Improved EMCCD gamma camera performance by SiPM pre-localization.

Area of Science:

• Nuclear physics
• Medical imaging instrumentation
• Radiation detection

Background:

• Electron-multiplying charge-coupled devices (EMCCDs) offer high spatial resolution for gamma imaging but are susceptible to noise.
• Silicon photomultipliers (SiPMs) have been previously used to reject false-positive EMCCD events using sum signals.

Purpose of the Study:

• To develop and evaluate a next-generation hybrid camera integrating individual SiPM signals with EMCCD readout.
• To enhance gamma-ray imaging by improving event discrimination and energy resolution.

Main Methods:

• Utilized individual SiPM signals and maximum likelihood estimation (MLE) for pre-localization to distinguish true from false events in CCD frames.
• Employed SiPM signals for improved energy discrimination.
• Tested the hybrid detector with a CsI:Tl crystal at 140 keV.

Main Results:

• Achieved a signal-to-background ratio (SBR) improvement of 5.9, 4.0, or 2.2 with MLE pre-localization (1.06 mm accuracy), at the cost of rejecting 47%, 9%, or 4% of events, respectively.
• Improved energy resolution from 50% to (19 ± 3)% by combining pre-localization and SiPM energy estimation.
• Maintained spatial resolution at 180 µm.

Conclusions:

• The hybrid CCD-SiPM camera effectively discriminates true events and enhances gamma-ray imaging performance.
• This technology offers significant improvements in signal-to-background ratio and energy resolution for scintillator-based detectors.