A beam-driven proton irradiation setup for precision radiation damage tests of silicon detectors

Abstract

A proton irradiation site for silicon detectors has been developed and commissioned at the Bonn Isochronous Cyclotron. The accelerator provides 14 MeV proton beams of up to 1 $\hat{I}¼$A at beam widths of a few mm to the setup. Devices Under Test (DUTs) are irradiated inside a cooled, thermally-insulated box at $\le$-20°C, while being moved through the beam in a row-based scan pattern to achieve uniform fluence distributions. Custom-made diagnostics allow for beam-based, on- and offline dosimetry, enabling a beam-driven irradiation routine which produces uniform fluence distributions with standard deviations $\ll 1\%$. Dedicated irradiations of thin titanium foils are performed to compare the commonly-used dosimetry via metallic foil activation to the beam-based approach. Within the error margins, both methods are in agreement, whereas the beam-based technique yields lower uncertainties of typically $\le 2\%$. Simulations indicate a reduction of the initial proton energy to 12.28(6) MeV on the DUT. Characterization of six, 150 $\hat{I}¼$m-thin, passive LFoundry sensors before and after irradiation yield a proton hardness factor of $\hat{I}{º}_{\text{p}}=3.71(11)$, which is in agreement with expectations, allowing to irradiate up to $10^{16}{\text{n}}_{eq}/{\text{cm}}^2$ within a few hours.