Problem in simulating field errors

[dxiang]

Hi All,
I want to simulate the residual R51 in a symmetric 4-dipole chiane caused by field error. In the 'error_element' command, I can define the error type (type=angle for my case) and amplitude of the error. But in the 'CSBEND', I can also define the FSE which also seems to be field error. I'd like to know the correct way of setting the errors. If both the 'amplitude' and 'FSE' are set, how does the code handle it?
I tried to make FSE=0 and give some value to the 'amplitude' in the 'error_element', but the output is the same from run to run. It seems the error is not a Gaussian distribution as it should be by default.
Right now I have to use a very stupid method to do the simulation: for each run I generate a Gaussian distribution from MATLAB first, and then add these values to the bending angle of each dipole. It does work, but I have to change the input file frequenty. So I still want to let Elegant do all the job.
I guess you guys must have a lot of experience doing this. Please help me get through it.
Thanks.

Dao

[michael_borland]

Dao,

To simulate errors in dipole magnets, you should use error_element to add errors to the FSE and/or ETILT fields. FSE gives the strength error while ETILT gives the roll error about the incoming axis. For example, for independent 0.1% rms strength errors on all bending magnets, use

&error_element name=*, element_type=*BEN*, item=FSE, amplitude=1e-3, bind=0 &end

Attached is a set of files that demonstrates this.

--Michael