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BetaBeat.src

Since 2025, the former omc3 branch has been moved to the master branch of the GUI and is now the default for all new users. The "BetaBeat.src" branch of the GUI has been retired from master to the BetaBeatSrc branch and is no longer under active development.

Legacy version are still available on CAS.

Meaning of the Output Files

The naming of output files in Beta-Beat.src analysis can be very unintuitive. Namely, one will see similar output files for a quantity which go as get_*.out, get_*_free.out and get_*_free2.out, where * is the calculated quantity (betas, phase, etc.). These each correspond to a variation of the calculated quantity, explained below.

When doing our measurements, we use AC-Dipole driven excitations of the beam for a better signal-to-noise ratio in data acquisition. However, as the AC-Dipole has an effect on the beam optics functions the reconstructed optics from these measurements are the driven optics, not those of the accelerator itself. One can compensate for this deviation in different ways, which is why there are several output files for each optics quantity computed.

Meaning of Different Output Files

Nomenclature Meaning
get_*.out The optics functions without compensation, from the driven excitation data.
get_*_free.out The optics functions compensated analytically using an equation2.
get_*_free2.out The optics functions compensated the other way, see bellow.

In the case of the get_*_free2.out files, the compensation is done differently depending on the computed quantity. For some quantities (for instance for \(\beta\) from phase) this uses the model values, for others (for instance the coupling RDTs \(f_{1001}\) and \(f_{1010}\)) it is a rescaling in which the model values are used indirectly.

The method used to output the get_*_free2.out files is sometimes more robust as it does not rely on the existence of certain BPMs in the output (which could be missing after cleaning), and in some edge cases is more accurate1.

Do Compare Outputs

For debugging purposes, if the final result looks unbelievable, it might be of advantage to check the uncompensated output to rule out (or confirm) a failure in the recalibration method.

  1. Reaching the Sub Per Mil Level Coupling Corrections in the LHC", E. Høydalsvik and T. Persson, IPAC 2021 
    @inproceedings{IPAC:Hoydalsvik:SubPerMilCouplingLHC,
    title        = {Reaching the {{Sub Per Mil Level Coupling Corrections}} in the {{LHC}}},
    author       = {Høydalsvik, Eirik and Persson, Tobias},
    booktitle    = {Proceedings of the 12th {{International Particle Accelerator Conference}}},
    publisher    = {{JACoW Publishing, Geneva, Switzerland}},
    volume       = {IPAC2021},
    doi          = {10.18429/JACOW-IPAC2021-THPAB001},
    isbn         = {978-3-95450-214-1},
    url          = {https://accelconf.web.cern.ch/ipac2021/papers/thpab001.pdf},
    date         = 2021,
    langid       = {english}
}

    ↩

  2. Measurement of Coupling Resonance Driving Terms with the AC Dipole", R. Miyamoto, BNL--94350-2010-IR, 1013520 
    @report{MiyamotoMeasurementCouplingRDTsACDipole,
    title        = {Measurement of {{Coupling Resonance Driving Terms}} with the {{AC Dipole}}},
    author       = {Miyamoto, R.},
    year         = 2010,
    month        = 10,
    number       = {BNL--94350-2010-IR, 1013520},
    doi          = {10.2172/1013520},
    url          = {https://www.bnl.gov/isd/documents/74582.pdf},
    langid       = {english}
}

    ↩