LHC Status Maria Girone CERN IT material from













- Slides: 13

LHC Status Maria Girone, CERN IT (material from Roger Bailey, CERN AB, LHC Operations)

September 10

September 10 th n Achieved n n n n Beam 1 injected IP 2 Threaded around the machine in 1 h Trajectory steering gave 2 or 3 turns Beam 2 injected IP 8 Threaded around the machine in 1 h 30 Trajectory steering gave 2 or 3 turns Q and Q’ trims gave a few hundred turns

First Beam Events

September 10 th to 19 th 2008 n n n n n Nearly all circuits good for 5 Te. V operation Few details still needing attention Main circuits in 7 sectors fully commissioned in stages to a current of 9. 3 k. A, which corresponds to beam energy of 5. 5 Te. V Dipole circuit of sector 34 had only been to 7 k. A (lack of time) Machine set to 450 Ge. V Injection and first turn of beams 1 and 2 Work on beam 2 over next 2 days Lot of progress made, until electrical fault IP 8 (transformer) No beam possible during subsequent cryogenic recovery Revert to finishing power tests in sector 34

Incident September 19 th 2008 n n Making the last step of dipole circuit in sector 34, to 9. 3 k. A At 8. 7 k. A, development of resistive zone in the dipole bus bar splice between Q 24 R 3 and the neighbouring dipole n Electrical arc developed which punctured the helium enclosure Helium released into the insulating vacuum n Rapid pressure rise inside the LHC magnets n n n n Large pressure wave travelled along the accelerator both ways Self actuating relief valves opened but could not handle all Large forces exerted on the vacuum barriers located every 2 cells These forces displaced several quadrupoles and dipoles Connections to the cryogenic line affected in some places Beam vacuum also affected

Cross section of cryodipole

LHC cryodipole 7 Te. V • 8. 33 T • 11850 A • 7 MJ

All have to be interconnected (dipole bus bar is behind)

LHC arc cell n n n 23 regular cells in each arc 106. 9 m long, made from two 53. 45 m long half-cells Half cell n n 3 15 m cryodipole magnets, each with spool-piece correctors 1 Short Straight Section (~6 m long) n Quadrupole and lattice corrector magnets

Consequences ! Insulating vacuum barrier every 2 cells in the arc n n Considerable collateral damage over few hundred metres Contamination by soot of beam pipes Damage to superinsulation blankets Large release of helium into the tunnel (6 of 15 tonnes) Some moved

Repair ! n Present strategy assumes treating all magnets Q 19 to Q 31 n n n 5 quadrupoles and 24 dipoles are thought to be damaged May have to treat slightly further outside this zone (to Q 33) Components are at CERN Estimate (preliminary) November 08 to March 09 Then have to finish interconnection, cool down, power test

Timescales for restart will be determined by n Efficiency of logistics of magnets removal / installation Efficiency of magnet repair Efficiency of beam pipe repair / cleaning Efficiency of interconnection activities n Strategy adopted to ensure no repeat n n Time to cool down Time to re-commission power circuits n Clearer picture expected by December n n n