Numerical Studies of the Shapes of Drift Tubes and Linac Cavities

At the Los Alamos Scientific Laboratory, a computer program for calculating the nmgaetic and electric fields in resonant cavities has been developed. This program, LALA, will compute the fields in any cavity having cylindrical symmetry; arbitrary shapes for both drift tubes and external boundaries can be treated. Both ¿-mode and 2¿-mode cavities can be handled. Calculations of several ¿-mode cavities at about 800 Mc/sec frequency have been carried out. At this frequency, for the ¿-mode, and in a cavity containing a drift tube, an external conducting boundary having a circular cross-section gives about a ten percent increase in ZT2 from the more normal rectangular external boundary.