An intense collimated beam of metastable helium atoms by two-dimensional laser cooling

compact apparatus has been developed to generate an intense beam of helium atoms in the metastable 2 S-3 state. A liquid nitrogen cooled DC discharge with a 0.25 mm diameter nozzle produces a beam with an intensity of 2 X 10(14) metastable atoms per second per sterad, an average velocity upsilon = 1030 m/s and a velocity spread of Delta upsilon(FWHM)/upsilon=0.3. Transverse two-dimensional laser cooling using curved wavefronts has been applied to capture atoms within a 30 mrad cone, to collimate the atomic beam and to enhance its intensity by a factor 50. An atomic beam with a cross section of 3 X 3 mm(2) and an intensity of 1 X 10(10) metastable triplet atoms per second per mm(2) has been realised using a laser cooling section with an interaction length of 18 cm.