The development of detectors for protons and heavy particles is a long-lasting research topic not only for fundamental applications, but more recently, in the medical field for hadron therapy of cancer. In this application, ion beams are used for the controlled treatment of cancer by focusing them onto small volumes, to avoid the spreading of the radiation to healthy tissues. For this reason, there is an increasing demand of systems optimized for the accurate in-situ, real-time recording and mapping of the dose delivered during a treatment plan.
In the framework of the project FIRE-“Flexible organic Ionizing Radiation dEtectors” (CSN5), which propose to develop innovative radiation detectors based on Organic Thin Film Transistors (OTFTs), we study a novel approach to direct detect protons by organic materials.
The direct detection of 5-MeV protons by flexible organic thin film devices is here reported for the first time . Mechanical flexibility, portability, low cost of fabrication and human tissue equivalence are important properties which make this technology an excellent candidate for the development of wearable proton dosimeters to be employed during proton therapy treatments or in other areas. Moreover, exploiting the coupling between the organic semiconductor and the plastic substrate, this class of detectors offers the unique possibility to operate them both in real-time mode and in integration mode. In fact, while the energy absorbed from the proton beam by the organic semiconductor is registered by an instantaneous increase of current, the energy released in the plastic substrate generates an accumulation of trapped charges which induces an increase of the device conductivity proportionally to the total dose absorbed by the system. This allows to measure simultaneously and independently the instantaneous and the cumulative dose absorbed by the device recording two different information regarding the irradiation condition of the sensing system.
 I. Fratelli, A.Ciavatti et al, Science Advances, 7, 16, eabf4462 (2021)