Machine Plans for the LHC Upgrade

ATLAS Upgrade Workshop, 1 October 2006Machine Plans for SLHC, Frank Zimmermann

Machine Plans for the LHC Upgrade

Frank ZimmermannCERN, AB/ABP

Thanks to Ralph Assmann, Michael Benedikt, Rama Calaga, Ulrich Dorda, Angeles Faus-Golfe, Roland Garoby,Jean-Pierre Koutchouk, Javier Resta, Francesco Ruggiero, Rogelio Tomas, Walter Scandale


Large Hadron Collider (LHC)

c.m. energy 14 TeV7x Tevatron

design luminosity1034 cm-2s-1

~100x Tevatron

transverse beamenergy density1 GJ/mm2

~1000x Tevatron

nominal LHC already a very challenging machine!


outline1) motivation 2) pushing the luminosity3) beam scenarios & upgrade schemes

- luminous region- lifetime & integrated luminosity

4) IR upgrade 5) intensity limitations 6) injector upgrade7) towards higher energy 8) questions to ATLAS9) summary


(1) motivation


time scale of an LHC upgrade

L at end of year

time to halve error

integrated L

radiationdamage limit~700 fb-1

(1) life expectancy of LHC IR quadrupole magnets is estimated to be <10 years due to high radiation doses

(2) statistical error halving time exceeds 5 years by 2011-2012 → it is reasonable to plan a machine luminosity upgrade based

on new low- IR magnets around ~2014-2015

design luminosity

ultimate luminosity

Jim Strait, 2003


European Accelerator Network on

November 2004: 1st CARE-HHH-APD Workshop (HHH-2004) on ‘Beam Dynamics in Future Hadron Colliders and Rapidly Cycling High-Intensity Synchrotrons’, Proc. CERN-2005-006

September 2005: 2nd CARE-HHH-APD Workshop (LHC-LUMI-05)on ‘Scenarios for the LHC Luminosity Upgrade’, Proc. CERN-2006-008

October 2006: 3rd CARE-HHH-APD Workshop (LHC-LUMI-06)‘Towards a Roadmap for the Upgrade of the LHC and GSI Accelerator Complex’ .../LUMI-06/LHC-LUMI-06-invitation.pdf

High Energy High Intensity Hadron Beams http://care-hhh.web.cern.ch/care-hhh/

http://care-hhh.web.cern.ch/care-hhh/




upgrade stages• push LHC performance w/o new hardware

luminosity →2.3x1034 cm-2s-1, Eb=7→7.54 TeV• LHC IR upgrade

replace low- quadrupoles after ~7 yearspeak luminosity →4.6x1034 cm-2s-1

• LHC injector upgradepeak luminosity →9.2x1034 cm-2s-1

• LHC energy upgradeEb→13 – 21 TeV (15 → 24 T dipole magnets)


(2) pushing the luminosity


2*

2

14

profilerevbb FfNnLluminosity

frequency revolution:revf

bunchper protons# :bN

beamper bunches# :bn

emittance se transver)(geometric : pointcollision at function beta :*

angle crossing full :c

lengthbunch rms :z

pointcollision at sizespot e transversrms :**, yx

bunch uniform longfor 42.1~bunchGaussian for 1

profileF

angle Piwinski :2 *

,yx

zc

parameters that enter:


limited by arc aperture and field quality at injection limited by final triplet aperture & crossing angle

& long-range beam-beam & collimation & chromatic correction (& beam lifetime)c limited by geometric luminosity loss & long-range

collisions & triplet aperture & triplet field errorsnbNb ~ total current, limited by collimation, machine

protection, beam dump nb limited by electron cloud heating

Nb limited by image-current heating & collimation &

pile-up events

there are many parameter constraints, for example


x

zcF

2

;1

12

Piwinski angle

luminosity reduction factor

nominal LHC

nominal crossing angle “at the edge”


212

pbbb

rNQ

Qbb < 0.01- 0.015 , beam-beam limit for

hadron colliders (from experience)SpSp

total beam-beam tune shift at two IPs with alternating crossing

another important constraint is the (head-on) beam-beam tune shift


profilebb

p

revb FQrfnL 22

*2 1

for operation at the beam-beam limitluminosity equation can be rewritten as

IR upgrade

injector upgrade

LHC +injectorchanges

LHC+injectorchanges


(3) beam scenarios & upgrade schemes


parameter symbol nominal ultimate baseline alternative backuptransverse emittance [m] 3.75 3.75 3.75 7.5 3.75

protons per bunch Nb [1011] 1.15 1.7 1.7 3.4 6bunch spacing t [ns] 25 25 12.5 25 75beam current I [A] 0.58 0.86 1.72 1.72 1longitudinal profile Gauss Gauss Gauss Gauss flat

rms bunch length z [cm] 7.55 7.55 3.78 3.78 14.4beta* at IP1&5 [m] 0.55 0.5 0.25 0.25 0.25

full crossing angle c [murad] 285 315 445 630 430

Piwinski parameter cz/(2*x*) 0.64 0.75 0.75 0.75 2.8peak luminosity L [1034 cm-2s-1] 1 2.3 9.2 9.2 8.9events per crossing 19 44 88 176 510

Initial lumi lifetime L [h] 22 14 7.2 7.2 4.5

effective luminosity (Tturnaround=10 h)

Leff [1034 cm-2s-1] 0.46 0.91 2.7 2.7 2.1Trun,opt [h] 21.2 17.0 12.0 12.0 9.4

effective luminosity (Tturnaround=5 h)

Leff [1034 cm-2s-1] 0.56 1.15 3.6 3.6 2.9Trun,opt [h] 15.0 12.0 8.5 8.5 6.6

e-c heat SEY=1.4(1.3) P [W/m] 1.07 (0.44) 1.04 (0.59) 13.34 (7.85) 2.56 (2.05) 0.26

SR heat load 4.6-20 K PSR [W/m] 0.17 0.25 0.5 0.5 0.29

image current heat PIC [W/m] 0.15 0.33 1.87 3.74 0.96gas-s. 100 h (10 h) b Pgas [W/m] 0.04 (0.38) 0.06 (0.56) 0.113 (1.13) 0.11 (1.13) 0.07 (0.7)


bunch structure

25 ns

nominal & ultimate LHC

~12.5 ns

more (&shorter) bunches

concerns:e-cloudLRBBimpedance

upgrade path 1

upgrade path 3

75 nsconcerns:event pile upimpedance

longer (&fewer) bunches

transitions by bunch merging or splitting;new rf systems required for cases 1 and 3

plus:can use crab cavitiesevent pile up tolerable

plus:no e-cloud?less current

upgrade path 2

25 nsbigger (&shorter?) bunches concerns:

impedance heating,LR compensation,may need 1-TeVinjector

plus:limited e-cloudlimited pile up


luminosity upgrade: baseline schemes

increase Nb

bblimit?

increase F2/12

*21

zcF

no

yes

c>mindue to LR-bb

crab cavities

BBLRcompen-sation

reduce z

by factor ~2using higherfrf & lower ||

(largerc ?)

2.3reduce c

(squeeze *)

use large c

& pass each beamthrough separatemagnetic channel

reduce * byfactor ~2

new IRmagnets

increase either nb or (Nb& by factor ~2

if e-cloud, dump &impedance ok

9.2

1.0

4.6

simplified IR design with large c

peak luminosity gain1.72 A

0.86 A

0.58 A

0.86 A

beam current


luminosity upgrade: backup scheme

reduce * byfactor ~2

new IRmagnets

decrease F2/12

*21

zcF

increase zc

increase Nb

no bb

pb Q

FrN

2

?

yes

reduce #bunchesby 1/3 to limit total current

flatten profile

8.9

1.0

1.0 A

luminosity gain

beam current

0.58 A


2

,*

2

22 221

yx

c

zl

rms length of luminous region

due to the crossing angle, colliding long bunches does not mean the events are spread out over a large area

nominal ultimate baseline alternative backupl [cm] 4.5 4.3 2.1 2.1 3.5

luminous region is largest for nominal LHC


optimum run time, integrated luminosity, etc.

2

0

0

0

,...),,,,(11

/1/1

111

bzyxbIBS

x

x

b

bbIP

bb

vacvacbb

IPb

b

NNt

tN

ntNLnN

N

VNc

NnLn

tN

N

collisions, gas scattering

intensity evolution for collisions only

intrabeam scattering (IBS) growth

burn-off collision lifetime with ~100 mbarn, nIP~2: Lpeak=1034 cm-2s-1 in 2808 bunches, Nb~1.15x1011:

~45 h (luminosity lifetime 22 h)Lpeak=1035 cm-2s-1 in 5616 bunches, Nb~1.7x1011:

~14 h (luminosity lifetime 7 h)gas > 100 h (luminosity lifetime 50 h)IBS~105 h (horizontal emittance growth time;

luminosity lifetime 210 h)burn-off dominates over gas scattering and IBS


Lpeak [cm-

2 s-1]beam lifetime eff [h]

turnaround [h] Trun [h] Int L over 200 days[fb-1]

1034 45 10 21 79 1034 45 5 15 97 1035 14 10 12 473 1035 14 5 8 629

2/1

ˆ

efftLtL

luminosity time evolution

turnaroundrunruneff

runeffave TTT

TLL

ˆaverage luminosity

turnaroundeffoptimumrun TT ,→ optimum run time

6x

8x


(4) IR upgrade


factors driving IR design: • minimize * • minimize effect of LR collisions• large radiation power directed towards the IRs• crab cavities or beam-beam compensators, • integration of elements inside detector• compatibility with upgrade path

IR upgradegoal: reduce * by factor 2-5

maximize magnet aperture,minimize distance to IR

options: NbTi ‘cheap’ upgrade, NbTi(Ta), Nb3Sn new quadrupoles new separation dipoles

T. Sen et al., PAC2001T. Taylor, EPAC02J. Strait et al., PAC2003F. Ruggiero et al., EPAC04


IR

UPGRADE

reduced # LR collisions;collision debris hits first dipole

N. Mokhov et al., PAC2003

“open midplane s.c. dipole”

(studied by US LARP)

“dipole first”

“quadrupolesfirst”

minimumchromaticity


not so short bunches & near head-on collision

triplet magnetsD0 dipole

near head-on collisionbut large separation

triplet magnets

D0 dipole

IR schemes with D0 dipole deep inside detector (e.g., ~3 m from IP)

IR schemes with Q0 doublet deep inside detector (7.5 or 13 m from IP)

short bunches & minimum crossing angle & BBLR

crab cavities & large crossing angle

crab cavitytriplet

magnetstriplet magnetsBBLRQ0 doublet

Q0 doublet

triplet quadsmuch easier,less Q’,could be combinedwith D0

less LRcollisions.no geometriclumi. loss


higher-luminosity IR opticsweb site

http://care-hhh.web.cern.ch/care-hhh/SuperLHC_IRoptics/IRoptics.html

Candidate solutions:Combined function NbTi magnets with large l* (O. Bruning)Dipole first options with Nb3Sn (CERN & FNAL)Quad 1st Nb3Sn (T. Sen)Quad 1st “pushed” NbTi (O. Bruning, R. Ostojic, F. Ruggiero)Quad 1st with detector-integrated dipole (J.-P. Koutchouk)Quad 1st flat beam (S. Fartoukh)Quad 1st Nb3Sn or NbTi plus crab cavities (R.Tomas & F.Z.)Detector-integrated quadrupole doublet (E. Laface, W. Scandale, et al)

Rating criteria: aperture, energy deposition, technology, chromatic correction, beam-beam compensation,…,risks, development time scales, operational difficulties




(5) intensity limitations


ultimate LHC intensity limitations

• electron cloud• long-range & head-on beam-beam effects• collimator impedance & damage• injectors • beam dump & damage• machine protection• …


electron cloud in the LHC

schematic of e- cloud build up in the arc beam pipe,due to photoemission and secondary emission

[Courtesy F. Ruggiero]


arc heat load vs. spacing, Nb=1.15x1011, ‘best’ model

cooling capacity

R=0.5


long-range beam-beam collisions perturb motion at

large transverse amplitudes, where particles come close to opposing beam

may cause high background, poor beam lifetime

increasing problem for SPS, Tevatron, LHC,...

#LR encountersSPS 9Tevatron Run-II 70LHC 120


long-range beam-beam compensation by wire

prototype wire compensator “BBLR” installed in the SPS


crab voltage compared with bunch-shortening rf

crab cavity 100-1000x more effective than bunch-shortening rf!

crab cavities


KEKB Super-KEKB

ILC Super-LHC

x* 100 m 70 m 0.24 m 11 m

c 22 mrad 30 mrad 10 mrad 1 mrad

t 6 ps 3 ps 0.03 ps 0.002 ps

IP offset of 0.2 x*

IP offset of 0.6 nm, ~5x10-5 *

crab-cavity timing tolerance jitter tolerances

cIPcnxtmax2

(0.02 ps XFEL!)

tight jitter tolerance might prevent this scheme


graphite collimator impedance renders nominal LHC beam unstable

stability border(s) fromLandau octupoles

complex coherent tune shift plane

+ 43 collimators

resistive wall& broadband

Elias Metral LHC is limited to 40% of nominal intensity until “phase-2 collimation”


LHC phase-2 collimation options• high chromaticity and/or transverse feedback

(poor lifetime & emittance growth)• consumable low-impedance collimators (rotating

metal wheels; prototype from US LARP / SLAC to be installed in 2008)

• nonlinear collimation; pairs of sextupoles to deflect halo particles to larger amplitudes & open collimator gaps

• use crystals to bend halo particles to larger amplitudes & open collimator gaps

several proposed solutions


Channeling in flat crystal

U0

U0

U0

U0

θ1θ1

Channeled

1

0212 )(

2pvU

1

01 )(

2pvU

L

1

0212

12

1

)(21)(21

sinsin

pvUUU

mv

( Landau and Lifshitz, Mechanics)

Y. Ivanov, PNPI


Channeling and reflection in bent crystal

U0

U0

U0

U0

U0

θ1

θ3

θ2

Reflected

Channeled

LL Rd 3

2

Rd

212

Rd

LL 23

L 1

Y. Ivanov, PNPIreflecting crystals couldserve as primary collimators


crystal channeling & reflection demonstrated in SPS H8 -12.09.2006

Si-strip detector65 m behindCrystal

400 GeV p

10-rad reflectionover 1 m distance ↔~20000 T field!

>99% efficiency

channeledreflected

unperturbedor scattered


(6) injector upgrade


injector upgrade - motivationsraising beam intensity (higher bunch charge, shorter spacing etc.), for limited geometric aperture, L~N, may be essential for alternative scheme

reduction of dynamic effects (persistentcurrents, snapback, etc.)

→ improvement of turn-around time byfactor ~2, effective luminosity by ~50%

benefit to other CERN programmes ( physics, beams,…)


LHC injector upgradeSPS+

extraction energy 450 GeV →1 TeV PS2 or PS2+

extraction energy 26 GeV → 50 or 75 GeV LHC+

injection energy 450 GeV → 1 TeV

Super ISR is alternative to Super PS

Superferric ring “pipetron” in LHC tunnel is alternative to Super SPS – issue: detector bypass


parameter lists for new injectors under construction


PS2?

Super-SPS

Super-LHC

Super-Transferlines

Upgraded CERN Complexfast cycling dipoles for

Super-LHC injectors

PS2


(7) towards higher energy


ultimate LHC “upgrade”: higher beam energy

7 TeV→14 (21) TeV?

R&D on stronger magnets


0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Training quench number

Mag

netic

fiel

d (T

)

Next European Dipole

Six institutes: CCLRC/RAL (UK), CEA/DSM/DAPNIA (France), CERN/AT (International), INFN/Milano-LASA & INFN/Genova (Italy), Twente University (the Netherlands), Wroclaw University (Poland).Three s.c. wire manufacturers (also contributing financially): Alstom/MSA (France), ShapeMetal Innovation (the Netherlands), Vacuumschmelze (now European Advanced Superconductors, Germany)

proof-of principle & world record: 16 T at 4.2 K at LBNL (in 10 mm aperture).

(S. Gourlay, A. Devred)

develop and construct a large-aperture (up to 88 mm), high-field (up to 15 T) dipole magnet model that pushes the technology well beyond present LHC limits.

European Joint Research Activity

http://www.tn.utwente.nl/lt/images/nedlogo1.jpg


proposed design of 24-T block-coil

dipole for LHCenergy tripler

P. McIntyre, Texas A&M, PAC’05

magnets are getting more efficient!


(8) questions to ATLAS


questions to ATLAS

• is the back up solution with peak pile up of 500 events per crossing a viable option?

• can “slim" s.c. magnets be installed deep inside the upgraded ATLAS detector, and, if so, under which boundary conditions, such as envelope, volume, material, or fringe field?


(9) summary


nominal LHC is extremely challengingthree paths to 10x higher luminosityLHC experience will determine the choice IR upgrade alone: factor 2-3 increase; integration of D0 or Q0 in ATLAS?

questions of joint interestraising beam intensity: factor ~4 gainnew injectors: ~3x higher peak & average luminosity; 1st step of energy upgradevigorous R&D programme needed


Francesco Ruggiero 2008: LHC Upgrade Conceptual Design Report2010: LHC Upgrade Technical Design Report2015: New IR, Beam-Beam Compensation>2015: Luminosity ~5x1034 cm-2s-1


thank you for your attention!

Machine Plans for the LHC Upgrade

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