  Multipacting is seen as a performance limiting phenomenon for the
superconducting radio frequency (SRF) cavities. Numerical simulations are
essential to pre-empt the experimentally observed multipacting conditions.
Readily available codes(e.g. FISHPACT, MULTIPACT,CST etc.) are widely used to
simulate the phenomenon of multipacting in such cases. Most of the contemporary
two dimensional (2D) codes are unable to detect multipacting in the elliptical
cavities because they use a simplistic secondary emission model, where a
constant value of emission kinetic energy of secondary electrons is assumed.
Some three-dimensional (3D) codes, which use a more realistic and sophisticated
secondary emission model (Furman model) by following a probability distribution
for the emission kinetic energy of secondary electrons, are able to correctly
predict the occurance of multipacting. These 3D softwares however require large
data handling and are slower than contemporary 2D codes. We have developed a 2D
code for the multipacting analysis for axisymmetric structures, which is based
on the Furman model. Since our code is 2D, it is faster than the 3D codes. This
makes it possible to perform an accurate multipacting analysis of multipacting
within a resaonalble computational time, thus achieving an accuracy as good as
in the case of 3D codes, but requiring significantly less computing time. We
have used our code for determining the multipacting prone range of values for
Eacc in beta_g =0.61 and beta_g =0.9, 650 MHz mid-cell elliptical cavities that
we have recently designed for the medium and high energy section of the
proposed Indian Spallation Neutron Source (ISNS) project.

Accelerator Physics