Wide-range tracking and LET-spectra of energetic light and heavy charged particles

摘要

We developed a highly-selective technique to measure the energy loss and linear-energy-transfer (LET) spectra of energetic charged particles in high-resolution and over a large collection of particle-event types. Precise and wide-range spectral and tracking measurements were performed with a single semiconductor pixel detector. The quantum-counting sensitivity, high-granularity and per-pixel spectrometric response of the Timepix ASIC chip enable the detailed spectral-tracking registration of single charged particles across the detector semiconductor sensor. Both the deposited energy along the particle trajectory (energy loss) and the path length of the particle track across the semiconductor sensor are precisely measured for each particle. This allows for the determination of the particle LET in silicon in high accuracy and over a wide-range of energies, particle types and directions. The tracking and energy loss response together with the resolving power at the particle-event level make it possible to selectively provide LET distributions of the light and heavy charged particle components in mixed-radiation and omnidirectional fields. This technique applies to energetic (E ＞ 10 MeV/u) charged particles generating tracks greater than the pixel size and incident at non-perpendicular direction (＞20°) to the sensor plane. The technique applies also to electrons of energy above few MeV as well as highly energetic and minimum-ionizing-particles (MIPs). We make use of existing and in part newly collected data at well-defined radiation fields with proton and light ion beam accelerators. Flexible measurements, ease of deployment and online response are possible by the use of compact readout electronics such as the miniaturized radiation camera MiniPix (size ＜ 8 cm, weight ＜ 50 g) operable by any PC. Results are given for protons and light ions (He, C) of selected energies above 10 MeV/u and directions (2π FoV). We include also electrons (20 MeV). Selective and detailed LET spectra are produced over a wide range (10~(-1) to 10~2 keV/μm) in silicon.