Speaker
Description
Neutrons are a highly penetrating radiation which can dominate the total adsorbed dose by the human body. Therefore, in different kind of facilities, it is essential to monitor neutron dose rates in order to ensure a minimal risk for workers, patients and public. This task is typically achieved by using commercial portable neutron detectors known as ambient neutron dosimeters. However, there are several concerns about the reliability of commercial ambient neutron dosimeters in modern facilities. In particular, those producing radiation fields with an important high energy contribution (E>20MeV) or a complex time structure [1, 2]. Reliability is a major issue indeed for the dosimetry and radiation protection in: 1) medical facilities, such as proton therapy, where high energy neutrons up to 250 MeV are produced as secondary stray radiation; 2) around synchrotron or cyclotron facilities, where either intended pulsed beams or beam losses produce short bursts of secondary neutron radiation; 3) pulsed facilities for fundamental research and applications, such as spallation, fusion neutron sources or high intensity lasers. Moreover, the International Commission on Radiation Units and Measurements (ICRU) has recently recommended the use of alternative definitions for the operational quantities that are currently in use for radiation protection. The new ICRU recommendation impacts directly on the expected performance of neutron dosimeters for energies lower than 100 eV and higher than 50 MeV. Accordingly, the LINrem project has been launched in 2018 in order to provide solutions to the new requirements of energy sensitivity and time resolution in neutron dosimetry with an special focus on medical applications.
In this work, the technical challenges for active and time-resolved neutron dosimetry in particle therapy are reviewed. It is discussed the impact of the new ICRU recommendation on the assessment, using commercial dosimeters, of neutron doses in hadron therapy. The nuclear data needs for novel high energy detector designs are also discussed. The conceptual design of LINrem dosimeters is presented and its performance is quantified by means of Monte Carlo simulations. Results are presented of the experimental validation of LINrem dosimeters in different facilities including proton therapy and pulsed neutron sources.
References
[1] J. Farah et al., Med. Phys. 42:5 (2015) 2572-2584.
[2] M. Caresana et al., NIMA 737 (2014) 203–213.