Download Machine Protection and Interlock Systems for the LHC - Indico

The challenges of protecting the
super-conducting magnets and
powering system
Rüdiger Schmidt and Karl Hubert Mess
Academic Training May 2008
1
During tests the energy of 2 MJ from the SPS beam
was directed into a metal target (LHC 360 MJ)
V.Kain
2
During tests the energy of 7 MJ in one of 154 magnets
was released into one spot in the coil (interturn short)
P.Pugnat
3
Overview
• Energy in beams and magnets ….and their controlled discharge
• Beam and powering interlock systems
• Quenches in superconducting magnets
• LHC powering architecture
• Powering system: magnet types and electrical circuit types
• Protection for the electrical circuits
• Procedure for commissioning of (the protection systems) an electrical
circuit and recent experience
• Interlocks systems during beam operation
Academic Training May 2008
4
Energy stored in magnets and beam
E dipole = 0.5  L dipole  I 2dipole
Energy stored in one dipole operating at 7 TeV
with 11850 A is 7.4 MJoule
For 154 dipoles in one sector:
~1.2 GJoule
For all 1232 dipoles in the LHC: ~9 GJoule
E beam = N p  N bunches  Energy
Energy stored in one beam with 2808 bunches,
each 1.15  1011 protons at 7 TeV is 360 MJoule
Academic Training May 2008
5
LHC cycle and stored beam energy
7000
Energy [GeV/c]
6000
energy ramp
5000
25 MJ  360 MJ
circulating beam
2808 bunches
4000
360 MJ
circulating beam
3000
2000
1000
coast
beam dump
injection phase
3 MJ  25 MJ
beam transfer
circulating beam
discharge of energy
into beam dump block
0
-4000
12 batches from
the SPS (every-2000
20 sec)0
2000
one batch 216 / 288 bunches
4000
time from start of injection (s)
3 MJ per batch
Academic Training May 2008
6
LHC cycle and stored magnet energy (main dipoles)
12000
10000
Current [kA]
current ramp
36 MJ  9 GJ for
1232 dipole
magnets
8000
9 GJ
6000
4000
2000
1
coast
in case of quench
injection current
760 A
0.53 T
discharge of energy
into resistors
0
-4000
-2000 0
2000
4000
time from start of injection (s)
Academic Training May 2008
7
Livingston type plot: Energy stored magnets and beam
Energy stored in the beam [MJ]
10000.00
LHC
energy in
magnets
1000.00
LHC top
energy
LHC injection
(12 SPS batches)
100.00
Factor
~200
SPS fixed
target and CNGS
10.00
ISR
HERA
SPS batch to
LHC
1.00
0.10
LEP2
TEVATRON
RHIC
proton
SPS
ppbar
0.01
1
10
100
1000
10000
Momentum [GeV/c]
based on graph from R.Assmann
Academic Training May 2008
8
What does this mean?
The energy stored in the
LHC magnets corresponds
approximately to 8 such
trains running at 280 km/h
Sufficient to heat up and
melt more than 10 tons of
Copper!!
The energy of an 200 m long
fast train at 155 km/hour
corresponds to the energy
stored in one LHC beam
• 90 kg of TNT
• 8 litres of gasoline
• 15 kg of chocolate
It’s the time for the energy release
(instantaneous power) that matters !!
Academic Training May 2008
9
Machine Protection during all phases of operation
•
During commissioning of the powering system and operation: protection
of magnets, busbars connecting magnets and High Temperature
Superconductor current leads is mandatory
•
The magnet protection and powering interlock systems become
operational during this time, long before starting beam operation
•
In case of failure, the energy of the superconducting magnets must
be discharged into resistors
•
During beam commissioning and operation: protection from the injection
process, during the energy ramps and at 7 TeV is mandatory
•
The only component that can stand a loss of the full beam is the
beam dump block - all other components would be damaged
– The LHC beams must ALWAYS be extracted into the beam dump blocks, at
the end of a fill and in case of failure
•
In general, a failure in an electrical circuit leads to beam extraction
Academic Training May 2008
10
Beam dumping system in IR6
Septum magnet
deflecting the
extracted beam
Beam 1
Q5L
H-V kicker
for painting
the beam
Beam Dump
Block
Q4L
about 700 m
Fast kicker
magnet
Q4R
about 500 m
Q5R
Beam 2
AB - Beam Transfer Group
Academic Training May 2008
11
LHC Machine Protection Overview
Beam Interlock System
Beam
Dumping
System
Injection
Interlock
Academic Training May 2008
12
LHC Machine Protection Powering
>50% of all interlocks
Beam Interlock System
Powering
Interlocks
sc magnets
Powering
Interlocks
nc magnets
Magnets
MPS
(several
1000)
System
Beam
Dumping
System
Injection
Interlock
Magnet
Current
Monitor
Power
Converters
Power
AUG UPS Cryo
Converters
OK
~800
Academic Training May 2008
13
LHC Machine Protection
Access System
Beam
Dumping
System
Beam Interlock System
Powering
Interlocks
sc magnets
Powering
Interlocks
nc magnets
Magnets
MPS
(several
1000)
Magnet
Current
Monitor
Access
System
Injection
Interlock
Power
Converters
Power
AUG UPS Cryo
Converters
OK
~800
Doors
Academic Training May 2008
EIS
14
LHC Machine Protection
Vacuum System
Beam
Dumping
System
Beam Interlock System
Powering
Interlocks
sc magnets
Powering
Interlocks
nc magnets
Magnets
MPS
(several
1000)
Magnet
Current
Monitor
Injection
Interlock
Access Vacuum
System System
Power
Converters
Power
AUG UPS Cryo
Converters
OK
~800
Doors
Academic Training May 2008
EIS
Vacuum
valves
Access
Safety
Blocks
RF
Stoppers
15
LHC Machine Protection
Beam Loss Monitors
Beam
Dumping
System
Beam Interlock System
Powering
Interlocks
sc magnets
Powering
Interlocks
nc magnets
Magnets
MPS
(several
1000)
Magnet
Current
Monitor
Power
Converters
Power
AUG UPS Cryo
Converters
OK
~800
Beam loss
monitors
BLM
Injection
Interlock
Access Vacuum
System System
Monitors Monitors
aperture
in arcs
limits
(several
(some 100)
1000)
Doors
Academic Training May 2008
EIS
Vacuum
valves
Access
Safety
Blocks
RF
Stoppers
16
LHC Machine Protection Collimation
~99% of all interlocks
System
Collimator
Positions
Environmental
parameters
Collimation
System
Beam
Dumping
System
Beam Interlock System
Powering
Interlocks
sc magnets
Powering
Interlocks
nc magnets
Magnets
MPS
(several
1000)
Magnet
Current
Monitor
Power
Converters
Power
AUG UPS Cryo
Converters
OK
~800
Beam loss
monitors
BLM
Injection
Interlock
Access Vacuum
System System
Monitors Monitors
aperture
in arcs
limits
(several
(some 100)
1000)
Doors
Academic Training May 2008
EIS
Vacuum
valves
Access
Safety
Blocks
RF
Stoppers
17
LHC Machine Interlocks
LHC
LHC
LHC
Devices
Devices
Devices
Safe Beam
Parameter
Distribution
Safe
LHC
Parameter
Movable
Detectors
Beam Loss Experimental
Monitors
Magnets
BCM
Software Sequencer Operator
LHC
Interlocks
Buttons Experiments
CCC
Safe
Beam
Flag
Collimator
Positions
Transverse
Feedback
Beam
Aperture
Kickers
Environmental
parameters
Collimation
System
Beam
Dumping
System
Beam Interlock System
Powering
Interlocks
sc magnets
Powering
Interlocks
nc magnets
Magnets
Magnet
Current
Monitor
RF
System
Power
Converters
MPS
Power
AUG UPS Cryo
(several Converters
OK
1000)
~800
Special
BLMs
Injection
Interlock
Beam loss
Beam Access Vacuum Screens /
monitors Lifetime System System Mirrors
BLM
FBCM
BTV
Timing System
(Post Mortem
Trigger)
Monitors Monitors
aperture
in arcs
limits
(several
(some 100)
1000)
Doors
Academic Training May 2008
EIS
Vacuum
valves
Access
Safety
Blocks
RF
Stoppers
18
Operational margin of a superconducting magnet
Applied Magnetic Field [T]
Applied field [T]
Bc critical field
Bc
8.3 T
Normal state
quench with fast local
loss of ~5 · 106 protons
Superconducting
state
quench with fast local
loss of ~5 · 109 protons
0.54 T
1.9 K
Temperature
[K]
Temperature [K]
Academic Training May 2008
QUENCH
Tc critical
temperature
9K
19
Quench - transition from superconducting state to normalconducting state
Quenches are initiated by an energy in the order of mJ
• Movement of the superconductor by several µm (friction and
heat dissipation)
• Failure in cooling
• Beam losses
To limit the temperature increase after a quench
• The quench has to be detected
• The magnet current has to be switched off within << 1 sec
• For main magnets: the energy stored in the quenching magnet
is distributed inside the magnet by force-quenching the magnet
coils using quench heaters
• For magnets powered in series: the quenching magnet is
isolated from the other magnets using a power diode
Academic Training May 2008
20
Superconducting wire and cable
Filament diameter 6 m
Wire diameter 1 mm
Typical value for operation at 8 T and 1.9 K: 800 A
width 15 mm
Rutherford cable
current ~12000 A
Academic Training May 2008
21
Power into superconducting cable after a quench
2
Cross section :
Asc  10  mm
Current :
Isc  10000  A
Length of superconductor :
Lsc  1  m
Copper resistance at 300 C:
 cu  1.76  10
2 Lsc
Psc   cu  Isc 
Asc
6
 ohm  cm
5
Psc  1.76  10 watt
Specific
temperature
of 300
copper
Specific heat
of copper at
C: at 300 C :
cvcu  3.244 
joule
K  cm
Psc
Temperature increase of copper
T 
Temperature increase within one second:
T  5.425  10
Academic Training May 2008
3
Asc  Lsc  cvcu
3K
s
22
LHC Powering in 8 Sectors
5
4
Powering Sector:
6
154 dipole magnets
about 50 quadrupoles
total length of 2.9 km
Octant
DC Power feed
3
DC Power
LHC
27 km Circumference
7
Powering Subsectors:
8
2
Sector
• long arc cryostats
• triplet cryostats
• cryostats in matching section
1
P.Proudlock
Academic Training May 2008
23
Magnet in one arc cell of 110 m length
6 main dipole
magnets (12 kA)
2 arc quadrupole
magnets (12 kA)
Lattice sextupole
magnets in arcs
(600 A)
Multipole and
other correctors
in arcs
Powered in series
752 arc orbit corrector
magnets powered
individually (60 A)
Correctors to adjust beam
parameters (trim
quadrupoles, orbit
correctors, etc., 80 – 600 A)
Powered individually
SSS
quadrupole orbit
MQF
corrector
main
dipole
MB
special
lattice
corrector sextupole
(MQS)
(MS)
sextupole
corrector
(MCS)
main
dipole
MB
quadrupole orbit
MQD
corrector
main
dipole
MB
decapole
octupole
corrector
(MCDO)
main
dipole
MB
special
corrector
(MO)
lattice
sextupole
(MS)
quadrupole
orbit
MQF
corrector
main
dipole
MB
main
dipole
MB
special
lattice
corrector sextupole
(MO)
(MS)
F0D0 cell 110 m
R.Schmidt
24
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 and protection of an individual orbit
corrector magnet (60 A, 9 kJ) and a circuit including 154 main dipole
magnets (12 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 superconducting magnets, one for circuits with
normal conducting magnets)
• The attribution of an electrical circuit to a type depends on the energy
stored in the magnets of the electrical circuit, and the way of protecting
magnets, busbars and current leads
• Commissioning procedures are essentially identical for electrical
circuit types
Academic Training May 2008
25
Sector 7-8 and magnet cryostats
IR7
Cleaning
Matching
section
DFBMH
• IR Quadrupoles
• Correctors
Arc cryostat
(3 km)
DFBAN
Matching
section
DFBAO
• 154 Arc dipole magnets and
correctors
• Short straight sections with
quadrupoles and correctors
DFBMC
DFBMA
Inner
Triplet
IR8
LHCb
DFBX
• IR Quadrupoles
• Correctors
• Insertion dipoles
• IR Quadrupoles
• Correctors
Power Converters
(60A) for 94 orbit
corrector magnets
Academic Training May 2008
26
Sector 7-8 and power converters
IR7
Cleaning
Matching
section
DFBMH
Arc cryostat
(3 km)
DFBAN
Matching
section
DFBAO
DFBMC
DFBMA
Inner
Triplet
IR8
LHCb
DFBX
Energy
extraction
UJ76
RR77
UA83
Power Converters
for 34 electrical circuits
and other equipment
Power Converters
for 72 electrical circuits
and other equipment
Academic Training May 2008
27
Conditions for powering
Cryogenics: correct
conditions
1.9K, 4.5K, other
conditions
Safety systems
ready (AUG – arret
urgence general, UPS
– uninterruptible power
supplies, …)
Power
converter ready
Magnet protection
system ready
Power
converters
Operator / Controls:
must give permission to
start powering
Quench in a
magnet inside
the electrical
circuit
Powering Interlock
Controller (PIC)
Energy
extraction
Beam
Interlocks
Warming up of the
magnet due to
quench in an
adjacent magnet
Warming up of the
magnet due to failure
in the cryogenic
system
Academic Training May 2008
AUG or
UPS fault
Power
converter
failure
28
Main dipoles in arc cryostat
•
Time for the energy ramp is about 20-30 min (Energy from the grid)
•
Time for regular discharge is about the same (Energy back to the grid)
DFB
Magnet 2
Magnet 1
Energy
Extraction:
switch closed
Magnet 4
Magnet 3
Magnet 152
Magnet 5
Magnet 154
DFB
Magnet 153
Energy
Extraction:
switch closed
Academic Training May 2008
Power
Converter
29
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 for >10 ms
DFB
Magnet 2
Magnet 1
Energy
Extraction:
switch closed
Magnet 4
Magnet 3
Quench
Detector
Magnet 152
Magnet 5
Magnet 154
DFB
Magnet 153
Energy
Extraction:
switch closed
Academic Training May 2008
Power
Converter
30
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
Magnet 2
Magnet 1
Energy
Extraction:
switch open
Magnet 4
Magnet 3
Quench
Detector
Magnet 152
Magnet 5
Quench
Heater PS
Academic Training May 2008
Magnet 154
DFB
Magnet 153
Energy
Extraction:
switch open
Power
Converter
31
Magnet and busbar quench detection
To detect a quench: U = R  I (about 1 V need to be detected)
But one needs to substract from U1:
a) U2 = Rwarm  I
b) During energy ramp: U = dI/dt  L  154 = 77  (U3 + U4)
DFB
Magnet 2
Magnet 1
U2
Magnet 4
Magnet 3
U3
Magnet 152
Magnet 5
U4
World FIP - deterministic Fieldbus
Academic Training May 2008
Magnet 154
DFB
Magnet 153
U1
Power
Converter
32
Simpler way to discharge the energy?
• assume one magnet quenches
• assume the magnets in the string have to be discharged in, say, 200 ms
• the inductance is about 15 H, the current about 12 kA
with U = l  dI/dt
Ldipole  Idipole
Udischarge_1 
0.2s
3
Udischarge_1  6.426  10 V
154Ldipole  Idipole
Udischarge_154 
0.2s
5
Udischarge_154  9.896  10 V
Discharge with about 1 MV: not possible
Academic Training May 2008
33
Challenges for quench protection
• Detection of quenches for all main dipole and quadrupole magnets (1600
magnets powered in 24 electrical circuits)
– Voltage across the dipole magnet chain up to 180 V during ramping - 1 V
needs to be detected in presence of noise etc.
– During discharge the quench detectors are connected to equipment at high
voltage (1000 V)
• Detection of quenches in about 800 other circuits
• Global quench detection for circuits operating at 600 A
• Inductance of magnets change as a function of current
• Detection of quenches across all HTS current leads (2000) with very low
voltage threshold ~ 3 mV for 1 sec across HTS part
• Systems must be very safe in order not to damage equipment (any
quench must be detected)
• Systems must be very reliable in order not to disturb operation (the
system should not trigger in case of noise etc.)
Academic Training May 2008
34
Energy extraction switch house 13 kA
Energy extraction switch 13 kA
Energy extraction resistors MB
Academic Training May 2008
Diode for 13 kA
35
Objective of powering tests
Why the lengthy commissioning?
• Most components in the electical circuit have been tested before (e.g. all
magnets)
• Short circuit tests of the power converters have been done
Validate the entire electrical circuits for the first time
• Busbars ok? 70000 superconducting connections ok? Magnets still ok
(after storage)? All other systems ok?
• Protection systems work? Switch-off for different failure cases ok?
• Discharge of 1 GJoule ok?
• All interlock systems ok?
Test protection in case of quench, of water cooling problems, of a
failure in the UPS system, of an AUG activation
Test protection in case of a problem in the cryogenic system
Academic Training May 2008
36
One of ~1700 interconnections: busbars and tubes
Academic Training May 2008
37
Steps in the commissioning procedure
Verification of the correct functioning of the interlock systems at low current
• in case of quench: fire quench heaters and fast switch off power converter
• in case of power converter failure: extraction of energy stored in the circuit
• in case of UPS failure: switch off power converter
• in case of CRYO failure: slow abort of power converter
Verification of magnet protection by firing quench heaters at low current
Verification of magnet protection by firing quench heaters at high current
For circuits with energy extraction systems
• Verification of the energy extraction functionality by switching the resistor
into the circuit at different current levels
Academic Training May 2008
38
Commissioning procedure for quadrupoles (example)
D.low
Nisbetcurrent
, N. Catalan Lasheras 1-12-2007 current
I_PNO (3.6 - 5.9kA)
PLI2.E3 Slow PA
PLI1.C3 Fast PA
I_injection < 350 A
PLI2.F3 Heaters
PLI1
PIC2
Power_permit_B1
Power_permit_B2
Powering_Failure_B1
Powering_Failure_B2
Quench_B1
Quench_B2
Fast_PA_B1
Fast_PA_B2
Load identification configuration
PLI2
Tests at nominal
current
PNO.C3
Fast Abort
Tests at
PNO.F4
Unbalanced Quench
Tests of interlock
Individually powered quadrupoles
systempowering
at very cycle
intermediate
PNO.F3 Quench
PNO
I_PNO_mid
I_interm_1 (300 - 900 A)
I_interm_1_mi
d
I_min_op < 200 A
~ 2 hrs
Converter ok? (PO) ; QPS ok? (QPS) ; Magnet ok? (MPP)
Iout (B1) current lead
Iout (B2) current lead
Iout central current
lead
4 min flat top; Check loop stability (PO) Check current leadfs and CRYO (MPP)
60 min flat top: check current leads and cryo valves (MPP)
Academic Training May 2008
39
Academic Training May 2008
40
RD4: Fast Power Abort from 200A (circuit quench via magnet
protection system)
time [s]
Academic Training May 2008
41
Fast Power Abort from 350A (Fast Abort request via powering interlock
system)
I_MEAS
400.000
350.000
300.000
250.000
200.000
I_MEAS
150.000
100.000
50.000
0.000
350.000
400.000
450.000
500.000
550.000
600.000
650.000
700.000
750.000
800.000
850.000
time [s]
Academic Training May 2008
42
Fast Power Abort from 5500A (PNO.C2)
time [s]
Academic Training May 2008
43
Quench from 5500A
I_MEAS
6000.000
5000.000
4000.000
3000.000
I_MEAS
2000.000
1000.000
0.000
350.000
400.000
450.000
500.000
550.000
600.000
650.000
700.000
750.000
800.000
850.000
time [s]
Academic Training May 2008
44
Quench - detail
time [s]
Academic Training May 2008
45
Quench detection and beam dump trigger
Quench
Quench Quench
detector trigger
threshold
reached
Diode opens
Current
bypasses
magnet
Quench
Heaters
fire
15 – 130 ms
3 - 200
ms
10
ms
time
1.5 ms
7 - 9 ms
Energy extraction
Current decay
starts
time
3-4 ms
0.2 ms
Powering
Interlock
triggered
< 0.4 ms
Beam
Interlock
triggered
Academic Training May 2008
Beam
extracted
46
Response to Quenches
Quench
detected
(+ 0 ms)
Current decay
starts (+ 9 ms)
3.4 ms
73 ms
Interlock
triggered
(+ 5 ms)
Beam would
be dumped
(+ 5.6 ms)
5/23/2017
0.01% of beam
would lost (+91 ms)
[email protected]
Academic
Training May 2008
47
47
Conclusions
• Protection has high priority, a failure can lead to substantial equipment
damage
• Several systems are involved in protection: magnet protection system,
powering interlock system, power converters, cryogenics, UPS, AUG …
• The commissioning of the machine protection systems is mandatory for
safe operation
• The complexity of the LHC powering system is unprecedented and
requires the application of strict procedures for commissioning
• The procedures have been automised, and therefore commissioning
could become very efficient
• In case of a failure (quench, failure of a power converter, failure of a
supply system such as water and electricity) the beam will be dumped.
During hardware commissioning more than 50% of all interlock channels
are being tested.
• Commissioning experience: worked in general very well, but the lengthy
work is fully justified (a number of non-conformities were detected)
Academic Training May 2008
48
Acknowledgement
Many colleagues have been involved in the work that is presented here, as
CERN staff, as project associates and as industrial support.
It is not possible to list all the names, but I very much appreciate the
enthusiastic work of all them.
Teams responsible for protection systems:
– Magnet Protection, Powering Interlocks, Beam Interlocks, Beam Dumping System,
Beam Loss Monitors, Collimation System
Teams responsible for systems involved in powering:
– Power Converters, Vacuum, Cryogenics, (cold) Electrical Engineering
Teams responsible for service systems:
– Water cooling, Ventilation, Access System, AC and DC distribution
Other teams:
– Controls and Networking, Operation, Magnet “Owners”
– Collaborators from abroad (US, Japan), Project Engineers
Academic Training May 2008
49