Optimizing timing performance of CdTe detectors for PET.

Area of Science:

• Medical Physics
• Semiconductor Detector Technology
• Nuclear Instrumentation

Background:

• Compound semiconductor detectors like CdTe and CdZnTe offer attractive properties but suffer from poor timing performance, limiting their use in commercial PET imaging.
• The standard constant-fraction discriminator method for pulse timing in these detectors yields a time resolution of ~10 ns (FWHM), with significant loss of coincidence events (~50%).

Purpose of the Study:

• To investigate parameters limiting the timing performance of Ohmic contact planar CdTe detectors using standard pulse timing methods.
• To develop and validate a novel digital pulse timing method for improved timing and energy resolution in CdTe detectors for PET applications.

Main Methods:

• Detailed investigation of jitter and time-walk errors using simulation and experimental measurements with standard pulse timing.
• Development of a new digital pulse timing method based on pattern recognition.
• Application of the digital method to correct for charge-trapping effects.

Main Results:

• The standard method resulted in ~10 ns time resolution (FWHM) and ~50% loss in coincidence events.
• The new digital method achieved a time resolution of 3.29 ± 0.10 ns (FWHM) for energies between 300-650 keV.
• Energy resolution improved from 4.83 ± 0.66% to 2.78 ± 0.002% (FWHM) at 511 keV after applying the digital method to correct charge trapping.

Conclusions:

• The developed digital pulse timing method significantly enhances the timing and energy resolution of CdTe detectors.
• This advancement overcomes limitations of standard methods, enabling full detection efficiency and improved PET imaging performance.
• Further improvements are possible with detector cooling and application to other detector structures.