1. Powering LHC magnets
version 30/3/2007

2. 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)

3. 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

4. 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)

5. 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

6. Effect of 7.6 MJ on a dipole coil
P.Pugnat

7. 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

8. More magnets?

9. 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)

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

11. MAD file with all magnets and positions
SSS
SSS

12. 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:

13. 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

14. 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

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

16. DFBs with current leads - feeding current from warm to cold
DFB and current leads

17. Interconnecting busbars

18. Bus bar interconnections right of point 8 (19/3/2007)
600 A bus bars (NLine)
6 kA bus bars
Link electrical circuits on CDD:

19. 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

20. 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

21. 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

22. 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

23. Main dipoles in arc cryostat
Time for the energy ramp is about 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

24. 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

25. 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

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

27. 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

28. 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

29. 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

30. 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

31. Electrical Layout Database
LHC Database link:
Link to power converters, magnets, all other elements in an electrical circuit, powering subsector, powering interlock controller, …

32. 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

33. 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

34. 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

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