1. Proposals for 2015 impedance-related MD requests for PSB and SPS
C. Zannini, H. Bartosik, G. Rumolo

2. PSB impedance-related MDs for 2015
Coherent tune shift measurements
Transverse Instability measurements to integrate 2013 MDs

3. PSB impedance-related MDs for 2015
Coherent tune shift measurements
Transverse Instability measurements to integrate 2013 MDs

4. Coherent tune shift measurements
K. Li, N. Mounet
2013
D. Quatraro, Collective effects for the LHC injectors: non-ultrarelativistic approaches. PhD thesis, Bologna, University of Bologna, CERN-THESIS
Ring2, Ekin= 160 MeV

5. Coherent tune shift measurements campaign (2014)
MD week 40 (0.5 day)
Setup for 160 MeV tune shift measurements
MD week 41 (0.5 day)
Tune shift measurements in ring2 at 160 MeV
MD week 42 (0.5 day)
Setting up the cycle for high intensity
MD week 43 (1 day)
Measurements up to 900e11 in ring2 at 160MeV
The results confirm the measurements of week 41
MD week 44 (0.5 day)
Measurements in bunch shortening mode
MD week 45 and 46 (1.5 day)
Measurements in all rings at 160 MeV
MD week 47, 48 and 49 (1.5 day)
Measurements in all rings at 1.4 GeV
MD week 50 (0.5 day)
Measurements in all rings at 60 MeV
Measurements in all rings have been performed at 60 MeV, 160 MeV and 1.4 GeV
Measurements at 1.0 GeV would give a more complete picture of the PSB impedance

6. Coherent tune shifts at 60 MeV in ring2
Measurements 2014 (week 50)
The very good agreement validates the indirect space charge model

7. Coherent tune shifts at 60 MeV in ring2
Measurements 2014 (week 50)
The very good agreement validates the indirect space charge model

8. Coherent tune shift at 160 MeV in ring2
Measurements 2014 (week 41)
Very good agreement between model and measurements

9. Coherent tune shift at 160 MeV in ring2
Measurements 2014 (week 41)
Very good agreement between model and measurements

10. Vertical tune shift at 1.4 GeV in ring2
Measurements 2014 (week 48)
The model explain about 80% of the measured coherent tune shift at 1.4 GeV

11. Vertical tune shift at 1.4 GeV in ring2
Measurements 2014 (week 48)
The model explain about 80% of the measured coherent tune shift at 1.4 GeV

12. PSB impedance-related MDs for 2015
Coherent tune shift measurements
Transverse Instability measurements to integrate 2013 MDs

13. Transverse Instability measurements K. Li, N. Mounet, G. Rumolo et al
Measurements of the PSB instability versus chromaticity with feedback off at different intensities
With natural chromaticity (ξx≈-1, ξy≈-2)
Horizontal plane (unstable)
Vertical plane (unstable for coupling)
Decreasing horizontal chroma (less negative or even positive)
Horizontal plane (more unstable)
Increasing horizontal chroma (more negative)
Horizontal plane (tends to be stabilized)
Vertical plane (stable)
Vertical chromaticity is very nonlinear
Can we conclude on a classical headtail instability?
Resistive wall seems to be excluded
Data analysis is ongoing

14. Summary for the PSB Coherent tune shift measurements at 1.0 GeV
Motivation: Complete the picture of the PSB imaginary impedance
People: K. Li, C. Zannini
If needed transverse Instability measurements to integrate 2013 MDs
To be defined according to the outcome of the data analysis

15. SPS impedance-related MDs for 2015
Coherent tune shift measurements
Headtail instability growth rates for negative chromaticity
TMCI measurements
Multi bunch behaviour
Tune shift measurements
Coupled bunch instability
Parasitic MDs (beam induced heating of critical elements (e.g. kickers)) 

16. SPS impedance-related MDs for 2015
Coherent tune shift measurements
Headtail instability growth rates for negative chromaticity
TMCI measurements
Multi bunch behaviour
Tune shift measurements
Coupled bunch instability
Parasitic MDs (beam induced heating of critical elements (e.g. kickers)) 

17. Benchmarking the SPS transverse impedance model: coherent tune shift
Vertical coherent tune shift: Measurements performed in September 2012
The SPS impedance model explains more than 90% of the measured vertical coherent tune shift

18. Benchmarking the SPS transverse impedance model: coherent tune shift
Horizontal coherent tune shift: Measurements performed in February 2013
The SPS impedance model predicts a very small horizontal tune shift (almost flat) in agreement with the measurements

19. Benchmarking the SPS transverse impedance model: coherent tune shift
As expected, tune shifts before and after LS1 are very similar
Dependence on chromaticity of the coherent tune shifts

20. SPS impedance-related MDs for 2015
Coherent tune shift measurements
Headtail instability growth rates for negative chromaticity
TMCI measurements
Multi bunch behaviour
Tune shift measurements
Coupled bunch instability
Parasitic MDs (beam induced heating of critical elements (e.g. kickers)) 

21. Headtail instability growth rates for negative chromaticity: vertical plane (2013)
Q20 optics
Q26 optics
Measurements and HEADTAIL simulations have been found in very good agreement

22. Headtail instability growth rates for negative chromaticity: horizontal plane (2014)
Measurements of the headtail instability horizontal growth rates for Q20 optics
With octupoles off the beam was not unstable due to amplitude detuning
With octupoles on (corrected amplitude detuning) the headtail instability has been observed
Measured growth rates significantly smaller with respect to the simulated ones
Effect of octupoles on second order chromaticity seems to explain the dicrepancy (HEADTAIL simulation studies are ongoing)
The picture is not yet completely clear: new measurement are needed

23. SPS impedance-related MDs for 2015
Coherent tune shift measurements
Headtail instability growth rates for negative chromaticity
TMCI measurements
Multi bunch behaviour
Tune shift measurements
Coupled bunch instability
Parasitic MDs (beam induced heating of critical elements (e.g. kickers)) 

24. Benchmark of the SPS transverse impedance model: TMCI thresholds
Two regimes of instability in measurements
Fast instability threshold with linear dependence on εl
Slow instability for intermediate intensity and low εl
Very well reproduced with HEADTAIL simulations
measurements
HEADTAIL simulations
nominal
Island of slow instability
4.5x1011 p/b
@ 0.35 eVs 24
TMCI measurements with the new transverse damper

25. SPS impedance-related MDs for 2015
Coherent tune shift measurements
Headtail instability growth rates for negative chromaticity
TMCI measurements
Multi bunch behaviour
Tune shift measurements
Coupled bunch instability
Parasitic MDs (beam induced heating of critical elements (e.g. kickers)) 

26. Multi-bunch behaviour N. Mounet et al. 2010
Coupled bunch instability measurements
Update of the measurements
Multi-bunch tune shift

27. SPS impedance-related MDs for 2015
Coherent tune shift measurements
Headtail instability growth rates for negative chromaticity
TMCI measurements
Multi bunch behaviour
Tune shift measurements
Coupled bunch instability
Parasitic MDs (beam induced heating of critical elements (e.g. kickers)) 

28. Parasitic MDs: beam induced heating
Heating monitoring during ecloud studies (2012)
Measured bunch length
Impedance model expectation
Similar parasitic studies took place during the 2014 scrubbing runs for ZS and MKPs
Monitor the impedance heating of critical elements

29. Summary for the SPS
Coherent tune shift measurements versus chromaticity
Motivation: verify that the dependence on chromaticity of the tune shift is consistent with the impedance model
People: H. Bartosik, B. Salvant, C. Zannini
Headtail horizontal instability growth rates for negative chromaticity
Motivation: benchmarking the real part of the horizontal impedance model and nonlinear modeling (amplitude detuning, second order chromaticity with octupoles)
People: H. Bartosik, C. Zannini
TMCI with new transverse damper
Motivation: Study the effect on the TMCI of the new transverse damper
People: HBDWG
Multi bunch behaviour (Tune shift measurements, Coupled bunch instability)
Motivation: benchmarking the low frequency part of the existing impedance model
People: H. Bartosik, G. Iadarola, B. Salvant, C. Zannini
Parasitic MDs (beam induced heating of critical elements (e.g. kickers))
Motivation: benchmark of the impedance model of single elements
When: in particular during operation with high intensity LHC beams (e.g. scrubbing run)

30. Thank you very much for your attention

31. Growth rate versus chromaticity: Measurements
Measurements performed on February 2013
ξ = ξ(ACNR)

32. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.04

33. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.14

34. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.34

35. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.54

36. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.74

37. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.84

38. Comparing measurements and impedance model: intra-bunch motion
ξ = -0.94

39. Comparing all PSB rings: vertical
According to the expectation measurements in all rings shows similar tune shifts

40. Comparing all PSB rings: horizontal
According to the expectation measurements in all rings shows similar tune shifts
The difference between ring 1-3 and ring 4 is in the measurements uncertainty

41. Benchmark of the SPS transverse impedance model: TMCI thresholds
measurements
HEADTAIL simulations
nominal
Island of slow instability
4.5x1011 p/b
@ 0.35 eVs 41

42. Benchmark of the SPS transverse impedance model: TMCI thresholds
measurements
HEADTAIL simulations
nominal
Island of slow instability
4.5x1011 p/b
@ 0.35 eVs 42