Rüdiger Schmidt1 The LHC collider project II Rüdiger Schmidt - CERN SUSSP Sumer School St.Andrews Challenges LHC accelerator physics LHC technology Operation

Rüdiger Schmidt 1

The LHC collider project II The LHC collider project II Rüdiger Schmidt - CERN

SUSSP Sumer School

St.Andrews

Challenges

LHC accelerator physics

LHC technology

Operation and protection

Rüdiger Schmidt 2

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

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

Rüdiger Schmidt 4

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

Rüdiger Schmidt 5

LHC injector complex - pre-accelerators existLHC injector complex - pre-accelerators exist

Rüdiger Schmidt 6

Injector ComplexInjector Complex

Pre-injectors: Linac, PS Booster and Proton Synchrotron deliver protons at 26 GeV to the SPS

The SPS accelerates protons from 26 GeV to 450 GeV

Both, the pre-injectors and the SPS were upgraded for the operation with nominal LHC beam parameters

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

Transfer Lines SPS - LHCTransfer Lines SPS - LHC

Two new transfer line tunnels from SPS to LHC are being built. The beam lines use normal conducting magnets.

Length of each line:about 2.8 km

Magnets are all available, made by BINP / Novosibirsk

Commissioning of thefirst line for 2004

Dipole magnets waiting for installation

Rüdiger Schmidt 8

LHC accelerator in the tunnelLHC accelerator in the tunnel

Rüdiger Schmidt 9

LHC TechnologyLHC Technology

…in particular superconducting dipole magnets…in particular superconducting dipole magnets

Challenges:

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

Rüdiger Schmidt 10

1232 main dipoles +

3700 multipole corrector magnets

392 main quadrupoles +

2500 corrector magnets

Regular arc:

Magnets

Rüdiger Schmidt 11

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

Rüdiger Schmidt 12

Insulation vacuum for the cryogenic distribution line

Regular arc:

Vacuum

Insulation vacuum for the magnet cryostats

Beam vacuum for

Beam 1 + Beam 2

Rüdiger Schmidt 13

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)

Rüdiger Schmidt 14

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

Dipole magnets for the LHCDipole magnets for the LHC

Rüdiger Schmidt

Coils for DipolmagnetsCoils for Dipolmagnets

Rüdiger Schmidt 16

Dipole field – approximate cosine teta current Dipole field – approximate cosine teta current distributiondistribution

In practice the above current distributions are approximated by real conductors, so the field contains also higher order harmonics (see later).

Intersecting ellipses generate uniform field.

Two intersecting ellipses, rotated of 90, generate a perfect quadrupole fields:.

ba

JbdB y +

= 0mSuch configuration follows:

Js = Jcos()

Rüdiger Schmidt 17

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

Rüdiger Schmidt 18

Rüdiger Schmidt 19

Two - in One MagnetTwo - in One Magnet

Rüdiger Schmidt 20

Beam tubes

Supraconducting coil

Nonmagetic collars

Ferromagnetic iron

Steelcylinder for Helium

Insulationvacuum

Supports

Vacuumtank

Rüdiger Schmidt

The Dipolmagnet in a cryostatThe Dipolmagnet in a cryostat

Rüdiger Schmidt 22

Discovery of Discovery of superconductivitysuperconductivity

1908 -- Kamerlingh Onnes liqufies Helium.

1911 -- R-T for Mercury

?"…. Mercury has passed into a new state, which on account

of its extraordinary electrical properties may be called the superconductive state …."

Copyright A.Verweij

Rüdiger Schmidt 23

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

Rüdiger Schmidt 24

Typical SupraconductorsTypical Supraconductors

The high critical field of supraconductor type II allows the construction of high field magnets.

1962 – commerically available supraconducting wires

Niobium-Titan (NbTi)

Charactersisation of superconductors:• Temperature• Magnetic Field• Current density

Copyright A.Verweij

Rüdiger Schmidt 25

Helium:Helium:PhasediagramPhasediagram

T>T: He I

T<T: He II(superfluid Helium)

T=2.17 K

LHC:

T=1.9 K

P1.2 bar

Copyright A.Verweij

Rüdiger Schmidt 26

Helium ParameterHelium Parameter

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7Temperature (K)

Cp

(J

/g/K

)

T

Specific heat of Helium as function of T

Phasetransition at 2.18 Kelvin

Superfluid Helium (He II)

Copyright A.Verweij

He II, 1.9K He I, 4.2K Water, 300K SC @ 8T,1.9K

SC @ 8T,4.2K

thermal cond. ~100,000 0.02 1 ~400 ~400

viscosity 0.01 – 0.1 3 1000

Cp 4 5 0.0001 0.0004

Rüdiger Schmidt 27

Supraconducting wireSupraconducting wire

1 mm6 mm

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

Copyright A.Verweij

Rutherford cableRutherford cable

width 15 mm

Rüdiger Schmidt 28

Fabrication of superconducting dipolesFabrication of superconducting dipoles

Dipole assembly in industry

Rüdiger Schmidt 29

Snapshot at industrySnapshot at industry

L.Rossi

Rüdiger Schmidt 30

Cryostating and measurements (main Cryostating and measurements (main dipoles and other magnets)dipoles and other magnets)

SMA18 cryostating hallat CERN for installing dipole magnets into cryostats

SM18: 12 measurement stations are prepared for cold tests of possibly all superconducting magnets

Rüdiger Schmidt 31

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 mm)

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

Rüdiger Schmidt 32

LHC Progress Dashboard - on the WEBLHC Progress Dashboard - on the WEB

Rüdiger Schmidt 33

Operation and machine Operation and machine protectionprotection

Rüdiger Schmidt 34

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 Strategy for Protection of the LHC machine

Rüdiger Schmidt 35

Energy stored in LHC magnetsEnergy stored in LHC magnets

Approximation: energy is proportional to volume inside magnet aperture and to the square of the magnet field

about 5 MJ per magnet

Accurate calculation with the magnet inductance:

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

Energy stored in twin dipole magnet: Estored 2Bdipole

2length rdipole

2

m0=

Rüdiger Schmidt 36

What does this mean?What does this mean?

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

corresponds to the energy produced by of one nuclear power plant during about 10 seconds

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

Rüdiger Schmidt 37

OutlineOutline





Rüdiger Schmidt 38

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

beam dump

injection phase

coast

coast

LHC magnetic cycleLHC magnetic cycle

L.Bottura

450 GeV

7 TeV

start of the

ramp

Rüdiger Schmidt 39

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

Rüdiger Schmidt 40

Sector

1

5

DC Power feed

3 DC Power

2

4 6

8

7LHC

27 km Circumference

LHC Powering in 8 Sectors

Powering Subsectors allow for progressive Hardware Commissioning - starting two years before beam

P.Proudlock

Powering Sector

Powering Subsectors:

triplet cryostats cryostats in matching section long arc cryostats

Rüdiger Schmidt 41

Ramping the current in a string of dipole Ramping the current in a string of dipole magnetmagnet

Magnet 1 Magnet 2

Power Converter

Magnet 154Magnet i

LHC powered in eight sectors, each with 154 dipole magnets Time for the energy ramp is about 20-30 min (Energy from the grid) Time for discharge is about the same (Energy back to the grid)

Rüdiger Schmidt 42

OutlineOutline





Rüdiger Schmidt 43

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

Rüdiger Schmidt 44

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 45

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 mm (friction and heat dissipation)

Beam losses

Failure in cooling

To limit the temperature increase after a quench

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

Current after quench

0

2000

4000

6000

8000

10000

12000

-0.05 0.15 0.35 0.55

Time [seconds]

Cur

rent

[A]

Gaussian approximation

Current after quench

Current in a dipole magnets after a quench, when heaters are fired (7 TeV) - 7 MJ within 200 ms into magnet

Rüdiger Schmidt 47

Quench - Emergency discharge of energy …Quench - Emergency discharge of energy …

Magnet 1 Magnet 2

HTS leads 1 HTS leads 2

Power Converter

Magnet 154Magnet i

assume one magnet quenches assume the magnets in the string have to be discharged in, say, 200 ms

Discharge with about 1 MV: not possible

Udischarge_1Ldipole Idipole

0.2s= Udischarge_154

154Ldipole Idipole

0.2s=

Udischarge_1 6.426 103 V= Udischarge_154 9.896 10

5 V=

Rüdiger Schmidt 48

……..and how it being done in the LHC..and how it being done in the LHC

Magnet 1 Magnet 2

Power Converter

Magnet 154

Magnet i

when one magnet quenches, quench heaters are fired for this magnet the current in the quenched magnet decays in about 200 ms the current in all other magnets flows through the bypass diode that can stand the current for about 100-

200 seconds

Bypass Diode …

installed in 1.9 K system (not accessible)

needs to carry 12 kA during the exponential discharge for about 150 seconds

needs to be radiation tolerant

need to be very reliable (all diodes tested at cold before installation)

one diode for each dipole magnet

two diodes for each arc quadrupole magnets

F.Rodriguez-Mateos, D.Hagedorn

F.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

Rüdiger Schmidt 51

OutlineOutline





Rüdiger Schmidt 52

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

Rüdiger Schmidt 53

Regular operation: some challengesRegular operation: some challenges

High radiation environment close to interaction point

Moderate radiation load in the arcs (in the order of 1 Gy / year)

Even less radiation dose in tunnel enlargements (about factor of 10 less compared to the tunnel - to be reviewed)

A large fraction of the electronics for quench protection, beam monitoring, vacuum monitoring, cryogenics and powering is located in areas with some radiation

Single Event Upsets (for example bit flips by radiation) introduce failures of the electronics

Development and qualification of radiation tolerant electronics since several years in many groups

Rüdiger Schmidt 54

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

Rüdiger Schmidt 55

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

Rüdiger Schmidt 56

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

Rüdiger Schmidt 57

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

Rüdiger Schmidt 58

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

AB - Beam Transfer Group

about 500 m

Fast kicker magnet

Rüdiger Schmidt 59

Beam Dump Block - LayoutBeam Dump Block - Layout

about 8 m

L.Bruno

concrete shielding

beam absorber (graphite)

Rüdiger Schmidt 60

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

Rüdiger Schmidt 61

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 C

Rüdiger Schmidt 62

L.Bruno: Thermo-Mechanical Analysis with ANSYS

Hydrostatic stress after beam depositionHydrostatic stress after beam deposition

Rüdiger Schmidt 63

Beam dump must be synchronised with particle free gap

Strength of kicker and septum

magnets must match energy of the beam

« Particle free gap » must be free of

particles

Requirement for clean beam dumpRequirement for clean beam dump

particle free abort gapof 3 ms

Kicker magnets constant angle

Beam dump block

Time

Kicker strength

Illustration of kicker risetime

Rüdiger Schmidt 64

OutlineOutline





Lifetime of the beam with nominal intensity at Lifetime of the beam with nominal intensity at 7 TeV7 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

Rüdiger Schmidt 66

+- 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

Rüdiger Schmidt 67

+- 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

Rüdiger Schmidt 68

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

Rüdiger Schmidt 69

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 mmmmScatter protons of primary haloConvert primary halo to secondary off-momentum halo

Secondary collimators: Intercept secondary haloImpact parameter: ~ 200 Impact parameter: ~ 200 mmmmAbsorb 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

Rüdiger Schmidt 70

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

Rüdiger Schmidt 71

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

Rüdiger Schmidt 72Half gap b [m]

LHC impedance without collimators

Typical collimator half gap at 7 TeV: 1.5 mm

F.Ruggiero, L.Vos

Impedance for different materials as a Impedance for different materials as a function of collimator half gapfunction of collimator half gap

Rüdiger Schmidt 73

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 ….

Rüdiger Schmidt 74

OutlineOutline





Multiple turn beam loss

due to many types of failures

Passive protection Avoid such failures (high reliability

systems - work is ongoing to better estimate reliability)

Rely on collimators and beam absorbers

Active Protection Failure detection (from beam monitors

and / or equipment monitoring) Issue beam abort signal Fire Beam Dump

Single turn beam loss

during injection and beam dump

In case ofIn case of any failureany failure oror unacceptable beam lifetimeunacceptable beam lifetime, , thethe beam beam must bemust be dumpeddumped immediately, immediately, safely into thesafely into the beam dump block beam dump block

Rüdiger Schmidt 76

Beam Loss MonitorsBeam Loss Monitors

Primary strategy for protection: Beam loss monitors at collimators and other aperture limitations continuously measure beam losses

Beam loss monitors indicate increased losses => MUST BE FAST

When beam losses exceed threshold:

Beam loss monitors break Beam Permit Loop Beam dump sees “No Beam Permit” => dump beams

Rüdiger Schmidt 77

B.Dehning

1.E+04

1.E+06

1.E+08

1.E+10

1.E+12

1.E+14

1.E+16

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

duration of loss [ms]

qu

ench

leve

ls [

pro

ton

/s]

total quench levels at 450 GeV

total quench levels at 7 TeV

max range

min range

max range

min range

DynamicRange of

108

Beam loss monitors: quench levels as function Beam loss monitors: quench levels as function of loss durationof loss duration

BLMCs at aperture limitations and

Collimator - 0.1 ms

BLMAs in arcs2.5 ms

450 GeV 7 GeV

Rüdiger Schmidt 78

Beam loss monitors: Ideas for realisationBeam loss monitors: Ideas for realisation

ionisation chamber

gas N2

normal pressure

800 to 1800 V

# of electron / ion pairs: 50 - 70 MIP / cm

Current to frequency converter

first stage (input cable length up to 400 m)

dynamics about 107

input current: 30 pA to 50 mA

output frequency: 0.05 Hz to several MHz

second stage (optical fibre length up 1.5 km)every channel with micro controller (FPGA)

several mean loss values

in parallel

energy tracking

chamber

B.Dehning

Rüdiger Schmidt 79

Architecture of the BEAM INTERLOCK SYSTEM Architecture of the BEAM INTERLOCK SYSTEM

Pt.1

Pt.2

Pt.3

Pt.4

Pt.5

Pt.6

Pt.7

Pt.8ATLAS

CMS

LHC-BALICE

Momentumcleaning

RF Beam Dump

Betatroncleaning

BEAM 1clockwise

BEAM 2counter-clockwise

InjectionBEAM II from SPS

InjectionBEAM I from SPS

BEAM DUMPCONTROLLERS

BPC

BIC

BPCBPC

BPCBPCBPC

BIC

BIC

BIC

BIC BIC

BIC

BIC

BIC

BIC

BIC

BIC

BICBIC

BIC

BIC

Beam Interlock Loopssignal transmitted viaoptical fibre at 10 MHz

Rüdiger Schmidt 80

Electron CloudElectron Cloud

81Rüdiger Schmidt

Electron cloud: bunch train coming inElectron cloud: bunch train coming in

T = t0 proton emits a photon (synchrotron radiation)

82Rüdiger Schmidt

Electron cloud: photon creates electronElectron cloud: photon creates electron

T = t1 photon hits vacuum chamber and creates electron

83Rüdiger Schmidt

Electron cloud: more secondary electronsElectron cloud: more secondary electrons

T = t2 electron accelerated by the potential of the next bunch, then hits vacuum chamber, and generates more electrons

84Rüdiger Schmidt

Electron cloud: many bunches to come...Electron cloud: many bunches to come...

T = t3 electrons accelerated by the potential of the next bunch,

hit vacuum chamber, and generates more electrons

Rüdiger Schmidt 85

Effects from the electron cloudEffects from the electron cloud Several nasty effects

• Vacuum degradation

• Heat load in cryogenics system

• Beam instability

Has been obseved at several accelerators with intense bunch trains• B-factories

• SPS as injector for LHC

Depends on many parameters• Bunch distance and intensity

• Surface of vacuum chamber (cleanliness, coefficient for desorption)

Cures• Special surface materials for vacuum chamber

• Avoid too close bunch distance (LHC: 75 ns should be ok)

• “Beam Scrubbing” to clean surfaces

Rüdiger Schmidt 86

LHC: From today to colliding beamsLHC: From today to colliding beams

2003 - Spring: Start of installation of general services

(electricity, ventilation, ....)

2003 – July: Start of installation of the cryogenic

distribution line

2004 – Spring: Start of magnet installation

2005: Hardware commissioning of first LHC sector

2006: First beam test – injection from SPS through 1/8 of

the LHC (to be confirmed soon)

2007: Finish installation and hardware commissioning

2007 : Commissioning with two beams and first proton

proton collision

From the summary of the Large Hadron Collider From the summary of the Large Hadron Collider Machine Advisory Committee in March 2002Machine Advisory Committee in March 2002

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

The Status and the complexity of the LHC is documented in more than 80 papers at this conference (EPAC 2002) - this talk is considered as a very brief overview

Machine Advisory Committee, chaired by

Prof. M. Tigner, March 2002

Rüdiger Schmidt 88

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

Rüdiger Schmidt 89

…….and thanks to the organisers of SUSSP for inviting me giving this presentation

Rüdiger Schmidt 90

Some references (...more in write-up)Some references (...more in write-up)Accelerator 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

Documents

Rüdiger Schmidt1 The LHC collider project II Rüdiger Schmidt - CERN SUSSP Sumer School St.Andrews Challenges LHC accelerator physics LHC technology Operation