System for ionization and selective detection in mass spectrometers

摘要

A mass spectrometer is disclosed which includes an ionizer, a collector slit disposed at a predetermined distance from the ionizer, and an electrostatic field source disposed between the ionizer and the collector slit. The electrostatic field source has a selected amplitude which is substantially uniform within a space between the ionizer and the collector slit. The electrostatic field is oriented substantially perpendicular to a line between the ionizer and the collector slit. The mass spectrometer includes a magnetic field source disposed between the ionizer and the collector slit. The magnetic field source induces a substantially uniform magnetic field within the space. The magnetic field has a direction perpendicular to both the electrostatic field and to the line between the ionizer and the collector slit. The spectrometer includes a detector disposed behind the collector slit. The selected electrostatic field amplitude is chosen so that ions having a particular mass number traverse a substantially cycloidal path between the ionizer and the collector slit. The cycloidal path has a linear component which is substantially equal to the selected distance at a position substantially along the line.