Juhee Lee and Sunkee Kim

1. The Simulation of the quenching factor and the channeling effect for the CsI(Tl) and NaI(Tl) crystals Juhee Lee and Sunkee Kim 151-747 Seoul National University Shillim-dong Kwanak-gu Seoul Korea, Republic of. ABSTRACT We simulate the measured energy spectrum of the CsI(Tl) and NaI(Tl) crystal with a BC code and a scintillation efficiency curve described by the saturation model. This results are compared with experimental quenching factors and they show similar tendencies according to the ion’s kinetic energy. With this tool and the crystallographic configuration, we also study about the channeling and the blocking effects in those crystals. Although these effects could modulate the estimated cross-section between a WIMP and a target nucleus, since there are few events of the blocking effect and the various amounts of their contributions to the ion’s penetrations, we can hardly discriminate those events in the measured energy spectrum in our simulation. In the saturation model, the scintillation efficiency can be described by the stopping power of an ion and the concentration of activated ions. It is supported by the experiments for the electron, proton and alpha(fig.1) and can be extended to other ions of higher atomic numbers. With that relation and the simulation tool, we can reproduce the measured energy spectrum of a scintillation detector. We use MARLOWE and TRIM as BC and MD simulation tools respectively. When an ion goes into the symmetric axis or plain, it can interact with only electrons, thus, its penetration and light yield are drastically increased. It is due to the channeling or blocking effect according to the start position of an ion. We can simulate these effects in MARLOWE and estimate the measured energy spectrum with this consideration. Theoretical background Scintillation efficiency Energy loss functions Fig.1 Scintillation efficiency of CsI(Tl) Black ones are experimental results and Red ones from calculation. Fig.2 The electronic Stopping Power in the amorphous CsI Red line is MARLOWE and Blue line TRIM. ReSULTS Fig.8 Initial theta distributions of tail events Red <111>, Black<100>, Blue<110>,Brown <random> Fig.5 Penetrations from an empty site Red<111>,Blue<100>,Black<110> Fig.6 Initial theta distribution of tail events Fig.3 Quenching factors for Cs in CsI(Tl) Fig.7 Penetrations from a lattice point Table.1 Comparing of the axial critical angles A Cs ion goes into the symmetric axes of CsI(Tl). Black one is Lindhard ‘s 2, Red one  of Fig6. Fig.4 Quenching factors for NaI(Tl) Red is for Na ion and Black for I ion. Table.2 Comparing of the critical angles An I ion goes into the symmetric axes of NaI(Tl). Fig.9 Measured energy of tail events