Mass spectrometer

Claim 1

A transit time mass spectrometer for analyzing ions produced by pulsed laser radiation and having different energies, comprising, in combination: (a) means forming a drift path to be traversed by the ions in a predetermined direction, said drift path comprising a cyclindrical section having an input end and an output end; (b) an ion detector arranged downstream of said output end and having an entrance opening; (c) an electrostatic lens system for focussing as well as for accelerating the ions and including a plurality of electrodes, including three which are in the form of cylindrical sections, one of said three electrodes being constituted by said cylindrical section serving as said drift path and the other two of said sections being arranged upstream of said input end, said lens system being a means for focussing onto said entrance opening only those ions which have a predetermined energy interval lying in the region of the maximum energy distribution; (d) means for holding an ion-emitting test specimen which is to be subjected to the laser radiation, said holding means being constituted by that electrode of said lens system which is the furthest upstream of the input end of the drift path; and (e) means forming an aperture diaphragm arranged between an ion-emitting test specimen which is held by said holding means and the next downstream cylindrical section, said diaphragm having an aperture which is as small as possible without impairing the ion flow, said diaphragm being at the same potential as said next downstream cylindrical section.