ABSTRACT
When the absorbed dose for high-energy radiation beams is measured by using a plastic scintillation detector (PSD), most of the light reaching the light-measuring device is scintillating light emitted from the scintillator. However, a portion of the light is a result of the stem effect within the optical fiber itself and it has an adverse influence on the real-time measurement of the pure scintillation signal as a noise component. https://www.w3.org/1998/Math/MathML"> Â 1 - 5 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315372655/b2ce6ef4-5376-4be5-9af3-87940a039f56/content/eq564.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> The main components causing the stem effect in the optical fiber during beam irradiation are fluorescence and Čerenkov radiation or a combination of these two noise components, as described previously in Chapter 1. First, fluorescence is the emission of light stimulated in an optical fiber simultaneously with the absorption of incident radiation, and it has an average lifetime of nanoseconds range. https://www.w3.org/1998/Math/MathML"> Â 6 N e x t https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315372655/b2ce6ef4-5376-4be5-9af3-87940a039f56/content/eq565.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , Čerenkov radiation or light is produced by the direct action of charged particles passing through a transparent medium at a velocity greater than that of light in the same medium. https://www.w3.org/1998/Math/MathML"> Â 3,7 , 8 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315372655/b2ce6ef4-5376-4be5-9af3-87940a039f56/content/eq566.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> This phenomenon is akin of a supersonic airplane reaching Mach speed.
