Transit detector for intermediate monitoring in time-of-flight mass analyzers

We present a particle detector for intermediate monitoring of beams of ion bunches (e.g., in time-of-flight mass analyzers). Its principle is secondary electron emission from a thin wire whose cross section is small (i.e., <5%) compared with the cross section of the primary ion beam. By means of a special experimental setup, anionic, cationic, or neutral particle beams can be formed; in addition, a tandem arrangement of our transit detector and a second detector at the end of the ion flight region allows us to test this transit detector. The influence on mass resolution, reliability of ion peak heights, dependence on kinetic energy and charge of the primary particles, and linearity have been investigated. This new detector may be useful for tandem mass spectrometric experiments, e.g., in time-of-flight analyzers with secondary excitation by collisions or photon absorption.