Post on 14-Dec-2015
R.Schmidt - TU Darmstadt Januar 2008
1
Der LHC Beschleuniger am CERN: Der LHC Beschleuniger am CERN: Kollisionen intensiver Teilchenstrahlen bei Kollisionen intensiver Teilchenstrahlen bei
hoher Strahlenergiehoher Strahlenergie
Rüdiger Schmidt - CERN
TU Darmstadt
Januar 2008
Der LHC: “Just another collider?”
Kollision intensiver Teilchenstrahlen
Injectorkomplex und LHC
Operation und Betriebssicherheit
Status und Ausblick
R.Schmidt - TU Darmstadt Januar 2008
2
Vortrag GradKolleg 2004
R.Schmidt - TU Darmstadt Januar 2008 3
Installation of cryogenic distribution Installation of cryogenic distribution line in the LHC tunnel – started line in the LHC tunnel – started during summer 2003during summer 2003
Status 2007
R.Schmidt - TU Darmstadt Januar 2008 4
Energy and Luminosity Energy and Luminosity Particle physics requires an accelerator colliding beams with a centre-of-mass energy substantially exceeding 1TeV
In order to observe rare events, the luminosity should be in the order of 1034 [cm-2s-1] (challenge for the LHC
accelerator)
Event rate:
Assuming a total cross section of about 100 mbarn for pp collisions, the event rate for this luminosity is in the order
of 109 events/second (challenge for the LHC experiments)
Nuclear and particle physics require heavy ion collisions in the LHC (quark-gluon plasma .... )
][][ 212 cmscmLtN
R.Schmidt - TU Darmstadt Januar 2008 5
The CERN Beschleuniger The CERN Beschleuniger KomplexKomplex
LEP e+e-
(1989-2000)
104 GeV/c
LHC pp und Ionen
7 TeV/c
26.8 km Umfang
8.3 Tesla supraleitende Magnete
CERN Hauptgelände
SchweizGenfer See
Frankreich
LHC Beschleuniger (etwa 100m unter der Erde)
SPS Beschleuniger
CERN-Prevessin
CMS
ALICE
LHCb
ATLAS
R.Schmidt - TU Darmstadt Januar 2008 6
The LHC: just another collider ?The LHC: just another collider ?Name Start Particles Max proton
energy [GeV]
Length [m]
B Field [Tesla]
Stored beam energy [MJoule]
TEVATRONFermilab Illinois USA
1983 p-pbar 980 6300 4.5 1.6 for protons
HERA DESY HamburgGermany
1992 p – e+p – e-
920 6300 5.5 2.7 for protons
RHICBrookhavenLong Island USA
2000 Ion-Ionp-p
250 3834 4.3 0.9 per proton beam
LHCCERNGeneva Switzerland
2008 Ion-Ionp-p
7000 26800 8.3 362 per proton beam
R.Schmidt - TU Darmstadt Januar 2008 7
Challenges for LHCChallenges for LHC
High-field (8.3 Tesla) superconducting magnets operating at a temperature of 1.9 K with an energy stored in the magnets of 10 GJ
Beam-parameters pushed to the extreme• Energy stored in the beam two orders of magnitude above others
• Transverse energy density three orders of magnitude compared to other accelerators
• Consequences for several systems (machine protection, collimation, vacuum system, cryogenics, …)
GJoule beams running through superconducting magnets that quench with mJoule
Complexity of the accelerator (most complex scientific instrument ever constructed) with 10000 magnets powered in 1712 electrical circuits
R.Schmidt - TU Darmstadt Januar 2008 8
New approaches and novel technologies New approaches and novel technologies
Two-In-One superconducing magnets inside helium 1.9 K system Compressors operating at cold to provide helium at 1.9 K Beam screen inside vacuum chamber at higher temperature High Temperature Superconductors at an industrial scale, for current
leads High current power convertors and control of the current with an
unprecedented accuracy of 1 ppm New devices and materials for absorbing the particles Radiation studies for the accelerator at an unprecedented scale Development of radiation tolerant electronics and highly radiation
resistant optical fibres Overall consideration for machine protection: an accidental release of
the energy can lead to massive damage Approach for machine protection systems driven by studies on safety,
reliability and availability using formal methods
R.Schmidt - TU Darmstadt Januar 2008 9
A total number of 1232 dipole magnets are required A total number of 1232 dipole magnets are required to close the circleto close the circle
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LHC dipole magnet lowered into the tunnel LHC dipole magnet lowered into the tunnel First cryodipole lowered on 7 March 2005First cryodipole lowered on 7 March 2005 Descent of the last magnet, 26 April 2007Descent of the last magnet, 26 April 2007
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Interconnecting two magnets out of 1700Interconnecting two magnets out of 1700
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Current leads with High Temperature Current leads with High Temperature Superconductor Superconductor
12
Feedboxes (‘DFB’) : transition from copper cable to super-conductor
Water cooled Cu cables
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DFB with ~17 out of 1600 HTS current leads DFB with ~17 out of 1600 HTS current leads
R.Schmidt - TU Darmstadt Januar 2008 14
RF cavities, four per beam with some 10 MVoltRF cavities, four per beam with some 10 MVolt
R.Schmidt - TU Darmstadt Januar 2008 15
LHC: From first ideas to realisationLHC: From first ideas to realisation
1982 : First studies for the LHC project
1983 : Z0 detected at SPS proton antiproton collider
1985 : Nobel Price for S. van der Meer and C. Rubbia
1989 : Start of LEP operation (Z-factory)
1994 : Approval of the LHC by the CERN Council
1996 : Final decision to start the LHC construction
1996 : LEP operation at 100 GeV (W-factory)
2000 : End of LEP operation
2002 : LEP equipment removed
2003 : Start of the LHC installation
2005 : Start of hardware commissioning
2008 : Commissioning with beam planned
R.Schmidt - TU Darmstadt Januar 2008 16
Colliding very intense Colliding very intense proton beamsproton beams
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High luminosity by High luminosity by colliding trains of bunchescolliding trains of bunches
Number of „New Particles“
per unit of time:
The objective for the LHC as proton – proton collider is a luminosity of about 1034 [cm-1s-2]
• LEP (e+e-) : 3-4 1031 [cm-2s-1]
• Tevatron (p-pbar) : some 1032 [cm-2s-1]
• B-Factories : > 1034 [cm-2s-1]
~40 m in straight section (not to scale)
212 cmscmLT
N
IP
R.Schmidt - TU Darmstadt Januar 2008 18
Luminosity parametersLuminosity parameters
point ninteractio at dimensions beam
beamperbunchesofnumbern
frequency revolution f
bunch per protons of Number N
: with
4
nfNL
yx
b
yx
b
2
What happens with one particle experiencing the force of the em-fields or 1011 protons in the other beam during the collision ?
R.Schmidt - TU Darmstadt Januar 2008 19
Limitation: beam-beam interactionLimitation: beam-beam interaction
Quadrupole Lense
Beam - Beam Lense
Force
Force
Y
Y
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Electromagnetic force on a particle in the Electromagnetic force on a particle in the counterrotating beamcounterrotating beam
4
nfNL
yx
b
2
2r
1r
12
eNrF
:Force Lorentz calculate and
particle test of frame into ngtransformiby nCalculatio
beam. other on act beam one of fieldnetic Electromag
2
22
0
2
)exp(
)()(
Bunch intensity limited due to this strong non-linearity to about N = 1011
Optimising luminosity by increasing N
R.Schmidt - TU Darmstadt Januar 2008 21
Beam beam interaction determines parametersBeam beam interaction determines parameters
Number of protons N per bunch limited to about 1011
f = 11246 Hz
Beam size at IP σ = 16 m for = 0.5 m (beam size in arc σ = ~0.2 mm
with one bunch Nb=1
with Nb = 2808 bunches (every 25 ns one bunch)
L = 1034 [cm-2s-1]
1230
yx
b
2
scm10534
nfNL
.
=> 362 MJoule per beam
R.Schmidt - TU Darmstadt Januar 2008 22
Livingston type plot: Livingston type plot: Energy stored magnets and beamEnergy stored magnets and beam
based on graph from R.Assmann
0.01
0.10
1.00
10.00
100.00
1000.00
10000.00
1 10 100 1000 10000Momentum [GeV/c]
En
erg
y s
tore
d in
th
e b
ea
m [
MJ
]
LHC topenergy
LHC injection(12 SPS batches)
ISR
SNSLEP2
SPS fixed target HERA
TEVATRON
SPSppbar
SPS batch to LHC
Factor~200
RHIC proton
LHC energy in magnets
R.Schmidt - TU Darmstadt Januar 2008 23
What does this mean?What does this mean?
10 GJoule: the energy of an A380 at 700 km/hour
corresponds to the energy stored in the LHC magnet system:
Sufficient to heat up and melt 12 tons of Copper!!
362 MJoule: the energy stored in one LHC beam corresponds
approximately to…
• 90 kg of TNT
• 8 litres of gasoline
• 15 kg of chocolate
It’s how ease the energy is released that matters most !!
R.Schmidt - TU Darmstadt Januar 2008 24
Very high beam current: consequencesVery high beam current: consequences
Dumping the beam in a safe way Beam induced quenches (when 10-8-10-7 of beam hits magnet at 7 TeV)
Beam cleaning (Betatron and momentum cleaning) Radiation, in particular in experimental areas from beam collisions
(beam lifetime is dominated by this effect)
Beam instabilities due to impedance Synchrotron radiation at 7 TeV - power to cryogenic system Photo electrons - accelerated by the following bunches
Single particle dynamics: dynamic aperture and magnet field quality, in particular in the presence of dynamic effects in superconducing magnets during the ramp
R.Schmidt - TU Darmstadt Januar 2008 25
The LHC accelerator The LHC accelerator complexcomplex
Complexity due to the LHC main ring Complexity due to the LHC main ring AND due to the injector chainAND due to the injector chain
R.Schmidt - TU Darmstadt Januar 2008 26
LHC Layout
eight arcs (sectors)
eight long straight section (about 700 m long)
IR6: Beam dumping system
IR4: RF + Beam instrumentation
IR5:CMS
IR1: ATLAS
IR8: LHC-BIR2:ALICE
InjectionInjection
IR3: Momentum Beam Cleaning
(warm)
IR7: Betatron Beam Cleaning (warm)
Beam dump blocks
R.Schmidt - TU Darmstadt Januar 2008 27
The CERN accelerator complex: The CERN accelerator complex: injectors and transferinjectors and transfer
High intensity beam from the SPS into LHCat 450 GeV via TI2 and TI8
LHC accelerates from 450 GeV to 7 TeV
LEIR
CPS
SPS
Booster
LINACS
LHC
3
45
6
7
8
1
2TI8
TI2
Ions
protons
Beam 1
Beam 2
Beam size of protons decreases with energy: 2 = 1 / E
Beam size large at injection
Beam fills vacuum chamber at 450 GeV
R.Schmidt - TU Darmstadt Januar 2008 28
TI 8
LHC
SPS 6911 m
450 GeV
LSS6
IR2
TT40
LSS4
IR8TI 8 beam tests 23/24.10.04
6/7.11.04
TI 2 beam test 28/29.10.07
• combined length 5.6 km
• over 700 magnets
• ca. 2/3 of SPS
LHC transfer lines and injections - overview
TT40 beam tests
8.9.03
TI 2
R.Schmidt - TU Darmstadt Januar 2008 29
Transfer line TI8 (MIBT magnet)Transfer line TI8 (MIBT magnet)
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LHC accelerator LHC accelerator
LHC Main Systems
Superconducting magnetsCryogenicsVacuum systemPowering (industrial use of High Temperature Superconducting material)
R.Schmidt - TU Darmstadt Januar 2008 31
1232 main dipoles +
3700 multipole corrector magnets
392 main quadrupoles +
2500 corrector magnets
Regular arc:
Magnets
R.Schmidt - TU Darmstadt Januar 2008 32
Regular arc:
Cryogenics
Supply and recovery of helium with 26 km long cryogenic distribution line
Static bath of superfluid helium at 1.9 K in cooling loops of 110 m length
Connection via service module and jumper
R.Schmidt - TU Darmstadt Januar 2008 33
1232 DipolemagnetsLength about 15 mMagnetic Field 8.3 TTwo beam tubes with an opening of 56 mm
Dipole magnets for Dipole magnets for the LHCthe LHC
R.Schmidt - TU Darmstadt Januar 2008 34
The superconducting state only occurs in a limited domain of temperature, magnetic field and transport current density
Superconducting magnets produce high field with high current density
Lowering the temperature enables better usage of the superconductor, by broadening its working range
T [K]
B [T]
J [kA/mm2]
Operating temperature of superconductorsOperating temperature of superconductors
J [kA/mm2]
R.Schmidt - TU Darmstadt Januar 2008 35
Critical current density of technical superconductorsCritical current density of technical superconductors
+ 3 tesla
Ph.Lebrun
R.Schmidt - TU Darmstadt Januar 2008 36
Beam tubes
Supraconducting coil
Nonmagetic collars
Ferromagnetic iron
Steelcylinder for Helium
Insulationvacuum
Supports
Vacuumtank
Dipole magnet cross sectionDipole magnet cross section16 mBar cooling tube
R.Schmidt - TU Darmstadt Januar 2008 37
Specific heat of liquid helium and copperSpecific heat of liquid helium and copper
0,00001
0,0001
0,001
0,01
0,1
1
10
100
0 1 2 3 4 5Temperature [K]
Spe
cific
hea
t [J/
g.K
]
LHeCu
Discovery of He II phase transition (1927) by W.H. Keesom and M.Wolfke
R.Schmidt - TU Darmstadt Januar 2008 38
Equivalent thermal conductivity of He IIEquivalent thermal conductivity of He II
0
500
1000
1500
2000
1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2
T [K]
Y(T
) ±
5%
T
K T,q q Y T
dT
dX
q
Y(T)
q in W / cm
T in K
X in cm
2.4
3.4
2
Copper OFHC
Helium II
G. Bon Mardion et al.
R.Schmidt - TU Darmstadt Januar 2008 39
Principle of He II cooling of LHC magnetsPrinciple of He II cooling of LHC magnets
R.Schmidt - TU Darmstadt Januar 2008 40
4 stages1st stage cartridge
Air Liquide & IHI-Linde
Axial-centrifugal impeller
Cold compressors of LHC 1.8 K unitsCold compressors of LHC 1.8 K units
R.Schmidt - TU Darmstadt Januar 2008 41
Operation and machine Operation and machine protectionprotection
R.Schmidt - TU Darmstadt Januar 2008 42
0
2000
4000
6000
8000
10000
12000
-4000 -2000 0 2000 4000
time from start of injection (s)
dip
ole
cu
rre
nt (A
)
injection phase12 batches from the SPS (every 20 sec)
one batch 216 / 288 bunches
LHC magnetic cycle and beam operationLHC magnetic cycle and beam operation
L.Bottura
450 GeV
7 TeV
beam dump
energy
ramp
coast
coast (2360 MJ)
start of the ramp
R.Schmidt - TU Darmstadt Januar 2008 43
Beam lifetime with nominal intensity at 7 TeVBeam lifetime with nominal intensity at 7 TeVBeam lifetime
Beam power into equipment (1 beam)
Comments
100 h 1 kW Healthy operation
10 h 10 kW Operation acceptable, collimation must absorb large fraction of beam energy
(approximately beam losses = cryogenic cooling power at 1.9 K)
0.2 h 500 kW Operation only possibly for short time, collimators must be very efficient
1 min 6 MW Equipment or operation failure - operation not possible - beam must be dumped
<< 1 min > 6 MW Beam must be dumped VERY FAST
Failures will be a part of the regular operation and MUST be anticipated
R.Schmidt - TU Darmstadt Januar 2008 44
What happens in case the full LHC beam impact onto
material?
Since 2003/4 collaboration with GSI and TU Darmstadt, N.Tahir (GSI), D.H.H.Hoffmann and many others
R.Schmidt - TU Darmstadt Januar 2008 45
Beam losses into materialBeam losses into material
Proton losses into material lead to particle cascades The energy deposition increases the temperature For the maximum energy deposition as a function of material there is no straightforward expression Programs such as FLUKA are being used for the calculation of the energy deposition
The material could be damaged…..• losing their performance (mechanical strength)
• melting and vaporisation
Magnets could quench…..• beam lost - re-establish condition will take hours
Repair could take a long time
R.Schmidt - TU Darmstadt Januar 2008 46
Damage of material for impact of a pencil beamDamage of material for impact of a pencil beam
Maximum energy deposition in the proton cascade (one proton): Emax_C 2.0 106
J
kg
Specific heat of graphite is cC_spec 710.60001
kg
J
K
To heat 1 kg graphite by, say, by T 1500K , one needs: cC_spec T 1 kg 1.07 106 J
Number of protons to deposit this energy is: cC_spec T
Emax_C5.33 10
11
Maximum energy deposition in the proton cascade (one proton): Emax_Cu 1.5 105
J
kg
Specific heat of copper is cCu_spec 384.56001
kg
J
K
To heat 1 kg copper by, say, by T 500K , one needs: cCu_spec T 1 kg 1.92 105 J
Number of protons to deposit this energy is: cCu_spec T
Emax_Cu1.28 10
10 copper
graphite
R.Schmidt - TU Darmstadt Januar 2008 47
Full LHC beam deflected into copper target
Target length [cm]
vaporisation
melting
Copper target
2 m
Energy density [GeV/cm3] on target axis
2808 bunches
R.Schmidt - TU Darmstadt Januar 2008 48
SPS experiment: Beam damage at 450 GeV SPS experiment: Beam damage at 450 GeV
Controlled SPS experiment 81012 protons clear damage beam size σx/y = 1.1mm/0.6mm
above damage limit
21012 protons
below damage limit
25 cm
0.1 % of the full LHC beam energy
10 times the beam area
6 cm
81012 610124101221012
R.Schmidt - TU Darmstadt Januar 2008 49
STEP1: Calculation of energy deposition of a 7 TeV proton beam in material with a beam of =0.2 mm (FLUKA)
copper,one bunch
carbon, one bunch
copper, per proton
carbon, one bunch
at 16 cm
R.Schmidt - TU Darmstadt Januar 2008 50
STEP2: Hydrodynamic simulations with BIG-2 including the response of the target with LHC beam for copper
• After an impact of some bunches, pressure and temperature in the beam heated region increase drastically.
• A hydrodynamic simulation with a model including a multiphase semi-empirical equation-of-state describes the target behaviour during the diffferent phases of heating and expansion.
• State changes and pressure waves are taken into account by the numerical simulation.
0 0.2 0.4 0.6 0.8 1Target Transverse Coordinate (cm)
0
10
20
30
40
Pre
ssu
re (
GPa
)
t = 500 nst = 1000 nst = 1500 nst = 2000 nst = 2500 ns
At 16 cm in the target along the beam
0 0.2 0.4 0.6 0.8 1Target Transverse Coordinate (cm)
1000
10000
1e+05
Tem
pera
ture
(K
)
t = 500 nst = 1000 nst = 1500 nst = 2000 nst = 2500 ns
At 16 cm in the target along the beam
N.Tahir (GSI), D.H.H.Hoffmann et al.
R.Schmidt - TU Darmstadt Januar 2008 51
Target radial coordinate [cm]
radial
copper solid state
100 bunches – target density reduced to ~10%
Density change at 16 cm in target after impact of 100 bunches
N.Tahir (GSI), D.H.H.Hoffmann et al.
• After an impact of about 100 bunches, the beam heated region has expanded drastically and the density in the inner region decreases by about a factor of ~10.
• The bulk of the following beam will not be absorbed and continues to tunnel further and further into the target, between 20 and 40 m.
• Such effects have been observed for heavy ion beams.• The LHC might be an interesting tool to study HighEnergyDensityMatter.
R.Schmidt - TU Darmstadt Januar 2008 52
The only component that can stand a loss of the full beam is the beam dump block
all other components would be damaged
about 8 m
concrete shielding
beam absorber (graphite)
about 35 cm
R.Schmidt - TU Darmstadt Januar 2008 53
Schematic layout of beam dump system in IR6Schematic layout of beam dump system in IR6
Q5R
Q4R
Q4L
Q5L
Beam 2
Beam 1
Beam Dump Block
Septum magnet deflecting the extracted beam H-V kicker
for painting the beam
about 700 m
about 500 m
Fast kicker magnet
R.Schmidt - TU Darmstadt Januar 2008 54
L.Bruno: Thermo-Mechanical Analysis with ANSYS
Temperature of beam dump block at 80 cm insideTemperature of beam dump block at 80 cm inside
up to 800 0C
R.Schmidt - TU Darmstadt Januar 2008 55
Operational margin of a superconducting magnetOperational margin of a superconducting magnet
Temperature [K]
App
lied
field
[T]
Superconductingstate
Normal state
Bc
Tc
9 K
Applied Magnetic Field [T]
Bc critical field
1.9 K
quench with fast loss of
~5 · 109 protons
quench with fast loss of ~5 · 106 protons
8.3 T
0.54 T
QUENCH
Tc critical
temperature
This is about 1000 times more critical than for TEVATRON, HERA,
RHIC
Temperature [K]
Applied magnetic field [T]
R.Schmidt - TU Darmstadt Januar 2008 56
Beam Cleaning SystemBeam Cleaning System
Primary collimator
Secondary collimators Absorbers
Protectiondevices
Tertiarycollimators
Tripletmagnets
Beam
Primaryhalo particle Secondary halo
Tertiary halo
+ hadronic showers
hadronic showers
• Multi-stage beam halo cleaning (collimation) system to protect sensitive LHC magnets from beam induced quenches and damage
• Halo particles are first scattered by the primary collimator (closest to beam)
• Scattered particles (forming the secondary halo) are absorbed by the secondary collimators, or scattered to form the tertiary halo.
• More than 100 collimators jaws needed for the nominal LHC beam.
• Primary and secondary collimators made of Carbon to survive severe beam impact !
• Collimators must be precisely aligned (< 0.1 mm) to guarantee a high efficiency above 99.9% at nominal intensities.
It’s not easy to stop 7 TeV protons !!
Experiment
R.Schmidt - TU Darmstadt Januar 2008 57
Accidental kick by the beam dump kicker at 7 TeVAccidental kick by the beam dump kicker at 7 TeV part of beam touches collimators (about 20 bunches from 2808)part of beam touches collimators (about 20 bunches from 2808)
P.Sievers / A.Ferrari / V. Vlachoudis
Beryllium
R.Schmidt - TU Darmstadt Januar 2008 58
RF contacts for guiding image currents
Beam spot
R.Schmidt - TU Darmstadt Januar 2008 59
First collimator in the First collimator in the tunneltunnel
R.Assmann et al
Vacuum tank with two jaws installed
Designed for maximum robustness: Advanced Advanced Carbon Composite material Carbon Composite material for the jaws with water for the jaws with water cooling!cooling!
R.Schmidt - TU Darmstadt Januar 2008 60
+- 3 ~1.3 mm
56.0 mm
Beam in vacuum chamber with beam screen at 7 TeVBeam in vacuum chamber with beam screen at 7 TeV
• Interception of beam-induced heat loads at 5-20 K (supercritical helium)
• Shielding of the 1.9 K cryopumping surface from synchrotron radiation
• High-conductivity copper lining for low beam impedance
• Low-reflectivity sawtooth surface at equator to reduce photoemission and electron cloud
R.Schmidt - TU Darmstadt Januar 2008 61
About 3600 beam loss monitors to detect About 3600 beam loss monitors to detect particle losses and to trigger a beam dumpparticle losses and to trigger a beam dump
• Ionization chambers to detect beam losses
– Montitors in the arc
– Monitors close to all collimators
– Simulation and experiments to determine threshold for beam losses
• Student from TU Darmstadt involved for his Masters project
R.Schmidt - TU Darmstadt Januar 2008 62
Status summaryStatus summary
Installation and magnet interconnections finished Cryogenics
• Nearly finished and operational (e.g. cryoplants)
• Two sectors been at 1.9 K, third sector being cooled down
• Cooldown for other sectors to start soon
Powering system: commissioning on the way• Power converters commissioning on short circuits in tunnel
finished
• Magnet powering tests started in two sectors, main dipoles at 8.5 kA corresponding to 5 TeV
Other systems (RF, Beam injection and extraction, Beam instrumentation, Collimation, Interlocks, Controls)• Essentially on schedule for first beam in 2008
Injector complex and transfer lines ready
R.Schmidt - TU Darmstadt Januar 2008 63
LHC sector 78 - First cooldown
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
15/01/0718:00
21/01/0718:00
27/01/0718:00
02/02/0718:00
08/02/0718:00
14/02/0718:00
20/02/0718:00
26/02/0718:00
04/03/0718:00
10/03/0718:00
Time (UTC)
Tem
per
atu
re (
K)
Supply temperature Magnet temperature (average over sector)
Return temperature Thermal shields temp. (average over sector)
Active cooling in all thermal shields and
cryogenic tranfer lines. All magnets isolated.
Thermal shield
temp.
Supply
temperature
Return
temperature
Magnet
temp.
Re-start of active cooling for cryogenic
transfer lines
Re-start of active cooling for magnets
Active cooling in all thermal shields and
cryogenic tranfer lines. All magnets isolated.
LHC Sector 78 – First cooldown
From 300K to 80K precooling with LN2. 1200 tons of LN2 (64 trucks of 20 tons). Three weeks for first sector.
From 80K to 4.5K. Cooldown with refrigerator. Three weeks for the first sector. 4700 tons of material to be cooled.
From 4.5K to 1.9K. Cold compressors at 15 mbar. Four days for the first sector.
R.Schmidt - TU Darmstadt Januar 2008 64
Magnet temperature in one sectorMagnet temperature in one sector
R.Schmidt - TU Darmstadt Januar 2008 65Courtesy F.Bordry
2ppm
Current tracking between the three main circuits of Current tracking between the three main circuits of Sector 78Sector 78
R.Schmidt - TU Darmstadt Januar 2008 66
Ramping the dipole magnets to a current for 5 TeVRamping the dipole magnets to a current for 5 TeV
8000 A
4000 A
Dipole magnet current
12 hours
R.Schmidt - TU Darmstadt Januar 2008 67
Temperature after an induced quenchTemperature after an induced quench
10 minutes
R.Schmidt - TU Darmstadt Januar 2008 68
ConclusionsConclusions
R.Schmidt - TU Darmstadt Januar 2008 69
Always smooth progress? No ….. this is unrealisticAlways smooth progress? No ….. this is unrealistic
The LHC is a machine with unprecedented complexity The technology is pushed to its limits The LHC is a ONE-OFF machine The LHC was constructed during a period when CERN had to
substantially reduce the personel
Problems came up and were solved / are being solved, such as dipole magnets, cryogenics distribution line, collimators, inner triplet, RF fingers (PiMS), He level gauges, ….
In my view what makes such project a success: not absence of problems, but because problems are detected and adressed with competent and dedicated staff and collaborators that master all different technologies
R.Schmidt - TU Darmstadt Januar 2008 70
Typical (recent) examples
R.Schmidt - TU Darmstadt Januar 2008 71
Repair of the inner triplettRepair of the inner triplett
R.Schmidt - TU Darmstadt Januar 2008 72
RF bellows in the 1700 interconnectionsRF bellows in the 1700 interconnections
R.Schmidt - TU Darmstadt Januar 2008 73
Arc plug-in module at warm temperatureArc plug-in module at warm temperature
R.Schmidt - TU Darmstadt Januar 2008 74
Arc plug-in module at working temperatureArc plug-in module at working temperature
R.Schmidt - TU Darmstadt Januar 2008 75
Solution is on the way…Solution is on the way…
Problem: fingers bend into beampipe obstructing the aperture Due to wrong angle of RF fingers PLUS size of the gap between the
magnet apertures larger than nominal (still inside specification) Laboratory tests and finite element analysis confirm the two factors Only part of the interconnects is affected Complete survey of sector 78 using X-ray techniques Repair is not so difficult…once bad PiM identified
A technique was developed for quickly checking at warm the LHC beam aperture
Using air flow blowing a light ball equipped with a 40MHz transmitter through the beam vacuum pipe, use BPMs to detect it as it passes
R.Schmidt - TU Darmstadt Januar 2008 76
Recalling LHC challenges and outlookRecalling LHC challenges and outlook
Enormous amount of equipment Complexity of the LHC accelerator New challenges in accelerator physics with LHC beam
parameters pushed to the extreme
2005 2006 2007
1 2 3 4 5 6 7 8 9 10 11 121 2 3 4 5 6 7 8 9 10 11 121 2 3 4 5 6 7 8 9 10 11 12
Fabrication of equipment
Installation
LHC Beam commissioning
LHC “hardware” commissioning
2008
1 2 3 4 5 6 7 8 9 10 11 12
R.Schmidt - TU Darmstadt Januar 2008 77
ConclusionsConclusions
The LHC is a global project with the world-wide high-energy physics community devoted to its progress and results
As a project, it is much more complex and diversified than the SPS or LEP or any other large accelerator project constructed to date Machine Advisory Committee, chaired by Prof. M. Tigner, March 2002
We recognize that the planned schedule is very aggressive, given the complexity and potential for damage involved in the initial phases of operation.
It will be important to understand the performance of the machine protection system, the collimation system and the orbit feedback system as well as cycle repeatability and adequate beta-beat control before proceeding to run with significant stored beam energy. Pressure to take shortcuts must be resisted.
Machine Advisory Committee, chaired by Prof. M. Tigner, June 2005
R.Schmidt - TU Darmstadt Januar 2008 78
Acknowledgement Acknowledgement
The LHC accelerator is being realised by CERN in collaboration The LHC accelerator is being realised by CERN in collaboration with institutes from many countries over a period of more than with institutes from many countries over a period of more than 20 years20 years
Main contribution come from the USA, Russia, India, Canada, Main contribution come from the USA, Russia, India, Canada, special contributions from France and Switzerland special contributions from France and Switzerland
Industry plays a major role in the construction of the LHCIndustry plays a major role in the construction of the LHC
TU Darmstadt and GSI among the contributors TU Darmstadt and GSI among the contributors
Thanks for the material from:
R.Assmann, R.Bailey, F.Bordry, L.Bottura, L.Bruno, L.Evans, B.Goddard, M.Gyr, Ph.Lebrun
R.Schmidt - TU Darmstadt Januar 2008 79
Vielen Dank für die Einladung
Möglichkeiten für zukünftige Zusammenarbeit im Bereich von Strahlverlust, Betriebssicherheit, HighEnergyDensity States of Matter,…..
Beteiligung bei einem SPS Experiment, in dem der hochintensive 450 GeV Strahl auf Targets gelenkt wird?
Viele andere Bereiche……..