Analytical Estimation of Dynamic Aperture Limited by Wigglers in a Storage Ring

1. Analytical Estimation of Dynamic Aperture Limited by Wigglers in a Storage Ring 高傑 J. Gao 弘毅 Laboratoire de L’Accélérateur Linéaire CNRS-IN2P3, FRANCE KEK, Feb. 24 2004

2. Contents • Dynamic Apertures of Limited by Multipoles in a Storage Ring • Dynamic Apertures Limited by Wigglers in a Storage Ring • Discussions • Perspective • Conclusions • References • Acknowledgement

3. Dynamic Aperturs of Multipoles Hamiltonian of a single multipole Where L is the circumference of the storage ring, and s* is the place where the multipole locates (m=3 corresponds to a sextupole, for example). Eq. 1

4. Important Steps to Treat the Perturbed Hamiltonian • Using action-angle variables • Hamiltonian differential equations should be replaced by difference equations Since under some conditions the Hamiltonian don’t have even numerical solutions

5. Standard Mapping • Near the nonlinear resonance, simplify the difference equations to the form of STANDARD MAPPING

6. Some explanations • Definition of TWIST MAP where

7. Some explanations • Classification of various orbits in a Twist Map, Standard Map is a special case of a Twist Map.

8. Stochastic motions • For Standard Mapping, when global stochastic motion starts. Statistical descriptions of the nonlinear chaotic motions of particles are subjects of research nowadays. As a preliminary method, one can resort to Fokker-Planck equation .

9. m=4 Octupole as an example Step 1) Let m=4 in , and use canonical variables obtained from the unperturbed problem. Step 2) Integrate the Hamiltonian differential equation over a natural periodicity of L, the circumference of the ring Eq. 1

10. m=4 Octupole as an example Step 3)

11. m=4 Octupole as an example Step 4) One gets finally

12. General Formulae for the Dynamic Apertures of Multipoles Eq. 2 Eq. 3

13. Super-ACO Lattice Working point

14. Single octupole limited dynamic aperture simulated by using BETA x-y plane x-xp phase plane

15. Comparisions between analytical and numerical results Sextupole Octupole

16. 2D dynamic apertures of a sextupole Simulation result Analytical result

17. Wiggler Ideal wiggler magnetic fields

18. Hamiltonian describing particle’s motion where

19. Particle’s transverse motion after averaging over one wiggler period In the following we consider plane wiggler with Kx=0

20. One cell wiggler • One cell wiggler Hamiltonian • After comparing with one gets one cell wiggler limited dynamic aperture Eq. 4 Eq. 4 Eq. 1 Using one gets Eq. 2

21. A full wiggler Eq. 3 • Using one finds dynamic aperture for a full wiggler or approximately where is the beta function in the middle of the wiggler

22. Multi-wigglers • Many wigglers (M) • Dynamic aperture in horizontal plane

23. Numerical example: Super-ACO • Super-ACO lattice with wiggler switched off

24. Super-ACO (one wiggler)

25. Super-ACO (one wiggler)

26. Super-ACO (one wiggler)

27. Super-ACO (one wiggler)

28. Super-ACO (two wigglers)

29. Discussions The method used here is very general and the analytical results have found many applications in solving problems such asbeam-beam effects, bunch lengthening, halo formation in proton linacs,etc…

30. Maximum Beam-Beam Parameter in e+e- Circular Colliders • Luminosity of a circular collider where

31. Beam-beam interactions • Kicks from beam-beam interaction at IP

32. Beam-beam effects on a beam • We study three cases (RB) (FB) (FB)

33. Round colliding beam • Hamiltonian

34. Flat colliding beams • Hamiltonians

35. Dynamic apertures limited by beam-beam interactions • Three cases • Beam-beam effect limited lifetime (RB) (FB) (FB)

36. Recall of Beam-beam tune shift definitions

37. Beam-beam effects limited beam lifetimes • Round beam • Flat beam H plane • Flat beam V plane

38. Important finding Defining normalized beam-beam effect limited beam lifetime as An important fact has been discovered that the beam-beam effect limited normalized beam lifetime depends on only one parameter: linear beam-beam tune shift.

39. Theoretical predictions for beam-beam tune shifts Relation between round and flat colliding beams For example

40. First limit of beam-beam tune shift (lepton machine) or, for an isomagnetic machine where Ho=2845 *These expressions are derived from emittance blow up mechanism

41. Second limit of beam-beam tune shift (lepton machine) • Flat beam V plane

42. Some Examples • DAFNE: E=0.51GeV,xymax,theory=0.043,xymax,exp=0.02 • BEPC: E=1.89GeV,xymax,theory=0.039,xymax,exp=0.029 • PEP-II Low energy ring: E=3.12GeV,xymax,theory=0.063,xymax,exp=0.06 • KEK-B Low energy ring: E=3.5GeV,xymax,theory=0.0832,xymax,exp=0.069 • LEP-II: E=91.5GeV,xymax,theory=0.071,xymax,exp=0.07

43. Some Examples (continued) • PEP-II High energy ring: E=8.99GeV,xymax,theory=0.048,xymax,exp=0.048 • KEK-B High energy ring: E=8GeV,xymax,theory=0.0533,xymax,exp=0.05

44. Beam-beam effects with crossing angle • Horizontal motion Hamiltonian • Dynamic aperture limited by synchro-betatron coupling

45. Crossing angle effect • Dynamic aperture limited by synchro-betatron coupling • Total beam-beam limited dynamic aperture Where is Piwinski angle

46. KEK-B with crossing angle • KEK-B luminosity reduction vs Piwinski angle

47. Perspective It is interesting and important to study the tail distribution analytically using the discrete time statistical dynamics, technically to say, usingPerron-Frobeniusoperator.

48. Conclusions 1) Analytical formulae for the dynamic apertures limited by multipoles in general in a storage ring are derived. 2) Analytical formulae for the dynamic apertures limited by wigglers in a storage ring are derived. 3) Both sets of formulae are checked with numerical simulation results. 4) These analytical formulae are useful both for experimentalists and theorists in any sense.

49. References • R.Z. Sagdeev, D.A. Usikov, and G.M. Zaslavsky, “Nonlinear Physics, from the pendulum to turbulence and chaos”, Harwood Academic Publishers, 1988. • R. Balescu, “Statistical dynamics, matter our of equilibrium”, Imperial College Press, 1997. • J. Gao, “Analytical estimation on the dynamic apertures of circular accelerators”, NIM-A451 (2000), p. 545. • J. Gao, “Analytical estimation of dynamic apertures limited by the wigglers in storage rings, NIM-A516 (2004), p. 243.

50. Acknowledgement Thanks go to Dr. Junji Urakawa for inviting the speaker to work on ATF at KEK, and to have this opportunity to make scientific exchange with you all, i.e.以文会友.