1. Status and Outlook of the LHC
Massimo Giovannozzi
CERN – Beams Department
On behalf of the whole LHC Team
Introduction
Challenges and performance during Run I
Some numbers for Run II
Upgrade path
Outlook
Acknowledgements: O. Brüning, S. Fartoukh, J. Jowett, M. Lamont, L. Rossi, F. Zimmermann

2. The LHC and its Injector Complex
SPS: 26 -> 450 GeV
PS: 1.4 -> 26 GeV
PSB: 50 MeV -> 1.4 GeV
LINAC2: 50 MeV
LHC: 450 -> 7000 GeV

3. Collimation Injection B2 Beam dumps Injection B1 Collimation RF
1720 Power converters
> 9000 magnetic elements
7568 Quench detection systems
1088 Beam position monitors
4000 Beam loss monitors
150 t Helium, ~90 t at 1.9 K
140 MJ stored beam energy in 2012
370 MJ design and > 500 MJ for HL-LHC!
450 MJ magnetic energy per sector at 4 TeV ≈ 10 GJ 7 TeV

4. LHC bunch structure 27 km 1380 (@50ns)/ 2760 (@25ns) bunches
1 SPS injection
27 km bunches
Abort gap
John Jowett
bmax ~4.5 km
b* 60 cm
Operation with 2760 bunches features approximately 30 unwanted collision points per Interaction Region (IR).
Efficient operation requires large beam separation at unwanted collision points Separation of 9 s is at the limit of the triplet aperture for nominal b* values!

5. Nominal LHC beam in PS
At PS extraction the bunches have the nominal 25 ns spacing

6. Triple bunch splitting
The stable fixed point bifurcates and three stable ones are generated.
Courtesy R. Garoby

7. LHC Timeline 1380 2008 2009 2010 2011 2012 September 19, 2008
August 2008
First injection test
4 July, 2012
Higgs discovery
August, 2011
2.3e33, 2.6 fb-1
1380 bunches
November 29, 2009
Beam back
September 10, 2008
First beams around
October
1e32
248 bunches
1380
June
1380 bunches (50ns)
6 June, 2012
6.8e33
April 2010
Squeeze to 3.5 m
2008
2009
2010
2011
2012
September 19, 2008
Disaster Accidental release of 600 MJ stored in one sector of LHC dipole magnets
March 30, 2010
First collisions at 3.5 TeV
November 2010
Ions
18 June, 2012
6.6 fb-1
to ATLAS & CMS
LHC Timeline

8. 2011 50 ns Courtesy M. Lamont 75 ns 4. Increase bunch intensity
3. Squeeze further
1. Increase number of bunches
2. Reduce beam size from injectors

9. Integrated Luminosity in Run I
2010: 0.04 fb-1
7 TeV CoM
Commissioning
2011: fb-1
Exploring the limits
2012: fb-1
8 TeV CoM
Production

10. Z μμ event from 2012 data with 25 reconstructed vertices
2011: average
12 events/xing,
with tails up to ~20
2012: ~30 events/xing
at beginning of fill
with tails up to ~ 40.
Z μμ
Z μμ event from 2012 data with 25 reconstructed vertices
Huge efforts over last months to prepare for high lumi and pile-up expected in 2012:
optimized trigger and offline algorithms (tracking, calo noise treatment, physics objects)
 mitigate impact of pile-up on CPU, rates, efficiency, identification, resolution
in spite of x2 larger CPU/event and event size  we do not request additional computing
resources (optimized computing model, increased fraction of fast simulation, etc.)

11. The injectors delivered in 2012 3 ×the nominal brightness
Peak Performance in Run I
The injectors delivered in 2012
3 ×the nominal brightness
2010
2011
2012
Nominal
Bunch spacing [ns]
150 50 25
No. of bunches
368
1380
2808
beta* [m]
ATLAS and CMS
3.5
1.0
0.6
0.55
Max bunch intensity [1011 p/bunch]
1.2
1.45
1.7
1.15
Normalized emittance [mm]
~2.0
~2.4
~2.5
3.75
Peak luminosity [1034 cm-2s-1]
0.021
0.37
0.77
Mean weekly [fb-1]
0.2
0.72

12. Peak Performance Summary
Max. luminosity in one fill
237 pb-1
Max. luminosity delivered in 7 days
1350 pb-1
Longest time in stable beams (2012)
22.8 hours
Longest time in stable beams for 7 days
91.8 hours (55%)
77 % of design luminosity:
at 4/7 design energy
much larger than nominal bunch intensity
~70 % nominal emittance
b* = 0.6 m (design 0.55 m) at 4 TeV
50 ns: half nominal number of bunches and twice the nominal pile-up!
Impressive performance after only 3 years of operation and at E = 4 TeV!

13. Some LHC challenges - I Large crossing angle operation
Reduction of long range beam-beam interactions
Reduction of head-on beam-beam parameter
Reduction of the mechanical aperture
Reduction of luminous region
Reduction of instantaneous luminosity
Collective effects
Resistive wall: huge contribution from the collimator system. Upgrade envisaged to reduce resistivity of collimators
Cleaning and machine protection
2011: collimators gap of about 3.1 mm
2012: collimators gap of about 2.2 mm
Overall: inefficient use of the stored protons
Small gaps means large impedance

14. Some LHC challenges - II
Emittance blow up in LHC
Prevents full exploitation of the excellent performance of injectors
Beam dumps (UFOs and SEU)
Cleaning effect observed during Run I (UFOs)
Mitigation measures (relocation) implemented during LS1 (SEU).
E-cloud
Beam scrubbing needed: how long?
During 25 ns scrubbing run last December the reduction in the secondary electron yield (SEY) flattened out.
A concentrated scrubbing run will probably be insufficient to fully suppress electron cloud from the arcs for 25 ns beams in future operation.
Heat load: might limit performance reach

16. 2015 – post LS1 Energy: 6.5 TeV Bunch spacing: 25 ns
BCMS = Batch Compression and Merging and Splitting
Energy: 6.5 TeV
Bunch spacing: 25 ns
pile-up considerations !
Injectors potentially able to offer nominal intensity with even lower emittance
BCMS = Almost factor 2 gain in Brightness at the ‘cost’ of 10% less bunches!
Number of bunches Ib
LHC FT[1e11]
Emit
LHC [um]
Peak Lumi
[1034 cm-2s-1]
~Pile-up
Int. Lumi per year
[fb-1]
25 ns low emit
2520
1.15
1.9
1.7 52
~45

17. Performance projections
Courtesy L. Rossi

18. Upgrade ideas (until 2010) Assumptions (or common belief)
Lifetime of triplets under nominal conditions is few years (radiation due to debris) -> they should be replaced
Nominal parameters are probably tight and nominal luminosity might be difficult to achieve (triplets’ aperture)
Hence, two-stage approach:
Phase 1: “Consolidate” the machine with new triplets aiming at reaching ~ 2-3×1034 cm-2 s-1.
Phase 2: “Real” luminosity upgrade aiming at cm-2 s-1.. This includes a major upgrade of the detectors.

19. S. Fartoukh at Chamonix 2010 Workshop
Phase 1 in short
Rough summary of Phase 1 approach
Replace “only” triplets with larger aperture magnets to enable reaching smaller b*.
Intense studies performed:
Minimum b* achievable: ~ 30 cm
Limits have been found in other parts of the machine -> much more elements than the triplets should be changed!
Very complex optical gymnastics in order to fulfill the correction of chromatic aberrations -> not much operational flexibility left.
S. Fartoukh at Chamonix 2010 Workshop

20. Scope of High-Luminosity upgrade of LHC
Targets:
A peak luminosity of 5×1034 cm-2s-1 with leveling
An integrated luminosity of 250 fb-1 per year, enabling the goal of 3000 fb-1 in twelve years.
Courtesy E. Todesco

21. Luminosity - I The peak luminosity depends on LHC-specific
Injectors-specific
Due to the crossing angle, the geometrical reduction factor F is different from unity and reads
L vs. b*
NB: b* enters in the factor F via
qc and s*: no gain in reducing b*
below a certain value.
Flat beams mitigate this effect.

22. Luminosity - II Possible strategies for upgrading performance:
Maximize bunch brightness (beam-beam limit)
Minimize beam size (aperture in triplets)
Maximize number of bunches (beam power, e-cloud)
Compensate for F
LHC Upgrade (HL-LHC):
Smaller b*; new triplets quadrupoles; new technology (Nb3Sn instead of Ni-Ti).
Mitigation measures for higher currents (e.g., collimator system upgrade, cooling, beam-beam compensation wires)
Flat beams and/or crab cavities
Injectors’ Upgrade (LIU):
Increase beam brightness
Mitigation measures for higher currents (e.g., coating SPS vacuum chambers).

23. LHC upgrade: parameter space (tentative)
25 ns is the baseline,
50 ns is a back-up (e.g. for e-cloud).
Parameters still under discussion with the LHC Injector Upgrade project.
Relies on crab-cavity
LHC nominal
HL-LHC
25 ns
50 ns
# Bunches
2808
1404
p/bunch [1011]
1.15 (0.58A)
2.0 (1.01 A)
3.3 (0.83 A)
eL [eV.s]
2.5
sz [cm]
7.5
sdp/p [10-3]
0.1
gex,y [mm]
3.75
3.0
b* [cm] (baseline) 55 15
X-angle [mrad]
285
590 (12.5 s)
590 (11.4 s)
Lumi loss factor (F)
0.84
0.30
0.33
Peak lumi [1034]
1.0
6.0
7.4
Virtual lumi [1034]
1.2
20.0
22.7
Tleveling 5E34
n/a
7.8
6.8
#Pile 25
123
247
Courtesy S. Fartoukh

24. HL-LHC : work around the ring > 1.2 km
3000 fb-1 in 10 years
Limited pile up : 140  levelled
Nov 2011 : FP7 HiLumi LHC Design Study
20 (+1) Institutes from EU, Ru, USA and JP
Courtesy L. Rossi

25. Point 4 : Cryoplant for RF (LS2 2018)
Main aim is to separate SC RF from the arc cooling, but will have capability for a harmonic RF system and for e-lens SC solenoid
Courtesy L. Rossi

26. Point 7: horizontal SC links (LS2 2018)
Courtesy L. Rossi

27. P2 - DS collimators ions – 11 T (LS2 -2018)
Recommended by the Collimation Review
11 T Nb3Sn
Courtesy L. Rossi

28. P7 DS collimation – 11 T (LS2 2018)
Collimation review: prepare and then check real need during Run II
11 T Nb3Sn
Courtesy L. Rossi

29. Low impedence collimators(LS2 & LS3)
New material: MoGr
Courtesy L. Rossi

30. P1-P5 IR Magnets (IT-D1) Powering, TAS
IT : LARP –CERN
D1: KEK
Courtesy L. Rossi

31. P1-P5 MS Magnets, Powering, TAN
Stronger Q5 IR6
2 magnets
Q4-Q5-Q6
MS in Q10 in Sectors 12,45,56,81
Courtesy L. Rossi

32. Proposed optics and crab cavities
The Achromatic Telescopic Squeeze optics (by S. Fartoukh) enables:
Reaching very small b* values
Enhancing the strength of the chromatic sextupoles thus enabling the compensation of chromatic aberrations that stem from the new triplets.
The scheme proved to work in
the LHC!
Courtesy S. Fartoukh

33. Potential issues of crab cavities and fancy use…
RF Noise
Design
Limited transverse space in the LHC
Two types are needed: H and V crossing
Machine protection!
Crab kissing in parallel separation plane
All curves have an area of 140 pile up events.
Black: baseline
Others: variants of crab kissing schemes
Courtesy S. Fartoukh
Crab kissing scheme: a novel approach to mitigate pile up

34. Luminosity levelling Three options at hand:
Vary crossing angle (crab cavities help here!)
It can be performed with dipoles
Easy, but requires aperture in triplets
Vary separation
Easy (already tried with LHCb), but requires aperture
Vary b*
Never tried in existing machines
Requires an excellent control of optics and crossing scheme

35. Project Options beyond HL-LHC
Medium Term Future:
Linear Collider (ILC / CLIC)
LHeC ep collider & Higgs factory
SAPPHiRE gg Higgs factory
Long Term Future:
HE-LHC/VHE-LHC pp/AA collider
TLEP/LEP3 e+e- Higgs factory ++
TLHeC/VHE-LHeC ep colliders…

36. HE-LHC HE-LHC SPS+ higher energy transfer lines 20-T dipole magnets
2-GeV Booster
Linac4
Can perhaps bring a factor 2-3 increase in CM collision energy
Magnet technology (15 T – 20 T)?!?
Investment versus physics case?!?!

37. VHE-LHC VHE-LHC 20-T dipole magnets VHE-LHC-LER= TLEP
Courtesy L. Rossi
VHE-LHC-LER= TLEP
Still at early R&D and study stage (20 T magnets!!!): magnets, beam power and machine protection, injectors...
New tunnel would provide synergies with other machines: e.g. TLEP as a Higgs factory

38. 80-100 km tunnel: Geneva option
“Pre-Feasibility Study for an 80-km tunnel at CERN”
John Osborne and Caroline Waaijer,
CERN, ARUP & GADZ, submitted to ESPG
even better
100 km?

39. Conclusions and outlook
Remarkable performance of the LHC and of its injectors!
After LS1: nominal energy and 25 ns.
Very rich upgrade programme:
HL-LHC:
Studies and R&D on beam dynamics and hardware (the nominal machine can be used to perform beam dynamics experiments).
Contributions from US-LARP and HiLumi partners (FP7 EU Project).
LIU:
Vigorous programme of consolidation and upgrade of the injectors.
Several future options available:
(Very) High-Energy LHC
LHeC, TLEP

40. Thank you for your attention