Optical pumping of thick alkali vapor for high-intensity polarized ion source

One-dimensional calculation of the polarization distribution in an alkali cell is applied to examine the optical pumping of a thick Rb target. Attenuation of pumping laser power is calculated in a long Rb cell by considering the radiation trapping. The results of the calculation for realistic laser power agree with experimental data of the mean value of the polarization in the cell. The effect of the attenuation on the polarization is clarified to relate to not only the thickness of the vapor. The results show that the maximum Rb thickness, in which a fixed polarization is achieved, is approximately proportional to the square root of the length of the cell.