Fabrication and measurements of plastic scintillating fibers

Abstract

Sixty kilometers of plastic scintillating fibers, 1 mm in diameter, have been manufactured using a preform/tube technology. The fibers consist of a polystyrene core surrounded by a polymethylmethacrylate cladding. The fabrication method is described and evaluated both qualitatively and quantitatively. A great effort has been made in order to measure the optical properties of the polymer at the different steps of the production. The global process efficiency is not more than 40% due to the yield of the polymerization process. Using a ternary blue scintillator, the mean light yield for a minimum ionizing particle, passing through a 1 mm diameter fiber at a distance of 1 m, is 5.4±0.6 photoelectrons. The mean attenuation length fitted between 0.5 and 2.0 m is 1.9±0.2 m. Some specific experiments that give independent measurements of core and interface losses are also reported. The principal cause of light loss is due to the lack of transparency of the polystyrene which leads to a spectral shift in fiber emission. This absorption already appears in the preform rods indicating that the purification and the polymerization process are of great importance. The attenuation length related to core losses is measured at the level of 3 m. The interface losses are about 10 −5–10 −4 per reflection leading to an equivalent attenuation length of 7 m.