cavity2: lcavity, tracking_method = runge_kutta, mat6_calc_method = tracking, n_cell = 2, 
rf_frequency = 1.3e9, 
field_calc = fieldmap,
L = 	0.470	, !Grid extends to 0.484. Center of the 2 cells is at 0.286 m 
field = { 
 mode = {
 m = 0,
 harmonic = 1, 
 master_scale = voltage,   !To be used when autophasing is off
grid = call::cavity2_grid.bmad }}

cavity2[voltage] = 5e6 ! Maximum on-axis Ez in V/m