| Article | |
| Title | Impact of beam-coupling impedance on the Schottky spectrum of bunched beam |
| Author(s) | Lannoy, C (CERN ; LPHE, Lausanne) ; Lasocha, K (CERN) ; Pieloni, T (LPHE, Lausanne) ; Alves, D (CERN) ; Mounet, N (CERN) |
| Publication | 2024 |
| Number of pages | 21 |
| In: | JINST 19 (2024) P03017 |
| In: | 68th ICFA Advanced Beam Dynamics workshop on high-Intensity and High-Brightness Hadron Beams (HB 2023), CERN, Geneva, Switzerland, 9 - 13 Oct 2023, pp.P03017 |
| DOI | 10.1088/1748-0221/19/03/P03017 |
| Subject category | Accelerators and Storage Rings |
| Accelerator/Facility, Experiment | CERN LHC |
| Abstract | The Schottky monitors of the Large Hadron Collider (LHC) canbe used for non-invasive beam diagnostics to estimate various bunchcharacteristics, such as tune, chromaticity, bunch profile orsynchrotron frequency distribution. However, collective effects, inparticular beam-coupling impedance, can significantly affectSchottky spectra when large bunch charges are involved. In suchconditions, the available interpretation methods are difficult toapply directly to the measured spectra, thus preventing theextraction of beam and machine parameters, which is possible forlower bunch charges. To study the impact of impedance on suchspectra, we introduce a method for building Schottky spectra frommacro-particle simulations performed with the PyHEADTAIL code,applied to LHC beam conditions. In this case, the use of a standardFast Fourier Transform (FFT) algorithm to recover the spectralcontent of the beam becomes computationally intractable memory-wise,because of the relatively short bunch length compared to the largerevolution period. To circumvent this difficulty, a semi-analyticalmethod was developed to efficiently compute the Fouriertransform. The simulated Schottky spectrum is then compared againsttheoretical formulas and measurements of Schottky signals previouslyobtained with lead ion beams in the LHC where impedance effects areexpected to be limited. Furthermore, this study providespreliminary interpretations of the impact of beam-coupling impedanceon proton Schottky spectra by incorporating longitudinal andtransverse resonator-like impedance models into the simulations. Atheoretical framework is also introduced for the case of thelongitudinal impedance, allowing the extension of the existingtheoretical formalism. |
| Copyright/License | publication: © 2024-2025 The Author(s) (License: CC-BY-4.0) |
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Record created 2024-04-04, last modified 2024-09-06
