Thin segmented silicon detectors for single ion tracking in carbon ion beam therapy: Performance insights

Carbon ion radiotherapy (CIRT) leverages the unique physical and radiobiological properties of carbon ions to achieve superior dose distribution and enhanced biological effectiveness, making it an effective treatment for challenging tumors while maximizing the sparing of healthy tissues. Accurate beam monitoring is essential to ensure that the dose distribution aligns with the prescribed treatment plan, requiring devices that provide precise and rapid real-time feedback on beam parameters to the dose delivery system. Single-particle discrimination could provide the best sensitivity and allow particle tracking; however, this feature presents a challenge for a transparent and large device, as needed for a beam monitor in particle therapy.

This work reports the performance of thin (20-60 µm thick) strip and pad silicon detectors with carbon ions at clinical energies and fluences.

The results demonstrate that their fast and short response times (∼ ns) allow discriminating individual carbon ions in a therapeutic beam, producing well-defined signals that can be easily distinguished from noise and achieving a single-hit temporal resolution lower than 26 ps. Furthermore, potential issues such as charge sharing, which can lead to counting inefficiencies, were found to be negligible.

These findings suggest that thin segmented silicon detectors are a promising technology for developing devices for monitoring therapeutic carbon ion beams with single particle sensitivity. Such a demanding feature will increase the beam delivery flexibility needed for many applications discussed in this work, such as range verification through prompt gamma timing, radiobiological experiments with very low beam intensity, and ionradiography.