Boron thin films and CR-39 detectors in BNCT: A method to measure the ¹⁰B(n,α)⁷Li reaction rate

The working principle of the Boron Neutron Capture Therapy (BNCT) is the selective delivery of a greater amount of boron to the tumor cells than to the healthy ones, followed by the neutron irradiation that will induce the emission of α-particles and recoil ⁷Li nuclei through the ¹⁰B(n,α)⁷Li reaction. The objective of this work is to present a setup composed of a boron thin film coupled with CR-39. Alpha and ⁷Li particle coming from the boron films are used to quantify neutron boron reaction and are detected by CR-39. The nuclei compounding of this detector, H, C and O, will undergo fast neutrons reactions, which will be detected in the CR-39 itself. In this way, the ¹⁰B(n,α)⁷Li reaction and the contribution of fast neutrons to the flux can be determined at the same time. These measurements are essential for treatment planning as well as for studies of the biodistribution of ¹⁰B-carrier drugs and tissue microdosimetry. The boron films were deposited on stainless steel substrates through the sputtering technique and irradiated with thermal neutrons at the reactor IEA-R1 located at IPEN, São Paulo/SP, Brazil. Here we show the first results on the characterization of these thin films and calibration of the proposed setup. - Highlights: ► Homogeneous boron thin films were successfully deposited using the sputtering technique. ► Boron thin films allow for the direct measurement of the ¹⁰B(n,α)⁷Li reaction rate. ► CR-39 was calibrated for the evaluation of fast neutron contribution in BNCT irradiations