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Summary of e - cloud activity in straight sections during the scrubbing run 2012

Summary of e - cloud activity in straight sections during the scrubbing run 2012. C. Octavio Dom ínguez. Thanks to the machine Coordinators, Cryogenics, Damper, EN/STI, Injection, Operation, Vacuum teams, ABP, RF and BI colleagues contributing to measurements.

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Summary of e - cloud activity in straight sections during the scrubbing run 2012

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  1. Summary of e- cloud activity in straight sections during the scrubbing run 2012 C. Octavio Domínguez Thanks to the machine Coordinators, Cryogenics, Damper, EN/STI, Injection, Operation, Vacuum teams, ABP, RF and BI colleagues contributing to measurements 11 January 2013 - e-cloud meeting

  2. Overview Nb (Beam 1) Nb (∙1014 p+) VGI.454.4R7.B VGI.99.4L3.B P (∙10-8 mbar) Time (hours) 11 January 2013 - e-cloud meeting

  3. Overview Nb (Beam 1) Fill 3398 Fill 3405 Fill 3407 Fill 3397 Nb (∙1014 p+) Fill 3396 Fill 3406 VGI.454.4R7.B VGI.99.4L3.B Norm. P (∙10-22 mbar/p+) Time (hours) 11 January 2013 - e-cloud meeting

  4. Overview • No dedicated fills for straight sections benchmarking • Instable beams  Losses  No stable pressure  Some needed considerations: 10 April 2011 19 May 2011 11 January 2013 - e-cloud meeting

  5. Overview • No dedicated fills for straight sections benchmarking • Instable beams  Losses  No stable pressure  Some needed considerations: DPav DPav DP4 DP3 DPav DP2 DP1 11 January 2013 - e-cloud meeting

  6. dmax evolution Fill 3396 ≈ Fill 3397 … 250 ns 925 ns 925 ns 925 ns Coarse grid! 11 January 2013 - e-cloud meeting

  7. dmax evolution Coarse grid! 11 January 2013 - e-cloud meeting

  8. Further analysis Fill 3406 ≈ Fill 3407 … 250 ns 925 ns 925 ns 925 ns • Scrubbing effect can be noticed from fill to fill Small DP No DP! 11 January 2013 - e-cloud meeting

  9. Further analysis Fill 3407 … 250 ns 925 ns 925 ns 925 ns • We can check into simulations to find a pair of values [dmax, R] which fulfills: • not to saturate for a batch of 144 bunches (at the measured pressure) • to saturate for a batch of 288 bunches (at the measured pressure) • We find dmax< 1.24 for any R, and dmax≈ 1.22 if we consider R=0.2  In agreement with previous analysis No DP! 11 January 2013 - e-cloud meeting

  10. Further analysis … … Fill 3405 Fill 3406 vs. Quality factor  • Qmindmax = 1.23 and R=0.2 • Not very accurate in this case because: • N = 1  too small • dmaxmight have varied during fill 3405  difficult comparison • But still in agreement with previous estimations 11 January 2013 - e-cloud meeting

  11. Threshold • A revision of the threshold has become necessary (previous value given for injection energy was dmax= 1.25) • I used 3 trains of 4 batches each • For R=0.2 the threshold at 450 GeV would be dmax≈ 1.16 11 January 2013 - e-cloud meeting

  12. Summary • The scrubbing effect is clearly visible through the reduction of the DP along the different fills • Several fills at injection energy have been used to infer beam chamber properties in straight sections (where pressure gauges are located) • Analysis is still on going but a clear reduction of can be observed (from ~1.3 to ~1.23) • Different methods point out to a similar solution at the end of the fills at injection energy (dmax ≈ 1.23 and R ≈ 0.2 ) • The threshold at injection energy for these locations has been calculated: • dmax ≈ 1.16 with R ≈ 0.2 11 January 2013 - e-cloud meeting

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