Skimmer for the AP2 supersonic laser vaporization cluster-beam apparatus. In the discovery of buckyballs, pulsed laser beams directed at a sample of carbon in the main chamber of the AP2 instrument created a plume of vaporized carbon hotter than the temperature at which some stars are formed. A stream of helium brought about sudden and extreme cooling and the clustering of carbon atoms. A skimmer at the threshold of an adjacent vacuum chamber collected the clusters for analysis by a mass spectrometer.