Geometry File

**description:**This page describes the structure of the geometry file used with the`define_geometry`namelist. The file is similar to those used with the program POISSON.**example:**! new RF gun, first cell &po x=0.000, y=0.000 &end &po x=0.000, y=0.006 &end &po x=0.0016, y=0.0135 &end &po x=0.0016, y=0.0427755 &end &po x=0.0060, y=0.0427755 &end &po nt=2, x0=0.006, y0=0.0181355, r=0.02464, theta=0.0 &end &po x=0.03064 , y=0.014818 &end &po nt=2, x0=0.02861, y0=0.014818, r=0.00203, theta=-90.0 &end &po x=0.02836, y=0.012788 &end &po nt=2, x0=0.02836, y0=0.010588, r=0.0022, theta=180.0 &end &po x=0.02616, y=0.01008 &end &po nt=2, x0=0.03116, y0=0.01008, r=0.005, theta=270.0 &end &po x=0.0348, y=0.00508 &end &po x=0.0348, y=0.00 &end &po x=0.000000, y=0.00 &end

**synopsis and defaults:**&point int nt = 1; double x = 0; double y = 0; double x0 = 0; double y0 = 0; double r = 0; double theta = 0; double potential = 0; &end

**details:**`nt`: The segment type, where 1 (the default) indicates a line segment; 2 indicates an arc of a circle; 3 indicates the start of a separate structure; and 4 indicates a definition of an in-vacuum point.`x, y`: For`nt=1`, the endpoint of the line. x corresponds to z (the longitudinal coordinate) and y corresponds to r (the radial coordinate). For`nt=3`, the first point on the new shape. For`nt=4`, the coordinates of the in-vacuum point.`x0, y0`: For`nt=2`, the center of the circular arc.`r`: For`nt=2`, the radius of the circular arc.`theta`: For`nt=2`, the angle in degrees of the end of the arc as seen from the center of the arc. If this angle is less (greater) than the angle of the starting point (which is on ), then the sense of the arc is clockwise (counter-clockwise).`potential`: The potential of the segment, in volts.