1. 1 SC-13 – Consequences for us? Overview of the SC-13 Workshop Some Highlights Main Outcome Questions and Responses Our Week with the Code Experts 5/31/2013 FSOutcome of SC-13

2. 22 SC-13 Workshop Organization The scientific program by IAC: Y.Alexahin (FNAL), O. Boine ‐ Frankenheim(TUD/GSI), Hofmann (GSI/HI-Jena), J. Holmes (SNS), S. Machida (RAL), E. Metral (CERN), K. Ohmi (KEK), J. Qiang (LBL), F. Zimmermann (CERN) The program, the presentations and session and workshop summaries are available at the indico page: https://indico.cern.ch/conferenceDisplay.py?confId=221441 Approved/Sponsored: ICFA, EUCARD, ACCNET, HIC4FAIR, LIU 5/31/2013 FSOutcome of SC-13

3. 3 SC-13 Workshop Participants 5/31/2013 FSOutcome of SC-13 There have been 82 registrants distributed over the following countries, laboratories and companies: Switzerland (CERN) ------------------------------------------------------------------ 38 Germany (GSI, Frankfurt University) ------------------------------------------- 13 UK (STFC) ------------------------------------------------------------------------------- 12 USA (Fermilab, SNS, LANL, LBNL, MIT, Tech-X Cor., Muon Inc.) ---- 11 Japan (KEK) ---------------------------------------------------------------------------- 2 Austria (MedAustron) --------------------------------------------------------------- 1 China (IHEP) ---------------------------------------------------------------------------- 1 France (Saclay) ------------------------------------------------------------------------ 1 Mexico (universidad de sonora) ------------------------------------------------- 1 Russia (ITEP) --------------------------------------------------------------------------- 1 Sweden (ESS) -------------------------------------------------------------------------- 1

4. 5/31/2013 FSOutcome of SC-13 SC-13 The Group Photo

5. 5 SC-13 Workshop Sessions 5/31/2013 FSOutcome of SC-13 The workshop lasted for 3 and half days and the program has been grouped in the following sessions: 16 th of April Stimulus/Project Modeling/Theory/Overview Schmidt, Bartosik Space Charge Studies Ohmi, Huschauer Discussion Hofmann, Fitterer 17 th of April Machine model (Theory and Instruments) Prior, Forte Code development Alexahin, Wagner Discussion Holmes, Aumon 18 th of April High intensity effects Machida, Noll Synergies Zimmermann, Hein Discussion Metral, Wasef 19 th of April Mitigation and advanced techniques Boine-Frankenheim, Hernalsteens Joint Discussion/Outlook Hofmann, Holmes, Metral, Bartosik, Rijoff

6. 1.The LIU goal: “Double the number of particles per bunch” ➔ Space Charge has become very relevant for LHC injectors 1.Generational Problem for the Injectors ➔ We have started to create a new team of expertise on space charge covering all 3 rings 2.Strengthen Collaboration with other Laboratories (resurrected or new): a)GSI b)KEK c)Fermilab/SNS d)Others? 3.We are at a crossroad for our LIU studies: a)Huge effort made to do experiments until this spring b) ➔ This workshop c)Simulations to understand and improve our machines to reach LIU goal Why this SC-13 Workshop? General CERN Interest 5/31/2013 FSOutcome of SC-13

7. This can only be a small sample with emphasis and direct relevance in view of LIU Apologies for having to leave out lots of relevant material! Looking for catchy statements that reflect what the space charge community is presently thinking… Some Hightlights 5/31/2013 FSOutcome of SC-13

8. 5/31/2013 FSOutcome of SC-13 Chris Prior SpaceChargeModel

9. 5/31/2013 FSOutcome of SC-13 Chris Prior SpaceChargeModel

10. Status of the space charge studies and measurements in the CERN PSB Vincenzo Forte – Space charge workshop – CERN - 16/04/2012 Measurements: half integer resonance crossing… (static w. point above 2Qy=9) @ C450 (switching off QNO correctors) Nice case for code benchmarking (simulations are on-going) Transverse emittances constant Vincenzo PSB 5/31/2013 FSOutcome of SC-13

11. III. 4 th order Resonance  The 4 th order resonance seems to be excited by space charge Raymond WASEF, Space Charge Workshop, 16/04/13, CERN 8 Wasef PS

12. 12 Compensation of resonances beforeafter Compensation of 2q x +q y =1 3q y =1 is clearly enhanced vertical tune constant horizontal tune constant Huschauer PS

13. 13 Compensation of resonances beforeafter Compensation of 3q y =1 additionally: reduction of 2q x +q y =1 vertical tune constant horizontal tune constant Huschauer PS

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17. 5/31/2013 FSOutcome of SC-13 Bartosik SPS

18. Slow extraction in Debuncher using Orbit 3-order resonance with variable tune Qx and sext. str. K2 First “strange” results for extraction: “intensity drop” intensity vs turns “Intensity drop” was resolved simply at the beginning: Valery advised to make mesh refinements PIC: “Total Beam size increases at slow extraction => mesh number should be increased to keep the cell size” Kapin Fermilab 5/31/2013 FSOutcome of SC-13

19. 5/31/2013 FSOutcome of SC-13 Simulations with ORBIT by V. Nagaslaev Ramps are given in tables; Npart in bunch ~ 2.5e12 Kapin Fermilab

20. 5/31/2013 FSOutcome of SC-13 N_macro_surv vs Turn Number for the Debuncher Timing on CERN computer Macro version ~20-24h MADX-SC ~2-4h MAD-X V3 with Macros MADX-SC V5

21. Outcome of SC-13 3Q y =16 – uncorrected Phase and amplitude data obtained from Fourier spectra Beam intensityVertical beam positionNormalised phase space Fourier spectrum resonance strength and phase: 5/31/2013 FS Urschütz Driving terms (PSB)

22. 3Q y =16 – compensated Beam intensityVertical beam positionNormalised phase space Fourier spectrum Calculated compensation currents (for two independent skew sextupoles): I XSK2L4 = -29.3 A, I XSK9L1 = +15.3 A |h 0030 | = 9.0±0.6*10 -3 mm -1/2 ψ 0030 = -21º±14º Results from the measurements: Urschütz Driving terms (PSB) 5/31/2013 FSOutcome of SC-13

23. Machida PIC 5/31/2013 FSOutcome of SC-13

24. Machida PIC 5/31/2013 FS

25. Outcome of SC-13 Machida PIC

26. 5/31/2013 FSOutcome of SC-13 Machida PIC

27. 5/31/2013 FSOutcome of SC-13 Ohmi J-PARC MR

28. 5/31/2013 FSOutcome of SC-13 Ohmi J-PARC MR

29. Holmes pyORBIT 5/31/2013 FSOutcome of SC-13

30. 5/31/2013 FSOutcome of SC-13 Some History Micro-scale unphysical effects: H-detuning (left), fake tune evolutions, artificial dipole oscillations,…May jeopardize the validity of beam modeling Without SC – NO Micro-scale unphysical effects.WANTED: Consistency between ~Exact Trackers and Approximate SC Solvers Search for remedies Recent findings, when using ORBIT: Frank Schmidt, et al. Micro-scale effects APC Seminar at Fermilab, November 2012 “Benchmarking of PTC_ORBIT & SYNERGIA ”, https://indico.fnal.gov/conferenceDisplay.py?confId=6115

31. 5/31/2013 FSOutcome of SC-13 Library of Templates Pre-Assigned densities Ring Disc Template General  Halo Hollow Beam 3.A Hybrid Solvers, SC Templates Private Communications: A. Friedman, D. Grote, I. Hofmann, M. Reiser, J. Struckmeier and R. York

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35. 5/31/2013 FSOutcome of SC-13

36. 5/31/2013 FSOutcome of SC-13 Nghiem

37. 5/31/2013 FSOutcome of SC-13 Hofmann GSI

38. 38 SC-13 Main Outcome I 5/31/2013 FSOutcome of SC-13 1) The workshop has shown a rich activity on space charge related topics at CERN (LIU), GSI (FAIR), and RAL (ISIS upgrade).Several studies have been presented on experimental work and in particular concerning the LIU studies and ISIS upgrade. 2) In the session of code developments, the issue of code benchmarking has found a lot of attention with regards to long-term tracking. The presentation of the status of code benchmarking has been discussed and the issue about the noise created by PIC codes has evoked intense discussions. This topic has raised broader interest, in particular by J. Amudson, Eric Stern, J. Holmes, Ji Qiang, and Jean-Luc Vay. The decision has been taken to use the GSI test suite for benchmarking of frozen space charge models also for the benchmarking of PIC codes, both 2.5D and 3D. Firm plans have been made to benchmark Synergia and Orbit and hopefully also IMPACT and WARP.

39. 39 SC-13 Main Outcome II 5/31/2013 FSOutcome of SC-13 3) Some discussion has focused on role of GPU in the high intensity beam dynamics. Effort reported by GSI, RAL, FNAL were discussed at a deep technical level, and the present difficulties were highlighted. 4) Interesting from a theoretical standpoint has been a discussion about possibly equating PIC noise with intrabeam-scattering. To this end, previous work by J. Struckmeier has been reviewed on the effect of PIC noise on emittance growth. The audience has expressed the interest to study this topic in some detail.

40. During the Joint Discussion Session 7 Question have been presented to the community. These questions have been formulated beforehand both at CERN & GSI I have modified them for this talk The full set can be found on the web: ➔ http://indico.cern.ch/internalPage.py?pageId=9&confId=221441 5/31/2013 FSOutcome of SC-13 Question & Responses

41. 41 Question 1 5/31/2013 FSOutcome of SC-13 1) What about the modelling of our machines? Responses: What we really need is a better description of the machines Our simulations codes are more or less fine ➔ benchmarking! The question is how we can improve the nonlinear description of our machines? What are the possible methods?  Modeling of linear and nonlinear chromaticity  Resonance driving terms (correct chromaticity, kick in both planes, ) o some data in PS, PSB: difficult since only 1 family of sextupoles  Experience at other labs: o Chromaticity, DTA o ISIS: turn-by-turn o Octupolar components by local bumps There has been a significant amount of work being done for the PS in particular. But we still need a reliable magnet by magnet model which would require a more structured effort.

42. 42 Question 2 5/31/2013 FSOutcome of SC-13 2) What are the relevant mechanisms for beam loss and emittance growth? Responses: There seems to be consensus that resonances due to non-linear fields in conjunction with the tune spread due to space charge seems to lead to both problems: just approaching a resonance leads to emittance blow-up and resonance crossings may lead to losses. On a deeper level the community is split about the questions if these incoherent or also coherent effects are important, as being discussed concerning the half integer resonance crossing in the PSB.

43. 43 Question 3 5/31/2013 FSOutcome of SC-13 3) Which instrumentation do we need to measure our space charge effects? Responses: Concerning instrumentation there has mainly been proposals to provide 1000 turn BPM systems with good resolution Further the developments concerning wire scanners to allow for instance a better resolution of beam halo, i.e. improving existing instrumentation. Transverse tomography and collimators to reconstruct the transverse profile have been proposed as possible new tools. It was also mentioned that kickers in both planes are important to study coupled resonances. There has been a proposal to study coherent effects: A quadrupolar pickup should allow to measure coherent response of the beam to the half integer resonance. In fact, this pickup would allow for the first time the measurement of the real space charge tune spreads in a machine.

44. 44 Question 4 5/31/2013 FSOutcome of SC-13 4) PIC versus Frozen model: Which difference is "normal" and which is not? Responses: This issue has been central in the discussion during the workshop. On the one hand, benchmarking of several PIC codes have now been pursued and compared with the results of frozen space charge codes. ➔ This effort will take the better part of this year! On the other hand, renewed interest has been expressed to look into the noise issue of PIC codes in long-term storage ring simulations in more detail by several teams. It has been mentioned by PIC code developers that the single particle behavior allows a lot of in-sight into the understanding the working of the PIC codes.

45. 45 Question 5-7 5/31/2013 FSOutcome of SC-13 5) There seem to be some beams in the PS with most of the beam in the PS below the integer resonance ➔ not too many losses nor emittance growth. Can we explain this? 6) What is the maximum allowed space charge tune shift? 7) What can we do from the optics point of view to reduce space charge effects? Responses 5) No clear position from the audience except that the experimental data would have to be well documented to allow for a clarification. Responses 6-7) Both of the last 2 questions simply would need more studies. In fact, our simulation tools have to be better understood and benchmarked with experiments before a reliable answer can be given.

46. 46 Code Developer Meeting 22-26.04.13 5/31/2013 FSOutcome of SC-13 Invitation of code developers after SC-13 workshop Jeff Holmes(SNS) ORBIT proper Leonid Vorobiev ORBIT expert of Fermilab Eric Stern for Synergia Giuliano Franchetti stayed on for a few days Main goals Learn from the experts about the 2 PIC codes Demonstrate issues we had with un-physical behavior Plan benchmarking effort for both codes Mitigation efforts for the noise problem Alternative approaches Lively discussions and presentations all week long

47. 47 Code Developer Meeting II The support for the ORBIT code as we know it will be discontinued this year! It will be replaced by pyORBIT Mainly replacing Interface Hopefully they will introduce a hook to PTC There might even be a manual! Jeff gave a lecture about the most relevant ORBIT modules Benchmarking is agreed to proceed 5/31/2013 FSOutcome of SC-13

48. 48 Code Developer Meeting III Eric explained MPI as used in Synergia and gave a detailed report on the RUN facilities in their code. Jeff raised the question if PIC codes are the proper tool for long-term studies in storage rings! He expressed hope that the so-called FMM technique might be the right approach for the future. Leonid explained in detail both his mitigation proposal for minimizing the noise in ORBIT and his space charge templates as a possible long-term solution. Summary: http://frs.web.cern.ch/frs/Source/space_charge/SC- 13/Code_developer_meeting_22-26.04.13/ 5/31/2013 FSOutcome of SC-13

49. 49 Reserve 5/31/2013 FSOutcome of SC-13

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52. 5/31/2013 FSOutcome of SC-13 Ohmi J-PARC MR

53. 53 Question 1 5/31/2013 FSOutcome of SC-13 1) What we are really missing at the moment is a better description of our machines WRT to nonlinearities and in particular the variation from magnet to magnet. How can we determine this true non-linear model of the machine and how shall we treat our limited knowledge about it (keywords: sigma of the individual multipolar component, how many seeds). What are the different methods, which can be used to make some progress in this aspect (and time scale)? Which instrumentation do we need to measure "properly" the machine nonlinearities? 1.1)What is the meaning of “properly” in a space charge dominated regime that require 10 5 turns of storage time? In particular, the requirements are significantly affected by the physics: there are regimes in which 10% error in the knowledge of nonlinear components is enough for a good description of the machine, but there are other regimes where the concept of “good” or “properly” is difficult to be defined. Responses: What we really need is a better description of the machines; our simulations codes are more or less fine; The question is how we can improve the nonlinear description of our machines? What are the possible methods?  linear and nonlinear chromaticity  resonance driving terms (correct chromaticity, kick in both planes, ) o some data in PS, PSB: difficult since only 1 family of sextupoles  experience at other labs: o chromaticity, DTA o ISIS: turn-by-turn o octupolar components by local bumps There has been a significant amount of work being done for the PS in particular. But we still need a reliable magnet by magnet model which would require a more structured effort.

54. 54 Question 2 5/31/2013 FSOutcome of SC-13 2) For the actual necessity of projects what are the mechanisms for beam loss and emittance growth that are most important => Review of the relevant issue of each project and review of their relevant mechanisms including a comparison with some simple formulae Do we have good agreement? Responses: There seems to be consensus that resonances due to non-linear fields in conjunction with the tune spread due to space charge seems to lead to both problems: just approaching a resonance leads to emittance blow-up and resonance crossings may lead to losses. On a deeper level the community is split about the questions if these incoherent or also coherent effects are important, as being discussed concerning the half integer resonance crossing in the PSB.

55. 55 Question 3 5/31/2013 FSOutcome of SC-13 3) Which instrumentation do we need to measure our space charge effects? What has been the progress in instrumentation in the past years and what are the plans for the future? Responses: Concerning instrumentation there has mainly been proposals to provide 1000 turn BPM systems with good resolution and further the developments concerning wire scanners to allow for instance a better resolution of beam halo, i.e. improving existing instrumentation. Transverse tomography and collimators to reconstruct the transverse profile have been proposed as possible new tools. It was also mentioned that kickers in both planes are important to study coupled resonances. There has been a proposal to study coherent effects: A quadrupolar pickup should allow to measure coherent response of the beam to the half integer resonance. In fact, this pickup would allow for the first time the measurement of the real space charge tune spreads in a machine.

56. 56 Question 4 5/31/2013 FSOutcome of SC-13 4) The numerical aspects of beam physics codes with space charge are very important => In particular when we benchmark codes of either type frozen model or PIC type: which difference is "normal" and which is not. Responses: This issue has been central in the discussion during the workshop. On the one hand benchmarking of several PIC codes have now been pursued and compared with the results of frozen space charge codes. This effort will take the better part of this year. On the other hand, renewed interest has been expressed to look into the noise issue of PIC codes in long-term storage ring simulations in more detail by several teams. It has been mentioned by PIC code developers that the single particle behavior allows a lot of in-sight into the understanding the working of PIC codes.

57. 57 Question 5-7 5/31/2013 FSOutcome of SC-13 5) There seem to be some beams in the PS with most of the beam below the integer resonance and with not too many loses and emittance growth. Can we explain this? 6) What is the maximum space charge tune shift evolution over the past years / decade in the different machines. Did we make progress? Can we dream to reach more than 0.4? What are all the possibilities to push forward the limit? Is the only possibility to fight space charge to increase the injection energy? 7) What can we do from the optics point of view to reduce space charge effects? Responses 5) No clear position from the audience except that the experimental data would have to be well documented to allow for a clarification. Responses 6-7) Both of the last 2 questions simply would need more studies. In fact, our simulation tools have to be better understood and benchmarked with experiments before a reliable answer can be given.