Ps- (Positronium negative ion) station


A positron may be bound with an electron to form a positronium atom, a boud state like an hydrogen atom. It is also possible to form a positronium negative ion (Ps-) by binding one more electron. Ps- ions are emitted from a tungsten surface when it is bombarded with a slow positron beam. Its formation efficiency increases drastically when alkali metals such as Na and Cs is deposited on the surface. This station is for the formation of pulse Ps- by bombarding such a surface with a slow positron pulse and the applications. Recently an experiment of photodetachment of Ps- (dissociation into Ps and an electron by an irradiation of a laser beam) was successfully conducted (2011). Then an energy tunable neutral Ps beam was created by using this technique (2012).
(This station is connected to a general purpose beam line branch.)