apex_gun: E_GUN, L = 0.15, field_calc = fieldmap, tracking_method = time_runge_kutta, 
    rf_frequency = 187e6, 
    grid_field = call::apex_gun_grid.bmad 

r_large = 0.02

! Simple 1 inch pipe at 4 cm
apex_gun[wall] = {
	section = { s = 0,
	  v(1) = {0, 0, 0.0254/2}},
	section = { s = 0.001,
	  v(1) = {0, 0, r_large}},
	section = { s = 0.0399,
	  v(1) = {0, 0, r_large}},
	section = { s = 0.04,
	  v(1) = {0, 0, 0.0254/2}},
	section = { s = 0.15,
	  v(1) = {0, 0, 0.0254/2}}}


!!apex_gun[voltage] = 750e3 !Voltage in V