A source for a high-intensity pulsed beam of metastable helium atoms

The operational characteristics and technical details of a high-intensity d ischarge source for a pulsed beam with a high flux of helium atoms in their metastable states (exceeding 4 x 10(15) atoms sr(-1) s(-1)) are discussed. Owing to the high ionization potential of helium, stable operation of a pu lsed discharge in an atomic beam is difficult to achieve. In this work we d escribe a simple, robust and easy-to-operate design of a reliable high-inte nsity pulsed source for metastable helium atoms. The principle of operation relies on injection seeding the discharge with electrons emitted from a ho t wire, permitting a strong enhancement both in efficiency and instability of the production of metastable atoms.