Monte Carlo calculation of β+ particle annihilation probability in the marinelli beaker (MB)

Using the MC method, β+ particle's annihilation probability in the MB's space and on the MB's internal surface are calculated. Some results are gotten from the calculations: the annihilation probability of β+ particle on the MB's internal surface is much larger than that inside the MB, and is proportional to the surface area approximately; although the gas source is homogeneous, the annihilation one in MB's space is not homogeneous profile and gets to maximum in the center of the MB