Description
This work presents the first tests performed with the Timepix4 detector in scattered electron beams used for FLASH radiotherapy. Unlike conventional radiotherapy, FLASH delivers radiation at ultra-high dose rates, where the temporal structure of the beam plays a key role in the radiobiological response. Since standard dosimetry devices face important limitations under these conditions, Timepix4 was investigated as a potential tool for beam monitoring and characterization. Measurements carried out at the Mobetron accelerator at CHUV demonstrated that the detector can resolve individual pulses and provide detailed timing information, including pulse frequency, pulse width, and intensity. The results showed good agreement with the nominal machine parameters and revealed pulse-to-pulse variations in high dose rate operation that could be relevant for ensuring beam reproducibility.
In addition, Timepix4 was used to study the characteristics of the scattered radiation field and to compare conventional and high dose rate modalities. Particle cluster analysis showed no statistically significant differences between the two modes, supporting the use of measurements from either modality for future ambient dose assessments. Measurements outside the treatment room also demonstrated the capability of the detector to detect radiation levels below the sensitivity of conventional monitoring systems and to resolve individual beam pulses. Although saturation effects and readout limitations were observed at high particle rates, correction methods partially restored linearity. Ongoing work focuses on understanding the detector rate capability and optimizing measurements for accurate characterization of the scattered field and future in-beam applications.