Laser cooling system of ortho-positronium

We have studied laser cooling (Doppler cooling) of ortho-positronium to achieve Bose–Einstein condensation of positronium atoms. We have been developing a long-pulse laser with the wavelength of 243 nm, a bunched slow positron beam to realize the proposed experiment and a Monte Carlo simulation program for theoretical understanding. The Monte Carlo analysis clarified that we were able to obtain 7% of ortho-positronium atoms which were cooled down to 1 K and confined within a small volume without using a trap system.