What is the function of the Light Pipe?

• A. Convert photons to electrons
• B. Shield radiation
• C. Generate gamma rays
• D. Help direct photons from crystal into Photomultiplier Tubes (PMTs)

Answer: (D)

Light pipes act as optical guides that channel the light produced in the scintillator crystal toward the photomultiplier tubes. They use total internal reflection to transport photons efficiently, increasing the number that reach the PMTs and improving the detector’s signal quality. The purpose is to couple the scintillation light to the PMTs so it can be converted into an electrical signal. The other options describe functions not performed by light pipes: converting photons to electrons happens at the PMT’s photocathode, shielding radiation is done by shielding materials, and generating gamma rays is not a role of the light pipe.