The performance of the new KETEK low-noise SiPM array series: Characterization in a Compton camera study

Compton cameras (CC) allow for spatially resolved γ detection. The γ-ray origins are reconstructed by measuring the interaction positions and energy deposits in the scatter and absorber components, allowing to determine the scattering angle. Consequently, the energy resolution of the CC components plays a major role in the component selection and detector design. For scintillators the energy resolution strongly depends on the scintillation material, but also on the photosensor and signal processing electronics. For our CC prototype, built from a 16 × 16 GAGG scintillation array (scatterer) with 1.6 mm crystal pitch and a monolithic LaBr3:Ce block (51 × 51 × 30 mm3), we investigated the energy resolution of the components in a readout configuration involving the new KETEK low-noise SiPM array series (PA33XXWL-0808) for the individual camera components and compared the performance to that of the previous generation (PA33XXWB-0808). Furthermore, we commissioned a CC prototype equipped with the new SiPM series, evaluated its energy resolution and performed a systematic study of the imaging capabilities for γ rays of 1274 keV (using a 22Na point source). For the GAGG scatterer an energy resolution of 9.4% was measured. An improvement between 0.9% and 1.8% was achieved due to the superior balance of SiPM saturation, PDE and noise compared to KETEK's previous SiPM array generation. For the absorber detector a comparable energy resolution was obtained for SiPM arrays of the two generations with comparable microcell sizes (47 μm vs. 50 μm). However, the reduced noise of the WL-SiPM arrays allowed to obtain an excellent energy resolution of 4.1% over a wider range of applied bias voltages (5.0 V - 6.0 V), and thus gains. The Compton camera prototype provided a spatial resolution below 6 mm and was capable of resolving shifts of the radiation source of 2 mm with an accuracy well below 1 mm.