Efficient and robust anion source, based on a microchannel plate electron source

Abstract

In this work, an efficient, cheap, and robust anion source is described, which is based on a high-pressure supersonic expansion crossed with a pulsed high-energy electron beam. The special property of this anion source is “soft” electron attachment and efficient stabilization and cooling, which results predominantly in molecular and cluster anions of intact molecules. As electron source, a stack of microchannel plates is used, which is seeded by photoelectrons generated by a weak ultraviolet light pulse. By this special electron source 109–1010 electrons of 1 keV energy are provided at a pulse width of 150 ns. These operational conditions can be maintained up to a repetition rate of 4 kHz. Further advantages of this device are its long lifetime even at relatively high vacuum pressures and its stability against reactive samples, such as oxygen and organic molecules.