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## 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.

Next: define_antenna Up: Manual Pages Previous: define_geometry
Robert Soliday 2005-06-28