From LEP to the LHC:

1. the good, the bad, the ugly, and the unforeseen From LEP to the LHC: Abstract: I will try to point out the strong overlap and interconnection between the 2 colliders not only through the common tunnel but also through the people, the technologies, and accelerator science Steve Myers

2. Some Milestones • ISR (proton-proton) (70s and early 80s) • LEP design started in the late 70s (Schnell Keil, Zilverschoon) • 1983 while designing LEP: proposal for LHC in same tunnel (LEP Note 440; Myers and Schnell) • 1989 First Collisions • 1989-2000 Operation • 2001-2003 Dismanteling S. Myers From LEP to the LHC

3. From LEP to LHC Timelines S. Myers From LEP to the LHC

4. From LEP to LHC Timelines S. Myers From LEP to the LHC

5. (April 1983) S. Myers From LEP to the LHC

6. Some extracts from LEP Note 440 • ..assume throughout that the maximum energy per beam is 8 TeV (9 T bending field) and injection is at 0.4 TeV. • We assume that a twin-ring pp collider would also employ bunched beams, a likely choice if only to limit the stored energy in the beams. • proposal by R. Palmer, pairs of magnets might be combined into "two-in-one" units, each having a common core and cryo- stat. • the use of protons in both beams permits higher luminosities, a large number of bunches, eliminating the problem of unresolvable multiple events within one bunch-bunch crossing. • the copper accelerating cavities will have already been replaced by superconducting ones before a p-LEP starts operation. • At the highest proton currents, the synchrotron radiation power becomes a problem for cold-bore magnets . • AcknowledgementThis work originated from a stimulating discussion with G. Briantiwho also gave us a first report of the most recent developments in the United States.

7. Following LEP Note 440 • LEP Note 450 (June 1983) • “Beam Separations in p-bar LEP” (Myers and Schnell) • LEP Note 460 (August 1983) • “Transverse Emittance and Beam Separation in a Large ppbar Collider” (Myers and Schnell) • LEP Note 470 (October 1983) • “Acceleration in the LEP Hadron Collider”. (Henke, Myers and Schnell) S. Myers From LEP to the LHC

8. Very difficult period for LHC construction due to the parallel running on LEP2, SPS, PS, etcetc Restructuring difficult period for LHC approval. Approval of the (SSC) in 1987 severely jeopardized hopes for the approval of the less powerful LHC collider. Following a series of cost reviews which pushed the SSC cost from 4.4 billion to more than 11 billion dollars, the US congress cancelled the project in 1993. S. Myers From LEP to the LHC

9. The LEP/LHC Tunnel trace 27km circumference underground tunnel (cross-section diameter 4m) (was built for LEP collider in 1985) S. Myers QUB March 11, 2009 9

10. LEP Lay-Out S. Myers From LEP to the LHC

11. Why was LEP so Big? Why SC RF? Losses due to Synchrotron Radiation E0 = .511MeV for electrons and 938.256 for protons Power Dissipated in the walls of the Cu cavities Power to Beam from the SC cavities..... So to minimise power you need  to be as large as possible i.e. large radius. The radius for LEP1 was optimised for around 80GeV with Cu cavities LHC For protons since E0 is a factor of 1836 higher, the RF power is not an issue and the bending radius can be made as low as is technically possible. i.e. High fields For sc cavities the power needed is “only” proportional to the 4th power of energy. NOTE to operate LEP at 103 GeV with copper cavities would have needed 1280 cavities and 160MW of RF power!! Impossible for many reasons S. Myers From LEP to the LHC

12. Competition from SLC: 1989 Start-Up • The Economist August 19, 1989 “The results from California are impressive, especially as they come from a new and unique type of machine. They may provide a sure answer to the generation problem before LEP does. This explains the haste with which the finishing touches have been applied to LEP. The 27km-long device, six years in the making was transformed from inert hardware to working machine in just four weeks--- a prodigious feat, unthinkable anywhere but at CERN. Even so, it was still not as quick as Dr. Carlo Rubbia, CERN’s domineering director-general might have liked”. S. Myers From LEP to the LHC

13. Short History with Beam • 1988: July 12: Octant test • 1989: • July 14, First turn (15 minutes ahead of schedule!) • August 13, First Collisions • Aug13--Aug 18: Physics pilot run • Aug 21--Sept 11: Machine Studies • Sept 20-- Nov 5 Physics • 1990--1994: Z physics • 1995: Z + 65 & 70 GeV • 1996: 80.5--86 GeV • 1997: 91--92 GeV • 1998: 94.5 GeV • 1999: 96--102 GeV • 2000: 102--104.4 GeV  Exciting period, But usually not very productive S. Myers From LEP to the LHC

14. Summary of Performance S. Myers From LEP to the LHC

15. Modes of Operation Every Year was Different: Chamonix Workshops S. Myers From LEP to the LHC

16. S. Myers From LEP to the LHC

17. 1989 Start-Up S. Myers From LEP to the LHC

18. 1993--2000 S. Myers From LEP to the LHC

19. Limitations and Solutions(the bad and the good) S. Myers From LEP to the LHC

20. Single Bunch Intensity Limitations: TMCI S. Myers From LEP to the LHC

21. More Bunches: Pretzel Scheme S. Myers From LEP to the LHC

22. More Bunches:BunchTrains Scheme S. Myers From LEP to the LHC

23. Beam-Beam(the bad) S. Myers From LEP to the LHC

24. Limitations: Beam-Beam 1994, Pretzel Operation S. Myers From LEP to the LHC

25. Limitation: Beam-Beam 1995: 65GeV S. Myers From LEP to the LHC

26. Beam-Beam Effect 1999: 98GeV S. Myers From LEP to the LHC

27.  and lifetime Inserting LEP parameters (+ y =4cm) At 100 GeV and x=.07, tb =4.5 hours Luminosity (x) is maximised by tuning on lifetime S. Myers From LEP to the LHC

28. Beam-Beam Footprint QV (98--99) Cross half integer resonance 94.5; no problem Qh (96--97) S. Myers From LEP to the LHC

29. Technical Limitations(the ugly) S. Myers From LEP to the LHC

30. damaged area of cables Beam tube super insulation blanket Limits 1998: Antennae Cable Heating • 97/98 shutdown • many RF antennae cables electrically damaged, some melted • Limitation on the beam current in 1998 • bunch length dependent • energy ramp modified to maximise the bunch length S. Myers From LEP to the LHC

31. Cold Cable extrapolated From Measurements with beam Heating of RF antennae cables • antennes used for cavity control • heated by coupling to beam • 8W limit imposed • 30 antennae in the last three weeks of running in 1998 S. Myers From LEP to the LHC

32. Bunch Length Control during Ramp S. Myers From LEP to the LHC

33. Ponderomotive Oscillations • At high beam current and high field, cavities oscillate mechanically at 100Hz solution: • keep cavities on resonance:   0 •  changes as a function of beam current  need different setpoints • new tuning/damping scheme culprit: ponderomotive oscillations growth rate  E2.( detuning angle) S. Myers From LEP to the LHC

34. Super Bad: A Fortnight in Hell! (Mike) • 5 June RF unit dephased, lifetime 4 hours in physics • 5 June power supplyunstable • 5 & 7 Junetwo vacuum leaks in SPS plus fault on main power supply • 8 - 10 June transformer, vacuum valves, power supplies, access system, main power supply in SPS, problemswith the ‘ramp’ in LEP • 12 June vacuum leaknear a wire scanner, TWICE • 13 June vacuum valves blocked in position • 13 June RF frequencysynthesiserbroken • 13 Juin vacuum leak on a separator (local heating by SR) S. Myers From LEP to the LHC

35. The Unforeseen S. Myers From LEP to the LHC

36. Energy Calibration: Polarization S. Myers From LEP to the LHC

37. Very Unexpected “Problem”: Use of transverse polarization Precise determination of the LEP beam energy (10-5 relative accuracy, ~ 1 MeV) Precise measurement of the Z mass and width Small changes of energy accurately measured (energy change from 1mm circumference change) S. Myers From LEP to the LHC

38. Circumference variations S. Myers From LEP to the LHC

39. Noise on the Beam Energy S. Myers From LEP to the LHC

40. TGV: The Fast Train • Influence on the beam energy • the moon, sun and tides • the level of lake Geneva • the amount of rain • AND the fast train......... S. Myers From LEP to the LHC

41. TGV induces current in LEP vacuum chamber S. Myers From LEP to the LHC

42. 1996: Some things are sent to try us! (beam will not circulate) Single Turn Stopper QL10.L1 positrons S. Myers From LEP to the LHC

43. Zoom sur Quadrupole beer bottle S. Myers From LEP to the LHC

44. 10 metres to the right beer bottle Unsociable sabotage: both bottles were empty!! S. Myers From LEP to the LHC

45. My present: Heineken Beam Stopperemail card UK advertising at the time: Heineken; the beer that gets to places no other beer can! S. Myers From LEP to the LHC

46. Problems with sextupole families tripping after about 10-20 minutes Oops!! S. Myers From LEP to the LHC

47. Synchrotron Radiation: To keep ourselves sane! We would write prose about our technical problems During the cruel year of 1997 the evil Lord of Synchrotron Radiation came to wage war against the peaceful tribes of the LEP2 region in the province of PCR (Prevessin Control Room). The Cruel Lord, with the help of his personal guard, the evil Wigglers, burned vacuum transitions, scorched separators and melted the lead homes of the tribe of the Pious Polarizers. Antoni Gaudi would have been proud of the newly melted lead shielding installed to protect the polarimeter against synchrotron radiation S. Myers From LEP to the LHC

48. Other Problems with cables Where is the dirty rat who ate my cables? S. Myers From LEP to the LHC

49. Even “Romeo and Juliette” was BAD • Quote from our LEP memoirs (unpublished)by Helmut Burkhardt, Mike Lamont,Steve Myers, John Poole. • Facts • Electrical short circuit dumped the beams • At the location of the short circuit, two deers were found dead (electrocuted) in a lovers’ embrace • Conclusion from the fact-finding team • Juliette bit into the electric cable • Romeo got a painful shock ….. S. Myers From LEP to the LHC

50. Increasing the Beam Energy (the RF guys)(the good, but expensive!) S. Myers From LEP to the LHC