Design optimization of a 1-D array of stemless plastic scintillation detectors

Area of Science:

• Medical Physics
• Materials Science
• Detector Physics

Background:

• Stemless plastic scintillation detectors (SPSDs) combine plastic scintillators and organic photodiodes.
• SPSDs are suitable for dosimetry in small radiation fields.
• Previous work has not systematically optimized the photodiode component of SPSDs.

Purpose of the Study:

• To optimize the design of a 1D array of SPSDs to maximize measured signal.
• To improve spatial resolution without degrading signal-to-noise ratio.
• To retain benefits of plastic scintillation detectors while avoiding challenges of optical fiber systems.

Main Methods:

• Fabrication involved etching ITO-covered PET, spin-coating with PSS and P3HT:PCBM, and adding aluminum electrodes.
• Optimization variables included spin coater speed (film thickness), P3HT:PCBM ratio, solution concentration, and scintillator coating.
• Substrate cleaning and material deposition were performed using specific chemical and physical processes.

Main Results:

• Increasing film thickness from ~80 nm to ~138 nm increased signal by ~7.7 times.
• A P3HT:PCBM ratio of 4:1 yielded ~3.5 times higher signal compared to 1:1.
• Optimized devices showed a 24-fold increase in sensitivity (~0.02 nC/cGy to ~0.5 nC/cGy).

Conclusions:

• The photodiode component of SPSDs was systematically optimized to enhance signal output.
• The most efficient device utilized a 2:1 P3HT:PCBM ratio and 4% solution concentration.
• Coating the scintillator with white paint improved signal output by approximately 2.2 times.