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TMCI for LHC collimators (very preliminary results)

This study aims to improve the impedance of LHC collimators for the Phase 2 collimation project. Initial results indicate the need to assess single bunch effects and integrate simulation steps effectively.

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TMCI for LHC collimators (very preliminary results)

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  1. TMCI for LHC collimators (very preliminary results) Benoit, Elias, Giovanni, Nicolas Thanks to Adriana and the collimation team for the collimator parameters

  2. Context • Phase 2 collimation project to replace the existing collimation system. Objectives: divide the impedance by 10 while keeping collimator robustness and flatness • Need to give answers to the Phase 2 collimation project, in particular in terms of the impedance of preferred materials. • Need to assess the multibunch and single bunch effects of changing materials. Here we look at single bunch effects • Integration of the preprocessing and postprocessing steps to obtain the impedance and launch Headtail simulations for a set of collimators.

  3. Example of TMCI for a Phase 1 graphite collimator (gap=6 sigma) in IR7 TMCI between modes 0 and -1 Instability threshold at ~1014 p/b

  4. Changing the collimator resistivity (Here, the thresholds were obtained using the Sacherer formula) - We are quite far from the threshold - Worst case seems to be for resitivity of around 1 Ohm.m

  5. Changing the collimator permittivity (Here, the thresholds were obtained using the Sacherer formula) - We are quite far from the threshold - Worst case seems to be again for resitivity of around 1 Ohm.m

  6. To be continued…

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