Exploring the limiting timing resolution for large volume CZT detectors with waveform analysis.

Area of Science:

• Nuclear Instrumentation
• Detector Physics
• Materials Science

Background:

• Accurate timing is crucial for many applications of radiation detectors, including Compton scattering imaging and time-of-flight measurements.
• Large-volume 3D position-sensitive detectors offer advantages in sensitivity and spatial resolution but present challenges in achieving precise timing.

Purpose of the Study:

• To investigate the limiting timing resolution of a large-volume 3D position-sensitive Cadmium Zinc Telluride (CZT) detector.
• To determine the impact of waveform modeling on timing accuracy.
• To establish a theoretical lower bound for timing error and compare it with experimental results.

Main Methods:

• Utilized a 3D position-sensitive CZT detector with a volume of 1 cm³.
• Obtained interaction timing information by fitting measured cathode waveforms to pre-defined waveform models.
• Compared the timing resolution achieved using several different waveform models.
• Developed a detailed model of the cathode waveform as a function of interaction location and energy deposition.

Main Results:

• Achieved timing resolutions of approximately 9.5 ns for 511 keV full-energy events and 11.6 ns for events with energy deposition above 250 keV.
• Derived a theoretical lower bound for timing error, which closely matched experimental predictions.
• Identified the correlation between sampled amplitudes in cathode waveforms as a significant factor limiting achievable timing resolution.

Conclusions:

• The best achievable timing resolution in the tested 1 cm³ CZT detector is approximately 10 ns.
• Detailed modeling of cathode waveforms is essential for optimizing timing resolution.
• Understanding waveform amplitude correlations is critical for further improvements in timing performance for CZT detectors.