Steady state multipactor and dependence on material properties

The interaction of multipactor discharge and an rf circuit is analyzed with the use of a simple model, in which the multipactor electrons are in the form of a single sheet that is released from the surface with a monoenergetic velocity. An explicit formula is derived for the saturation level of multipactor current in steady state. This formula is given in terms of the secondary electron yield properties of the multipactoring surfaces and the level of the external rf drive. It is valid when the quality factor Q of the rf circuit is higher than 10, in which case the space charge effects do not contribute significantly to the saturation level. When it occurs, the steady state multipactor may consume tens of percents of the external rf power that is needed to sustain the gap voltage. Numerical computations determine the accessibility to steady state from the transient buildup. In particular, they suggest various conditions for the multipactor to exhibit in a burst mode or in a steady state mode. The dynamic linkage of the rf circuit and material properties allows the construction of the susceptibility diagram for various materials, within the limitations imposed by the present model. © 1997 American Institute of Physics. @S1070-664X~97!03702-6#