Powering LHC magnets version 30/3/2007

Overview LHC Layout: sectors, arcs, insertions, straight sections Why so many magnets (~10000)? Magnet types and their function Magnets powered in series Magnets powered individually Powering and machine protection Why so many DC electrical circuits for magnet powering (~1618)? Electrical circuit types Main systems involved in magnet powering Power converters, Magnet protection, Energy extraction, Powering interlocks Elements of the electrical circuits Normal conducting cables, current leads and superconducting cables (bus bars)

eight long straight sections (insertions) about 700 m long LHC Layout eight sectors eight arcs eight long straight sections (insertions) about 700 m long Beam dump blocks IR5:CMS IR4: RF + Beam instrumentation IR6: Beam dumping system IR3: Momentum Beam Cleaning (warm) IR7: Betatron Beam Cleaning (warm) IR8: LHC-B IR2:ALICE IR1: ATLAS Injection Injection

LHC arcs: dipoles and short straight sections 1232 superconducting dipoles magnets magnetic field 8.3 T (7 Tev), each magnet 15 m long, operating at 1.9 K Deflection of all main dipoles: 2, in total 19 km main dipole magnets Arc length ~21 km (dipoles + short straight sections + interconnects)

Energy stored in LHC main dipole magnets E dipole = 0.5  L dipole  I 2dipole Energy stored in one dipole is 7.6 MJoule For all 1232 dipoles in the LHC: 9.4 GJ 9.4 GJ corresponds to the energy stored in 2 tons of TNT that could melt 20 tons of copper Too much energy for one electrical circuit charging the energy requires too much voltage discharging the energy is even more critical Divide LHC powering into 8 sectors 154 main dipole magnets in series for one sector Stored energy in other magnets much less, but could still cause damage

Effect of 7.6 MJ on a dipole coil P.Pugnat

LHC Powering in 8 Sectors For superconducting magnets, no DC powering across IPs Main DC power feed at even points (MB, MQ), some DC power feed at odd points NC magnets not discussed today 5 4 6 DC Power feed Octant 3 DC Power 7 arc cryostat LHC Sector 2 8 Commissioning possible for each sector independent of other sectors Sector 1 P.Proudlock

More magnets?

A cell in the LHC arcs Vertical / Horizontal plane (QF / QD) Quadrupole magnets controlling the beam size „to keep protons together“ (similar to optical lenses) LHC Cell - Length about 110 m (schematic layout) SSS sextupole corrector (MCS) quadrupole MQF orbit corrector quadrupole MQD orbit corrector quadrupole MQF orbit corrector main dipole MB main dipole MB main dipole MB main dipole MB main dipole MB main dipole MB special corrector (MQS) lattice sextupole (MS) decapole octupole corrector (MCDO) special corrector (MO) lattice sextupole (MS) special corrector (MO) lattice sextupole (MS)

Short straight section: Short straight section: quadrupole, sextupole, orbit correctors and special magnets

MAD file with all magnets and positions SSS SSS

Magnet inventory (arcs + insertions) Powered in series Main dipole magnets (13 kA) Focusing and defocusing arc quadrupole magnets (13 kA) Lattice sextupole magnets in arcs (600 A) to correct the trajectories for off-energy particles Multipole and other correctors in arcs (trim quadrupoles, sextupoles, decapoles, octupoles, 600 A) to correct field imperfections, to suppress instabilities, etc. Powered individually 752 arc orbit corrector magnets powered individually (60 A) to ensure that the beam follows the design orbit (within about 0.5 mm) Most correctors to adjust beam parameters (trim quadrupoles, orbit correctors, etc., 80 – 600 A), arcs and insertions Insertion main dipole and quadrupole magnets (4 – 8 kA) to ensure beam crossing / to increase the interbeam distance / to focus beams for experiments etc. Equipment catalogue in EDMS: http://edms.cern.ch/cedar/plsql/navigation.tree?top=1459088716

From superconducting magnet to electrical circuit The magnet needs to be cooled at 1.9 K or 4.5 K Installed in a cryostat The magnet needs to be powered Power converter at room temperature to supply the current The magnet must be connected By superconducting cables inside the cryostat By normal conducting cables outside the cryostat Cryostat Magnet DFB Current Leads HTS The superconducting cables must be connected to the normal conducting cables Connection via current leads inside special cryostat (DFB) Power Converter

Interconnection of magnets inside arc cryostat Cryostated magnets with length 15 m for dipoles, 5 m for SSS Many cryostated magnets interconnected to make continuous arc cryostat All superconducting bus bars need to be connected for each interconnect Magnet in the center of the arc still powered from DFB Only 60 A orbit correctors powered locally Cryostat DFB Magnet Magnet Magnet Current Leads HTS Interconnection shown only for one circuit Power Converter

Power converters and water cooled cables Water cooled cables 13 kA Power converter 6 kA

DFBs with current leads - feeding current from warm to cold http://hcc.web.cern.ch/hcc/cryogenics/cryo_dfbs.php DFB and current leads

Interconnecting busbars

Bus bar interconnections right of point 8 (19/3/2007) 600 A bus bars (NLine) 6 kA bus bars Link electrical circuits on CDD: https://edms.cern.ch/cdd/plsql/c4w_guided.guided_equip_terminal?cookie=1080365&p_equip_id=LSD

Cyostats in sector 7-8 5 cryostats IP7 RR77 RE82 UJ76 TZ76 PM76 UJ83 Point 7 Ferney IP7 RR77 RE82 UJ76 TZ76 PM76 Point 8 Prevessin UJ83 UA83 5 cryostats - Q6 (DFBMH) A78 (DFBAN - DFBAO) Q5 (DFBMC) - Q4 /D2 (DFBMA) - XL8 (DFBXG) IP8 19

Sector 7-8 and magnets IR7 Cleaning Matching section Arc cryostat (3 km) Matching section Inner Triplet IR8 LHCb DFBMH DFBAN DFBAO DFBMC DFBMA DFBX IR Quadrupoles Correctors 154 Arc dipole magnets and correctors Short straight sections with quadrupoles and correctors IR Quadrupoles Correctors Insertion dipoles IR Quadrupoles Correctors Each cryostat has its own set of PC. Only the beam, the access, the vaccuum, and the cryogenics couple Each cryostat one PPC (arc needs two, because fed from both sides) PPC close to the PC

Sector 7-8 and underground areas IR7 Cleaning Matching section Arc cryostat (3 km) Matching section Inner Triplet IR8 LHCb DFBMH DFBAN DFBAO DFBMC DFBMA DFBX Each cryostat has its own set of PC. Only the beam, the access, the vaccuum, and the cryogenics couple Each cryostat one PPC (arc needs two, because fed from both sides) PPC close to the PC UJ76 RR77 UA83

Sector 7-8 and power converters IR7 Cleaning Matching section Arc cryostat (3 km) Matching section Inner Triplet IR8 LHCb DFBMH DFBAN DFBAO DFBMC DFBMA DFBX Energy extraction Each cryostat has its own set of PC. Only the beam, the access, the vaccuum, and the cryogenics couple Each cryostat one PPC (arc needs two, because fed from both sides) PPC close to the PC UJ76 RR77 UA83 Power Converters for 34 electrical circuits and other equipment Power Converters for 72 electrical circuits and other equipment

Main dipoles in arc cryostat Time for the energy ramp is about 20-30 min (Energy from the grid) Time for discharge is about the same (Energy back to the grid) DFB DFB Magnet 2 Magnet 4 Magnet 152 Magnet 154 Magnet 1 Magnet 5 Magnet 153 Magnet 3 Energy Extraction: switch closed Energy Extraction: switch closed Power Converter

Main dipoles: quench of a magnet Quench in one magnet: Resistance and voltage drop across quenched zone Quench is detected: Voltage across magnet exceeds 100 mV DFB DFB Magnet 2 Magnet 4 Magnet 152 Magnet 154 Magnet 1 Magnet 5 Magnet 153 Magnet 3 Energy Extraction: switch closed Energy Extraction: switch closed Quench Detector Power Converter

Main dipoles: magnet protection Quench heaters warm up the entire magnet coil: energy stored in magnet dissipated inside the magnet (time constant of 200 ms) Diode in parallel becomes conducting: current of other magnets through diode Resistance is switched into the circuit: energy of 153 magnets is dissipated into the resistance (time constant of 100 s for main dipole magnets) DFB DFB Magnet 2 Magnet 4 Magnet 152 Magnet 154 Magnet 1 Magnet 5 Magnet 153 Magnet 3 Energy Extraction: switch open Energy Extraction: switch open Quench Detector Quench Heater PS Power Converter

Energy extraction switch house 13 kA Energy extraction resistors MB Energy extraction switch 13 kA Diode for 13 kA

Conditions for powering Cryogenics: correct conditions (L.Serio) Safety systems ready (AUG – arret urgence general, UPS – uninterruptible power supplies, …) (T.Pettersson) Power converter ready (D.Nisbet) Quench protection system ready (R.Denz) Power converters Operator / Controls: must give permission to power Powering Interlock Controller (PIC) (M.Zerlauth) Energy extraction Quench in a magnet inside the electrical circuit Warming up of the magnet due to quench in an adjacent magnet Warming up of the magnet due to failure in the cryogenic system AUG or UPS fault Power converter failure

Main Systems: PC, PIC and QPS Arc cryostat DFBAO Quench Detector Quench Heater PS Quench Detector Quench Heater PS Quench Detector Energy Extraction Power Converter Each cryostat has its own set of PC. Only the beam, the access, the vaccuum, and the cryogenics couple Each cryostat one PPC (arc needs two, because fed from both sides) PPC close to the PC QPS Controller Tunnel Cryogenics ready Powering Interlock Controller (PIC) UPS / AUG OK QPS  OK UA83 Operator / Controls

Sector 7-8 and powering subsectors IR7 Cleaning Matching section Arc cryostat Matching section Inner Triplet IR8 LHCb DFBMH DFBAN DFBAO DFBMC DFBMA DFBX Each cryostat has its own set of PC. Only the beam, the access, the vaccuum, and the cryogenics couple Each cryostat one PPC (arc needs two, because fed from both sides) PPC close to the PC UJ76 RR77 UA83 Powering Subsector PIC odd point 34 electrical circuits Powering Subsector PIC even point 43 electrical circuits Powering Subsector one PIC 15 electrical circuits Powering Subsector one PIC 14 electrical circuits Powering Subsectors: LHC-D-ES-0002 EDMS Document No. 361532

Types of electrical circuits There are more than 50 different types of magnets Magnets can be powered in series or individually As an example, powering of an individual orbit corrector magnet (60 A, 9 kJ) and the main dipole magnets (13 kA, 1.2 GJ) is very different Risks, magnet protection, interlocks, commissioning procedures, etc. 1618 electrical circuits grouped into nine “Electrical Circuit Types” (eight for circuits with sc magnets, one for nc magnets) The electrical circuit type depends on the energy stored in the magnets of an electrical circuit, and the way of protecting magnets and current leads Commissioning procedures will be similar for electrical circuits of the same type

Electrical Layout Database LHC Database link: http://layout.web.cern.ch/layout/default.aspx?file=navigators.aspx&topid=0&version=1.4&navigator=electrical Link to power converters, magnets, all other elements in an electrical circuit, powering subsector, powering interlock controller, …

Types of electrical circuits with sc magnets 13kA Main: Main dipoles and main quadrupoles (24 circuits) IT: Inner triplet quadrupoles (8 circuits) IPQD: Individual powered insertion main magnets (94 circuits) Extraction of the energy stored in the magnets is performed by the QPS system 600A EE: most 600 A corrector magnets powered in series (202 circuits) Extraction of the energy stored in the magnets is performed with an energy extraction unit back to back to the power converter rack 600A no EE crowbar: most individual 600 A trim quadrupoles (136 circuits) Extraction of the energy stored in the magnets is performed with the power converter 600A no EE: inner triplet correctors (56 circuits) No energy extraction unit required 80-120A: 80 A and 120 A (300 circuits) No energy extraction unit required 60A: 60 A (752 circuits) No energy extraction unit required, no connection to Powering Interlock Controller

Summary Powering in sectors, and in powering subsectors Electrical circuits with electrical circuit elements: magnets, superconducting busbars, current leads, normal conducting cables and power converters Main systems for magnet powering are power converters, magnet protection system and powering interlocks Several other systems have to be commissioned before powering tests: cryogenics and vacuum We rely on general services: electrical distribution, cooling and ventilation, safety systems (ODH, access, AUG, …) Controls system provides a view on the very complex systems

Glossary Sector Arc Long straight sections and insertions Tunnel and underground areas Matching sections Inner triplet Cryostats Powering subsector Magnets: dipoles, quadrupoles, sextupoles, octupoles, decapoles, … Magnets powered individually Magnets powered in series Short straight sections Warm cables (normal conducting cables) Water cooled cables Electrical circuit Electrical circuit type DFB Current leads Magnet interconnections Bus bars Energy extraction Powering interlocks and powering interlock controller Interlock type

Glossary Quench Quench detector Quench heater Diode AUG (arret urgence general) and UPS (uninterruptible power supply) MTF MTF step Layout Database Circuit Database