The Simulation of the quenching factor and the channeling effect for the CsI(Tl) and NaI(Tl) crystals Juhee Lee and Sunkee Kim Seoul National University Shillim-dong Kwanak-gu Seoul Korea, Republic of. 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. Scintillation efficiency Energy loss functions Fig.1 Scintillation efficiency of CsI(Tl) Black ones are experimental results and Red ones from calculation. 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. Fig.2 The electronic Stopping Power in the amorphous CsI Red line is MARLOWE and Blue line TRIM. 5keV10keV15keV20keV50keV [111] [100] [110] 9.4  7.9  7.2  6.7  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. 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.3 Quenching factors for Cs in CsI(Tl) Fig.3 Quenching factors for Cs in CsI(Tl) Fig.4 Quenching factors for NaI(Tl) Red is for Na ion and Black for I ion. Fig.4 Quenching factors for NaI(Tl) Red is for Na ion and Black for I ion. Fig.9 Measured energy of tail events Fig.9 Measured energy of tail events Fig.7 Penetrations from a lattice point Fig.7 Penetrations from a lattice point 5keV10keV15keV20keV50keV [100] [110] [111] 9.5 · 8.0 · 7.2 · 6.7 · 5.3 · Table.2 Comparing of the critical angles An I ion goes into the symmetric axes of NaI(Tl). Table.2 Comparing of the critical angles An I ion goes into the symmetric axes of NaI(Tl). Fig.6 Initial theta distribution of tail events Fig.6 Initial theta distribution of tail events Fig.8 Initial theta distributions of tail events Red, Black, Blue,Brown Fig.8 Initial theta distributions of tail events Red, Black, Blue,Brown Fig.5 Penetrations from an empty site Red,Blue,Black Fig.5 Penetrations from an empty site Red,Blue,Black