Use of imaginary elastic wall method to simulate the action of moving particle's on the wall of vessel at balance state was suggested. The physical bases, the efficiency of saving CPU time of the method were discussed. The extra error caused by using imaginary elastic walls in quasi-balance states was estimated also. In the last part of this article an example by using the method was placed out.

The physics process of γ-detection of γ-spcctrometer with Compton suppression shields has been simulated using Monte-Carlo method. The results calculated for the γ-source ¹³⁷Cs with energy of 662 keV and for the cascade γ-source ⁶⁰Co with energies of 1173 keV and 1332 keV were in agreement with measurements. This work should be useful in the physics design, for γ-spectrometers with Compton suppression shields.

In this article, the attenuation of broad beam of γ-ray passing through a medium has been researched with Monte-Carlo method and it was pointed out that the beam obeys the exponential rule if an equivalent absorption coefficient is used. A new idea of design forγ-ray thicknessmeter was then advanced for weakening radiation intensity, increasing count, and improving measurement precision. An absorption experiment of broad beam of γ-ray with energy of 60 keV in aluminium has been done and the result agrees with Monte-Carlo calculation.