Construction of a low velocity metastable helium atomic beam

We have constructed an atomic beam of metastable helium atoms He(2 3S) with a mean velocity of 300 m/s (15 K) and a yield of 3×1012 atoms/s sr. The metastable atoms are produced in a dc discharge in a cryogenic environment cooled by liquid helium. Using a hexapole magnetic lens, we have increased further the beam intensity by focusing the metastable atoms. Initial studies show a factor of 2.5 increase in the beam flux but more is expected when the hexapole is constructed from permanent hexapole magnets. The He(2 3S) atoms are subsequently loaded into a magneto-optical trap.