Verification of a Multipacting Computer Code and Analysis of an RF Test Cavity

A design study has been carried out at CERN to define layout and parameters of a future neutrino factory. The reference scheme of this neutrino factory incorporates a muon cooling channel, which partly consists of 88 MHz accelerating cavities. In order to reveal possible technical difficulties in achieving the desired gradient of 4 MV/m, a 88 MHz test cavity has been constructed. The present work aimed to test this cavity for multipacting discharges. For this purpose CERN has acquired the multipacting simulation code MultP. In a first step two known examples of multipacting were analysed, to check the functionality of the code. The tests revealed that MultP lacked some means to predict multipacting. Moreover, MultP partly produced erroneous results. In order to find their origin and to gain a deeper understanding in numerical simulations of multipacting, a multipacting test code has been programmed for those two examples. The test code was then succesfully used to find the origin of the errors. Two new functions were eventually implemented into MultP: the electron counter and the distance function. Thus, the analysis became more reliable and easier to perform. Finally, a multipacting analysis of the test cavity was carried out. Two possible barriers have been discovered. The first barrier is between 180 kV and 200 kV gap voltage, and the second is at 130 kV gap voltage. They are both far below the operating level of 4 MV. An experimental verification of these multipacting levels shall be done at CERN.