LARGE ION VOLUME TIME-OF-FLIGHT MASS-SPECTROMETER WITH POSITION-SENSITIVE AND VELOCITY-SENSITIVE DETECTION CAPABILITIES FOR CLUSTER BEAMS

We have developed and tested a high-performance time-of-flight mass spectrometer for clusters in a molecular beam. Several important improvements over conventional designs have been implemented that include a large ionization volume, a perfected ion steering system and a large area efficient ion detector. Cluster ions that are produced within the 200-cm3 ion volume can be simultaneously detected over a size range of from 1 to about 10 000 amu with a resolution of about 1000. The mass spectrometer can also be operated in a position-sensitive mode for cluster beam deflection measurements, and in velocity-sensitive mode to determine the cluster velocities. The performance of the spectrometer is demonstrated with Al and Fe clusters. We present mass spectra of cluster beams and also velocity, and magnetic and electric deflection measurements of collimated iron and aluminum cluster beams.