From LEP to the LHC:

From LEP to the LHC:

Steve Myers

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

the good, the bad, the ugly, and the unforeseen

S. Myers From LEP to the LHC 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

25th July 2014 CERN 60 Years

25th July 2014 CERN 60 Years S. Myers From LEP to the LHC 3

From LEP to LHC Timelines


1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

DG H. Schopper C. Rubbia C. Llewellyn-Smith L. Miaini R. Aymar R. Heuer

Director of Accelerators G. Brianti K. Hubner CW S. Myers F. Bordry

LEP Construction (EP + GP) LEP 1 Operation (AH + SM) LEP2 Operation (SM)

LEP Upgrade Project LEP2 (CW + SM)

LHC SM WS paper

Project Preparation for Approval (GB) approval LHC construction (LE) LHC Repair and

Operation (SM) LS1

Accelerator Depts. (SL)

(AB) SPS-LEP Department (LE + KHK + SM) SL - AB Department (SM) BE Department (PC)

Accelerator Depts. (AT) AT Department (PL) TE Department (FB + MJ)

Accelerator Depts. (TS) TS Department (AS + PC) EN Department (VV + RS)

From LEP to LHC Timelines


(April 1983)

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• the copper accelerating cavities will have already been replaced by superconducting ones before a p-LEP starts operation.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. Brianti who also gave us a first report of the most recent developments in the United States.

6

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 825th July 2014 CERN 60 Years

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

DG H. Schopper C. Rubbia C. Llewellyn-Smith L. Miaini R. Aymar R. Heuer

Director of Accelerators G. Brianti K. Hubner CW S. Myers F. Bordry

LEP Construction (EP + GP) LEP 1 Operation (AH + SM) LEP2 Operation (SM)

LEP Upgrade Project LEP2 (CW + SM)

LHC SM/WS paper Project Preparation for Approval (GB) appro

val LHC construction (LE) LHC Operation (SM) LS1

Accelerator Depts. (SL)

(AB) SPS-LEP Department (LE + KHK + SM) SL - AB Department (SM) BE Department (PC)

Accelerator Depts. (AT) AT Department (PL) TE Department (FB + MJ)

Accelerator Depts. (TS) TS Department (AS + PC) EN Department (VV + RS)

RestructuringVery difficult period for LHC construction due to the parallel running on LEP2, SPS, PS, etc etc

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 QUB March 11, 2009 927km circumference underground tunnel (cross-section diameter 4m)

(was built for LEP collider in 1985)

The LEP/LHC Tunnel trace

9


LEP Lay-Out


11

Why was LEP so Big? Why SC RF?

sh28

0

8b

sh

2RF

Cu lr11

E

ElrV

P

sRF40

4b

0 sinV1

E

EU

tot

40

4b

0totscI

E

EUIP

Losses due to Synchrotron Radiation

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

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

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

E0 = .511MeV for electrons and 938.256 for protons

25th July 2014 CERN 60 Years S. Myers From LEP to the LHC


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”.


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


14

Summary of Performance

Year int L Eb kb 2 kb Ib Peak Lumi y

(pb-1) (GeV) (mA) (10^30 cm-2 s-1) 1989 1.7 45.6 4 2.6 4 0.0171990 8.6 45.6 4 3.6 7 0.0201991 18.9 45.6 4 3.7 10 0.0271992 28.6 45.6 4/8 5.0 12 0.0271993 40.0 45.6 8 5.5 19 0.0401994 64.5 45.6 8 5.5 23 0.0471995 46.1 45.6 to 70 8/12 8.4 34 0.0301996 24.7 80.5 to 86 4 4.2 36 0.0401997 73.4 90 to 92 4 5.2 47 0.0551998 199.7 94.5 4 6.1 100 0.0751999 253.0 98 to 101 4 6.2 100 0.083


15

Modes of OperationYear Optics Comments Bunch scheme 1989 60/60 LEP commissioned 4 on 4 1990 60/60 4 on 4 1991 60/60 90/90 optics tested 4 on 4 1992 90/90 Pretzel commissioned 4 on 4 / Pretzel 1993 90/60 Pretzel 1994 90/60 Pretzel 1995 90/60 tests at 65-68 GeV Bunch trains 1996 90/60 108/90 tested 4 on 4 1997 90/60 108/60 and 102/90 tested 4 on 4 1998 102/90 4 on 4 1999 102/90 4 on 4

Every Year was Different: Chamonix Workshops25th July 2014 CERN 60 Years S. Myers From LEP to the LHC



1989 Start-Up



1993--2000Integrated luminosity

seen by experiments from 1993 to 2000

0

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1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

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Number of scheduled days (from start-up)

inte

grat

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(pb-

1)

Physics 93 Zo

Physics 94 Zo

Physics 95 Zo, 65-70 GeV

Physics 96 80.5 - 86 GeV

Physics 97 91 - 92 GeV

Physics 98 94.5 GeV

Physics 99 96-102GeV

Physics 00 100-104GeV

LEP statistics in 2000 CERN - BD/SL division

Last Value

(14.06.00) : 70.12 pb-1



Limitations and Solutions(the bad and the good)



Single Bunch Intensity Limitations: TMCI


More Bunches: Pretzel Scheme


More Bunches:Bunch Trains Scheme


Beam-Beam(the bad)



Limitations: Beam-Beam

1994, Pretzel Operation



Limitation: Beam-Beam

1995: 65GeV



Beam-Beam Effect

1999: 98GeV



and lifetime

bbrevBIP

t

IPB

t

t

b

IPBt

ik

Lefn

N

Ln

dtN

dN1

Lndt

dN

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fn

r2

yb

1

)GeV(E

31)hours(

Inserting LEP parameters (+ y =4cm)

At 100 GeV and x=.07, tb =4.5 hours

Luminosity (x) is maximised by tuning on lifetime



Beam-Beam Footprint

9 6 .2 9 6 .4 9 6 .6 9 6 .8 9 7

9 8 .2

9 8 .4

9 8 .6

9 8 .8

9 9

Qh (96--97)

QV (98--99)

Cross half integer resonance 94.5; no problem


Technical Limitations(the ugly)



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

Beam tube

damaged areaof cables

super insulation blanket


Heating of RF antennae cables

Room Temp.Test Cable

200.0

250.0

300.0

350.0

400.0

450.0

500.0

550.0

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Power [W]

Tem

p [K

]

200

523

Cold Cable extrapolated

From Measurements with beam

• antennes used for cavity control

• heated by coupling to beam

• 8W limit imposed

• 30 antennae in the last three weeks of running in 1998


Bunch Length Control during Ramp

4.0

4.5

5.0

5.5

6.0

6.5

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13:48:00 13:50:53 13:53:46 13:56:38 13:59:31 14:02:24 14:05:17

Time

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CablePow

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P7Wigg

Bunch Length

Fill 5300


S. Myers From LEP to the LHC

Ponderomotive Oscillations

solution: keep cavities on resonance:

0

changes as a function of beam current need different setpoints

new tuning/damping scheme

Field Amplitude oscillates (by any reason ...)

Radiation "pressure"oscillates (instantly)

Cavity shapeoscillates(delay needed)

Cavity RF-frequencyoscillates (instantly)

Field amplitudeoscillates

(delay needed)

At high beam current and high field, cavities oscillate mechanically at 100Hz

culprit: ponderomotive oscillations

growth rate E2. ( detuning angle)

25th July 2014 CERN 60 Years 33

Super Bad: A Fortnight in Hell! (Mike)• 5 June RF unit dephased, lifetime 4 hours in physics

• 5 June power supply unstable

• 5 & 7 June two 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, problems with the ‘ramp’ in LEP

• 12 June vacuum leak near a wire scanner, TWICE

• 13 June vacuum valves blocked in position

• 13 June RF frequency synthesiser broken

• 13 Juin vacuum leak on a separator (local heating by SR)


The Unforeseen



Energy Calibration: Polarization


37

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)

Very Unexpected “Problem”:



Circumference variations



Noise on the Beam Energy



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.........



TGV induces current in LEP vacuum chamber


1996: Some things are sent to try us! (beam will not circulate)

QL10.L1Single Turn Stopper positrons


Zoom sur Quadrupole

beer bottle


10 metres to the right

beer bottle

Unsociable sabotage: both bottles were empty!!25th July 2014 CERN 60 Years S. Myers From LEP to the LHC 44

My present: Heineken Beam Stopperemail card

UK advertising at the time:Heineken; the beer that gets to places no other beer can!


Oops!!


Problems with sextupole families tripping after about 10-20 minutes

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).

Synchrotron Radiation: To keep ourselves sane!


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

We would write prose about our technical problems

Other Problems with cables

Where is the dirty rat who ate my cables?



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 …..


Increasing the Beam Energy (the RF guys)

(the good, but expensive!)



2900

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Date

MV Copper

SC

RF: pumping up the voltage

96 GeV

98 GeV

100 GeV

101/100 GeV

Strategy to maximise physics time:¨ Run at an energy where we have some RF margin¨ Increase the RF voltage gradually¨ When stable at sufficient voltage, increase the energy¨ Drink the champagne¨ Repeat as many times as possible...

But...keeping it there requires a huge effort!


With plenty of volts, it’s OK...

• 2 days at 101 GeV ...– available RF voltage 3510 MV– margin 210 MV (2 klystrons can trip)

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ty/

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Delphi

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IDC

...with a few less, it’s less easy • Still at 101 GeV...

– but available RF voltage down to 3440 MV– margin 140 MV (1 klystron can trip) This fill at 100 GeV

53

2000: Need More Beam Energy:


Reducing Jx :

As well as increasing the RF volts, we pulled out every trick we knew in order to squeeze the last drop of energy increase for the machine. E.g. using the horizontal orbit correctors as bending magnets.


Tunnel Movements Affecting Operation

ID Task Name

1 SPS [614]+TI12 [120] (USA15)

2 SPS [614]+TI12 [120] (UX15)

3

4 IP1 (UX15)

5 TI8 cross-over [QD24.R8]

6 QL1.R5 (PX56)

7 IP5 (pillar)

dy<5mm

dy<5mm

dy<30mm

dx<2,dy<4mm

dy<3mm

dx<20mm

Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q22000 2001

LHC civil engineering (bad at the time, good now)


56

Performance in 2000


58

Performance in 2000


Year 2000: Run LEP2 in 2001 or STOP?

LEP vs LHC (old vs new)• running LEP would delay LHC by 0, 1, 1.5, 2 (?)

years• the competition with Tevatron• manpower transfers needed from LEP to LHC• “materials“ budget considerations (+electrical

power etc)

The first and only Civil war in CERN

• no consensus25th July 2014 CERN 60 Years S. Myers From LEP to the LHC 59


The abridged story of 2000• 14th June: First candidate event 206.7 GeV

– Reconstructed Higgs mass 114.3 GeV/c2• 20th July: LEP Committee

– ALEPH present excess at high masses– Not seen by other experiments BUT combined excess for mass

hypothesis of 115 GeV/c2 of 1.1.– 2 reserve weeks - end of September granted

• 31st July & 21st Aug: events 2 & 3 for ALEPH– Things are heating up!

• 5th September: LEP Committee– Excess only in ALEPH, only 4 jets– Combination however agrees with Mh 114-115 GeV/c2– Request 2 months extension

• To double amount of lumi at 206.5 GeV which had already been collected.

• September 14th: Research board:– ONE MONTH GRANTED (LHC startup)


October 10th: LEPC: Update of the results The signal excess grows up to 2.6s

16th October: Missing energy candidate from L3... November 2nd: end of LEP operations

We only managed about 50% of request to double sample. (half the time half the integrated lumi)

November 3rd, LEPC: The new data confirm the excess again. The significance grows up to 2.9s

Additional 2001 running not granted

LEP running in 2001 is requested

November 3rd LEPC - closed session: No unanimous recommendation

November 7th: Research board No unanimous recommendation (vote split 8 - 8)

November 8th: “LEP has closed for the last time:”


NOT A POPULAR DECISION!BUT the right one! This allowed massive redeployment of skilled and experienced CERN staff from LEP2 to the LHC design. With this new focus, the design of the LHC gathered real momentum with L. Evans leading the overall project and the 3 accelerator department heads leading the technical design of the components (P. Lebrun (magnets, cryogenics and vacuum), P. Ciriani (infrastructure and technical services), S. Myers (radio frequency, accelerator physics, beam diagnostics, controls, injection extraction and beam dump, machine protection, and power supplies). It is important to highlight the enormous contributions of the CERN technical groups and group leaders in the design, fabrication, and testing of these very complex systems. The strength of CERN is imbedded in its technical groups.

Use the experience and expertise gained in LEP to prepare beam commissioning and operation of the LHC collider

LCC (LMC) Mission February 14, 2001

Following the decision to close LEP

LHC Commissioning Committee (LCC 1)BAILEY Roger, CLAUDET Serge, CORNELIS Karl, EVANS Lyn, FAUGERAS Paul, FERNQVIST Gunnar, JEANNERET Jean-Bernard, KOUTCHOUK Jean-Pierre, LAMONT Mike, LINNECAR Trevor, MERTENS Volker, MYERS Steve (Chair), POOLE John, PROUDLOCK Paul, ROY Ghislain, RUGGIERO Francesco, SABAN Roberto, SASSOWSKY Manfred, SCANDALE Walter, SCHMICKLER Hermann, SCHMIDT Rudiger, TSESMELIS Emmanuel, WENNINGER Jorg

http://lhc.web.cern.ch/lhc/lcc/lcc.htm

63

• Evaluate and maximise the performance of the injectors,• Evaluate experience with other relevant machines,• Create a competent, experienced trained team,• Prepare a detailed scenario for initial commissioning,• Specify special software requirements for commissioning and operation.• Plan MD experiments for the LHC and its injectors

The physics data (luminosity, energy, energy calibration).

Operation in unique regime of ultra-strong damping:- Beam-beam limit with strong damping.- First confirmation of theory of transverse spin polarization.

LEP will be the reference for any future e+e- ring collider design.

Legacy to LHCRunning large accelerators (shutdown planning, cold checkouts…)

Training ground for future LHC leaders.Operation at high efficiency (controls software, control room management etc)Real-time feedback on beam parameters (orbit, tune, instabilities..)Running large Superconducting and cryo systems

…….

What is the Legacy of LEP?

64

LEP: Design and Reality

Parameter Design(55 / 95 GeV)

Achieved(46 / 98 GeV)

Bunch current 0.75 mA 1.00 mA

Total beam current 6.0 mA 8.4 / 6.2 mA

Vertical beam-beam parameter

0.03 0.045 / 0.083

Emittance ratio 4.0 % 0.4 %

Maximum luminosity 16 / 27 1030 cm-2s-1

23 / 1001030 cm-2s-1

IP beta function bx 1.75 m 1.25 m

IP beta function by 7.0 cm 4.0 cm

x 10

x 1.4 / 3.7

Reality better than design (result of many years work)! 65

66

The last beam in LEP (2000); A sad occasion

In the photo:• Roger Bailey, • Ralph Assmann, • Paul Collier, • Mike Lamont, • Steve Myers• Andy Butterworth

I had to prepare the dismantling with my LEP colleagues AArrggHH!

Goodbye my friends I must move on


67

Conclusions• LEP was a big challenge, a lot of effort but enormously

rewarding• Physics output was exceptional• LEP training of accelerator and detector people allowed the

rapid commissioning and exploitation of the LHC which resulted in the discovery of the Higgs’ boson.

• LEP achievements are based on the work of many hundreds of CERN technicians, engineers, and physicists from 1978 to 2000. 554 papers were published in Proceedings of the Chamonix workshops alone (from 118 authors).

• I would like to take this final opportunity to sincerely thank (once again) all those people who worked on LEP/LHC and the detectors for their motivation, devotion and hard work. It was a fantastic experience which none of us will ever forget


Thank you for your attention


From LEP to the LHC:

Documents

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steve myers abstract

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