Editing Multipactor effect (section)

==Effects of geometry==
Multipacting depends on the geometry of the surface and the exact distribution of the electric and magnetic fields. There are a number of geometry-based techniques to reduce or even eliminate the multipactor effect: One is through small-scale grooves which modify the direction of the electric fields exactly at the location of the electron emission, thereby kicking some of the electrons to directions that do not support the process.<ref>W. Xu et al., Multipacting-free quarter-wavelength choke joint design for BNL SRF, in Proceedings of IPAC2015. International Particle Accelerator Conference, Richmond, 2015,p. 1935</ref> Another approach is through large scale corrugations of the surface which periodically alter the time of flight of the electrons in two-point multipacting, thereby disrupting the multipactor resonance condition<ref>D. Naik, I. Ben-Zvi, Suppressing multipacting in a 56 MHz quarter wave resonator. Phys. Rev.ST Accel. Beams '''13''', 052001 (2010)</ref> Then there are specific changes in the curvature of a cavity's surface that spoil the chances of the electrons to return to the point of origin<ref>U. Klein, D. Proch, Multipacting in superconducting RF structures, in Proceedings of Conference on Future Possibilities for Electron Accelerators, Charlottesville, 1979, p. N1</ref> or cavity-beam pipe transition surface.<ref>S. Belomestnykh, V. Shemelin, Multipacting-free transitions between cavities and beam-pipes. Nucl. Instrum. Methods Phys. Res. A 595, 293 (2008)</ref> These various surface modifications techniques provide a powerful tool for the suppression of multipacting in various geometries.