4D & 6D emittance by errors study

[comunian]

Dear Didier,
may will be possbile to include in the errors study Statistic results also the 4D and 6D emittance ?
In some cases we have seen an emittance exchange between the planes and can be useful to check if the total emittance is conserved.
Best Regards,
Michele Comunian

[Didier]

Dear Michele,

Do you speak about "histogram" plots ?

Regards,

Didier

[comunian]

Dear Didier,
yes, you can include the 4D and 6D emittances on the histograms plots.
I mean on the file "Statistic_Errors_1_PAR_tot.txt" but you can also use the Density_Tot_PAR_1_xxx.dat file as you prefer.
Best Regards,
Michele Comunian

[Didier]

Dear Michele,

New TraceWin version available including 4D & 6D emitances in histogram charts.

Regards,

Didier

[comunian]

Dear Didier,
thank you for the 4D-6D emittance plot!
Best Regards,
Michele Comunian

[Bruce Yee]

Dear Didier,

Regarding the 6D emittance for the error studies, as Dr. Comunian pointed out, it is expected that the 6D emittance is preserved even when some transfer occurs in the planes.

However, I simulated an error case, asking for the results to be compared against the ideal case (Beam reference: Output).
The output file (attached) shows that in some cases, the 6D emittance is lower than the ideal case for non-beam losses cases.
In addition, the last run shown all the emittance decreased in all three planes, as well as the 6D emittance without beam losses.
Could you comment on that?

Finally, on the output file, the last column title shows "Emit_6D/Emit0_4D-1", but in the TraceWin Manual mentioned "Emit_6D/Emit0_6D-1".
Could you confirm what parameter is computed?

Best regards,

Bruce

[Didier]

Dear Bruce,

I made some correction in the last TraceWin version some weeks ago and in particular on the error in the title of the last column.
So I don't know if this explains your strange observations, but before looking any further, try running your tests again with the latest version. This may resolve your abnormal results. That said, the 4D and 6D emittance values are very relevant in matrix calculations (envelope), but they are sometimes more questionable because they are approximate in tracking mode.

Regards,

Didier

[Bruce Yee]

Dear Didier,

Thanks for your recommendations.
I updated to 2.25.2.4.

TW_version.png (31.89 KiB) Viewed 248 times

I attached the results of a short run. (I removed the last lines of the file where the type of errors is printed out).
1) The title of the last column is "Emit_6D/Emit0_4D-1"
2) The runs 7 (line 9) and 15 (last line) both present a decrease of 2D-emittances, 4D- and 6D, without beam losses. (The same results persists).

Thanks for your help and time,

Bruce

[Didier]

Dear Brune,

I'm sorry, mais the last version is 2.25.2.9 !!
Please upgrade your version

Regards,

Didier

[Bruce Yee]

Dear Didier,

Apologies for my delayed response. I updated the TraceWin version to 2.25.2.9.
The error cases that I simulated did not record beam losses. (See the attached figure)

Error.png (885.16 KiB) Viewed 10 times

I analyzed the cases, plotting the emittances, Emit4D, and Emit6D from the Statistic_Errors_1_PAR_tot.txt output file, as shown in the next plot

Error_data.png (178.27 KiB) Viewed 10 times

From the plots, Emit4D and Emit6D are not constants. This can be explained by your previous comments ( the 4D and 6D emittance values are very relevant in matrix calculations (envelope), but they are sometimes more questionable because they are approximate in tracking mode)

The emittance plot was what I expected, except for a case that I pointed out with a red arrow (around 25). No beam loss, but the emittance decreased in all the planes.

After looking for an explanation, I found in the Error_data.txt file that in some cases, the emittance error is negative, which I understand as the value is lower than the nominal. Is it correct?

Error_Datas.txt

(1.15 KiB) Downloaded 1 time

If that is the case, it could be that one random error selects emittance values lower than the nominal, thus, when I compared the emittance are lower than the nominal without beam losses.

Best regards,

Bruce