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For a wiggler, I would use the sine/cosine option.

Its format is:

period dirX dirY dirZ N
A1 B1
A2 B2
...
AN BN

Where period is the period of the sine and cosine function. DirX, dirY and dirZ are the same as before. N is the number of lines that follow.

A1, B1, A2, B2, ... are coefficients, to give the following magnetic field:

B(distance)=
A1*sin(distance*2PI/period) + B1*cos(distance*2PI/period) +
A2*sin^2(distance*2PI/period) + B2*cos^2(distance*2PI/period) +
...
AN*sin^N(distance*2PI/period) + BN*cos^N(distance*2PI/period)

 

For example, a simple wiggler, going along axis Z with 0.5 Tesla peak field, and 25 full-periods of 3cm would look like:

3 0 0 1 25 1
0.5 0

Update: the number 25 should be deleted, it was there by mistake. The number of periods will be determined by the region length (75 cm / 3cm period = 25 periods)

The magnetic region that loads this file should be 75 cm long, and its starting direction (theta angle) should be found with trial and error so that its endpoint is still on the Z axis.

If you need an example let me know and I'll attach.

Thank you! Your example input makes sense, we will try to use the sine/cosine input instead.

I am still curious how one would use the analytical expression if anyone knows.

The "Analytic expression" has been ported from the original (DOS) version of Synrad. Upon looking at it closer, it contains the analytic expression for describing the magnetic field in a wiggler following the Halbach wiggler field model:

Where k=2PI/wiggler_period.

If you use the Halbach wiggler model: you choose "Analytic" as the X component in Synrad's region editor, and define the k, kx and B0 parameters in an external MAG file. The x,y,z coordinates are aboslute, so you'll have to position your undulator at the origin.

That said, so far we always used the Sine/Cosine approximation.

Corrected the MAG file, it contained a mistake, sorry.

See correction in red in the original comment.

I've tested the new file and it works:

wiggler1.mag
wiggler1.param