LHC construction and operation Jrg Wenninger CERN Beams

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 J. Wenninger LNF Spring School, May 2010 1

Machine protection J. Wenninger LNF Spring School, May 2010 2

The price of high fields & high luminosity… When the LHC is operated at 7 Te. V with its design luminosity & intensity, q the LHC magnets store a huge amount of energy in their magnetic fields: per dipole magnet all magnets Estored = 7 MJ Estored = 10. 4 GJ q the 2808 LHC bunches store a large amount of kinetic energy: Ebunch = N x E = 1. 15 x 1011 x 7 Te. V = 129 k. J 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 ! J. Wenninger LNF Spring School, May 2010 3

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 J. Wenninger LNF Spring School, May 2010 4

Comparison… The energy of an A 380 at 700 km/hour corresponds to the energy stored in the LHC magnet system : Sufficient to heat up and melt 15 tons of Copper!! The energy stored in one LHC beam corresponds approximately to… • 90 kg of TNT • 10 -12 litres of gasoline • 15 kg of chocolate It’s how easily/quickly the energy is released that matters most !! J. Wenninger LNF Spring School, May 2010 5

Machine protection: beam J. Wenninger LNF Spring School, May 2010 6

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’: q Vacuum chamber ripped open. q 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 ! J. Wenninger LNF Spring School, May 2010 7

Beam impact in a target Simulation of a 7 Te. V LHC beam impact into a 5 m long Copper target 20 bunches 180 bunches 100 bunches 380 bunches The 7 Te. V LHC beam can drill a hole through ~35 m of Copper Courtesy N. Tahir / GSI J. Wenninger LNF Spring School, May 2010 8

From a real 450 Ge. V beam… 108 s 6 cm 30 c m Shoot a 450 Ge. V beam into a target… plate Shot Intensity / p+ A 1. 2× 1012 B 2. 4× 1012 C 4. 8× 1012 D 7. 2× 1012 m 6 c Cu plate ~20 cm inside the ‘target’. ~0. 1% nominal LHC beam A J. Wenninger LNF Spring School, May 2010 B D C 9

‘Safe’ beams at the LHC… 2011 ‘Un-safe beam’ ‘Safe beam’ L ~ 2 1028 cm-2 s-1 LHC 2010 J. Wenninger LNF Spring School, May 2010 10

Schematic layout of beam dump system in IR 6 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 ! Septum magnets deflect the extracted beam vertically Beam 1 Q 5 L Ultra-high reliability system !! Kicker magnets to paint (dilute) the beam Beam dump block Q 4 L 700 m 15 fast ‘kicker’ magnets deflect the beam to the outside Q 4 R 500 m The 3 ms gap in the beam gives the kicker time to reach full field. J. Wenninger LNF Spring School, May 2010 Q 5 R quadrupoles Beam 2 11

The dump block Simulation Measurement ONLY element in the LHC that can withstand the impact of the full beam ! q The block is made of graphite (low Z material) to spread out the showers over a large volume. q It is actually necessary to paint the beam over the surface to keep the peak energy densities at a tolerable level ! beam absorber (graphite) q The J. Wenninger LNF Spring School, May 2010 . 8 x ro m p Ap concrete shielding 12

Dump line in IR 6 J. Wenninger LNF Spring School, May 2010 13

Dump line J. Wenninger LNF Spring School, May 2010 14

Dump installation J. Wenninger LNF Spring School, May 2010 15

‘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): Beam loss over a single turn during injection, beam dump. Beam loss over multiple turns (~millisecond to many seconds) due to many types of failures. Passive protection - Failure prevention (high reliability systems). - Intercept beam with collimators and absorber blocks. Active Protection - Failure detection (by beam and/or equipment monitoring) with fast reaction time (< 1 ms). - Fire beam dumping system. q Because of the very high risk, the LHC machine protection system is of unprecedented complexity and size. q A general design philosophy was to ensure that there should always be at least 2 different systems to protect against a given failure type. J. Wenninger LNF Spring School, May 2010 16

Failure detection example : beam loss monitors q Ionization – – chambers to detect beam losses: N 2 gas filling at 100 mbar over-pressure, voltage 1. 5 k. V Sensitive volume 1. 5 l Reaction time ~ ½ turn (40 ms) Very large dynamic range (> 106) q There are ~3600 chambers distributed over the ring to detect abnormal beam losses and if necessary trigger a beam abort ! J. Wenninger LNF Spring School, May 2010 17

Beam loss monitoring J. Wenninger LNF Spring School, May 2010

Machine protection and quench prevention: collimation J. Wenninger LNF Spring School, May 2010 19

Operational margin of SC magnet Applied Field [T] The LHC is ~1000 times more critical than TEVATRON, HERA, RHIC Bc critical Bcfield quench with fast loss of ~106 -7 protons 8. 3 T / 7 Te. V QUENCH quench with fast loss of ~few 109 protons 0. 54 T / 450 Ge. V 1. 9 K J. Wenninger LNF Spring School, May 2010 Temperature [K] Tc critical temperature Tc 9 K 20

Quench levels The phase transition from the super-conducting to a normal conducting state is called a quench. q Quenches are initiated by an energy in the order of few milli. Joules q – – Movement of the superconductor by several m (friction and heat dissipation). Beam losses. Cooling failures. . . Example of the energy (m. J/cm 3) required to quench an LHC dipole magnet with an instantaneous loss. J. Wenninger LNF Spring School, May 2010 q Steep energy dependence. q Models are confirmed at 0. 45 Te. V. 21

Beam lifetime Consider a beam with a lifetime t : Number of protons lost per second for different lifetimes (nominal intensity): t = 100 hours t = 25 hours t = 1 hour 109 p/s 4 x 109 p/s Quench level ~ 106 -7 p 1011 p/s While ‘normal’ lifetimes will be in the range of 10 -100 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! J. Wenninger LNF Spring School, May 2010 22

Collimation A 4 -stage halo cleaning (collimation) system is installed to protect the LHC magnets from beam induced quenches. q A cascade of more than 100 collimators is required to prevent the protons and their debris to reach the superconducting magnet coils. q 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 J. Wenninger LNF Spring School, May 2010 23

Collimator settings at 7 Te. V q 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’ J. Wenninger LNF Spring School, May 2010 24

Collimation performance Measurements of the collimation efficiency from beam loss maps confirms the excellent performance : > 99. 9% efficiency ! Cleaning Momentum Cleaning IR 2 IR 5 Dump Protection IR 8 IR 1 Collimation team J. Wenninger LNF Spring School, May 2010 25

Machine protection: magnets J. Wenninger LNF Spring School, May 2010 26

LHC powering in sectors To limit the stored energy within one electrical circuit, the LHC is powered by sectors. q The main dipole circuits are split into 8 sectors to bring down the stored energy to ~1 GJ/sector. q Each main sector (~2. 9 km) includes 154 dipole magnets (powered by a single power converter) and 47 quadrupoles. q 5 4 6 DC Power feed 3 LHC DC Power 27 km Circumference 7 This also facilitates the commissioning that can be done sector by sector ! Powering Sector 8 2 Sector 1 J. Wenninger LNF Spring School, May 2010 27

Powering from room temperature source… 6 k. A power converter Water cooled 13 k. A Copper cables ! Not superconducting ! J. Wenninger LNF Spring School, May 2010 28

…to the cryostat Feedboxes (‘DFB’) : transition from Copper cable to super-conductor Cooled Cu cables J. Wenninger LNF Spring School, May 2010 29

Quench detection When part of a magnet quenches, the conductor becomes resistive, which can lead to excessive local energy deposition (t. T rise !!) due to Ohmic losses. q To protect the magnet: q – 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) J. Wenninger LNF Spring School, May 2010 30

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. J. Wenninger LNF Spring School, May 2010 31

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). J. Wenninger LNF Spring School, May 2010 32

Machine protection philosophy Stored magnetic energy Stored beam energy Power Permit → Authorises power on → Cuts power off in case of fault Beam Permit → Authorises beam operation → Requests a beam dump in case of problems BLMs Cryo RF access Experiments Beam permit Power permit Software interlocks vacuum Power Converters Collimators QPS J. Wenninger LNF Spring School, May 2010 Warm Magnets 33

Beam interlock system 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 ! Timing LHC LHC Devices Safe Mach. Param. Software Interlocks Movable Devices SEQ CCC Operator Buttons Safe Beam Flag BCM Beam Loss Experimental Magnets Experiments Transverse Feedback Collimator Positions Beam Aperture Kickers Environmental parameters Collimation System BTV screens FBCM Lifetime Mirrors BTV Beam Dumping System Beam Interlock System Injection BIS PIC essential + auxiliary circuits WIC Magnets QPS (several 1000) Power Converters ~1500 FMCM RF System Monitors aperture limits (some 100) Power Converters AUG UPS J. Wenninger LNF Spring School, May 2010 BLM Cryo OK Monitors in arcs (several 1000) BPM in IR 6 Doors Access System Vacuum System EIS Vacuum valves Timing System (Post Mortem) Access Safety Blocks RF Stoppers Isn’t it a miracle that it works ! 34

Incident of September 19 th 2008 & Consequences J. Wenninger LNF Spring School, May 2010 35

Event sequence on Sept. 19 th Introduction: on September 10 th when the first beam made it around the LHC, not all magnets had not been fully commissioned for 5 Te. V. A few magnets were missing their last commissioning steps. The last steps were finished the week after Sept. 10 th. q Last commissioning step of the dipole circuit in sector 34 : ramp to 5. 5 Te. V. q At ~5. 1 Te. V 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 n. W (should be 0. 3 n. W). q 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. q Large amounts of Helium were released into the insulating vacuum. In total 6 tons of He were released. J. Wenninger LNF Spring School, May 2010 36

Pressure wave q Pressure wave propagates in both directions along the magnets inside the insulating vacuum enclosure. q 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. J. Wenninger LNF Spring School, May 2010 37

One of ~1700 bus-bar connections Dipole busbar J. Wenninger LNF Spring School, May 2010 38

Incident location Dipole bus bar J. Wenninger LNF Spring School, May 2010 39

Collateral damage : displacements Quadrupole-dipole interconnection Quadrupole support Main damage area ~ 700 metres. 39 out of 154 dipoles, Ø 14 out of 47 quadrupole short straight sections (SSS) Ø from the sector had to be moved to the surface for repair (16) or replacement (37). J. Wenninger LNF Spring School, May 2010 40

Collateral damage : beam vacuum The beam vacuum was affected over entire 2. 7 km length of the arc. Clean Copper surface. J. Wenninger LNF Spring School, May 2010 Contamination with multilayer magnet insulation debris. Contamination with sooth. 60% of the chambers 20% of the chambers 41

Quench - discharge of the energy The bus-bar must carry the current for some minutes, through interconnections Magnet 1 Power Converter Discharge resistor Magnet 2 Magnet 154 Magnet i q In case of a quench, the individual magnet is protected (quench protection and diode). q 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 ! J. Wenninger LNF Spring School, May 2010 42

Bus-bar joint q 24’ 000 bus-bar joints in the LHC main circuits. q 10’ 000 joints are at the interconnection between magnets. They are welded in the tunnel. Nominal joint resistance: • 1. 9 K • 300 K 0. 3 nΩ ~10 μΩ For the LHC to operate safely at a certain energy, there is a limit to maximum value of the joint resistance. J. Wenninger LNF Spring School, May 2010 43

Joint quality q 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. q A copper bus bar with reduced continuity coupled to a superconducting cable badly soldered to the stabilizer can lead to a serious incident. Solder No solder wedge bus U-profile bus X-ray of joint q J. Wenninger LNF Spring School, May 2010 During repair work in the damaged sector, inspection of the joints revealed systematic voids caused by the welding procedure. 44

Normal interconnect, normal operation q Magnet q Everything is at 1. 9 Kelvin. Current passes through the superconducting cable. Magnet For 7 Te. V : I = 11’ 800 A Helium bath copper bus bar 280 mm 2 current copper bus bar 280 mm 2 Interconnection joint (soldered) superconducting cable with about 12 mm 2 copper This illustration does not represent the real geometry J. Wenninger LNF Spring School, May 2010 45

Normal interconnect, quench q Quench in adjacent magnet or in the bus-bar. q Temperature Magnet q The increase above ~ 9 K. superconductor becomes resistive. Magnet q During the energy discharge the current passes for few minutes through the copper bus-bar. copper bus bar 280 mm 2 superconducting cable interconnection J. Wenninger LNF Spring School, May 2010 46

Non-conform interconnect, normal operation q Interruption Magnet of copper stabiliser of the bus-bar. q Superconducting q Current cable at 1. 9 K Magnet passes through superconductor. copper bus bar 280 mm 2 superconducting cable interconnection J. Wenninger LNF Spring School, May 2010 47

Non-conform interconnect, quench. q Interruption of copper stabiliser. q Superconducting Magnet cable temperature increase to above ~9 K and cable becomes resistive. Magnet q Current cannot pass through copper and is forced to pass through superconductor during discharge. copper bus bar 280 mm 2 superconducting cable interconnection J. Wenninger LNF Spring School, May 2010 48

Non-conform interconnect, quench. q Magnet The superconducting cable heats up because of the combination of high current and resistive cable. copper bus bar 280 mm 2 Magnet copper bus bar 280 mm 2 superconducting cable interconnection J. Wenninger LNF Spring School, May 2010 49

Non-conform interconnect, quench. q Superconducting Magnet 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. q Circuit Magnet is interrupted an electrical arc is formed. copper bus bar 280 mm 2 superconducting cable interconnection Depending on ‘type’ of non-conformity, problems appear : Ø at different current levels. Ø under different conditions (magnet or bus bar quench etc). J. Wenninger LNF Spring School, May 2010 50

September 19 th hypothesis q Anomalous Magnet resistance at the joint heats up and finally quenches the joint – but quench remains very local. q Current sidesteps into Copper that eventually melts because the electrical contact is not good enough. copper bus bar 280 mm 2 Magnet copper bus bar 280 mm 2 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 (‘n. QPS’) J. Wenninger LNF Spring School, May 2010 51

LHC repair and consolidation 14 quadrupole magnets replaced New longitudinal restraining system for 50 quadrupoles 39 dipole magnets replaced Almost 900 new helium pressure release ports Collateral damage mitigation J. Wenninger LNF Spring School, May 2010 204 electrical interconnections repaired Over 4 km of vacuum beam tube cleaned 6500 new detectors and 250 km cables for new Quench Protection System to protect busbar joints: n. QPS 52

A glimpse in the future: the consolidated connection In the next long (> 1 year) shutdown all the connections will be re-done. q Latest design: o Better electrical contact o Mechanical clamping q Mechanical clamping (not present in Tevatron and Hera …) Courtesy F. Bertinelli J. Wenninger LNF Spring School, May 2010 53

LHC energy target - way down When All main magnets commissioned for 7 Te. V operation before installation Detraining found when hardware commissioning sectors in 2008 o 5 Te. V poses no problem o Difficult to exceed 6 Te. V Machine wide investigations following S 34 incident showed problem with joints Commissioning of new Quench Protection System (n. QPS) 7 Te. V 12 k. A 5 Te. V 9 k. A 3. 5 Te. V 6 k. A 1. 18 Te. V 2 k. A Why 2002 -2007 Design Summer 2008 Detraining Late 2008 Spring 2009 Nov. 2009 Joints n. QPS 450 Ge. V 54 J. Wenninger LNF Spring School, May 2010

LHC energy target - way up When Train magnets o 6. 5 Te. V is within reach o 7 Te. V will take time Repair joints Complete pressure relief system Commission n. QPS system 7 Te. V 6 Te. V 3. 5 Te. V 2014 ? Training 2013 Joint repair 2011 2010 1. 18 Te. V What n. QPS 2009 450 Ge. V 55 J. Wenninger LNF Spring School, May 2010

Beam operation J. Wenninger LNF Spring School, May 2010 56

Goals for 2010 -2011 2009 Repair of Sector 34 No Beam 2010 1. 18 n. QPS Te. V 6 k. A B 3. 5 Te. V Isafe < I < 0. 2 Inom 2011 3. 5 Te. V ~ 0. 2 Inom Ions β* ~ 2 m Beam Ambitious goal for the run: collect 1 fm-1 of data/exp at 3. 5 Te. V/beam. To achieve this goal the LHC must operate in 2011 with Mininum β* in various IP’s L ~ 2× 1032 Hz/cm 2 ~ Tevatron Luminosity which requires ~700 bunches of 1011 p/bunch (stored energy of ~ 30 MJ – 10% of nominal) Implications: Strict and clean machine setup. Machine protection systems at near nominal performance. J. Wenninger LNF Spring School, May 2010 β*inj β*min IP 1 / IP 5 11 m 2 m IP 2/IP 8 10 m 2 m IP 5 -TOTEM 11 m 90 m 57

LHC schedule q Proton run until November. q Lead ion setup and run November and Decenber. J. Wenninger LNF Spring School, May 2010 58

2010 commissioning milestones 27 th Feb First injection 28 th Feb Both beams circulating 5 th March Canonical two beam operation 8 th March Collimation setup at 450 Ge. V 12 th March Ramp to 1. 18 Te. V 15 th - 18 th March Technical stop – dipoles magnets good for 3. 5 Te. V 19 th March Ramp to 3. 5 Te. V 30 th March First 3. 5 Te. V collisions in all experiments (media event) 4 th - 5 th April 19 h-long physics fill with b* 10/11 m - L ~ 1027 cm-2 s-1 7 th April b*squeeze to 2 m in IP 1 and IP 5 24 th April 30 h-long physics fill with b* of 2 m - L ~ 1. 3 1028 cm-2 s-1 J. Wenninger LNF Spring School, May 2010 59

LHC machine cycle collisions beam dump energy ramp 7 Te. V start of the ramp injection phase preparation and access J. Wenninger LNF Spring School, May 2010 Squeeze 3. 5 Te. V 450 Ge. V 60

LHC cycle q Ramp-down/pre-cycle: 1 ½ - 2 hours o q Depending on initial conditions, the magnets must either be ramped down (3. 5 Te. V 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. o Nominal bunch sequence follows when beam parameters have been adjusted. o q Ramp: 40 minutes Machine energy is increase at constant optics (b-function) from 450 to 3. 5 Te. V. For the moment the ramp rate is limited to ~1 Ge. V/s. o Ramp rate to nominal value ~5 Ge. V/s in June >> ramp will become a lot faster! o q Squeeze: ~30 minutes Injection b* is larger (10 m in IR 1/5, 11 m in IR 2/8) because more aperture is needed to accommodate the larger beam emittance (triplet magnets). o 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. o J. Wenninger LNF Spring School, May 2010 61

Beam squeeze 11 m to 2 m Duration will soon be reduced to ~ 20 minutes 10 m to 2 m 30 min J. Wenninger LNF Spring School, May 2010 62

How equal are the IPs? q The b-function can be measured by exciting (shaking) the beams. q 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 (beam 1) Horizontal Vertical J. Wenninger LNF Spring School, May 2010 63

LHC cycle : physics q Stable beams: 10’s of hours and more… Period with quiet running conditions for the experiments (with HV ON, etc). o Beam tuning activity reduced to the minimum (to keep good lifetimes…). o Collimators in fixed positions (they move during ramp and squeeze). o Note however that abrupt beam loss can occur in any phase due to powering problems, cooling 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). o [1030 cm-2 s-1] J. Wenninger LNF Spring School, May 2010 64

Beam overlap q 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 !! q 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. J. Wenninger LNF Spring School, May 2010 65

Beam operation at 3. 5 Te. V q Luminosity (head on case, no crossing angle) : q 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 Te. V ! q The quench levels at 3. 5 Te. V are a factor ~10 higher wrt 7 Te. V and the stored beam energy is lower: advantage in the early days. J. Wenninger LNF Spring School, May 2010

Peak luminosity at 3. 5 Te. V q A consequence of the small beam size at the IP (small b*) is a large beam size in the triplet magnets. q The physical aperture in the triplet quadrupoles defines the minimum of b*. o Limits b* to ~2 m at 3. 5 Te. V (instead of 0. 5 m at 7 Te. V) Beam size s* increase by: Lower limit on b* (with crossing angle) § Factor 2 (‘naturally’ larger size) § Factor ~2 (b* limit) Luminosity loss wrt 7 Te. V of: § Present operating conditions (no crossing angle) @ 2 m J. Wenninger LNF Spring School, May 2010 Factor ~2 2 per plane (s*) >> overall factor ~8 for same beam intensity

Intensity increase plan Stage N (protons) k Stored E (k. J) Peak L (Hz cm-2) 3 fat pilots 1. 00 E+10 3 17 1. 34 E+28 4 bunches 2. 00 E+10 4 44. 8 7. 63 E+28 4 bunches 5. 00 E+10 4 112. 0 4. 77 E+29 8 bunches 5. 00 E+10 8 224. 0 9. 54 E+29 4 x 4 bunches 5. 00 E+10 16 448. 0 1. 91 E+30 8 x 4 bunches 5. 00 E+10 32 896. 0 3. 81 E+30 43 x 43 5. 00 E+10 43 1204. 0 5. 13 E+30 8 trains of 6 b 8. 00 E+10 48 2150. 4 1. 33 E+31 50 ns trains 8. 00 E+10 96 4300. 8 2. 67 E+31 Present phase Next step (coming days) Beams become rather dangerous Assumption: b* = 2 m nominal e q 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. q Some steps require additional (machine protection) commissioning. J. Wenninger LNF Spring School, May 2010 68

Performance estimate If all goes well, we could reach L 1032 cm-2 s-1 by November! 4 coll pairs 5 e 10 p/bch Weak bosons (W, Z) 4 coll pairs 2 e 10 p/bch 23. 4 -. . . b * 2 m 1. 1 e 10 p/bch charm, D’s, J/Psi 30. 3 - 19. 4 b * 10 m 1. 1 e 10 p/bch Apr 23 J. Wenninger LNF Spring School, May 2010 November 7 69

Integrated luminosity projections If maintain the high availability 100 pb-1 could be integrated until November Apr 23 J. Wenninger LNF Spring School, May 2010 70

LHC operation today q 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). q q q In physics at the moment: b* = 2 m at IPs s* 45 m N 1. 8 1010 p/bunch k = 2 bunches 1 colliding pair / IP L 1. 3 1028 cm-2 s-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-2 s-1 We have been able to collide bunches with nominal population (N = 1011) at 450 Ge. V: this is a good omen for 3. 5 Te. V (cross fingers…) o We may be able to push luminosity faster than anticipated (L N 2) J. Wenninger LNF Spring School, May 2010 71

To observe the LHC http: //op-webtools. web. cern. ch/op-webtools/vistars. php? usr=LHC 1 J. Wenninger LNF Spring School, May 2010 72

Outlook q The LHC beam commissioning has been progressing smoothly and rapidly so far – even we are sometimes surprised !! o q 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. o We have little operational experience. o We are still consolidating beam control software, debugging systems. . . o 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. q 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-2 s-1 by November is within reach ! J. Wenninger LNF Spring School, May 2010 73

From darkness… …to light Sept 2008 April 2010 J. Wenninger LNF Spring School, May 2010 74