A Microwave Secondary Electron Multiplier

Abstract

Articles you may be interested inSecondary electron multiplier for a retarding field energy analyzer with coaxial cylindrical electrodes Rev. Sci. Instrum. 60, 3341 (1989);A trial construction of a secondary electron multiplier with ringshaped dynodes Rev. Sci. Instrum. 60, 805 (1989);The construction and operation of a dynamic electron multiplier, of the type sometimes called a multi· pactor, is described. Briefly, the muitipactor consists of two parallel secondary emissive plates having an alternating voltage across them. The magnitude of the voltage is adjusted so that the transit time across the gap for electrons starting with zero velocity from one of the plates when the field is passing through zero shall be just one· half the period of the a.c. voltage. In this way, electrons and their secondary descen· dents can be made to bounce back and forth between the plates and multiplication takes place. The necessary phase relationships between the electrons and the field are discussed.The multipactor described here uses 10 cm microwave power to get the a.c. voltage. It has been used as a gamma·ray detector in which case the cavity is "broken down" by the multiplication of a Compton electron ejected from the cavity wall by a gamma-ray. This breakdown gives rise to a microwave pulse several millivolts high at a crystal rectifier. The efficiency of this process is about 1.5X 10-5 count/gamma·ray.The rise time of the pulse is calculated to be about 5 X 10-10 sec. and is measured to be less than 10-1 sec. The dead time is presumed to be about 5 microseconds.

Electron bunching from a dc-biased, single-surface multipactor with realistically broad energy spectrum and emission angle of secondary electrons

“…[3][4][5][6][7][8] Like other discharge processes, the multipactor is also associated with electron avalanche: some free initial electrons inside the device are accelerated by rf field to hit the material surface, yielding more secondary electrons. Then, the emitted secondary electrons hit again after several periods of the rf and make even more secondary electrons.…”

Multifactoring at a single electrode

“…A second practical application of a multipactoring oscil lation as a gamma ray detector was made by Greenblatt (7).…”