Rüdiger Schmidt - Wuppertal Januar 20041 Der LHC Beschleuniger Rüdiger Schmidt - CERN Universität Wuppertal Januar 2004 Herausforderungen LHC Beschleunigerphysik

Rüdiger Schmidt - Wuppertal Januar 2004

1

Der LHC Beschleuniger Der LHC Beschleuniger Rüdiger Schmidt - CERN

Universität Wuppertal

Januar 2004

Herausforderungen

LHC Beschleunigerphysik

LHC Technologie

Operation und Maschinenschutz

Rüdiger Schmidt - Wuppertal Januar 2004 2

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-1s-2] (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


109 events / second

LHC Event


CERN and the LHCCERN and the LHC

CERN is the leading European institute for particle physics

It is close to Geneva across the French Swiss border

There are 20 CERN member states, 5 observer states, and many other states participating in research

LHC

CMS

ATLAS

LEP: e+e-

104 GeV/c (1989-2000)

Circumference26.8 km

LHCproton-protonCollider7 TeV/c in theLEP tunnel2 rings

Injectionfrom SPS at450 GeV/c

ATLAS

CMS


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

2007 : Commissioning with beam planned


To make the LHC accelerator a reality: To make the LHC accelerator a reality: Accelerators physics and ....Accelerators physics and ....

Electromagnetism und Relativity Thermodynamics Mechanics Quantum mechanics Physics of nonlinear systems Solid state physics und surface physics Particle physics and radiation physics Vacuum physics

+ Engineering

Mechanical, Civil, Cryogenics, Electrical, Automation, Computing

Accelerator Physics: An Introduction• Why protons? Why in the LEP tunnel? Why superconducting magnets? Why “two”

accelerators in one tunnel?

LHC Layout The quest for high luminosity and the consequences Beam-Beam interaction Crossing angle and insertion layout LHC Parameters The CERN accelerator complex: injectors and transfer

LHC technology LHC Operation and machine protection Conclusions

OutlineOutline



LHC Layout The quest for high luminosity and the consequences Beam-Beam interaction Crossing angle and insertion layout Wrapping up: LHC Parameters The CERN accelerator complex: injectors and transfer

LHC technology LHC Operation and machine protection Conclusions

OutlineOutline


Particle accelerationParticle acceleration

2

1

s

s

U sdE

Acceleration of a charged particle by an electrical potential

Energy gain given by the potential

UqqEs

s

s

s

2

1

2

1

sdEsdF

For an acceleration to 7 TeV a voltage of 7 TV is required The maximum electrical field in an accelerator is in the

order of some 10 MV/m (superconducting RF cavities) To accelerate to 7 TeV would require a linear accelerator

with a length of about 350 km (assuming 20 MV/m)

12Rüdiger Schmidt - Wuppertal Januar 2004

Acceleration in a cavityAcceleration in a cavity

)(tE

U = 1000000 Vd = 1 mq = e0

E = 1 MeV

-+

beambunchedeConsequenc

mMVaboutfieldMaximum

)t(E(t)Ez

:

/

cos

20

field varying Time

0

13Rüdiger Schmidt - Wuppertal Januar 2004

How to get to 7 TeV: Synchrotron – circular How to get to 7 TeV: Synchrotron – circular accelerator and many passages in RF cavitiesaccelerator and many passages in RF cavities

LINAC (planned for several hundred GeV - but not above 1 TeV)

LHC circular machine with energy gain per turn some MeV


RF systemsRF systems: 400 MHz: 400 MHz

400 MHz system:

all 16 sc cavities (copper sputtered with niobium) for 16 MV/beam were built and assembled in four modules

Power test of the first module


Particle deflection: Lorentz ForceParticle deflection: Lorentz Force

The force on a charged particle is proportional to the charge, and to the vector product of velocity and magnetic field:

)( BvEF

q

• Maximaler Impuls 7000 GeV/c

• Radius 2805 m

• Ablenkfeld B = 8.33 Tesla

• Magnetfeld mit Eisenmagneten maximal 2 tesla, daher werden supraleitende Magnete benötigt

Rep

B

0

z

x

s

v

B

F

Radius

Lorenz Force = accelerating force

Particle trajectory

Radiation field

charged particle

Figure from K.Wille

Energy loss for charged particles by synchrotron radiation

Power emitted for one particle: Ps=e0

2 c

6 0 m0 c2 4

E4

2

with E = energy, m0 = rest mass, e0 = charge, and = radius


Energy loss for charged particles Energy loss for charged particles electrons / protons in LEP tunnelelectrons / protons in LEP tunnel

Elep 100GeV Elhc 7000GeV

Energy loss for one particle per turn:

Ulep 3.844 109 eV Ulhc 8.121 103 eV

Total power of synchrotronradiation:

Number of electrons in LEP: Nlep 1012 Number of protons in LHC Nlhc 1014

Ptotal_lep Nlep Plep Ptotal_lhc Nlhc Plhc

Ptotal_lep 1.278 107 W Ptotal_lhc 2.699 103 W

The power of the synchrotronradiation emitted at the LHC is very small, but the radiation goes into the supraconducting magnets at 1.9 K ... 20 K


assuming LEP with electrons at 7 TeV: lep7 1012

me c2eV

Ulep e02

lep4

3 0

Ulep 9.23 1016 eV

...just assuming to accelerate electrons ...just assuming to accelerate electrons to 7 TeV to 7 TeV

...better to accelerate protons...better to accelerate protons



LHC Layout The quest for high luminosity and the consequences Beam-Beam interaction Crossing angle and insertion layout The CERN accelerator complex: injectors and transfer Wrapping up: LHC Parameters

LHC technology LHC operation and machine protection Conclusions

OutlineOutline

LHC: eight arcs (approximatley circular) and eight long straight section (about 700 m long)

Momentum Cleaning

Betatron Cleaning

Beam dump system

RF + Beam instrumentation

CMS

ATLAS

LHC-BALICE


CMS DetektorCMS Detektor


Beam transportBeam transport

Need for keeping protons on a circle: dipole magnets

Need for focusing the beams:

Particles with different injection parameters (angle, position) separate with time• Assuming an angle difference of 10-6 rad, two particles would separate by

1 m after 106 m. At the LHC, with a length of 26860 m, this would be the case after 50 turns (5 ms !)

The beam size must be well controlled • At the collision point the beam size must be tiny

Particles with (slightly) different energies should stay together

Particles would „drop“ due to gravitation


The LHC arcs: FODO cellsThe LHC arcs: FODO cells

Dipole- und Quadrupol magnets– Particle trajectory stable for particles with nominal momentum

Sextupole magnets– To correct the trajectories for off momentum particles

– Particle trajectories stable for small amplitudes (about 10 mm)

Multipole-corrector magnets– Sextupole - and decapole corrector magnets at end of dipoles

– Particle trajectories can become instable after many turns (even after, say, 106 turns)

QF QD QFdipolemagnets

small sextupolecorrector magnets

decapolemagnets

LHC Cell - Length about 110 m (schematic layout)

sextupolemagnets


Particle stability and supraconducting magnets - Particle stability and supraconducting magnets - Quadrupolar- and multipolar fieldsQuadrupolar- and multipolar fields

LHC

Teilchenschwingungim Quadrupolfeld(kleine Amplitude)

Harmonische Schwingung(Koordinatentransformation)

Kreisbewegung im Phasenraum

z

y

y

y'

LHC

Teilchenschwingungbei nichlinearen Feldernund grosser Amplitude

Amplitude wächst bis zumTeilchenverlust

Keine Kreisbewegung im Phasenraum

z

y

y

y'

Particle oscillations in quadrupole field (small amplitude)

Harmonic oscillation after coordinate transformation

Circular movement in phase space

Particle oscillation assuming non-linear fields, large amplitude

Amplitude grows until particle is lost (touches aperture)

No circular movement in phasespace


Dynamic aperture and magnet imperfectionsDynamic aperture and magnet imperfections

Particles with small amplitudes are in general stable Particles with large amplitudes are not stable The dynamic aperture is the limit of the stability region The dynamic aperture depends on field error - without any field

errors, the dynamic aperture would be large

The magnets should be made such as the dynamic aperture is not too small (say, 10 the amplitude of a one sigma particle, assuming Gaussian distribution)

The dynamic aperture depends also on the working point and on the sextupole magnets for correction of chromatic effects





OutlineOutline


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-1s-2]

• Tevatron (p-pbar) : 3 1031 [cm-1s-2]

• B-Factories: 1034 [cm-1s-2]

212 cmscmLT

N


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 ?





OutlineOutline


Limitation: beam-beam interactionLimitation: beam-beam interaction

Quadrupole Lense

Beam - Beam Lense

Force

Force

Y

Y

Bunch intensity limited due to this strong non-linearity to about N = 1011


Beam beam interaction determines parametersBeam beam interaction determines parameters

Beam size 16 m, for = 0.5 m

f = 11246 Hz

Beam size given by injectors and by space in vacuum chamber

Number of protons per bunch limited to about 1011

L = N2 f n b / 4 xy

= 3.5 1030 [cm-2 s-1]

with one bunch

with 2808 bunches (every 25 ns one bunch) L = 1034 [cm-2s-1]





OutlineOutline


Large number of bunchesLarge number of bunches

IP

Crossing angle to avoid long range beam beam interaction



IP




IP



distance about 100 m

Interaction point

QD QD QF QD QF QD

Experiment

Focusing quadrupole for beam 1, defocusing for beam 2 High gradient quadrupole magnets with large aperture (US-JAPAN) Total crossing angle of 300 rad Beam size at IP 16 m, in arcs about 1 mm

Crossing angle for multibunch operationCrossing angle for multibunch operation


Layout of insertion for ATLAS and CMS Layout of insertion for ATLAS and CMS

200 m

inner quadrupoletriplet

separationdipole (warm)

recombinationdipole

quadrupoleQ4

quadrupoleQ5

ATLAS or CMS

inner quadrupoletriplet

separationdipole

recombinationdipole

quadrupoleQ4

quadrupoleQ5

collision point

beam I

Example for an LHC insertion with ATLAS or CMS

24 m

beamdistance194 mm

beam II



LHC Layout The quest for high luminosity and the consequences Beam-Beam interaction Crossing angle and insertion layout The CERN accelerator complex: injectors and transfer LHC Parameters


OutlineOutline


summarising constraints and summarising constraints and consequences….consequences….

Centre-of-mass energy must well exceed 1 TeV, LHC installed into LEP tunnel

Colliding protons, and also heavy ions Magnetic field of 8.3 T with superconducting magnets Large amount of energy stored in magnets

Luminosity of 1034

Need for “two accelerators” in one tunnel with beam parameters pushed to the extreme – with opposite magnetic dipole field

Large amount of energy stored in beams

Economical constraints and limited space Two-in-one superconducting magnets


Very high beam currentVery high beam current

Many bunches and high energy -

Energy in one beam about 330 MJ

Beam stability and magnet field quality Synchrotron radiation - power to cryogenic system

Dumping the beam in a safe way Beam induced quenches (when 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)

Photo electrons - accelerated by the following bunches


Challenges:Challenges: Energy stored in the beam Energy stored in the beam

courtesy R.Assmann Momentum [GeV/c]

Ene

rgy

stor

ed in

the

bea

m [

MJ]

Transverse energy density: even a factor of 1000 larger

x 200

x 10000

One beam, nominal intensity(corresponds to an energy that melts 500 kg of copper)


Accelerator Physics: An Introduction• Why protons? Why in the LEP tunnel? Why superconducting magnets? Why

“two” accelerators in one tunnel?

LHC Layout The quest for high luminosity and the consequences Beam-Beam interaction Crossing angle and insertion layout Wrapping up: LHC Parameters The CERN accelerator complex: injectors and transfer LHC technology LHC operation and machine protection Conclusions

OutlineOutline


Getting beam into the LHCGetting beam into the LHC

Beam size of protons decreases with energy: 2 = 1 / E Beam size large at injection Beam fills vacuum chamber at 450 GeV

If the energy would be lower ... larger vacuum chamber and larger magnets – increased cost magnets and power converter limitations (dynamic effects,

stability, …) issues of beam stability

Injection from the SPS at 450 GeV, via two transfer lines, into the LHC


Autumn 2004

Injector complex Injector complex

High intensity beam from the SPS into LHCat 450 GeV via TI2 and TI8

LHC accelerates to 7 TeV

LEIR

CPS

SPS

Booster

LINACS

LHC

3

45

6

7

8

1

2TI8

TI2

Ions

protons

Extraction

Beam 1Beam 2

Summer 2003

Spring 2006


Injector ComplexInjector Complex

Already today, beams are available close to the nominal beam parameters required for the LHC

Fast extraction from the SPS with a new system into a new line successfully done in summer 2003

B.Goddard


Accelerator Physics: An Introduction• Why protons? Why in the LEP tunnel? Why superconducting magnets? Why

“two” accelerators in one tunnel?

LHC Layout The quest for high luminosity and the consequences Beam-Beam interaction Crossing angle and insertion layout Wrapping up: LHC Parameters The CERN accelerator complex: injectors and transfer LHC technology LHC operation and machine protection Conclusions

OutlineOutline


LHC accelerator in the tunnelLHC accelerator in the tunnel

LHC Main Systems

Superconducting magnetsCryogenicsVacuum systemPowering (industrial use of High Temperature Superconducting material)


1232 main dipoles +

3700 multipole corrector magnets

392 main quadrupoles +

2500 corrector magnets

Regular arc:

Magnets


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


Insulation vacuum for the cryogenic distribution line

Regular arc:

Vacuum

Insulation vacuum for the magnet cryostats

Beam vacuum for

Beam 1 + Beam 2


Regular arc:

Electronics

Along the arc about several thousand electronic crates (radiation tolerant) for:

quench protection, power converters for orbit correctors and instrumentation (beam, vacuum + cryogenics)


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


1232 DipolmagnetsLength about 15 mMagnetic Field 8.3 TTwo beam tubes with an opening of 56 mm

Dipole magnets for the LHCDipole magnets for the LHC


Coils for DipolmagnetsCoils for Dipolmagnets


Superconducting cable for 12 kA

15 mm / 2 mm

Temperature 1.9 K cooled with Helium

Force on the cable:

F = B * I0 * L

with

B = 8.33 T

I0 = 12000 Ampere

L = 15 m

F = 165 tons

56 mm


Beam tubes

Supraconducting coil

Nonmagetic collars

Ferromagnetic iron

Steelcylinder for Helium

Insulationvacuum

Supports

Vacuumtank


Magnetic field - current density - temperatureMagnetic field - current density - temperature

Superconducting

material determines:

Tc critical temperature

Bc critical field

Production process:

Jc critical current density

Temperature [K]A

pplie

d fie

ld [

T]

Superconductingstate

Normal state

Bc

TcLower temperature

increased current density

Typical for NbTi:

2000 A/mm2

@ 4.2K, 6TFür 10 T, Operation less than 1.9 K required

Copyright A.Verweij


Supraconducting wireSupraconducting wire

1 mm6 m

Typical value for operation at 8 T and 1.9 K: 800 A

Copyright A.Verweij

Rutherford cableRutherford cable

width 15 mm


Dipole magnet production: Snapshot at industryDipole magnet production: Snapshot at industry

L.Rossi


Storage of dipole cold masses Storage of dipole cold masses waiting for cryostating waiting for cryostating


Histogram of the number of quenches to reach 8.33 Tesla for the f irst 53 LHC preseries dipoles

0

2

46

8

10

1214

16

18

2022

24

26

0 1 2 3 4 5 6 7 notreached

Number of quenches to reach 8.33T

Nu

mb

er o

f m

agn

ets

01 02 03

Performance of LHC dipole magnetsPerformance of LHC dipole magnets


Challenges for dipole productionChallenges for dipole production

The magnets must reach without quenching a field of at least 8.3 Tesla, and possibly 9 Tesla

The field quality must be excellent (relative field errors much less than 0.1 %, positioning of collars to some 10 m)

The geometry must be respected – and the magnet must be correctly bent

All magnets must be produced in time, delivered to CERN, installed in the cryostats, cold tested, and finally installed into the LHC tunnel


Operation and machine Operation and machine protectionprotection


OutlineOutline

Energy stored in the LHC magnets and beams Charging the energy LHC dipole magnets - discharging the energy

• irregular discharge - magnet quenches

LHC Beams - discharging the energy• regular and irregular discharge

Magnets facing Beams


Energy stored in dipole magnetsEnergy stored in dipole magnets

10 GJoule……

corresponds to the energy of 1900 kg TNT corresponds to the energy of 400 kg Chocolate corresponds to the energy for heating and melting 12000 kg of copper

Could this damage equipment: How fast can this energy be released?

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


OutlineOutline






0

2000

4000

6000

8000

10000

12000

-4000 -2000 0 2000 4000

time from start of injection (s)

dip

ole

cu

rre

nt (A

)

energy

ramp

preparation and access

injection phase

coast

coast

LHC magnetic cycleLHC magnetic cycle

L.Bottura

450 GeV

7 TeV

start of the

ramp


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 - Beam injectionLHC magnetic cycle - Beam injection

L.Bottura

450 GeV

7 TeV

beam dump


OutlineOutline






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


Quench - transition from superconducting Quench - transition from superconducting state to normalconducting statestate to normalconducting state

Quenches are initiated by an energy in the order of mJ (corresponds to the energy of 1000 protons at 7 TeV)

Movement of the superconductor by several m (friction and heat dissipation)

Beam losses

Failure in cooling

To limit the temperature increase after a quench (in 1s to 5000 K)

The quench has to be detected

The energy is distributed in the magnet by force-quenching the coils using quench heaters

The magnet current has to be switched off within << 1 second


OutlineOutline






Regular (very healthy) operationRegular (very healthy) operation

Assuming that the beams are colliding at 7 TeV

Single beam lifetime larger than 100 hours…..• corresponds to a loss of about 1 kW / beam

• far below the cooling power of the cryogenic system, even if all particles would be lost at 1.9 K

• losses should be either distributed across the machine or captured in the warm cleaning insertions

Collision of beams with a luminosity of 1034 cm-2s-1 • lifetime of the beam can be be dominated by collisions

• 109 protons / second lost per beam / per experiment (in IR 1 and IR 5 - high luminosity insertions) - this is about 1.2 kW

• large heat load to close-by superconducting quadrupoles

• heavy shielding around the high luminosity IPs


End of data taking in normal operationEnd of data taking in normal operation

Luminosity lifetime estimated to be approximately 10 h (after 10 hours only 1/3 of initial luminosity)

Beam current somewhat reduced - but not much Energy per beam still about 200-300 MJ Beams are extracted in beam dump blocks

The only component that can stand a fast loss of the full beam at top energy is the beam dump block - all other components would be damaged

At 7 TeV, fast beam losses with an intensity of about 5% of a “nominal bunch” could damage superconducting coils


LHC ringLHC ring: 3 insertions for machine : 3 insertions for machine protection systems protection systems

Beam Cleaning IR3 (Momentum)

Beam Cleaning IR7 (Betatron)

Beam dump system IR6

RF+ Beam monitors IR4


Beam losses into materialBeam losses into material

Proton losses lead to particle cascades in materials The energy deposition leads to a temperature increase 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

Magnets could quench…..• beam lost - re-establish condition will take hours

The material could be damaged…..• melting

• losing their performance (mechanical strength)

Repair could take several weeks


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


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


Beam Dump Block - LayoutBeam Dump Block - Layout

about 8 m

L.Bruno

concrete shielding

beam absorber (graphite)


Beam on Beam Dump BlockBeam on Beam Dump Block

about 35 cm

M.Gyr

initial transverse beam dimension in the LHC about 1 mm

beam is blown up due to long distance to beam dump block

additional blow up due to fast dilution kickers: painting of beam on beam dump block

beam impact within less than 0.1 ms


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


OutlineOutline






Beam lifetime with nominal intensity at 7 TeVBeam lifetime with nominal intensity at 7 TeV

Beam 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


+- 3 ~5 mm

Beam +/- 3 sigma

56.0 mm

Beam in vacuum chamber with beam screen at 450 GeVBeam in vacuum chamber with beam screen at 450 GeV


+- 3 ~1.3 mm

Beam +/- 3 sigma

56.0 mm

Beam in vacuum chamber with beam screen at 7 TeVBeam in vacuum chamber with beam screen at 7 TeV


Beam +/- 3 sigma

56.0 mm

1 mm

+/- 8 sigma = 4.0 mm

Example: Setting of collimators at 7 TeV - with luminosity opticsExample: Setting of collimators at 7 TeV - with luminosity optics Beam must always touch collimators first !Beam must always touch collimators first !

R.Assmanns EURO

Collimators at Collimators at 7 TeV, squeezed7 TeV, squeezedopticsoptics


Jaws (blocks of solid materials such as copper, graphite, ….) very close to the beam to absorb more than 99.9 % of protons that would be lost

Primary collimators: Intercept primary haloImpact parameter: ~ 1 Impact parameter: ~ 1 mmScatter protons of primary haloConvert primary halo to secondary off-momentum halo

Secondary collimators: Intercept secondary haloImpact parameter: ~ 200 Impact parameter: ~ 200 mmAbsorb most protonsLeak a small tertiary halo

Particles

Beam axis

Impactparameter

Collimator jaw

Basic concept of Basic concept of two stage two stage collimationcollimation

R.Assmann / J.B.Jeanneret


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 2800)part of beam touches collimators (about 20 bunches from 2800)

P.Sievers / A.Ferrari / V.Vlachoudis

circulating beam


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 2800)part of beam touches collimators (about 20 bunches from 2800)

P.Sievers / A.Ferrari / V. Vlachoudis

Beryllium


Optimisation of Cleaning systemOptimisation of Cleaning system

Requirements for collimation system take into account failure scenarios and imperfect operation

• Worst case is the impact of about 20 bunches on the collimator due to pre-firing of one dump kicker module

Material for collimator is being reconsidered - low Z material is favoured Impedance to be considered - conducting material is favoured More exotic materials are considered: copper loaded graphite,

beryllium, partially plated copper ….


ConclusionsConclusions


Recalling LHC challenges

Enormous amount of equipment Complexity of the LHC accelerator New challenges in accelerator physics with LHC beam

parameters

20052004

1 2 3 4 5 6 7 8 9 10 11 12

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

Beam in one sectorLHC Beam commissioning

LHC “hardware” commissioning


ConclusionsConclusions

The LHC is installed and commissioned in eight (rather)independent sectors - that allows for activities to be performed in parallel

…….... to avoid a lengthy and painful start-up when LHC hardware ready for two beam

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


citing Lyn Evansciting Lyn Evans

No one has any doubt that it will be a great challenge for both machine to reach design luminosity and for the detectors to swallow it.

However, we have a competent and experienced team, and 30 years of accumulated knowledge from previous CERN projects has been put into the LHC design


Acknowledgement Acknowledgement

The LHC accelerator is being realised by CERN in collaboration with The LHC accelerator is being realised by CERN in collaboration with institutes from many countries over a period of more than 20 yearsinstitutes from many countries over a period of more than 20 years

Main contribution come from the USA, Russia, India, Canada, special Main contribution come from the USA, Russia, India, Canada, special contributions from France and Switzerland 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

Thanks for the material from:

R.Assmann, L.Bottura, L.Bruno, R.Denz, A.Ferrari, B.Goddard, M.Gyr, D.Hagedorn, J.B.Jeanneret, P.Proudlock, B.Puccio, F.Rodriguez-Mateos, F.Ruggiero, L.Rossi, S.Russenschuck, P.Sievers, G.Stevenson, A.Verweij, V.Vlachoudis, L.Vos


Some referencesSome referencesAccelerator physics Proceedings of CERN ACCELERATOR SCHOOL (CAS),

http://schools.web.cern.ch/Schools/CAS/CAS_Proceedings.html• In particular: 5th General CERN Accelerator School, CERN 94-01, 26

January 1994, 2 Volumes, edited by S.TurnerSuperconducting magnets / cryogenics Superconducting Accelerator Magnets, K.H.Mess, P.Schmüser, S.Wolff, World

Scientific 1996 Superconducting Magnets, M.Wilson, Oxford Press Superconducting Magnets for Accelerators and Detectors, L.Rossi, CERN-AT-

2003-002-MAS (2003)LHC Technological challenges for the LHC, CERN Academic Training, 5 Lectures,

March 2003 (CERN WEB site) Beam Physics at LHC, L.Evans, CERN-LHC Project Report 635, 2003 Status of LHC, R.Schmidt, CERN-LHC Project Report 569, 2003 ...collimation system.., R.Assmann et al., CERN-LHC Project Report 640, 2003 LHC Design Report 1995 LHC Design Report 2003 - in preparation

http://schools.web.cern.ch/Schools/CAS/CAS_Proceedings.html


Power into superconductingPower into superconductingcable after a quenchcable after a quench

Cross section : Asc 10 mm2

Current : Isc 10000 A

Length of superconductor : Lsc 1 m

Copper resistance at 300 C: cu 1.76 10 6 ohm cm

Psc cu Isc2

Lsc

Asc Psc 1.76 105 watt

Specific temperature of copper at 300 C : cvcu 3.244joule

K cm3

Temperature increase of copper TPsc

Asc Lsc cvcu

Temperature increase within one second: T 5.425 103K

s

Rüdiger Schmidt - Wuppertal Januar 2004 98F.Rodriguez-Mateos, K.Dahlerup-Petersen

Energy extraction system in LHC tunnelEnergy extraction system in LHC tunnel

Resistors absorbing the energy

Switches - for switching the resistors into series with the magnets

Documents

Rüdiger Schmidt - Wuppertal Januar 20041 Der LHC Beschleuniger Rüdiger Schmidt - CERN Universität Wuppertal Januar 2004 Herausforderungen LHC Beschleunigerphysik