A cylindrical reflectron time-of-flight mass spectrometer

A new reflectron time-of-flight mass spectrometer with a cylindrical electrostatic mirror instead of the usual plane reflector is described. When it is mounted at right angles to the direction of an incoming molecular beam, this system automatically compensates for the transverse drift of the ions in the spectrometer due to their initial velocity parallel to the molecular beam direction. As a consequence, ions of any mass can be collected onto the detector, whatever their initial transverse velocity is. The mass range accessible in a single scan with our cylindrical reflectron is thus strongly increased as compared to the case of a usual plane reflectron. This article presents the general design of our cylindrical reflectron. A detailed description of the apparatus is given and its performances are illustrated on selected examples. Cluster mass spectra extending over a very wide size range are presented. A mass resolution of about 4000 is achieved in mass spectra of laser photoionized aluminum clusters. Moreover, the cylindrical geometry of the reflector gives rise to focusing properties onto the detector, which could be interesting in view of collection efficiency improvement. (C) 1997 American Institute of Physics.