Editing Multipactor effect (section)

==Mechanism==
The mechanism of multipactor depends on the orientation of an RF electric field with respect to the surface as well as the magnetic field and its orientation.{{r|Shem|pp=61–66}} There are two types of multipactor: two-surface multipactor on metals and single-surface multipactor on metal or dielectrics.

===Two-surface multipactor on metals===
This is a multipactor effect that occurs in the gap between metallic electrodes. Often, an RF electric field is normal to the surface. A [[resonance]] between electron flight time and RF field cycle is a mechanism for multipactor development.

The existence of multipactor is dependent on the following three conditions being met: The average number of electrons released is greater than or equal to one per incident electron (this is dependent on the [[secondary electron yield]] of the surface), ''and'' the time taken by the electron to travel from the surface from which it was released to the surface it impacts is an integer multiple of one half of the RF period, ''and'' the average secondary electron yield is greater than or equal to one.

===Single-surface multipactor===
The multipactor effect can take place on a single surface when magnetic fields are taken into account.{{r|Shem|pp=91–105}}<ref name=Ben>I. Ben-Zvi, J.F. Crawford, J.P. Turneaure, Electron multiplication in cavities, in Proceedings of PAC1973, Particle Accelerator Conference, San Francisco (1973), p. 54</ref> A single-surface multipactor event is also possible on a metallic surface in the presence of a crossed static magnetic field. It may also occur on a dielectric surface, where often an RF electric field is parallel to the surface. The positive charge accumulated on the dielectric surface attracts electrons back to the surface.