Abstract
Abstract
We characterize a novel instrument designed for radiation field decomposition and particle
trajectory reconstruction for application in harsh radiation environments. The device consists of
two Timepix3 assemblies with 500 µm thick silicon sensors in a face-to-face geometry. These
detectors are interleaved with a set of neutron converters: 6LiF for thermal neutrons,
polyethylene (PE) for fast neutrons above 1 MeV, and PE with an additional aluminum recoil proton
filter for neutrons above ∼4 MeV. Application of the coincidence and anticoincidence
technique together with pattern recognition allows improved separation of charged and neutral
particles, their discrimination against γ-rays and assessment of the overall directionality
of the fast neutron field. The instrument's charged particle tracking and separation capabilities
were studied at the Danish Center for Particle Therapy (DCPT), the Proton Synchrotron, and Super
Proton Synchrotron with protons (50–240 MeV), pions (1–10 GeV/c and 180 GeV/c). After developing
temporal and spatial coincidence assignment methodology, we determine the relative amount of
coincident detections as a function of the impact angle, present the device's impact angle
resolving power (both in coincidence and anticoicidence channels). The detector response to
neutrons was studied at the Czech Metrology Institute (CMI), at n_ToF and the Los Alamos Neutron
Science Center (LANSCE), covering the entire spectrum from thermal up to 600 MeV. The measured
tracks were assigned to their corresponding neutron energy by application of the time of flight
technique. We present the achieved neutron detection efficiency as a function of neutron kinetic
energy and demonstrate how the ratio of events found below the different converters can be used to
assess the hardness of the neutron spectrum. As an application, we determine the neutron content
within a PMMA phantom just behind the Bragg-peak during clinical irradiation condition with
protons of 160 MeV.