Computer simulation is an indispensable tool in assisting the design, construction, and operation of accelerators. In particular, computer simulation complements analytical theories and experimental observations in understanding beam dynamics in accelerators. The ultimate function of computer simulation is to study mechanisms that limit the performance of frontier accelerators. There are four goals for the benchmarking of computer simulation codes, namely debugging, validation, comparison and verification: (1) Debugging--codes should calculate what they are supposed to calculate; (2) Validation--results generated by the codes should agree with established analytical results for specific cases; (3) Comparison--results from two sets of codes should agree with each other if the models used are the same; and (4) Verification--results from the codes should agree with experimental measurements. This is the summary of the joint session among working groups A, B, and D of the HI32006 Workshop on computer codes benchmarking

HOFMANN, I.

SHAPOSHNIKOVA, E.

WEI, J.

ZIMMERMANN, F.

UNT Digital Library

BROOKHAUEN NATIOEkKL LABORATORY ./ BNL-7 7069 -2006-CP Summa y of General Working Group A+B+D: Codes Benchmarking Jie Wei (BNL), E. Shaposhnikova, F. Zimmermann (CERN) I. Hofmann (GSI) Presented at the HB2006 - 39”’ ICFA Advanced Beam mamics  Workshop High Intensig High Brightness Hadron Beams Tsukuba, JAPAN May29 - June2,2006 August 2006 Collider-Accelerator Department Brookhaven National Laboratory P.O. Box 5000 Upton, NY I 1973-5000 www.bnl.gov Notice: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-ACO2-98CH10886 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world- wide license to publish or reproduce the published form of this manuscrip4 or allow others to do so, for United States Government purposes. This preprint is intended for publication in a journal or proceedings. Since changes may be made before publication, it may not be cited or reproduced without the author‘s permission. ’ DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof SUMMARY OF GENERAL SESSION OF WORKING GROUPS A+B+D ON CODE BENCHMARKING * J. Weit, Brookhaven National Laboratory, New York, USA E. Shaposhnikova, E Zimmermann, CERN, Geneva, Switzerland I. Hofmann, GSI, Germany for the working group A, B, and D participants Abstract and electron cooling. Each topic contains one or more tasks for codes benchmarking. Information on many codes as well as some benchmark- ing examples can be found in the CARE-HHH accelerator physics code web repository [2]. This is the summary of the joint session among working groups A, B, and D of the HI32006 Workshop on computer codes benchmarking. INTRODUCTION son, 0 Computer simulation is an indispensable tool in assist- ing the design, construction, and operation of accelerators. In particula, computer simulation complements analytical theories and experimental observations in understanding beam dynamics in accelerators. The ultimate function of computer simulation is to study mechanisms that limit the performance of frontier accelerators. There are four goals for the benchmarking of computer simulation codes, namely debugging, validation, compari- and verification [ 11: 0 0 Debugging: codes should calculate what they are sup- posed to calculate; Validation: results generated by the codes should agree with established analytical results for specific cases; Comparison: results from two sets of codes should agree with each other if the models used are the same; Verification: results from the codes should agree with experimental measurements. Adequate debugging is the first goal that established codes should meet. In the following, we summarize the status of validation, comparison, and verification, and provide sug- gestions for each topic discussed, Speakers in the code benchmarking session were G. Franchetti (GSI), E Zirmnermann (CEJXN), V. Ko- rnilov (GSI), I. Hofmann (GSI), A. Burov (FNAL), K. Ohmi (KEK), and A. Fedotov (BNL). Authors whose presentations in other sessions are quoted in this sum- mary include V. Danilov (ORNL), S. Cousineau (ORNL), J. Holmes (OW), L. Prost (FNAL), J.-L. Vay (LBNL) and E. Benedetto (CERN). - CODES BENCHMARKING STATUS Four topics were covered by this session: space charge, electron cloud, instability driven by external impedances, *Work supported by the auspices of the US Department of Energy. t jwei@bnl.gov Space Charge Montague resonance and emittance exchange The aim is to compare the evolution of horizontal and vertical emittances as the transverse tunes are varied so as to cross the Montague resonance of 2u, - 2uy = 0. 0 Validation with 2D analytical theory is performed for most codes. Validation with 3D theory is performed only for a few cases. 0 Comparison is performed [3] between the codes ACC- SIM [4], IMPACT [5], MICROMAP [GI, ORBIT [7], SIMBAD [&I, SIMPSONS [9], and SYNERGIA [lo]. Good agreement is achieved using 2D models, track- ing for lo3 turns, and observing emittance evolution when the transverse tunes are swept to cross the Mon- tague resonance. * Verification is performed with IM€’ACT3D [5] against experiments on the CERN PS. When the vertical tune is fixed and various horizontal tunes are selected, the agreement is excellent on resonance but poor off res- onance. The agreement is poor when one tune is dy- namically varied over a time period of 4x lo4 turns. 0 Suggestion: Longitudinal synchrotron motion needs to be added, and lattice nonlinearities need to be in- cluded in all simulation codes. Resonance trapping with sextupoles The present airn is to compare space charge induced trapping of particles in the presence of sextupole magnets during long-term stor- age. The final airn is to determine halo density and beam loss during long-term storage of high intensity beams. 0 No quantitative analytical predictions are available for validation. 0 Comparison is performed [ l l ]  between codes MI- CROMAP [GI and SIMPSONS [9]. The comparison is satisfactory on space charge detuning and third-order resonance trapping. However, at the time of the work- shop there was about a factor of 2 difference in the full bunch emittance growth for 105-turn simulation using lo3 macroparticles. This factor has recently been re- solved and the two codes now are in nearly perfect agreement [ 121. e Verification is performed with MICROMAP against experiments on the CERN PS with satisfactory agree- ment. 0 Suggestion: More comparison is needed with fully self-consistent codes like ORBIT [71. Electron Cloud The aim is to compare the electron density in the beam and vacuum chamber and the electron flux on the chamber wall under beam induced electron mul- tipacting. Validation is limited to some special models of multi- pacting. e Comparison is performed [13, 14, 151 between the codes POSINST [16], PEI [17], ECLOUD [lSI, CLOUDLAND [19], EPI [2O];CSEC [21], andMEC [22]. The result is sensitive to often unknown and time dependent surface parameters including the inci- dent angular dependence of secondary emission yield S,,, (e)  and zero-energy reflectivity R. The agree- ment is typically within a factor of 2 to 3 in electron density. 0 Verification is performed with ECLOUD [lS] against SPS experimental data [23]. Fixing the vaccum pres- sure and using two fitted parameters (Sma = 1.35, R = 0.3), good agreement is achieved for all mea- surements (two types of bunch train spacing). Verifi- cation is also performed with the codes POSINST [ 161 against A P S  and PSR experimental data; good agree- ment is reached also here using two fitted parameters. e Suggestion: Benchmarking study on surface scrub- bing is needed. More bench measurements are needed on the secondary emission yield and the secondary- electron energy spectrum their dependence on the an- gle of primary incidence. Electron build-up Multi-bunch instability The aim is to study multi- bunch instability induced by the electron cloud in a posi- tively charged beam. 0 Some model validation is performed against analytical predictions based on simulated wake fields generated by the electron cloud. No comparison is performed between codes, since only one code, PEI-M [17,24], is available. e Verification is performed with code PEI-M [17] against KEKB experimental data [24]. Qualitative agreement is obtained on the mode frequency. On the other hand, when the solenoid is turned on, a good agreement is obtained only if a factor of 5 adjustment is made on the solenoid field. e Suggestion: It is preferable to combine multi-bunch electron cloud instability codes with single bunch in- stability codes. PEI-M [17] is the only example so far. Single bunch instability The aim is to study single bunch instability induced by electron cloud in a positively charged beam. * Two-particle and broadband resonator models are used to validate the codes with satisfactory agreement (within about 30% in predicted emittance growth). e Comparison is performed between the codes PEHT [25], PEHTS [26], HEADTAIL [27], and QUICKPIC [2S] with qualitative agreement on the predicted trans- verse emittance growth [29, 13, 301. Different from the other codes, PEHT [25] contains a ,micro-bunch model. e Verification is performed with the codes PEWS [26] and HEADTAIL [27] against KEK-B experimental data [25, 311 and with code the ORBIT [7] against SNS experimental data [32]. The intensity threshold for electron-proton instability is correctly predicted for the SNS ring [32]. The upper sideband phe- nomenon found in KEKB has been understood and reproduced [31] in simulations with PEHTS [25] and HEADTAIL [27]. Simulations should consider realistic electron distribution. e Suggestion: Incoherent effects The aim is to study incoherent ef- fects related to electron cloud including emittance growth caused by periodic resonance crossing due to electron- cloud induced tune shift and electron-cloud induced res- onance trapping or scattering. 0 Validation against analytical model is not yet per- formed. e Some comparison is performed between codes HEADTAIL [27], Franchetti’s codes [12], CLOUDMAD [33], and PEHTS [26] with qualitative agreements [34]. e Verification is performed with codes HEADTAIL [27] against SPS experiments with good agreement [34]. 0 Suggestion: KEKJ3 observations below the electron cloud instability threshold need to be bench-marked. Effects due to numerical noise caused by finite num- ber of seed electrons and due to slicing interpolation could fui-ther be checked. Analytical estimate needs to be developed for the emittance growth. Self-consistent modeling The aim is to develop a self- consistent model incorporating both the electron generation and the interaction between electrons and beam particles. e Analytical validation is not performed. No comparison is performed between the available codes: ORBIT [7], WARPROSINST [35, 161, PAR- SEC [36], andPEI-M 1171. Verification is performed with codes WARP/POSINST [35, 161 against experimental observation at HCX [37, 381. Good agreement is obtained for a “coasting” beam. 0 Suggestion: Careful comparison needs to be per- formed between codes. It is highly desirable to de- velop self-consistent codes addressing performance limiting mechanisms like transverse emittance growth in LHC, beam losses in RHIC, SPS, PSR, and SNS, and vacuum pressure rise in RHTC. Instability Driven by External Impedances Transverse instability The aim is to study the thresh- old and growth rates of transverse instability induced by external beam coupling impedances. 0 An attempt has been made to validate PATRIC [39] with the dispersion relations of Moehl and Laclare [40J. However, large discrepancies are found in the stability area. 0 No code comparison has been presented at the work- shop. PATRIC [39] and ORBIT [7] are available for such activities. 0 Verification is performed with the code ORBIT [7] against experimental observations on the SNS ring [32]. Instabilities due to the resistive wall impedance and the extraction-kicker broadband impedance are predicted at observed intensity thresholds and fre- quencies. 0 Suggestion: Comparison needs to be performed be- . tween codes like PATRIC [39] and ORBIT [7]. Codes need to be compared with more comprehensive theo- ries, e.g., one by M. Blaskiewicz [41]. . Longitudinal instability The aim is to study the threshold and growth rates of longitudinal instability in- duced by external beam coupling impedances. 0 No validation results have been presented at the work- shop. 0 No comparison between codes has been presented at the workshop. Codes like ESME [42] and ORBIT [7] are available. Verification is performed with ORBIT against obser- vations at PSR [43] and with ESME against observa- tions at SPS [44], in both cases with good agreement. 0 Suggestion: Codes for multi-bunch longitudinal insta- bility study are needed. Electron Cooling Friction Force magnetized and non-magnetized electron cooling. The aim is to study the cooling friction force in both 0 Code VOW& [45] is validated with Parkhmochuk’s expressions for magnetized cooling [46]. 0 Comparison is performed between codes BETA- COOL [47] and VORPAL [45] with good agreement 0 Verification is performed with codes BETACOOL [47] and VORPAL [45] against experilnental data from CELSIUS for magnetized cooling [48], and with ~461. BETACOOL [47] against experimental observations at the FNAL recycler for non-magnetized cooling [481. 0 Suggestion: None. SUMMARY ‘Everybody believes in experiments except the experi- mentalist; Nobody believes in simulation except the simu- lationalist.” The recent success at SNS predicting instabil- ities (resistive wall, broadband, electron-proton) [32] on a newly built machine gives us hope that such rules may be violated! REFERENCES [l] M. Furman, HHH-2004 workshop, CERN, Geneva, Session [2] littp://ornweD.cerii.c1z:9000/pls/lihl~code~weDsite.stnrti~p [3] I. Hofrnann et al, “Benchmarking of Simulation Codes Based on the Montague Resonance on the CERN Proton Synchrotron,” PAC’O5 Knoxville (2005). [4] F. W. Jones, G. H. Mackenzie, and H. Schonauer, Part. Ac- cel. 31 (1990) 199. [5] Contact: J. Qiang (LBNL), R. Ryne; J. Qiang et al, J. Comp. Phys. 163 (2000) 434. [6] Contact: G. Franchetti (GSI), S. Rambaldi, G. Turchetti, A. Bazzani, A. Orzhekhovskaya, Web site: http://www- linux.gsi.de/ giuliano/micrornap/rnanmimac-trnp.html [7] Contact: A. Shishlo, J. Holmes, S. Cousineau (ORNL), Web site http://www.ornl.gov/ jzh/JHolmes/ORBIT.html; ORBIT Useis Mniiiml, J. Galambos, J. Holmes, D. Olsen, A. Luccio, and J. Beebe-Wang, SNS/ORWAP TN 001 1 ,  (1999), http://www.ornl.gov/sns/APGroup/Codes/ ORBI- TUserManl-1O.html GB (2004). [8] Contact: A. Luccio and J. Beebe-Wang. [9] Contact: S. Machida (ASTEC), Web site: http://hadron.kek.jp/ machiddsirnpsond; S. Machida, Nucl. Instr. Meth. A 309 (1991) 43. [lo] J. Arnundson, P. Spentzouris, “SYNERGIA: A Hybrid, Par- allel Beam Dynamics Code with 3D Space Charge,” PAC 2003 Portland (2003) 3195. /trnppiiig_Deiicliiiz~ikiizgllllniii. lztinl proceedings. [ 1 I] littp://~~~~vw-liizzi.gsi.de/~iiilinizo/resenrcli-nctivity- [12] G. Franchetti, S. Machida, I. Hofrnann, THBWO1, these [13] E. Benedetto et al, Proc. EPAC 2004, Lucerne (2004) 2502. [I41 G. Bellodi, CARE-HHH-APD HHH-2004 workshop, [ 151 http://coif-ecloud02. weD.cer~z.cldco~f- [lG] Contact: M. Pivi (SLAC), M. A. Fur- project.slac.stanford.edu/ilc/testfac/ecloud/elec_cloud.h~; M. A. Furman and M. T. E Pivi, Phys. Rev. ST-AB, 5 (2003) 124404. CERN-2005-006 (2005) 251. ecloiidO2/CodeCoiiipn~isoi~/ecsii~iDi~.1itriz man (LBNL), Web site: http://www- [17] Contact: K. Ohmi (KEK); K. Ohmi, Phys. Rev. Lett. 75 [44] E. Shaposhnikova, TUBXO5, these‘proceedings. [45] Contact: D. Bruhwiler (TX-Corp), C. Nieter, J. Cary, (1995) 1526. 1181 Contact: F. Zimmermann (CERN), D. Schulte, G. Web site: http://www.txcorp.com/products/VORPAIJ Bellodi, G. Rumolo, 0. Bruning, X.-L. Zhang, and http://www.txcorp.com/pdf/VORPAL/ VOR- Web site: http://wwwslap.cern.ch/collective/electron- PAL-UsersGuide.pdf; C. Nieter and J. Cary, J. Comp. cloud/Programs/Ecloud/ecloud.html; G. Rumolo, F. Physics 196 (2006), 448; D. Bruhwiler et al., AIP Conf. Zimermann, Practical User Guide for ECloud, CERN- Proceed. 773 (2005), 394. SL-Note-2002-016 (2002). r461 A. Fedotov, WEAY04, these Droceedings. - -  - [I91 Contact: L. Wang (SLAC); L. Wang, H. Fukuma, K’ Ohmi, [47] Contact: A. Sidorin (JIM), A. Smirnov (JINR), E. Svresin. G. Trubnikov, I. Meshkov, I. Seleznev. Web site: et. al., Proc. PAC 2001 (2001) 701. [20] K. Ohmi et al, “Simulation of Ep Instability for a Coasting Beam in Circular Accelerators,” EPAC 2004 Lucerne (2004) http://lepta.jinr.ru and http:/flepta.jinr.ru/betacool/doc.zip; A. Sidorin et al., Nucl. Instru. Methods, A 558 (2006) 325. 2107. [21] Contact: M. Blaskiewicz (BNL). [22] U. Lriso, S. Peggs, “Maps for Fast Electron Cloud Simula- [23] D. Schulte et al, PAC 2005 (2005) 1371. [24] S.S. Win et al, Proc. ECLOUD’02, Geneva, CERN-2002- 001 (2002) 199. [25] K. Ohmi, E Zimmermann, “Head-Tail Instability Caused by Electron Cloud in Positron Storage Rings,” Phys. Rev. Lett. 85 (2000) 3821. [26] K. Ohmi, “Particle in Cell Simulation of Beam-Electron Cloud Interactions,” PAC 2001 Chicago (2001) 1895. [27] Contact: E Zimmermann, G. Rumolo (CERN); Practical User Guide for HEADTAIL, G. Rumolo and F. Zimmer- mann, CERN-SL-Note-2002-036 AP (2002) [28] Contact: B. Feng (USC), A. F. Z. Ghalam, C. Huang, V. Decyk. [29] G. Rumolo et al, “Electron Cloud Studies for KEKB,” PAC 2001 Chicago (2001) 1889. [30] http://coilf-ecloudO~.we6cerii.clz/coilf- ecloiidO2/CodeCoiizparisoi~/nzodelii~st.lzti~z [3 11 K. Ohmi, E. Benedetto, J. Flanagan, private communication; and K. Ohmi, HB2006, THBW04 (2006). [32] V. Danilov, S. Cousineau, TUAXO1, these proceedings. [33] D. Chen et al, “Single Bunch Electron Cloud Effects in the NLC Beam Delivery System”, SLAC-TN-03-051, LCC- 0126 (2003). tions at RHIC,” EPAC 2004 Lucerne (2004) 2870. [34] E. Benedetto et al, Phys. Rev. Lett. 97 (2006) 034801. [35] A. Friedman (LBNL), D.P. Grote, J.-L. Vay, Web site: [36] Contact: A. Adelmann (LBNL) and M. A. Furman; Proc. [37] J.-L. Vay, HB2006, THAW01 (2006). [38] A. Molvik, HB2006, THAW02 (2006). [39] Contact: 0. Boine-Frankenheim (GSI). [40] V. Kornilov, TUBX02, these proceedings. [41] M. Blaskiewicz, Phys. Rev. ST-AB 1 (1998) 044201. [42] Contact: J.A. MacLachlan (FNAL); J.A. MacLachlan, FER- [43] S. Cousineau, J. Holmes, C. Beltran et al, “Benchmark and Threshold Analysis of Longitudinal Microwave Instability in the PSR”, EPAC 2004 Lucerne (2004) 2224. http://hif.lbl.gov/theoiy/WARP-summary.htd PAC 2003 (2003) 3524 MILAB TM-1274 (1984). [48] A. Fedotov, FRAP05, these proceedings. 

SUMMARY OF GENERAL WORKING GROUP A+B+D: CODES BENCHMARKING.

https://digital.library.unt.edu/ark:/67531/metadc890317/m2/1/high_res_d/896441.pdf

SUMMARY OF GENERAL WORKING GROUP A+B+D: CODES BENCHMARKING.

Abstract

Similar works

Full text

Available Versions

UNT Digital Library