Where to buy Cesium

Cesium is one of the rare metals, it is usually difficult to see, in today's aerospace industry will be used, is a relatively high material, the development prospects are relatively good. What is the role of this rare metal in the aerospace industry? 　　The outer electrons of cesium atoms is very unstable, easily excited radiation out into cesium positively charged ions, so it is the ideal space ion rocket engine fuel". The working principle of cesium ion rocket is this: after the engine starts, produce large amounts of caesium, cesium vapor after ionization is the "process", a positively charged cesium ion, then the effect of the magnetic field up to one hundred and fifty kilometers per second, ejected from the nozzle, also give strong impetus to ion rocket the height, push forward the rocket.