LHC%20Status%20

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LHC Status Plans

• V. Kain, LHC Operations
• Input from J. Wenninger, F. Zimmermann, R.
  Assmann, S. Myers, J.P. Koutchouk, L. Evans, A.
  Verwej, H. Burkhardt....
• SLAC SLUO workshop 16th 17th of July

2
Outline

• Beam Commissioning
• September 19th Incident
• The cause, the problem...a cure?
• 2009/10 LHC run
• ...And beyond LHC Upgrade
• Summary

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LHC Cool-down
Cool-down time to 1.9 K 4-6 weeks/sector sector
1/8 LHC
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LHC Hardware Commissioning

• February to September 2008
• (Re-)commissioning of the magnets circuits
  (power converter, quench protection,
  interlocking..) following predefined test steps.
• 1700 circuits, 10000 magnets
• LHC was commissioned to 5.5 TeV (5 TeV target for
  physics in 2008).
• Magnet re-training required above 6 TeV.
• Commissioning of other equipment (kickers,
  instrumentation, RF,)

11122 test steps
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Injection Tests

• August September 2008
• Injection tests up to 4 adjacent sectors
• Almost all HW systems involved
• Essential checks for
• Control system
• Beam Instrumentation
• Optics (magnetic model) and aperture

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September 10th
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Beam Threading

• Threading by sector
• One beam at a time AND one beam per hour
• Collimators used to intercept beam (1 bunch, 2
  109 protons per bunch, 2 of nominal bunch)
• Beam through sector (1/8 of ring), correct
  trajectory, move out collimators, carry on.

Beam 2 threading
BPM availability 99
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ATLAS CMS events

• Beam-on-collimator events, synchronized to beam
  timing

Courtesy of CMS
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Beam Commissioning Progress

• September 10th
• 1030 Beam 1 around the ring (in 1 hour). Beam
  makes 3 turns
• 1500 Beam 2 around the ring. Beam makes 3-4
  turn
• 2200 Beam 2 circulates for 100s of turns
• September 11th
• Late evening beam 2 captured by RF.
• First emergency dump correctly executed.
• September 12th
• All basic instrumentation operational BPMs,
  BLMs, Tune, BCTs,...
• Good beam lifetime (gt 1 hour)
• Beta-beating measured

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Magnetic model beta-beating

• A sophisticated magnetic model (FIDEL) was
  developed to predict transfer functions and field
  errors for all magnets, backed by measurements
  and integrated into the control system for online
  corrections.

Beta-beat tolerance 20

• Horizontal beating 30
• Vertical beating up to 90-100

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September 19th incident
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Event sequence on 19th of September

• Last commissioning step on main dipole circuit in
  Sector 34 ramp to 9.3 kA (5.5 TeV)
• At 8.7 kA an electrical fault developed in the
  dipole bus bar in the interconnect between
  Q24.R34 and the neighbouring dipole
• Later correlated to a resistance of that splice
  in the interconnect of 220 nW (0.35 nW
  nominally)
• An electrical arc developed which punctured the
  He enclosure
• Secondary arcs developed along the circuit
• Around 400 MJ out of the 600 MJ stored in the
  circuit were dissipated into the coldmass and in
  electrical arcs.
• Tons of He were released into the insulation
  vacuum
• Pressure wave along the magnets in the insulation
  vacuum ? collateral damage

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Interconnection
Vac. chamber
Dipole busbar
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After the incident...
Dipole bus bar
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Collateral damage pressure wave

• He-pressure wave travels along magnet inside
  insulation vacuum up to vacuum barriers (every 2
  cells)
• Self actuating relief valves could not handle
  pressure
• Designed for 2 kg He/s incident 20 kg He/s
• Large forces exerted on vacuum barriers
• Designed for 1.5 bar incident 8 bar
• Several quadrupoles displaced by 50 cm
• Connection to cryo-line damaged
• Beam vacuum atmospheric pressure

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Collateral damage - beam vacuum

• Beam vacuum affected over entire length of arc
  2.7 km

Clean surface
Covered with MLI flakes 60 of all chambers
Covered with soot. 20 of all chambers
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LHC Repair
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The Cause, the problem...a cure?
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Incident cause poor quality joint

• Cryogenic measurements indicate local resistance
  of superconducting cable joint of 220 nOhm in
  cell where incident occured.
• Simulation of fatal ramp thermal runaway at
  8700 A
• 1 V detection threshold of OLD quench
  protection system (QPS) not adequate
• ? 0.3 mV is required to protect busbars ? new
  QPS system

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Busbar quench current through Cu stabilizer
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Bad connection in Cu stabilizer? New QPS does
not protect
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Bad Cu stabilizer bus bar quench

• Has to be measured at warm.

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Measurement at cold 1.9 K

• Goal for next run beam energy 4 TeV 5 TeV
• Splices above inadequate resistance have to be
  fixed

Cold 1.9K
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Measurement at300 K (80 K)

• Copper stabilizers... simulations are only as
  good as their input conditions...

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Measurement status strategy

• SC joint measurements calorimetry (down 40
  nOhm), high precision voltage (down to 1 nOhm)
  measurements,...
• 3 sectors still to be tested (S34, S23, S45) so
  far
• two bad internal joints found (50 nOhm, 100
  nOhm)
• Cu stabilizers
• 3 sectors still to be tested (S 23, S 78, S 81)
  so far
• MB 10 joints repaired gt 35 mOhm
• MQ 10 joints repaired gt 80 mOhm
• Strategy
• Measure remaining sectors
• Determine which splices need to be repaired as a
  function of safe current
• Discuss safe operating energy vs. start-date
  with beam

NEW QPS TO PROTECT!
DANGEROUS IN CASE OF QUENCH
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LHC run 2009/10 - Plans
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Current Planning

• Machine fully hardware-tested end of October.
• First beam end of October.
• ...followed by a long LHC run until November 2010
  with a short break around Christmas/New Year.
• Target energy 4 5 TeV

Cool-Down
Low cur. powering
High cur. powering
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Luminosity Goals

• Present 4-stage collimation system limits
  intensity to 10 of nominal.
• Operational goals 2009/10
• End of 2010 short Pb ion run foreseen

No. bunches/ beam Protons/ bunch of nominal intensity b (m) Peak L (cm-2 s-1)
43 5?1010 0.7 2 6.9x1030
156 5?1010 2.4 1 5.0x1031
156 1?1011 4.8 1 2.0x1032
720 (50 ns) 5?1010 11.1 2 1.2x1032
No crossing angle
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...And beyond LHC upgrade

• sLHC Luminosity upgrade

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Upgrade for Nominal - Collimation

• Issue loss of off-momentum particles in the
  dispersion suppressor right downstream of
  collimation zones.

• Coming either
• 2010/11 or 2013/14
• cryo-collimators
• low impedance collimators ? HiRadMat
• in-built BPMs

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LHC Luminosity Upgrade

• Luminosity upgrade ? sLHC

Limitations Nb, en injector chain nb electron
cloud effect F beam separation
schemes b insertion
sLHC Phase I
sLHC Phase II
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Plans...
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Phase I and Phase II

• Phase I - 2014
• New NbTi larger apterure triplets, new quadrupole
  absorbers (TAS), new separation dipoles ? b
  25 cm
• Linac4 ? ultimate intensity 1.7 1011 p per
  bunch
• Luminosity 3 1034 cm-2s-1
• Phase II - 2018
• Two new injectors SPL and PS2 ? 2x ultimate beam
  brightness (Nb/e)
• New triplets? Nb3Sn? More robust, larger aperture
  ? b 15 cm
• New separation schemes? Other compensatory
  measures?
• Luminosity 1035 cm-2s-1

Still open questions
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Phase II new separation scheme required
for nominal crossing angle (9.5 s), only modest
luminosity gain from reduced ß, if
not complemented by other measures
Crossing angle reduces beam-beam tune shift but
also luminosity.
Geometric factor
Piwinski angle
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Beam separation schemes/ Compensatory measures
possibilities

• Low emittance 1- 2mm
• Draw back limited by beam-beam tune shift and
  IBS
• Work against lumi-decrease from geometric overlap
  reduction different possibilities
• Long-range beam-beam compensation
• Early separation dipole magnets in experiment
• Plus possible crab cavities
• Full crab crossing with dedicated crab cavities
• Large Piwinski angle at beam-beam limit
  larger Piwinski angle (and/or larger emittance)
  increases luminosity 50 ns, 4.9 1011 p per
  bunch

Beam-beam compensation
1.7-2.3 1011 per bunch, 25 ns
Crab crossing
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Contact Names - Upgrade

• http//project-slhc.web.cern.ch/project-slhc/conta
  cts/
• sLHC project leader L. Evans
• Linac4 M. Vretenar, A. Lombardi
• SPL R. Garoby, A. Lombardi
• PS2 M. Benedikt, Y. Papaphilippou
• SPS upgrade E. Shaposhnikova
• IR upgrade (phase I) R. Ostojic, S. Fartoukh
  http//slhc-irp1.web.cern.ch/SLHC-IRP1/
• EuCARD Coordinator J.-P. Koutchouk
  https//eucard.web.cern.ch/EuCARD/about/
• Crab cavities J. Tuckmantel, F. Zimmermann
• Collimators R. Assmann
• High field magnets L. Rossi
• ....
• Other things
• Machine protection, operational issues,
  software,... J. Wenninger, R. Schmidt, V. Kain

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Summary

• With beam the LHC is a wonderful machine.
• All key systems were operational
• Remarkable performance of the beam
  instrumentation
• The incident of the 19th of September was most
  probably due to the poor quality of a bus-bar
  joint.
• ? Quench protection system upgrade
• ? Improvement of the pressure relief system
• ? Measurement campaign for all splices and
  stabilizers systematic problem
• Repair and further measurements are well under
  way
• We will start-up in autumn this year. The goal is
  to run until autumn 2010.
• Upgrade luminosity upgrade in several stages.
  Different work packages have been defined.
• Collimators need upgrade to go to nominal
  intensity
• The first upgrade phase is planned for 2014

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Reserve slides
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Bad surprise...voids in joints

• Voids are present in most of the joints. Solder
  (SnAg) flows out when soldering in situ.

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Splice and Stabilizer Measurements (Status June 5)
Sector Status on June 5 2009 Splices Calorimetric Ohmic Splices Calorimetric Ohmic Stabilizers Biddle R16 Stabilizers Biddle R16 Stabilizers Biddle Stabilizers Biddle
Sector Status on June 5 2009 1.9K 7kA 1.9K 7kA Warm Warm 80K 80K
Sector Status on June 5 2009 Dipoles Quads Dipoles Quads Dipoles Quads
12 warm Done Done Done Done No need No need
23 2K
34 warm Done Done No need No need
45 80K Analysis Problems
56 warm Done Done Done Done No need No need
67 warm Done Done Done Done No need No need
78 40K Done Done
81 40K Done Done