1. Intrabeam scattering simulations and measurements F. Antoniou, Y. Papaphilippou CLIC Workshop 2013, 30/1/2013

2. Outline Intrabeam scattering (IBS) effect IBS simulation tools ▫Benchmarking of MC codes with theoretical models ▫Comparison between the theoretical models IBS studies for the CLIC Damping Rings ▫Energy scaling ▫Optimization of the arc TME cell with respect to IBS ▫Optimization of the wiggler FODO cell with respect to IBS ▫Deliverable emittances from the CLIC DR IBS measurements at the SLS and observations at Cesr-TA Conclusions Intrabeam scattering (IBS) effect IBS simulation tools ▫Benchmarking of MC codes with theoretical models ▫Comparison between the theoretical models IBS studies for the CLIC Damping Rings ▫Energy scaling ▫Optimization of the arc TME cell with respect to IBS ▫Optimization of the wiggler FODO cell with respect to IBS ▫Deliverable emittances from the CLIC DR IBS measurements at the SLS and observations at Cesr-TA Conclusions F. Antoniou - CLIC Workshop 2013 2

3. Intrabeam scattering (IBS) Small angle multiple Coulomb scattering effect ▫Redistribution of beam momenta ▫Beam diffusion with impact on the beam quality  Brightness, luminosity, etc Small angle multiple Coulomb scattering effect ▫Redistribution of beam momenta ▫Beam diffusion with impact on the beam quality  Brightness, luminosity, etc 3 Different approaches for the probability of scattering ▫Classical Rutherford cross section ▫Quantum approach ▫Relativistic “Golden Rule” for the 2-body scattering process Different approaches for the probability of scattering ▫Classical Rutherford cross section ▫Quantum approach ▫Relativistic “Golden Rule” for the 2-body scattering process Several theoretical models and their approximations developed over the years  three main drawbacks: ▫Gaussian beams assumed ▫Betatron coupling not included ▫Impact on damping process? Several theoretical models and their approximations developed over the years  three main drawbacks: ▫Gaussian beams assumed ▫Betatron coupling not included ▫Impact on damping process? Monte Carlo (MC) tracking codes can investigate these. F. Antoniou - APF 17/1/2013

4. IBS calculations F. Antoniou - APF 17/1/2013 4 Steady State emittances The IBS growth rates in one turn (or one time step) Complicated integrals averaged around the ring. Horizontal, vertical and longitudinal equilibrium states and damping times due to SR damping If ≠0 If = 0 Steady state exists if we are below transition or in the presence of SR.

5. IBS simulation tools 5

6. IBS multi-particle tracking codes The IBS theoretical models consider Gaussian beam distributions and uncoupled frames  In reality it is not obvious if this is valid, especially in strong IBS regimes  Coupling could play an important role, especially for flat beams Those effects can be studied only with multi- particle tracking codes Recently two codes have been developed  SIRE (A. Vivoli, M. Martini)  Currently on “pause”  CMAD-IBStrack (T. Demma, M. Pivi)  It has the advantage that it can run in parallel mode  The work for taking into account the betatron coupling is already in progress The IBS theoretical models consider Gaussian beam distributions and uncoupled frames  In reality it is not obvious if this is valid, especially in strong IBS regimes  Coupling could play an important role, especially for flat beams Those effects can be studied only with multi- particle tracking codes Recently two codes have been developed  SIRE (A. Vivoli, M. Martini)  Currently on “pause”  CMAD-IBStrack (T. Demma, M. Pivi)  It has the advantage that it can run in parallel mode  The work for taking into account the betatron coupling is already in progress F. Antoniou - CLIC Workshop 2013 6

7. Benchmarking of MC codes with theories SIRE (top) and CMAD- IBStrack (bottom) benchmarking with theoretical models for the CLIC DR lattice ▫1 turn emittance evolution comparison Excellent agreement with Piwinski as expected All models and codes follow the same trend on the emittance evolution Clear dependence on the optics ▫Large contribution from the arcs SIRE (top) and CMAD- IBStrack (bottom) benchmarking with theoretical models for the CLIC DR lattice ▫1 turn emittance evolution comparison Excellent agreement with Piwinski as expected All models and codes follow the same trend on the emittance evolution Clear dependence on the optics ▫Large contribution from the arcs F. Antoniou - CLIC Workshop 2013 7 ARC STRAIGHT SECTION STRAIGHT SECTION STRAIGHT SECTION STRAIGHT SECTION Courtesy M. Pivi

8. CMADIBStrack benchmarking - SLS The output emittances of CMAD-IBStrack was benchmarked with Piwinski (solid, gray) and Bane (dashed, gray), for three different bunch current values (1mA, 10mA, 17mA), thus at different IBS regimes  Excellent agreement between models and code at weak IBS regimes  When the effect becomes stronger, the disagreement grows. F. Antoniou - CLIC Workshop 2013 8

9. Comparison between theoretical models Comparison between the theoretical models for the SLS lattice All results normalized to the ones from BM Good agreement at weak IBS regimes Divergence grows as the IBS effect grows ▫Benchmarking of theoretical models and MC codes with measurements is essential Comparison between the theoretical models for the SLS lattice All results normalized to the ones from BM Good agreement at weak IBS regimes Divergence grows as the IBS effect grows ▫Benchmarking of theoretical models and MC codes with measurements is essential F. Antoniou - CLIC Workshop 2013 9

10. Status of the simulation tools SIRE has been in “pause” the last 1-2 years but hopefully the development will continue soon CMAD-IBStrack is a very attractive tool, well advanced and with the ability to run in parallel mode which speeds up a lot the calculations  We hope to have it installed at CERN too in the near future ibs-madx not a tracking tool but rather analytical tool  it has been now debugged and crosschecked giving very good results.  However, needs to be used carefully  There are some notes in the madx-ibs manual and more will come soon SIRE has been in “pause” the last 1-2 years but hopefully the development will continue soon CMAD-IBStrack is a very attractive tool, well advanced and with the ability to run in parallel mode which speeds up a lot the calculations  We hope to have it installed at CERN too in the near future ibs-madx not a tracking tool but rather analytical tool  it has been now debugged and crosschecked giving very good results.  However, needs to be used carefully  There are some notes in the madx-ibs manual and more will come soon F. Antoniou - CLIC Workshop 2013 10

11. IBS studies for the CLIC DR 11

12. DR performance parameters F. Antoniou - CLIC Workshop 2013 12

13. The CLIC DR layout Racetrack configuration ▫2 arc sections filled with TME cells ▫2 long straight sections filled with FODO cells accommodating the damping wigglers Racetrack configuration ▫2 arc sections filled with TME cells ▫2 long straight sections filled with FODO cells accommodating the damping wigglers F. Antoniou - CLIC Workshop 2013 13

14. The CLIC DR layout F. Antoniou - CLIC Workshop 2013 14 Racetrack configuration ▫2 arc sections filled with TME cells ▫2 long straight sections filled with FODO cells accommodating the damping wigglers Racetrack configuration ▫2 arc sections filled with TME cells ▫2 long straight sections filled with FODO cells accommodating the damping wigglers

15. DR optics optimization with respect to IBS F. Antoniou - CLIC Workshop 2013 15

16. TME optimization with respect to IBS F. Antoniou - CLIC Workshop 2013 16 ε ra =6 ε ra : Detuning factor of the arc emittance

17. TME optimization with respect to IBS F. Antoniou - CLIC Workshop 2013 17

18. Optimization of the wiggler FODO cell F. Antoniou - CLIC Workshop 2013 18

19. Deliverable emittances from the CLIC DR F. Antoniou - CLIC Workshop 2013 19 CLIC is planned to be built in energy stages At low energies higher bunch charge for the high luminosity This will affect the performance of the DR ▫Higher bunch charge  Enhance the IBS effect CLIC is planned to be built in energy stages At low energies higher bunch charge for the high luminosity This will affect the performance of the DR ▫Higher bunch charge  Enhance the IBS effect For constant output vertical and longitudinal emittance scaling lows derived ε xr =f(I) ε xr =f(ε lr ) ε xr =f(ε lr ) independent on the vertical emittance For constant output vertical and longitudinal emittance scaling lows derived ε xr =f(I) ε xr =f(ε lr ) ε xr =f(ε lr ) independent on the vertical emittance

20. IBS measurements at the SLS and observations at the Cesr-TA 20

21. F. Antoniou - CLIC Workshop 2013 21 The SLS as a test facility for IBS measurements

22. Characterization of the machine F. Antoniou - CLIC Workshop 2013 22 N. Milas et al., TIARA-CONF-WP6-2012-003 Courtesy N. Milas

23. IBS measurements at the SLS F. Antoniou - CLIC Workshop 2013 23 V rf =600 kV V rf =2 MV The MI model very important for the comparison with theoretical models

24. IBS measurements at the SLS F. Antoniou - CLIC Workshop 2013 24

25. IBS observations at Cesr-TA F. Antoniou - CLIC Workshop 2013 25

26. IBS observations at Cesr-TA F. Antoniou - CLIC Workshop 2013 26

27. Conclusions  Intrabeam scattering is an effect which becomes predominant in the regimes of operation of the CLIC DR  Careful optics design taking into account the IBS effect is important  At weak IBS regimes good agreement between all theoretical models while divergence grows at strong IBS regimes  Benchmarking of the IBS analytical models and the tracking codes, in the presence of SR, with measurement data is the ultimate goal ▫IBS measurement campaigns at the SLS and at Cesr-TA are ongoing  Development of good machine models in order to disentangle IBS from other current dependent effects is of great importance!!  Intrabeam scattering is an effect which becomes predominant in the regimes of operation of the CLIC DR  Careful optics design taking into account the IBS effect is important  At weak IBS regimes good agreement between all theoretical models while divergence grows at strong IBS regimes  Benchmarking of the IBS analytical models and the tracking codes, in the presence of SR, with measurement data is the ultimate goal ▫IBS measurement campaigns at the SLS and at Cesr-TA are ongoing  Development of good machine models in order to disentangle IBS from other current dependent effects is of great importance!! F. Antoniou - CLIC Workshop 2013 27

28. Acknowledgements IBS simulations ▫A. Vivoli & M. Martini (SIRE), T. Demma & M. Pivi (CMAD-IBS), F. Zimmermann (“ibs” in madx) IBS measurements ▫A. Streun, N. Milas, M. Aiba, M. Boege, A. S. Hernandez (SLS/PSI) ▫Cesr-TA IBS group IBS simulations ▫A. Vivoli & M. Martini (SIRE), T. Demma & M. Pivi (CMAD-IBS), F. Zimmermann (“ibs” in madx) IBS measurements ▫A. Streun, N. Milas, M. Aiba, M. Boege, A. S. Hernandez (SLS/PSI) ▫Cesr-TA IBS group 28 THANK YOU FOR YOUR ATTENTION! F. Antoniou - APF 17/1/2013

29. Backup slides 29

30. IBS increments along a TME cell F. Antoniou - CLIC Workshop 2013 30 IBS increments of a nominal TME cell IBS increments of a TME cell with gradient in the dipole ▫Reduction of the IBS increments by a factor of 3

31. Analytical parameterization of the TME cell F. Antoniou - CLIC Workshop 2013 31

32. Parameterization with the emittance F. Antoniou - CLIC Workshop 2013 32 Parameterization of the horizontal dispersion and beta functions at the center of the dipole with the horizontal and vertical phase advances Relaxed conditions for low phase advances Parameterization of the horizontal dispersion and beta functions at the center of the dipole with the horizontal and vertical phase advances Relaxed conditions for low phase advances

33. Optimization of the DR TME arc cell F. Antoniou - CLIC Workshop 2013 33

34. Optimization of the DR TME cell F. Antoniou - CLIC Workshop 2013 34

35. Optimization of the DR TME cell F. Antoniou - CLIC Workshop 2013 35