The 'direct' method of ray tracing.

Two methods that can be used to trace the rays through the system, or in other words to integrate the trajectories, the 'direct' method and the 'mesh' method.

The direct method uses the potentials and fields calculated directly from the known charges on the electrodes. This method tends to be the more accurate for a single ray and for a given tracing time. It also tends to be the more accurate when the fields vary quickly with distance, as for example when a ray passes through a strong field near the edge of an electrode. It can however lead to a slowing down of the ray tracing when a ray passes through an electrode (because then time-consuming exact calculations of the potentials of the nearby segments have to be used).

In general the direct method is the safer of the two methods, although it can be the slower when the number of rays is large.

The direct method can be used for tracing rays in the presence of space-charge.

The direct method is the only one of the two methods that can be used with time-dependent voltages.

Return to general note on ray tracing.

For users who are editing or constructing an 'input data file' without the use of the data-builder -that is, pre-processor:

But Manual editing is certainly not recommended -it is a relic from the time when the databuilder was not available All users are strongly encouraged to use the databuilder, which always gives the correct formats and which has many options for which the formats are not described or easily deduced.

For the 'direct' method of tracing rays enter the letter 'd'.