No abstract

Compton imaging represents a promising technique for range verification in proton therapy treatments. In this work, we report on the advantageous aspects of the i-TED detector for proton-range monitoring, based on the results of the first Monte Carlo study of its applicability to this field. i-TED is an array of Compton cameras, that have been specifically designed for neutron-capture nuclear physics experiments, which are characterized by $$\gamma $$ γ -ray energies spanning up to 5–6 MeV, rather low $$\gamma $$ γ -ray emission yields and very intense neutron induced $$\gamma $$ γ -ray backgrounds. Our developments to cope with these three aspects are concomitant with those required in the field of hadron therapy, especially in terms of high efficiency for real-time monitoring, low sensitivity to neutron backgrounds and reliable performance at the high $$\gamma $$ γ -ray energies. We find that signal-to-background ratios can be appreciably improved with i-TED thanks to its light-weight design and the low neutron-capture cross sections of its LaCl$$_{3}$$ 3 crystals, when compared to other similar systems based on LYSO, CdZnTe or LaBr$$_{3}$$ 3 . Its high time-resolution (CRT $$\sim $$ ∼  500 ps) represents an additional advantage for background suppression when operated in pulsed HT mode. Each i-TED Compton module features two detection planes of very large LaCl$$_{3}$$ 3 monolithic crystals, thereby achieving a high efficiency in coincidence of 0.2% for a point-like 1 MeV $$\gamma $$ γ -ray source at 5 cm distance. This leads to sufficient statistics for reliable image reconstruction with an array of four i-TED detectors assuming clinical intensities of 10$$^{8}$$ 8 protons per treatment point. The use of a two-plane design instead of three-planes has been preferred owing to the higher attainable efficiency for double time-coincidences than for threefold events. The loss of full-energy events for high energy $$\gamma $$ γ -rays is compensated by means of machine-learning based algorithms, which allow one to enhance the signal-to-total ratio up to a factor of 2.

Since its start in 2001 the n_TOF collaboration developed a measurement program on fission, in view of advanced fuels in new generation reactors. A special effort was made on measurement of cross sections of actinides, exploiting the peculiarity of the n_TOF neutron beam which spans a huge energy domain, from the thermal region up to GeV. Moreover fission fragment angular distributions have also been measured. An overview of the cross section results achieved with different detectors is presented, including a discussion of the 237Np case where discrepancies showed up between different detector systems. The results on the anisotropy of the fission fragments and its implication on the mechanism of neutron absorption, and in applications, are also shown.