Compensation failures proceed

[Bruce Yee]

Dear Didier,

Thanks for your comments.

1) For your suggestion "For your first request, I could by default cancel intial ADJUST process at beggening of the run, when transient simulation is selected. What do you thing about this solution"

In that case, Can I still apply the matching options "Match with family & Twiss commands" and "Match using Diagnostics" at the begging of the simulation?

And, Can I use the above matching option in each step of the transient simulation?

2) I was using the example that tracewin provides.

Example.zip

(5.85 KiB) Downloaded 250 times

However, now I can not reproduce the previous results, but, I found something interesting.

I set up the two first cavities to -90 deg (originally were -20 degrees). The failure started at 0.5 ms. But, it can be seen that the synchronous phase change early.

Phase_for_cavity.png (94.72 KiB) Viewed 3562 times

The multiparticle simulations showed that the simulation got lost at 2.5 ms,

Screenshot (463).png (21.94 KiB) Viewed 3562 times

But if you see the synchronous phase stay stable, and then suddenly collapse.
I compared the evolution of the faulty cavity with the original setting (synchronous phase -20) and with a synchronous phase of -90 deg.

Comparison.png (97.78 KiB) Viewed 3562 times

The Eacc for -90 deg has some spikes, but, I don't understand why.

Thanks again for your help and support,

Bruce

[Didier]

Dear Bruce,

1) Matching options "Match with family & Twiss commands" are alway applied at the beggening and never during transien simulation. I propose to cancel "Match using Diagnostics" at the begging of the simulation when transien simulation are asked to avoid confusion about static and transien simulation.

2) In example you send to me, all cavities are set to 25° and see failure starting well at 0.5 ms !!

Regards,

Didier

[Bruce Yee]

Dear Didier,

About point 1). In addition to the "matching with family and twist command", I have a correction scheme using BPM and steering corrector. Thus, using your suggestion, I can not continue using the diagnostic correction.


2) Apologies, the failure time is correct. However,the settings of phase are the default one that corresponds to the right plots of the last figure.

I sent you the correct one.

Example.zip

(17.3 MiB) Downloaded 250 times

Best regards,

Bruce

[Bruce Yee]

Dear Didier,

I checked the performance of the "Twiss match with family and twiss command" for the transient simulations.

I made two runs of the same lattice. On the left is the normal simulation and on the right with transient one.

Test1.png (114.96 KiB) Viewed 3549 times

Both have the same setting for matching with "Twiss match with family and twiss command"

Test2.png (62.59 KiB) Viewed 3549 times

I tested the results several times, every time I remove the .cal file. For the transient case the failure never occurred, I simulated 3 times the lattice (every 10 us during 30 us).


I noticed that during the matching, both simulations did not get the same criterion value for matching

Test6.png (73.16 KiB) Viewed 3549 times

Test5.png (73.51 KiB) Viewed 3549 times

The performance of the transient was always lower than the normal simulation.

In addition, I compare the performance for similar conditions (i.e. for the transient simulation the time is 10 us when all the element performance ideally).
The synchronous phase and the mismatch are different.

Test3.png (87.74 KiB) Viewed 3549 times

Test4.png (59.92 KiB) Viewed 3549 times

I include the file, for more details

TEST_001.zip

(678.96 KiB) Downloaded 216 times

Best regards,

Bruce

[Didier]

Dear bruce,

1 - I fixed the issue making phase and other parameters colapsing (New TraceWin version availbale). Now cacity parametre stay instable when the synchonous phase of cavity is lower than -90°. In your case, it's already a little bit instable because you set cavities to -90.5°. -90° is much better. I have not yet figured out where these instabilities come from for the synchone phase below -90°.

2 - I understand well the problem you show in the following post about matching without and with transiant mode. It is quite complicated to solve, but I have the following approach which works very well.
- I calculate my linac and macthing without the transient option.
- I use the new file "...ResultsTEST_025.dat" to replace my initial file, because it contains the final version with all the elements set to matching values.
- I simulate in transient mode by removing the option "Match with family..."

Regards,

Didier

[Bruce Yee]

Dear Didier,

Thanks for your suggestion. As you recommended, I run a normal case to obtain the new lattice.

Lattice.PNG (206.88 KiB) Viewed 3547 times

In this case, you can see that the magnetic field of the solenoids for the left (normal matching case output) are the same as the ones in the new lattice (right).

With the new case, I run a normal simulation (i.e. without transient effect)without matching conditions.

Matching.PNG (27.27 KiB) Viewed 3547 times

The synchronous phase and the gradient of the quadrupole are the same (see the values inside the blue curves); however, the magnetic fields of the solenoids (red curves) are different.

Lattice2.PNG (152.44 KiB) Viewed 3547 times

I was using the same files that I sent you yesterday. Do you see the same effect?

Thanks for the help and support.

Bruce

[Didier]

Dear Bruce,

The solenoid fields change because of your SET_ADV commands. As you have changed the cavity parameters, so the transverse focus, the solenoids are adjusted to get the required transverse phase advance. You should therefore comment out the SET_ADV commands, or sconserve them if you insist on this constraint.

All this is perfectly expected, but the code does so many things at once, I understand that it becomes very complex for the user.

Regards,

Didier

[Bruce Yee]

Dear Didier,

Thank you very much for the information. Now, I can obtain the same results for both cases.

Best regards,

Bruce