Elegant users forum

Hi,

I've noticed a discrepancy between in the first-order transfer matrix (read via the .matext file, written from

&matrix_output
printout ="%s.matext"
printout_order = 2
SDDS_output="%s.mat"
SDDS_output_order=2
full_matrix_only=1
&end

There appears to be some dependence on this transfer matrix depending on what default_order is specified for tracking. Changing "default_order = 1" to "default_order = 2" in the &run_setup block produces the following change (truncated the transfer matrix just to show several of the changes). Of note are the fifth and sixth columns.


"default_order = 1"
C: 7.242487559697242e-04 2.484926385476421e-04 0.000000000000000e+00 0.000000000000000e+00 1.710070928372430e+01 -8.193165066476552e-04
R1: 8.335619846540105e-01 -2.803361304005287e+00 0.000000000000000e+00 0.000000000000000e+00 1.540391434852078e-01 2.193517664556615e-02
R2: 7.645791987162753e-01 -1.371724477005838e+00 0.000000000000000e+00 0.000000000000000e+00 3.352856859712416e-02 4.604423382828756e-03

"default_order = 2"
C: 7.246143875760628e-04 2.487342194818366e-04 0.000000000000000e+00 0.000000000000000e+00 1.710071682855462e+01 -8.182951192695051e-04
R1: 8.165524155515519e-01 -2.784564392068167e+00 0.000000000000000e+00 0.000000000000000e+00 1.860228464430133e+01 2.696346667360979e+00
R2: 7.587909465128337e-01 -1.365314750571623e+00 0.000000000000000e+00 0.000000000000000e+00 6.406591270588014e+00 9.285031409952567e-01

Is there any common reason why there would be this discrepancy? I assumed that changing the order would only change the T_ijk terms, but the displayed behavior is puzzling.

Thanks,
Chris Prokop

Chris,

The reason for this has to do with the way elegant computes the matrix for an RFDF element with non-zero length. It does this by splitting the element into many drift-cavity-drift slices, where the cavity slice is a zero length element represented by a second-order matrix. Because in general the orbit wanders from x=y=0 in tranversing an extended-length deflector, there can be feed-down from the second-order matrix of the zero-length slice into the first order matrix of the extended-length deflector. I think this is what you are seeing.
--Michael

Chris,

For some reason, I assumed you are using an RFDF element here. (Didn't you ask about them before.) Let me know if that isn't the case.

--Michael

michael_borland wrote:Chris,

For some reason, I assumed you are using an RFDF element here. (Didn't you ask about them before.) Let me know if that isn't the case.

--Michael

Hi Michael,

Yes, I am using an RFDF element.

Thanks! That explanation makes sense, and explains why it seemingly only affects a few of the terms of the transfer matrix.

Thanks again!