A novel detection system for laser cooling of ortho-positronium

摘要

We report on the development of a position-sensitive scintillation detector system for viewing laser-cooled ortho-positronium (oPs) annihilation points. Ortho-positronium can be cooled down to a recoil limit of 0.1 K by an ultraviolet laser in spite of its relatively short lifetime. In order to perform this experiment the wavelength of Cr:LiSAF laser is considered to be 243nm which corresponds to the transition energy of 1S-2P states of oPs. Thermal positronium plays an important role in laser cooling of oPs. We investigated various kinds and sizes of inorganic scintillators. Position resolutions of YAP:Ce and CsI(Tl), respectively, were determined to be 3.00 and 3.8mm. Extensive Monte Carlo simulation studies were performed to view the decay positions of oPs using the time-of-flight method. Related issues of position resolution measurements and oPs decaying points will be discussed.