Nuclear Instruments and Methods in Physics Research A 439 (2000) 158}166Range}energy relation, range straggling and response functionof CsI(Tl), BGO and GSO(Ce) scintillators for light ionsV. Avdeichikov*, A.S. Fomichev, B. Jakobsson, A.M. Rodin,G.M. Ter-AkopianDepartment of Physics, Lund University, Box 118, S-22100 Lund, SwedenJoint Institute for Nuclear Research, 141980 Dubna, RussiaReceived 9 June 1999; received in revised form 31 August 1999; accepted 16 September 1999AbstractRange}energy relations and range straggling of H and He isotopes with the energy +50A MeV are measuredfor the CsI(Tl), BGO and GSO(Ce) scintillators with an accuracy better than 0.2% and 5%, respectively. The Si-Sci/PDtelescope was exposed to secondary beams from the mass separator ACCULINNA. The experimental technique is basedon the registration of the `jumpa in the amplitude of the photodiode signal for ions passing through the scintillationcrystal. Light response of the scintillators for ions 1)Z)4 is measured in energy range (5}50)A MeV, the results are ingood agreement with calculations based on Birks model. The energy loss straggling for particles with ῀E/E"0.01}0.50and mass up to A"10 in 286 μm ῀E silicon detector is studied and compared with theoretical prescriptions. The resultsallow a precise absolute calibration of the scintillation crystal and to optimize the particle identi"cation by the῀E}E(Sci/PD) method. 2000 Elsevier Science B.V. All rights reserved.PACS: 29.40.Mc; 29.40.WkKeywords: Inorganic scintillators; Light ions; Range and straggling1. IntroductionInorganic scintillators (Sci) like CsI(Tl), BGOand GSO(Ce) with photodiode (PD) readout havebecome popular detectors for charged particle registration.In combination with thin silicon detectorthe ῀E-Sci/PD assembly allows identi"cation ofions in a wide range of charge Z, mass A andincident energy E through ῀E}E analysis. Some* Corresponding author. Tel.: #46-46-222-0486.E-mail address: email@example.com (V. Avdeichikov)multidetector systems contain hundreds of identicaltelescopes [1}5]. In principle, each Sci/PD orSci/PMT element has its unique light response. Theenergy calibration and light output stability controlfor each element of a multidetector system is a verydelicate problem. Di!erent sophisticated calibrationprocedures have been developed [1,6}8], oftenbased on direct exposure of the telescopes to secondarybeams selected by a magnetic spectrometer.A regular (re)calibration of scintillation detectors isneeded. For this purpose, e.g., the INDRA setup ,is equipped both with a number of silicon calibrationtelescopes and a fast light pulse laser source.0168-9002/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved.PII: S 0 1 6 8 - 9 0 0 2 ( 9 9 ) 0 0 9 4 4 - 4
162 V. Avdeichikov et al. / Nuclear Instruments and Methods in Physics Research A 439 (2000) 158}166Table 1Energy}range relations and projected range straggling of some light ions in GSO(Ce) and CsI(Tl) and BGO scintillatorsParticle Energy Range Straggling, σ(R)/R(MeV)Experiment TRIM95 PARPERTH Experiment TRIM95(mm) (mm) (mm) (%) (%)GSO(Ce)H 50.2 5.96 5.63 5.96 2.8 5.0H 67.8 5.96 5.69 5.96 3.1 4.2H 80.3 5.96 5.67 5.98 2.8 4.5He 205.7 5.96 5.92 5.76 3.1 4.2He 246.3 5.96 6.00 5.68 3.2 4.0CsI(Tl)H 53.9 10.94 10.42 11.27 3.2 5.1H 72.1 10.94 10.52 11.25 2.7 4.5H 84.5 10.94 10.37 11.04 2.3 4.6He 200.0 9.78 9.28 9.90 2.3 3.8He 257.7 10.94 10.86 11.42 2.2 4.0BGOH 67.2 9.98 9.43 9.89 2.8 5.0H 90.1 9.98 9.48 9.88 2.6 4.9H 105.7 9.98 9.31 9.68 2.6 4.6Ref.  Code is based on algorithm of Ref. .Ref.  Code is based on algorithm of Ref. .4. Response function4.1. ExperimentAn accurate measurement of the response functionof a scintillator is necessary in order to establishthe energy scale for each registered ion.Figs. 4}6 present measured light output (in channels)of CsI(Tl), BGO and GSO(Ce) scintillators tolight ions. By using a Bi beta source to irradiatethe PD from the side of the back contact we obtainedthe light response in keV. The position of thepoints of the light response could be determinedwithin 3}5 channels accuracy, while the uncertaintyin the energy is around 0.36%.The response of activated inorganic crystals toionizing particles is a non-linear function of theparticle energy. In the semiempirical model formulatedby Birks  and developed by Murrayand Meyer  this nonlinear response is causedby quenching process governed by the stoppingpower, dE/dx, along the particle path. The lightoutput per unit length, d¸/dx, isde"ned asdE/dxd¸/dx"const.(4)1#kB dE/dxwhere B dE/dx represents the density of quenchingcenters per unit distance and k is a quenchingparameter. For the purpose of analytical integrationof Eq. (4), authors  used the followingapproximation, suitable only for very light ions andfor energies higher than a few MeV/nucleon,dE/dxKc AZ(5)Ewhere c is a normalization constant. The resultingrelation is¸(E, A, Z)"a E!a AZ ln E#a AZa AZ (6)where a and a are free parameters. The solidcurves in Figs. 4}6 are least-squares "ts to theresponse function of Eq. (6) with parameters asgiven in the "gures.