK has been developing non-invasive beam monitors for medical accelerators. Accurate monitoring of the transverse beam profile is the first step toward achieving in-vivo dosimetry. The monitor, under development, utilizes a supersonic gas curtain that interacts with the charged particle beam, using the resulting impact ionization to measure the transverse beam profile. A prototype monitor was successfully tested for proof-of-concept measurements at the Dalton Cumbrian Facility’s pelletron accelerator (UK). Measurements were conducted using various beam parameters with both proton and carbon ion beams. This contribution presents the monitor's design and operating principle, experimental results from the measurements, and additional planned improvements aimed at achieving in-vivo dosimetry.