A LINEAR RADIO-FREQUENCY MASS SPECTROMETER

Abstract

A radio-frequency mass spectrometer is described using a system of electrodes similar to a linear accelerator to obtain velocity selection of tin ions. A beam of ions is directed through a series of axial radio-frequency fields with alternate polarity, and the ion with a velocity (proportional to [Formula: see text]) such that it traverses the individual stages in approximately one-half period of the radio-frequency field, acquires maximum energy from this field. A retarding field region prevents all ions, except the ion with maximum energy, from reaching the collector. An ion beam of large cross section is used. With 20 radio-frequency stages a mass resolution of 1% is obtained.