1. LHC : construction and operation
Jörg Wenninger
CERN Beams Department / Operations group
LNF Spring School 'Bruno Touschek' - May 2010
Part 2:
Machine protection
Incident and energy limits
Commissioning and operation

2. Machine protection

3. The price of high fields & high luminosity…
When the LHC is operated at 7 TeV with its design luminosity & intensity,
the LHC magnets store a huge amount of energy in their magnetic fields:
per dipole magnet Estored = 7 MJ
all magnets Estored = 10.4 GJ
the 2808 LHC bunches store a large amount of kinetic energy:
Ebunch = N x E = 1.15 x 1011 x 7 TeV = 129 kJ
Ebeam = k x Ebunch = 2808 x Ebunch = 362 MJ
To ensure safe operation (i.e. without damage) we must be able to dispose of all that energy safely !
This is the role of machine protection !

4. Stored Energy Increase with respect to existing accelerators :
A factor 2 in magnetic field
A factor 7 in beam energy
A factor 200 in stored energy

5. Comparison…
The energy of an A380 at 700 km/hour corresponds to the energy stored in the LHC magnet system :
Sufficient to heat up and melt 15 tons of Copper!!
90 kg of TNT
The energy stored in one LHC beam corresponds approximately to…
10-12 litres of gasoline
15 kg of chocolate
It’s how easily/quickly the energy is released that matters most !!

6. Machine protection: beam

7. To set the scale..
Few cm long groove of an SPS vacuum chamber after the impact of ~1% of a nominal LHC beam (2 MJ) during an ‘incident’:
Vacuum chamber ripped open.
3 day repair.
The same incident at the LHC implies a shutdown of > 3 months.
>> Protection of the LHC must be much stricter and much more reliable !

8. The 7 TeV LHC beam can drill a hole through
Beam impact in a target
Simulation of a 7 TeV LHC beam impact into a 5 m long Copper target
The 7 TeV LHC beam can drill a hole through
~35 m of Copper
20 bunches
180 bunches
100 bunches
380 bunches
Courtesy N. Tahir / GSI

9. Cu plate ~20 cm inside the ‘target’.
From a real 450 GeV beam…
Shoot a 450 GeV beam into a target…
108 plates
30 cm
Shot
Intensity / p+ A
1.2×1012 B
2.4×1012 C
4.8×1012 D
7.2×1012
6 cm
6 cm
Cu plate ~20 cm inside the ‘target’.
~0.1% nominal LHC beam
A B D C

10. ‘Safe’ beams at the LHC…
2011
‘Un-safe beam’
‘Safe beam’
L ~ 21028 cm-2s-1
LHC 2010

11. Schematic layout of beam dump system in IR6
When it is time to get rid of the beams (also in case of emergency!), the beams are ‘kicked’ out of the ring by a system of kicker magnets and send into a dump block !
Ultra-high reliability system !!
Septum magnets deflect the extracted beam vertically
Beam 1
Kicker magnets to paint (dilute) the beam
Q5L
Beam dump block
Q4L
15 fast ‘kicker’ magnets deflect the beam to the outside
700 m
Q4R
 500 m
Q5R
The 3 ms gap in the beam gives the kicker time to reach full field.
quadrupoles
Beam 2

12. beam absorber (graphite)
The dump block
Measurement
Simulation
beam absorber (graphite)
The ONLY element in the LHC that can withstand the impact of the full beam !
The block is made of graphite (low Z material) to spread out the showers over a large volume.
It is actually necessary to paint the beam over the surface to keep the peak energy densities at a tolerable level !
Approx. 8 m
concrete shielding

13. Dump line in IR6

14. Dump line

15. Dump installation

16. ‘Unscheduled’ beam loss due to failures
In the event a failure or unacceptable beam lifetime, the beam must be dumped immediately and safely into the beam dump block
Two main classes for failures (with more subtle sub-classes):
Passive protection
- Failure prevention (high reliability systems).
Intercept beam with collimators and absorber blocks.
Beam loss over a single turn
during injection, beam dump.
Active Protection
- Failure detection (by beam and/or equipment monitoring) with fast reaction time (< 1 ms).
- Fire beam dumping system.
Beam loss over multiple turns
(~millisecond to many seconds) due to many types of failures.
Because of the very high risk, the LHC machine protection system is of unprecedented complexity and size.
A general design philosophy was to ensure that there should always be at least 2 different systems to protect against a given failure type.

17. Failure detection example : beam loss monitors
Ionization chambers to detect beam losses:
N2 gas filling at 100 mbar over-pressure, voltage 1.5 kV
Sensitive volume 1.5 l
Reaction time ~ ½ turn (40 ms)
Very large dynamic range (> 106)
There are ~3600 chambers distributed over the ring to detect abnormal beam losses and if necessary trigger a beam abort !

18. Beam loss monitoring

19. Machine protection and quench prevention: collimation

20. Operational margin of SC magnet
Applied Field [T]
The LHC is ~1000 times more critical than TEVATRON, HERA, RHIC
Bc critical field Bc
quench with fast loss of ~106-7 protons
8.3 T / 7 TeV
QUENCH
Tc critical
temperature
quench with fast loss
of ~few 109 protons Tc
0.54 T / 450 GeV
1.9 K
Temperature [K]
9 K

21. Quench levels
The phase transition from the super-conducting to a normal conducting state is called a quench.
Quenches are initiated by an energy in the order of few milliJoules
Movement of the superconductor by several m (friction and heat dissipation).
Beam losses.
Cooling failures. ..
Example of the energy (mJ/cm3) required to quench an LHC dipole magnet with an instantaneous loss.
Steep energy dependence.
Models are confirmed at 0.45 TeV.

22. Beam lifetime Consider a beam with a lifetime t :
Number of protons lost per second for different lifetimes (nominal intensity):
t = 100 hours p/s
t = 25 hours 4x109 p/s
t = 1 hour p/s
While ‘normal’ lifetimes will be in the range of hours (in collisions most of the protons are actually lost in the experiments !!), one has to anticipate short periods of low lifetimes, down to a few minutes !
 To survive periods of low lifetime we must intercept the protons that are lost with very high efficiency before they can quench a magnet : collimation!
Quench level ~ p

23. Collimation
A 4-stage halo cleaning (collimation) system is installed to protect the LHC magnets from beam induced quenches.
A cascade of more than 100 collimators is required to prevent the protons and their debris to reach the superconducting magnet coils.
The collimators will also play an essential role for protection by intercepting the beams.
 the collimators must reduce the energy load into the magnets due to particle lost from the beam to a level that does not quench the magnets.
in front of the exp.
Exp.
Detectors
Courtesy C. Bracco

24. Collimator settings at 7 TeV
At the LHC collimators are essential for machine operation as soon as we have more than a few % of the nominal beam intensity at injection !
The collimator opening corresponds roughly to the size of Spain !
Carbon jaw
1 mm
Opening
~3-5 mm
RF contact ‘fingers’

25. Collimation performance
Measurements of the collimation efficiency from beam loss maps confirms the excellent performance : > 99.9% efficiency !
Cleaning
Momentum
Cleaning
IR2
Dump Protection
IR5
IR8
IR1
Collimation team

26. Machine protection: magnets

27. LHC powering in sectors
To limit the stored energy within one electrical circuit, the LHC is powered by sectors.
The main dipole circuits are split into 8 sectors to bring down the stored energy to ~1 GJ/sector.
Each main sector (~2.9 km) includes 154 dipole magnets (powered by a single power converter) and 47 quadrupoles.
 This also facilitates the commissioning that can be done sector by sector ! 5 4 6
DC Power feed
LHC 3
DC Power 7
27 km Circumference
Powering Sector 2 8
Sector 1

28. Powering from room temperature source…
6 kA power converter
Water cooled 13 kA Copper cables
! Not superconducting !

29. Feedboxes (‘DFB’) : transition from Copper cable to super-conductor
…to the cryostat
Feedboxes (‘DFB’) : transition from Copper cable to super-conductor
Cooled Cu cables

30. Threshold of quench protection system (QPS)
Quench detection
When part of a magnet quenches, the conductor becomes resistive, which can lead to excessive local energy deposition (tT rise !!) due to Ohmic losses.
To protect the magnet:
The quench must be detected: this is done by monitoring the voltage that appears over the coil (R > 0).
The energy release is distributed over the entire magnet by force-quenching the coils using quench heaters (such that the entire magnet quenches !).
The magnet current is switched off within << 1 second.
18/04/10
Example of the voltage signals over 5 quenching dipole magnets (beam induced at injection).
Threshold of quench protection system (QPS)

31. Quench - discharge of the energy
Power Converter
Discharge resistor
Magnet 1
Magnet 2
Magnet 154
Magnet i
Protection of the magnet after a quench:
The quench is detected by measuring the voltage increase over coil.
The energy is distributed in the magnet by force-quenching using quench heaters.
The current in the quenched magnet decays in < 200 ms.
The current flows through the bypass diode (triggered by the voltage increase over the magnet).
The current of all other magnets is dischared into the dump resistors.

32. Dump resistors
Those large air-cooled resistors can absorb the 1 GJ stored in the dipole magnets (they heat up to few hundred degrees Celsius).

33. Machine protection philosophy
Stored magnetic energy
Stored beam energy
Power Permit
Beam Permit
→ Authorises power on
→ Cuts power off in case of fault
→ Authorises beam operation
→ Requests a beam dump in case of problems
Collimators
access RF
Beam permit
Experiments
vacuum
BLMs
Warm Magnets
Software interlocks
Power permit
Power Converters
QPS
Cryo

34. Beam interlock system Isn’t it a miracle that it works !
Over 20’000 signals enter the interlock system of the LHC that will send the beam into the dump block if any input signals a fault !
CCC
Operator Buttons
Safe
Mach.
Param.
Software
Interlocks
LHC
Devices
SEQ
Movable Devices
Experiments
BCM
Beam Loss
Experimental Magnets
Collimation
System
Collimator
Positions
Environmental
parameters
BTV
BTV screens
Mirrors
Timing
Transverse Feedback
Beam
Aperture
Kickers
FBCM
Lifetime
Beam
Dumping System
Beam Interlock System
Safe
Beam
Flag
PIC essential
+ auxiliary
circuits
WIC
QPS
(several 1000)
Power
Converters
~1500
AUG
UPS
Power Converters
Magnets
FMCM
Cryo OK RF
System
BLM
BPM in IR6
Monitors
aperture limits
(some 100)
Monitors in arcs
(several 1000)
Access
System
Doors
EIS
Vacuum
System
valves
Access
Safety
Blocks
RF Stoppers
Injection BIS
Timing System
(Post Mortem)
Isn’t it a miracle that it works !

35. Incident of September 19th 2008 & Consequences

36. Event sequence on Sept. 19th
Introduction: on September 10th when the first beam made it around the LHC, not all magnets had not been fully commissioned for 5 TeV.
A few magnets were missing their last commissioning steps.
The last steps were finished the week after Sept. 10th.
Last commissioning step of the dipole circuit in sector 34 : ramp to 5.5 TeV.
At ~5.1 TeV an electrical fault developed in the dipole bus bar (the bus bar is the cable carrying the current that connects all magnet of a circuit).
Later traced to an anomalous resistance of 200 nW (should be 0.3 nW).
An electrical arc developed which punctured the helium enclosure.
Secondary arcs developed along the arc.
Around 400 MJ were dissipated in the cold-mass and in electrical arcs.
Large amounts of Helium were released into the insulating vacuum.
In total 6 tons of He were released.

37. Pressure wave
Pressure wave propagates in both directions along the magnets inside the insulating vacuum enclosure.
Rapid pressure rise :
Self actuating relief valves could not handle the pressure.
designed for 2 kg He/s, incident ~ 20 kg/s.
Large forces exerted on the vacuum barriers (every 2 cells).
designed for a pressure of 1.5 bar, incident ~ 10 bar.
Several quadrupoles displaced by up to ~50 cm.
Connections to the cryogenic line damaged in some places.
Beam vacuum to atmospheric pressure.

38. One of ~1700 bus-bar connections
Dipole busbar

39. Incident location
Dipole bus bar

40. Collateral damage : displacements
Quadrupole-dipole interconnection
Quadrupole support
Main damage area ~ 700 metres.
39 out of 154 dipoles,
14 out of 47 quadrupole short straight sections (SSS)
from the sector had to be moved to the surface for repair (16) or replacement (37).

41. Collateral damage : beam vacuum
The beam vacuum was affected over entire 2.7 km length of the arc.
Clean Copper surface.
Contamination with multi-layer magnet insulation debris.
Contamination with sooth.
 60% of the chambers
 20% of the chambers

42. Quench - discharge of the energy
The bus-bar must carry the current for some minutes, through interconnections
Power Converter
Discharge resistor
Magnet 1
Magnet 2
Magnet 154
Magnet i
In case of a quench, the individual magnet is protected (quench protection and diode).
Resistances are switched into the circuit: the energy is dissipated in the resistances (current decay time constant of 100 s).
>> the bus-bar must carry the current until the energy is extracted !

43. Bus-bar joint
24’000 bus-bar joints in the LHC main circuits.
10’000 joints are at the interconnection between magnets.
They are welded in the tunnel.
Nominal joint resistance:
1.9 K nΩ
300K ~10 μΩ
For the LHC to operate safely at a certain energy, there is a limit to maximum value of the joint resistance.

44. Joint quality
The copper stabilizes the bus bar in the event of a cable quench (=bypass for the current while the energy is extracted from the circuit).
Protection system in place in 2008 not sufficiently sensitive.
A copper bus bar with reduced continuity coupled to a superconducting cable badly soldered to the stabilizer can lead to a serious incident.
bus
U-profile
wedge
Solder
No solder
X-ray of joint
During repair work in the damaged sector, inspection of the joints revealed systematic voids caused by the welding procedure.

45. Normal interconnect, normal operation
Everything is at 1.9 Kelvin.
Current passes through the superconducting cable.
For 7 TeV : I = 11’800 A
Magnet
Magnet
Helium bath
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable with about 12 mm2 copper
current
Interconnection joint (soldered)
This illustration does not represent the real geometry

46. Normal interconnect, quench
Quench in adjacent magnet or in the bus-bar.
Temperature increase above ~ 9 K.
The superconductor becomes resistive.
During the energy discharge the current passes for few minutes through the copper bus-bar.
Magnet
Magnet
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable
interconnection

47. Non-conform interconnect, normal operation
Interruption of copper stabiliser of the bus-bar.
Superconducting cable at 1.9 K
Current passes through superconductor.
Magnet
Magnet
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable
interconnection

48. Non-conform interconnect, quench.
Interruption of copper stabiliser.
Superconducting cable temperature increase to above ~9 K and cable becomes resistive.
Current cannot pass through copper and is forced to pass through superconductor during discharge.
Magnet
Magnet
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable
interconnection

49. Non-conform interconnect, quench.
The superconducting cable heats up because of the combination of high current and resistive cable.
Magnet
Magnet
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable
interconnection

50. Non-conform interconnect, quench.
Superconducting cable melts and breaks if the length of the superconductor not in contact with the bus bar exceeds a critical value and the current is high.
Circuit is interrupted and an electrical arc is formed.
Magnet
Magnet
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable
interconnection
Depending on ‘type’ of non-conformity, problems appear :
at different current levels.
under different conditions (magnet or bus bar quench etc).

51. September 19th hypothesis
Anomalous resistance at the joint heats up and finally quenches the joint – but quench remains very local.
Current sidesteps into Copper that eventually melts because the electrical contact is not good enough.
Magnet
Magnet
copper bus bar 280 mm2
copper bus bar 280 mm2
superconducting cable
quench at the interconnection
>> A new protection system will be installed this year to anticipate such incidents in the future:
new Quench Protection System (‘nQPS’)

52. LHC repair and consolidation
14 quadrupole magnets replaced
39 dipole magnets replaced
204 electrical inter-connections repaired
Over 4km of vacuum beam tube cleaned
New longitudinal restraining system for 50 quadrupoles
Almost 900 new helium pressure release ports
6500 new detectors and 250km cables for new Quench Protection System to protect busbar joints: nQPS
Collateral damage mitigation

53. A glimpse in the future: the consolidated connection
6/16/2018
A glimpse in the future: the consolidated connection
In the next long (> 1 year) shutdown all the connections will be re-done.
Latest design:
Better electrical contact
Mechanical clamping
Mechanical clamping (not present in Tevatron and Hera …)
Courtesy F. Bertinelli

54. LHC energy target - way down
When
Why
All main magnets commissioned for 7TeV operation before installation
Detraining found when hardware commissioning sectors in 2008
5 TeV poses no problem
Difficult to exceed 6 TeV
Machine wide investigations following S34 incident showed problem with joints
Commissioning of new Quench Protection System (nQPS)
7 TeV
Design
12 kA
5 TeV
Summer 2008
Detraining
9 kA
3.5 TeV
Late 2008
Joints
6 kA
Spring 2009
1.18 TeV
Nov. 2009
nQPS
2 kA
450 GeV

55. LHC energy target - way up
When
What
Train magnets
6.5 TeV is within reach
7 TeV will take time
Repair joints
Complete pressure relief system
Commission nQPS system
7 TeV
2014 ?
Training
6 TeV
2013
Joint repair
2011
3.5 TeV
nQPS
2010
1.18 TeV
2009
450 GeV

56. Beam operation

57. Goals for
2009
2010
2011
Repair of Sector 34
1.18
TeV
nQPS
6kA
3.5 TeV
Isafe < I < 0.2 Inom
β* ~ 2 m
Ions
~ 0.2 Inom
No Beam B
Beam
Ambitious goal for the run: collect 1 fm-1 of data/exp at 3.5 TeV/beam.
To achieve this goal the LHC must operate in 2011 with
L ~ 2×1032 Hz/cm2 ~ Tevatron Luminosity
which requires ~700 bunches of 1011 p/bunch
(stored energy of ~ 30 MJ – 10% of nominal)
Mininum β* in various IP’s
β*inj
β*min
IP1 / IP5
11 m
2 m
IP2/IP8
10 m
IP5-TOTEM
90 m
Implications:
Strict and clean machine setup.
Machine protection systems at near nominal performance.

58. LHC schedule Proton run until November.
Lead ion setup and run November and Decenber.

59. 2010 commissioning milestones
27th Feb
First injection
28th Feb
Both beams circulating
5th March
Canonical two beam operation
8th March
Collimation setup at 450 GeV
12th March
Ramp to 1.18 TeV
15th - 18th March
Technical stop – dipoles magnets good for 3.5 TeV
19th March
Ramp to 3.5 TeV
30th March
First 3.5 TeV collisions in all experiments (media event)
4th - 5th April
19h-long physics fill with b* 10/11 m - L ~ 1027 cm-2s-1
7th April
b*squeeze to 2 m in IP1 and IP5
24th April
30h-long physics fill with b* of 2 m - L ~ 1.31028 cm-2s-1

60. LHC machine cycle 7 TeV 3.5 TeV 450 GeV collisions beam dump
energy ramp
collisions
3.5 TeV
7 TeV
start of the ramp
Squeeze
injection phase
preparation and access
450 GeV

61. LHC cycle Ramp-down/pre-cycle: 1 ½ - 2 hours
Depending on initial conditions, the magnets must either be ramped down (3.5 TeV  injection) or cycled (from access).
Injection: > 15 minutes
Probe beam: low intensity bunch (≤ 1010 p) that must be first injected when a ring is empty (safety !). Used to verify that beam parameters are OK for higher intensity.
Nominal bunch sequence follows when beam parameters have been adjusted.
Ramp: 40 minutes
Machine energy is increase at constant optics (b-function) from 450 to 3.5 TeV. For the moment the ramp rate is limited to ~1 GeV/s.
Ramp rate to nominal value ~5 GeV/s in June >> ramp will become a lot faster!
Squeeze: ~30 minutes
Injection b* is larger (10 m in IR1/5, 11 m in IR2/8) because more aperture is needed to accommodate the larger beam emittance (triplet magnets).
In the squeeze b* is reduced to its nominal physics value (presently 2 m in all IRs). This implies gradient changes of most quadrupoles in the straight sections and first part of the arc.

62. Duration will soon be reduced to ~ 20 minutes
Beam squeeze
11 m to 2 m
Duration will soon be reduced to ~ 20 minutes
10 m to 2 m
30 min

63. How equal are the IPs?
The b-function can be measured by exciting (shaking) the beams.
After correction of optics errors, the residual error is in a band of around +- 20% (specification).
>> b* may vary from IP to IP by up to 20% !
Example of optics errors along the ring for b* 2 m (beam1)
Horizontal
Vertical

64. LHC cycle : physics Stable beams: 10’s of hours and more…
Period with quiet running conditions for the experiments (with HV ON, etc).
Beam tuning activity reduced to the minimum (to keep good lifetimes…).
Collimators in fixed positions (they move during ramp and squeeze).
Note however that abrupt beam loss can occur in any phase due to powering problems, cooling etc etc – even in stable beams.
Experiments are protected by the collimators (shadowing), the LHC machine protection system and by their own protection system (BCM : Beam Condition Monitors).
[1030 cm-2s-1]

65. Beam overlap
Because the beams circulate most of the time in different vacuum chambers, they also see slightly different magnetic fields.
>> no guarantee that they collide at the IP ! Small beam sizes !!
To optimize the beam overlap (hor. and vert. planes) the beams are scanned across one another until the peak luminosity if found (typical +- 2 sigma).
>> settings are quite reproducible – more experience needed.

66. Beam operation at 3.5 TeV
Luminosity (head on case, no crossing angle) :
The beam size s depends on b /b* and on beam emittance en:
Everywhere in the ring the beam size scales with 1/g ~ 1/E.
Aperture margins are reduced wrt 7 TeV !
The quench levels at 3.5 TeV are a factor ~10 higher wrt 7 TeV and the stored beam energy is lower: advantage in the early days.

67. >> overall factor ~8 Present operating conditions
Peak luminosity at 3.5 TeV
A consequence of the small beam size at the IP (small b*) is a large beam size in the triplet magnets.
The physical aperture in the triplet quadrupoles defines the minimum of b*.
Limits b* to ~2 m at 3.5 TeV (instead of 0.5 m at 7 TeV)
Beam size s* increase by:
Factor 2 (‘naturally’ larger size)
Factor ~2 (b* limit)
Luminosity loss wrt 7 TeV of:
Factor ~22 per plane (s*)
>> overall factor ~8
for same beam intensity
Lower limit on b*
(with crossing angle)
Present operating conditions
(no crossing 2 m

68. Intensity increase plan
Stage
N (protons) k
Stored E (kJ)
Peak L (Hz cm-2)
3 fat pilots
1.00E+10 3 17
1.34E+28
4 bunches
2.00E+10 4
44.8
7.63E+28
5.00E+10
112.0
4.77E+29
8 bunches 8
224.0
9.54E+29
4x4 bunches 16
448.0
1.91E+30
8x4 bunches 32
896.0
3.81E+30
43x43 43
1204.0
5.13E+30
8 trains of 6 b
8.00E+10 48
2150.4
1.33E+31
50 ns trains 96
4300.8
2.67E+31
Present phase
Next step
(coming days)
Beams become rather dangerous
Assumption:
b* = 2 m
nominal e
To gain experience with the machine protection system, 2 weeks of running time (~10 fills, 40 h of physics) must be integrated before proceeding to the next step.
Some steps require additional (machine protection) commissioning.

69. Performance estimate L  1032 cm-2s-1 If all goes well, we could reach
by November!
4 coll pairs
5e10 p/bch
Weak bosons (W, Z)
4 coll pairs
2e10 p/bch
b * 2m e10 p/bch
charm, D’s, J/Psi
b * 10m 1.1e10 p/bch
Apr 23
November 7

70. Integrated luminosity projections
If maintain the high availability 100 pb-1 could be integrated until November
Apr 23
Apr 23

71. LHC operation today
So far LHC operation is amazingly stable and efficient (we are still in commissioning !!).
But we are working with ‘tiny’ beams (on the nominal LHC scale).
In physics at the moment:
b* = 2 m at IPs s*  45 mm
N  1.81010 p/bunch k = 2 bunches
 1 colliding pair / IP L  1.31028 cm-2s-1
The next step in intensity is most likely:
N  41010 p/bunch k = 2 bunches
 1 colliding pair / IP L  6.81028 cm-2s-1
We have been able to collide bunches with nominal population (N = 1011) at 450 GeV: this is a good omen for 3.5 TeV (cross fingers…)
We may be able to push luminosity faster than anticipated (L  N2)

72. To observe the LHC

73. Outlook
The LHC beam commissioning has been progressing smoothly and rapidly so far – even we are sometimes surprised !!
But the LHC remains a very complex machine, so far we operate under rather simple conditions.
The problem of the LHC: to reach ‚interesting‘ luminosities we must store very dangerous beams at a very early stage of the commissioning.
We have little operational experience.
We are still consolidating beam control software, debugging systems...
We must be sure that they are no unexpected flaws in the machine protection system (or totally unexpected situations).
>> for this reason we increase the intensity/L in rather modest steps.
Assuming there are no surprises, and once we have passed the main hurdle of the initial machine protection commissioning (soon !), progress should be faster:
>> so far the target of 1031 – 1032 cm-2s-1 by November is within reach !

74. From darkness… …to light
Sept 2008
April 2010