Elegant users forum

Hello,
I am trying to track a beam in a ~40 m long transfer line for a certain tuning of R56. Beam is generated through bunched_beam command (~8 ps). I defined drifts as CSRDRIFT in lattice file with "CSR_ON" option. Chirping is set to 1/R56 for compression. I am getting a message during run as "incrementing zStart by revolution length for CSRDRIFT (DA4 #2). If you are not simulating a ring, this could be a problem!", although before DA4, other CSRDRIFT are there. I am getting results also very strange i.e. in the file related to last dipole magnet (CSRCSBEND) bunch length is 5.785930e+033 (obtained through "sddsprintout bm4csrwake.wke -parameter=TotalBunchLength") and in .fin file also St is -1.#IND00e+000 ("sddsprintout tl2c_csr.fin -parameter=St). Line also has six sextupole magnets for T566 corrections. Line has a good stable solution.
Where my input is wrong? How I can get rid of this error?

Thanks and regards,
Amal.

Amal,

That's definitely odd. Can you post your input files or email them to me?

--Michael

Dear Sir,

I am attaching .ele and .lte file and also .fin file generated by programme. All the .wke files are bigger in size ( more than 100 kB), so I did not attache those files. Perhaps at somewhere I am making some mistake but could not pin point it......... (I am running programme on Windows-7)......
Thanks and regards,
Amal.

Amal,

This results from the large number of elements between the last CSRCSBEND and the CSRDRIFT, plus a comparison in the code that doesn't anticipate rounding error.

I work-around is to put a small negative drift space in front of DA4: I noticed that you have N_KICKS=1 on the CSRCSBENDs. I recommend N_KICKS=10 or more for accurate modeling.

--Michael

Dear Sir,

I am thankfull for your reply. It worked well.....
When I increase the N_KICKS, does programme generates bunch length and wake field in *.wke files after each kick i.e. I think magnet is simulated like ---DRIFT-KICK1-DRIFT-KICK2-DRIFT-KICK3-......KICKn-DRIFT and on each kick (for N_KICKS=n), bunch length and wake field is computed. Now if I want to plot data just at the kick, which is located near to half of the dipole magnet i.e. after KICKn/2 or say at the last of magnet i.e. KICKn, how it can be done? I think "sddsplot bm4csrwake.wke -col=s,LinearDensity" plots after each kick on same graph (similarly DeltaGammaT1 and DeltaGammaT2 etc.)?

Thanks and regards,
Amal.

Amal,

Each of the wake output files has one "page" for each kick. sddsplot allows you to plot the pages separately for any SDDS file, using a command like You can use the menu buttons or hot-keys on the plotting window to navigate between the pages.

There is a document http://www.aps.anl.gov/Accelerator_Syst ... thSDDS.pdf
that provides an introduction to SDDS. It might be helpful to review it if you haven't already.

--Michael

Dear Sir,

Thanks for help...

Regards,
Amal.