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

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

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

IBS calculations F. Antoniou - APF 17/1/ 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.

IBS simulation tools 5

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

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 ARC STRAIGHT SECTION STRAIGHT SECTION STRAIGHT SECTION STRAIGHT SECTION Courtesy M. Pivi

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

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

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

IBS studies for the CLIC DR 11

DR performance parameters F. Antoniou - CLIC Workshop

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

The CLIC DR layout F. Antoniou - CLIC Workshop 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

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

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

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

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

Deliverable emittances from the CLIC DR F. Antoniou - CLIC Workshop 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

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

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

Characterization of the machine F. Antoniou - CLIC Workshop N. Milas et al., TIARA-CONF-WP Courtesy N. Milas

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

IBS measurements at the SLS F. Antoniou - CLIC Workshop

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

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

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

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

Backup slides 29

IBS increments along a TME cell F. Antoniou - CLIC Workshop 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

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

Parameterization with the emittance F. Antoniou - CLIC Workshop 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

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

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

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