High energy proton induced luminescence in F-doped polyvinyltoluene L. Torrisi a, * , A. Desiderio b , G. Foti b a Dipartimento di Fisica, Istituto Nazionale di Fisica della Materia, Universit  a di Messina, Ctr. Papardo-Sperone 31, I-98166 S Agata, Messina, Italy b Dipartimento di Fisica, Istituto Nazionale di Fisica della Materia, Universit  a di Catania, Messina, Italy Abstract Fluorine-doped polyvinyltoluene (PVT) shows a luminescence peak emission at 432 nm under proton beam irra- diation. The conversion eciency, typically 2% at 60 MeV, has been investigated in the 5±62 MeV proton energy range. The luminescence yield has been measured as a function of the ionization energy loss. The energy loss has been evaluated through a thin ionization chamber in the range 1±10 MeV mm 1 . No dose-rate eect has been detected in the adopted proton ¯ux 10 6 ±4 ´ 10 8 cm 2 s 1 . The experimental data are discussed by modelling the interaction between proton±organic molecules as electronic excitations, including recombination processes up to the second order. Ó 2000 Elsevier Science B.V. All rights reserved. PACS: 42.70.Jk; 78.60.Ya Keywords: Plastic scintillator; Luminescence; Ionization energy loss; Quenching 1. Introduction Polyvinyltoluene (PVT) is an organic polymer, the monomer of which contains a benzenic ring bonded to a CH 3 -group and to a CH 2 ±CH-group. The high conversion eciency in the light emission up to 2% makes these scintillators very attractive as large nuclear detector [1,2]. In the organic medium the molecule itself is the primary agent for the energy conversion. Accord- ing to Birks [3], a small fraction of the energy of the incoming beam produces electronic excitation in the benzenic ring and singlet states whose de-excitations is responsible for the fast light emission, typically 2.4 ns. However, most of the ionization and excitation leads to wasteful pro- cesses in which the energy is eventually dissipated thermally or causes temporary or permanent mo- lecular damage at high proton ¯uency (1 KGy). Activators as ¯uorine can be added to obtain pe- culiar optical properties, such as wavelength shift, high scintillation eciency, and a better coupling with detector system [4]. In order to get a constant value of ionization energy loss for a variety of proton beam energy Nuclear Instruments and Methods in Physics Research B 166±167 (2000) 664±668 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +39-90-6765052; fax: +39-90- 601007. E-mail address: torrisi@alpme2.m3infn.it (L. Torrisi). 0168-583X/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 1 1 7 9 - 9