Title: Commissioning the LHC Accelerator and its Physics Programme
1Commissioning the LHC Accelerator and its Physics
Programme
- Emmanuel Tsesmelis (CERN)
- Presentation at The University of Oxford
- 6 March 2008
2Introduction
3LHC Accelerator Experiments
CMS/TOTEM
LHCb
ATLAS/LHCf
ALICE
4LHC LAY-OUT
- The LHC is a two-ring superconducting
proton-proton collider made of eight 3.3 km long
arcs separated by 528 m Long Straight Sections. - While the 8 eight arcs are nearly identical, the
4 straight sections are very different.
5LHC Nominal Beam Parameters
25 ns bunch spacing
6Main magnets
7LHC Main Bending Cryodipole
8.3 T nominal field 11850 A nominal field
8Lowering of Last Dipole Magnet 26 April 2007
30000 km underground at 2 km/h!
- 1700 cryo-magnets assemblies
- 1232 Main Dipoles
- 474 Short Straight Sections
- 16 Separation Dipoles
- 32 Low ß Triplets
- 200 warm magnets
9The LHC Arcs
10Short Straight Sections of the Arcs
- Cold masses of SSS contain main quadrupole
magnets and various lattice corrector magnets. - Parameters of MQ at 7 TeV
- Nominal Gradient 223 T/m
- Nominal Current
- 11870 A
11Inner Triplet Quadrupoles
US Japan collaboration
Inner triplet warm assembly in test hall
Inner Triplet at IR2
Nominal Gradient 215 T/m Nominal Current 7000
A
12cryogenics
13Cryogenics Infrastructure 4.5 K Refrigerators
141.8 K Refrigerators
15Cryogenic Distribution Infrastructure
16QRL Installation
Internal Compensators
- 3.3 km of QRL / sector
- 2100 internal welds made with automatic orbital
welding machines - 700 external manual welds
Special Connections
17Electrical feedboxes
18Electrical Feedbox Design
DFBA
19DFBA Installation
DFBAO-HCM Leaving Assembly Hall 183
DFBAO-HCM Lowered at Point 2
20DFB Interconnection
DFBAO in Sector 7-8
DFBMA in Sector 7-8
21Magnet interconnections
22Identification of Lines
23Magnet Interconnections
- Consist of several operations
- TIG welding of cryogenic channels (50 000 welds)
- Induction soldering of main superconducting
cables ( 10 000 joints) - Ultrasonic welding of auxiliary superconducting
cables ( 20 000 welds) - Mechanical assembly of various elements
- Installation multi-layer insulation ( 200 000
m2)
DIPOLE-DIPOLE INTERCONNECT BEFORE FINAL CLOSURE
All interconnections completed in November 2007
24Collimation system
25The Collimator Lay-out
TCTH
TCTV
ATLAS
26Installation Planning
- Collimation is a performance-driven system low
energy and low intensity requires much less
collimators. - Every installation plan adapted to LHC
performance goals, LHC schedule and collimator
production schedule. - Several scenarios have been defined
- Full system ? 116 collimators
- Minimal system 7 TeV (only required
collimators) ? 70 collimators - Starting system for 7 TeV ? 92 collimators
- Minimal system for 450 GeV ? 36 collimators
27Hardware commissioning
28Sector Hardware Commissioning
80K
1.9 K
Commissioning of technical systems without beam
Preparation for c-down
Pressure Test
Electrical Quality Assurance (ELQA)
- There are 8 sectors
- Utilities and machine technical systems are
sectorised - Assembly and commissioning almost independent
- Each system and utility tested and qualified
independently prior the Sector Test - Leak and pressure test
- Preparation for cool-down (flushing, filling,
repairs) - ELQA at warm
- Cool-down and ELQA at cold
- Power test power converters connected to the
magnets for the first time and tested up to the
nominal current
29A Systematic Approach
- The systems to be commissioned in the cold parts
of the machine include - Magnets, power converters, interlocks, quench
detection and energy extraction systems. - The associated utility systems AC distribution,
water cooling, ventilation, access control and
safety systems. - The systems in the Long Straight Sections
include - Injection, RF, beam dump, beam instrumentation,
collimators, and interlocks.
30Electrical Quality Assurance
31Power Converter Commissioning
32Power Converter Commissioning
Commissioning campaign in short circuit started
in mid-2006 100 commissioned
1720/1720 installed
33ELQA and Cool-down
Sector 7-8
2007
34Radiofrequency Cavities
35Summary LHC Cryogenics
4 March 2008
36LHC Cool-down Status
Sector 56
Sector 45
Sector 78
Sector 81
37Sector 4-5
Sector 56
Sector 45
38Sector 4-5 Evolution of Temperature
Quench of dipoles
25Jan08 Stop of 1.8K Ref. unit due to vacuum
interlock
13Feb08 Stop of 1.8K Ref. unit due to water stop
US45
21Jan08 Stop of 18kW due to oil system
Quench of Quads
39Sector 4-5 Power Converter Currents
19 February 2008 at 1500Hardware Commissioning
Team
Ramp of 138 power converters to a current
equivalent to 5.3 TeV 9 kA (including all high
current magnets with nominal LHC optics)
40Sector 4-5 Inner Triplet Squeeze Test
41LHC Transfer Lines and Injections
23.10.2004, 1339 ? first beam at end of TI 8
IR8
- combined length 5.6 km
- over 700 magnets
- ca. 2/3 of SPS
TI 8 beam tests 23./24.10.04 6./7.11.04
28.10.2007, 1203 ? first beam at end of TI 2
TT40 beam tests 8.9.03
TI 8
SPS
LHC
IR2
TI 2
TI 2 beam test 28./29.10.07
TI 2 upstream part installed and HW commissioned
by 2005.
PMI2
42Beam commissioning
43Schedule for 2008
- LHC Machine will be cold in mid-June 2008.
- Although the LHC Machine will not be fully
commissioned to 7 TeV by mid-June 2008, the plan
is to inject first beam at 450 GeV soon
thereafter. - 450 GeV operation is part of normal setting up
procedure for beam commissioning to high-energy. - Work to commission the LHC Machine to 7 TeV will
continue in parallel and be interleaved with the
450 GeV injection. - No provision in schedule for any major mishap,
e.g. additional warm-up/cool-down of sector
(3-month turn-around).
44Proton Commissioning Strategy
- Pilot physics run
- First collisions
- 43 bunches, no crossing angle, no squeeze,
moderate intensities - Push performance
- Performance limit 1032 cm-2 s-1 (event pileup)
- 75ns operation
- Establish multi-bunch operation, moderate
intensities - Relaxed machine parameters (squeeze and crossing
angle) - Push squeeze and crossing angle
- Performance limit 1033 cm-2 s-1 (event pileup)
- 25ns operation I
- Nominal crossing angle
- Push squeeze
- Increase intensity to 50 nominal
- Performance limit 2 1033 cm-2 s-1
- 25ns operation II
- Push towards nominal performance
45Beam Commissioning to 7 TeV Collisions
46Beyond Initial Run
Stage A
B
C
2008
No beam
Beam
D
2009
No beam
Beam
47Commissioning the physics programme
48ATLAS and CMS
- Of central importance for ATLAS CMS and for the
Collider is to elucidate the nature of
electroweak symmetry breaking for which the Higgs
mechanism (and accompanying Higgs boson(s)) are
presumed to be responsible. - The ATLAS CMS general-purpose detectors are now
well into their commissioning stage. - ATLAS and CMS are expected to have experiment
set-ups ready for the start of LHC operation in
2008.
49The ATLAS Experiment
50The CMS Experiment
51Search for Higgs at LHC Start-up
- Sizeable integrated luminosity is needed before
significant inroads can be made in SM Higgs
search. - However, even with moderate luminosity per
experiment, Higgs boson discovery is possible in
particular mass regions.
Example Reach ATLAS CMS
52Search for SUSY at LHC Start-up
- Due to their high production cross-sections,
squarks and gluinos can be produced in large
numbers even at modest luminosities. - Potential for discovery of SUSY is sizeable even
at LHC start-up.
53ATLAS and CMS Beam Conditions
Pile-up in CMS Inner Tracker ECAL H -gt ZZ -gt
2e 2?
- Machine operation at nominal conditions
- Maximize integrated luminosity in a low
machine-induced background environment. - 25 ns bunch spacing
- For a given L, 25 ns spacing preferable to 75 ns.
- Ebeam 7 TeV
- L ? 1033 cm-2 s-1
54The ALICE Experiment
- General-purpose heavy-ion experiment designed to
study physics of strongly interacting matter
quark-gluon plasma in nucleus-nucleus collisions. - LHC heavy-ion programme based on two components
- Collide largest available nuclei at highest
possible energy. - Systematic study of various collision systems
(pp, pA, AA) with various beam energies. - As number of possible combinations of collision
systems and energies is large, continuous
updating of priorities will be required as data
becomes available. - The ALICE experiment set-up is expected to be
ready for first LHC operation in 2008.
55ALICE Beam Conditions
- Proton-proton runs at ?s 14 TeV
- Commissioning starting-up experiment, reference
calibration data, pp minimum bias event
properties - L 1029 cm-2 s-1 ltngt1 event per TPC drift time
(88 ?s). - Preferably by tuning ? (if possible) rather than
displacing beams. - For L gt 1031 cm-2 s-1 would need to switch off
sub-detectors and risk of radiation damage to
sub-detectors increases. - Initial Pb Runs with Early Ion Scheme
- Request short run with ions (days) as early as
feasible and a 4-week ion run before the end of
first full LHC physics run. - In addition to ALICE, ATLAS CMS have the
potential to study ion-ion collisions.
56The LHCb Experiment
Calorimeters
Magnet
Muon detector
RICH-2
OT
RICH-1
VELO
57LHCb Beam Conditions
- Due to high production cross-sections, study of
B-mesons possible from the start of LHC
operations. - Also applicable to ATLAS and CMS
- Experiment designed for L 2 1032 cm-2 s-1 and
25 ns bunch spacing - Vary 2m. lt ? lt 50m. to reach nominal L even at
expected low bunch intensities in early LHC run - Physics maximised for single pp interaction
events.
58TOTEM Roman Pots at IR5
The TOTEM experiment will measure the total pp
cross section and study elastic scattering and
diffractive dissociation at the LHC.
59TOTEM Beam Conditions
60The LHCf Experiment
- The LHCf Collaboration will measure photons and
neutral pions in the very forward region of the
LHC - To provide information for the elaboration of the
cosmic-ray spectrum in the high energy region. - For the determination of the primary composition
of cosmic-rays. - The measurements may also be used to calibrate
Monte Carlo event generators, especially in the
forward region. - Experiment ready for first LHC run in 2008.
61LHCf Beam Conditions
- Operate with bunch spacing ? 2 ?sec in order to
reduce pile-up. - Data-taking is compatible with 43 bunch pattern
expected at LHC start-up. - L lt 1030 cm-2 s-1 to avoid contamination of data
with multiple events per bunch crossing. - Running LHCf down to L 1028 cm-2 s-1 would
provide adequate data rates.
62Lower Energy Runs
- Lowering Ebeam makes matters worse for Higgs and
SUSY searches for ATLAS and CMS. - No significant effect on B cross-section.
- TOTEM requests low energy runs
- ?s 1.8 TeV for comparison with TEVATRON
- ?s 8 TeV to probe smaller values of
four-momentum transfer. - Study of interference between nuclear and Coulomb
interactions
63Summary and Conclusions
- It is expected that first injection into the LHC
will take place in summer 2008. - Considerable experience has been gained on the
first sectors to be commissioned and it is
expected that future activities will thus be
greatly accelerated. - The experiments are expected to be ready with
their initial set-ups for the start of LHC
operation in 2008. - With the LHC, the world particle physics
community has the opportunity to address
fundamental questions such as What is the origin
of the mass of particles? and What is the nature
of dark matter? - The LHC will be the most powerful instrument ever
built to investigate properties of particles and
the physics results from the LHC will determine
the future course of high energy physics.