Multipactor is a pure electron discharge driven by radiofrequency (RF) electric fields that occurs in high-vacuum. Secondary electron emission is the growth mechanism of the discharge. Multipactor is ubiquitous in vacuum RF structures, resonators and vacuum windows. Simple models are used to investigate, separately, two-surface multipactor on metal in a resonant cavity, and single surface multipactor on a dielectric.;The frequency response of multipactor discharge in a resonant structure is examined. This leads to the construction of generalized susceptibility diagrams, determining the conditions for which multipactor can take place. Given the secondary electron emission characteristics of the surface material, RF amplitude and frequency, geometry, and quality factor of the resonator, the threat of multipactor discharge occurring can be determined. The steady state level of such a discharge is also calculated. It is found that the frequency bandwidth within which multipactoring may occur is asymptotically proportional to the gap voltage, and inversely proportional to the quality factor, Q, of the cavity. The dependence of the bandwidth on the secondary emission characteristics is more complex.;Suppression of two surface multipactor discharge in a metallic resonator, by use of an auxiliary signal, is studied. It is found that, in general, multipactor may be suppressed by use of an auxiliary signal with an amplitude in the range of 5--20% of the main signal amplitude, and at a frequency 0--5% removed from the frequency of the main signal. Optimal conditions allow the use of auxiliary signals as small as 2--3% of the main signal magnitude. Beam loading effects are found to be important in lowering the auxiliary signal magnitude for high Q resonators.;Single surface multipactor on a dielectric is believed to be responsible for vacuum window failure. The effects of the angle of incidence, of a RF wave upon the dielectric, are investigated with regards to susceptibility to multipactor discharge. It is found that for angles of obliqueness greater than approximately 10°, windows are more likely to be resistant to multipactor-induced failure. The effects of the RIF magnetic field are also studied. It is found that the RF has negligible effect upon the lower susceptibility boundary (which determines saturation levels) but may eliminate the upper susceptibility boundary.;A self-consistent theory for the effects of the self-electric field of the multipactor discharge is constructed, and closed form solutions for the average electron impact energy upon the dielectric, and the power deposited are given. Typically, multipactor deposits about 3 per cent of the RF power onto the dielectric, a factor of a few higher than earlier estimates that did not take into account consistent space charge effects.
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