Overview of Electron-Cloud Simulation Codes Session 6B Miguel A. Furman LBNL

1. Lawrence Berkeley National Laboratory Overview of Electron-Cloud Simulation Codes Session 6B Miguel A. Furman LBNL First CARE-HHH APD Workshop on Beam Dynamics in Future Hadron Colliders and Rapidly Cycling High-Intensity Synchrotrons CERN, 8-11 November 2004 HHH 2004

2. Acknowledgments Lawrence Berkeley National Laboratory I stole many slides from the ECLOUD’04 talks http://icfa-ecloud04.web.cern.ch/icfa-ecloud04/ My gratitude for collaboration or education over time to: A. Adelmann, G. Arduini, V. Baglin, M. Blaskiewicz, O. Brüning, Y. H. Cai, R. Cimino, I. Collins, O. Gröbner, K. Harkay, S. Heifets, N. Hilleret, J. M. Jiménez, R. Kirby, A. Kulikov, G. Lambertson, R. Macek, K. Ohmi, M. Pivi, G. Rumolo, D. Schulte, F. Zimmermann. • My apologies for the incompleteness of this talk • please bring omissions to my attention

3. Summary Lawrence Berkeley National Laboratory • List of codes and features; contact persons, status,… • Code features, sample results • The CERN e-cloud comparisons center • Current and future directions

4. Types of codes Lawrence Berkeley National Laboratory • EC buildup codes: • beam is prescribed (not dynamical, except possibly for multibunch dipole motion) • electrons are dynamical (macroparticles) • vacuum chamber geometry, various electron sources • Instability codes: • e-cloud is prescribed, at least initially; either lens or particle cloud • beam is dynamical (macroparticles) • Self-consistent codes: • various degrees of self-consistency • both beam and e-cloud are dynamical • typically 3D ; may accept an input lattice description • may or may not describe e-wall collisions (SEY) • ultimately: model gas desorption, photoelectric effect, ionization, stray particles/wall collisions, secondary ionization • Map code (MEC) (later)

5. Code table (incomplete; possible errors) Lawrence Berkeley National Laboratory SR=synchrotron rad. photoelectrons; SE=secondary electron emission; IZ=ionization of resid. gas; BPL=beam-particle losses SC=self-consistent;

6. Sample build up simulation: re vs. time Lawrence Berkeley National Laboratory ISIS PSR JPARC SNS AGS K. Ohmi, T. Koyama and C. Ohmori, PRSTAB 5, 114402 (2002)

7. E-cloud sample simulation in a quad (CLOUDLAND) Lawrence Berkeley National Laboratory L. Wang, ECLOUD’04

8. HEADTAIL simulation setup Lawrence Berkeley National Laboratory M. Pivi, ECLOUD’04

9. QUICKPIC and HEADTAIL results: s vs. time Lawrence Berkeley National Laboratory • Benchmarking: Single Kick QuickPIC vs. HEAD-TAIL (LHC params.) • For accurate benchmarking, QuickPIC is modified to be in single kick regime • Good agreement between the two codes. • LHC parameters have been used for benchmarking purpose. Red : QuickPIC(Single Kick Mode) Blue : HEAD-TAIL A. Ghalam, ECLOUD’04

10. QUICKPIC and HEADTAIL: more Lawrence Berkeley National Laboratory • Green : 4 Kicks/Turn • Blue : 2 Kicks/Turn • Red : 1Kick/Turn • Aqua : 16Kicks/Turn QuickPIC and HEADTAIL results for s vs. time E. Benedetto QuickPIC Results for LHC • Growth rate changes with the • number of kicks! HEAD-TAIL results for LHC A. Ghalam, ECLOUD’04

11. Contemporary developments Lawrence Berkeley National Laboratory • Do we need self-consistency? • Yes, in some cases: • At PSR, electron-cloud signal is 10-100 times larger for unstable beam than for stable • Do we need the 3rd dimension? • Yes, for long bunches (PSR) (see PSR quad movie) • Probably yes for long bunch trains and long/complicated machine lattices

12. PSR EC instability measurements Lawrence Berkeley National Laboratory R. Macek

13. PSR EC instability measurements Lawrence Berkeley National Laboratory “For high intensity unstable beams the electrons saturate our electronics. Setting up unstable beam at lower beam intensities allows us to see the electrons without saturation.” R. Macek R. Macek

14. Self-consistency plan Lawrence Berkeley National Laboratory roadmap for WARP+POSINST R. Cohen, ECLOUD’04

15. Self-consistency plan Lawrence Berkeley National Laboratory A. Shishlo, ECLOUD’04

16. Benchmarking ORBIT Lawrence Berkeley National Laboratory Y. Sato, ECLOUD’04 Theory: two-stream instability of coupled continuous beam-continuous ecloud: centroids as a f. of time (Koshkarev & Zenkevich; Keil & Zotter)

17. A map code (“MEC”) Lawrence Berkeley National Laboratory Relate ecloud density at time t to density at t-Dt by a heuristic nonlinear map U. Iriso, ECLOUD’04

18. CERN code comparisons centerhttp://wwwslap.cern.ch/collective/ecloud02/ecsim/ Lawrence Berkeley National Laboratory • Established by F. Zimmermann after ECLOUD’02 • Input parameters for “standard” test cases are spelled out • Everybody is invited to contribute!

19. CERN code comparisons center contd. Lawrence Berkeley National Laboratory Comparison of Build Up Simulations simulation results: electron line charge (total no. of e- per unit length) vs time # ECLOUD code (eps file) FZ,GR, 23.07.2002 # COUNTRYCLOUD code (eps file) Lanfa Wang, August 2002 # BNL code (eps file) Mike Blaskiewicz, August 2002 # PEI code (ps file) Kazuhito Ohmi, September 2002 # POSINST code (eps file) Mauro Pivi and Miguel Furman, September 2002; details of the LBNL simulation Last updated 23 August 2002, FZ Comparison of Instability Simulations simulation result: emittances vs. time # HEADTAIL code (ps file) Giovanni Rumolo, August 2002 # PEHTS code (ps file) Kazuhito Ohmi, November 2002, comments and additional studies (pdf) # QUICKPIC code (pdf file) Ali Ghalam, Tom Katsouleas, Giovanni Rumolo, November 2002 Last updated 29 November 2002, FZ Measurements and Parametrizations of Secondary Emission Secondary Electron Emission Data for the Simulation of Electron Cloud by N. Hilleret et al. (contribution to ECLOUD'02 Proceedings) Excel file by N. Hilleret Last updated 15 July 2002, FZ

20. Possible future developments Lawrence Berkeley National Laboratory • More “benchmarking” • debugging (code should calculate what is supposed to calculate) • validation (results should agree with established analytic result for specific cases) • comparisons (two codes should agree if the model is the same) • verification (code should agree with measurements) • ECLOUD simulations vs. SPS measurements • POSINST simulations vs. APS and PSR measurements • Others… • Move in 2 opposite directions: • More complete, detailed, quantitative predictions • Ultimately requires fully self-consistent 3D calculations • Simplified descriptions, few parameters, qualitative results with broad applicability • Identify a few basic relevant variables and input parameters (MEC code very promising in this regard)

21. Extra material

22. BIM in the APS (Advanced Photon Source, Argonne) Lawrence Berkeley National Laboratory • e+ beam, 10-bunch train, field-free region time-averaged e– flux at wall vs. bunch spacing measured simulated (Furman, Pivi, Harkay, Rosenberg, PAC01)

23. BIM for long bunches: PSR Lawrence Berkeley National Laboratory • bunch length ~60 m >> Dt • a portion the EC phase space is in resonance with the “bounce frequency” • “trailing edge multipacting” (Macek; Blaskiewicz, Danilov, Alexandrov,…) ED42Y electron detector signal 8mC/pulse beam (simulation input) electron signal 435 mA/cm2 (dmax=2.05) simulated(M. Pivi) measured(R. Macek)

24. Future computer Lawrence Berkeley National Laboratory Each center will get one: Sandia ORNL Pittsburgh • 2004: NERSC: 8000 processors (power PC3), ~8 Tflops • 2004: Red Storm: ~11600 processor Opteron-based MPP [>40 Tflops] • 2005: ~1280-Processor 64-bit Linux Cluster [~10 TF] • 2006 Red Storm upgrade ~20K nodes, 160 TF. • 2008--9 Red Widow ~ 50K nodes, 1000 TF. (?)