Lead-free MCP to improve coincidence time resolution and reduce MCP direct interactions

Area of Science:

• Nuclear Medicine
• Particle Physics Detectors
• Materials Science

Background:

• Direct, event-by-event imaging of positron annihilation is crucial for nuclear medicine.
• Cherenkov emission offers ultrafast timing for detectors.
• Current microchannel-plate photomultiplier tubes (MCP-PMTs) suffer from gamma ray interactions with lead, degrading timing.

Purpose of the Study:

• To develop a novel MCP-PMT with improved gamma ray insensitivity and timing performance.
• To overcome the limitations of lead-containing MCPs in high-resolution imaging.

Main Methods:

• Developed a new MCP-PMT utilizing a borosilicate glass-based MCP.
• Conducted coincidence experiments to evaluate gamma ray insensitivity and timing resolution.
• Optimized the voltage divider circuit for enhanced performance.

Main Results:

• Reduced direct gamma ray interactions with the MCP by a factor of 3.4.
• Achieved a coincidence time resolution of 35.4 ± 0.4 ps FWHM (5.31 mm position resolution) without pulse height/area cut.
• Improved resolution to 28.7 ± 3.0 ps with amplitude event selection.

Conclusions:

• The new borosilicate glass MCP-PMT significantly reduces gamma ray interactions, improving detector performance.
• This advancement is a key step towards enabling direct positron annihilation imaging.
• The enhanced timing resolution facilitates higher spatial accuracy in nuclear imaging.