Scenarios for the sLHC and the vLHC Walter Scandale, Frank Zimmermann CERN HCP2007 We acknowledge the support of the European Community-Research Infrastructure

Scenarios for the sLHC and the vLHC

Walter Scandale, Frank Zimmermann

CERN

HCP2007We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395)

outline• LHC upgrade: why and when ?• beam parameters• the two selected scenarios for luminosity upgrade– features, – Bunch structure– IR layout, – merits and challenges

• luminosity leveling ?• summary & recommendations for the sLHC

• perspective for higher energy hadron collisions– VLHC at FNAL – dLHC and tLHC at CERN– R&D– possible plans

0

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50

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0 2 4 6 8 10

years

nb-1

IR quadrupole lifetime ≥ 8 years owing to high radiation doses

halving time of the statistical error ≥ 5 y already after 4-5 y of operation

luminosity upgrade to be planned by the middle of next decade

LHC luminosity upgrade: why and when?

How fast performance is expected to increase:

4 y up to nominal L 4 y up to nominal L & 2 y up to ultimate L

4 y up to ultimate

0

2

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0 2 4 6 8 10 12 14 16

years

years to halving the statistical error0

200

400

600

800

1000

1200

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1600

integrated luminosity [fb-1]

LHC luminosity upgrade: the LARP perspective

Courtesy of V. Shiltsev - FNAL

Name Event DateName Event Date55

W. Scandale/F. Zimmermann, 13.02.2007

parameterparameter symbolsymbol nominalnominal ultimateultimate 12.5 ns, short

transverse emittancetransverse emittance [[m]m] 3.753.75 3.753.75 3.75

protons per bunchprotons per bunch NNbb [10 [101111]] 1.151.15 1.71.7 1.7

bunch spacingbunch spacing t [ns]t [ns] 2525 2525 12.5

beam currentbeam current I [A]I [A] 0.580.58 0.860.86 1.72

longitudinal profilelongitudinal profile GaussGauss GaussGauss Gauss

rms bunch lengthrms bunch length zz [cm] [cm] 7.557.55 7.557.55 3.78

beta* at IP1&5beta* at IP1&5 [m][m] 0.550.55 0.50.5 0.25

full crossing anglefull crossing angle c c [[rad]rad] 285285 315315 445

Piwinski parameterPiwinski parameter cczz/(2*/(2*xx*)*) 0.640.64 0.750.75 0.75

peak luminositypeak luminosity LL [10 [103434 cm cm-2-2ss-1-1]] 11 2.32.3 9.2

peak events per crossingpeak events per crossing 1919 4444 88

initial lumi lifetimeinitial lumi lifetime LL [h] [h] 2222 1414 7.2

effective luminosity effective luminosity (T(Tturnaroundturnaround=10 h)=10 h)

LLeff eff [10[103434 cm cm-2-2ss-1-1]] 0.460.46 0.910.91 2.7

TTrun,optrun,opt [h] [h] 21.221.2 17.017.0 12.0


LLeff eff [10[103434 cm cm-2-2ss-1-1]] 0.560.56 1.151.15 3.6

TTrun,optrun,opt [h] [h] 15.015.0 12.012.0 8.5

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

SR heat load 4.6-20 KSR heat load 4.6-20 K PPSRSR [W/m] [W/m] 0.170.17 0.250.25 0.5

image current heat image current heat PPICIC [W/m] [W/m] 0.150.15 0.330.33 1.87

gas-s. 100 h (10 h) gas-s. 100 h (10 h) bb PPgasgas [W/m] [W/m] 0.04 (0.38)0.04 (0.38) 0.06 (0.56)0.06 (0.56) 0.113 (1.13)

extent luminous regionextent luminous region l [cm] 4.54.5 4.34.3 2.1

commentcommentpartial wire

c.

(heat load induced by Sync.Rad + image current larger than the local heat load capacity)

baselineupgradeparameters2001-2005

abandonedatLUMI’06

total heat 15.6 W/m >> 2.4 W/m



parameterparameter symbolsymbol 25 ns, small * 50 ns, long

transverse emittancetransverse emittance [[m]m] 3.75 3.75

protons per bunchprotons per bunch NNbb [10 [101111]] 1.7 4.9

bunch spacingbunch spacing t [ns]t [ns] 25 50

beam currentbeam current I [A]I [A] 0.86 1.22

longitudinal profilelongitudinal profile Gauss Flat

rms bunch lengthrms bunch length zz [cm] [cm] 7.55 11.8

beta* at IP1&5beta* at IP1&5 [m][m] 0.08 0.25

full crossing anglefull crossing angle c c [[rad]rad] 0 381

Piwinski parameterPiwinski parameter cczz/(2*/(2*xx*)*) 0 2.0

hourglass reduction hourglass reduction 0.86 0.99

peak luminositypeak luminosity LL [10 [103434 cm cm-2-2ss-1-1]] 15.5 10.7

peak events per crossingpeak events per crossing 294 403

initial lumi lifetimeinitial lumi lifetime LL [h] [h] 2.2 4.5


LLeff eff [10[103434 cm cm-2-2ss-1-1]] 2.4 2.5

TTrun,optrun,opt [h] [h] 6.6 9.5


LLeff eff [10[103434 cm cm-2-2ss-1-1]] 3.6 3.5

TTrun,optrun,opt [h] [h] 4.6 6.7

e-c heat SEY=1.4(1.3)e-c heat SEY=1.4(1.3) P [W/m]P [W/m] 1.04 (0.59) 0.36 (0.1)

SR heat load 4.6-20 KSR heat load 4.6-20 K PPSRSR [W/m] [W/m] 0.25 0.36

image current heat image current heat PPICIC [W/m] [W/m] 0.33 0.78

gas-s. 100 h (10 h) gas-s. 100 h (10 h) bb PPgasgas [W/m] [W/m] 0.06 (0.56) 0.09 (0.9)

extent luminous regionextent luminous region l [cm] 3.7 5.3

commentcomment D0 + crab (+ Q0) wire comp.

New upgradescenarios

compromisesbetween# of pile up events and heat load

injector upgrade

Crossing with large Piwinski angle

aggressive triplet

challenges

PAF/POFPA Meeting 20 November 2006LHC Upgrade Beam Parameters, Frank ZimmermannW. Scandale/F. Zimmermann, 19.03.2007

for operation at beam-beam limitwith alternating planes of crossing at two IPs, luminosity equation can be written as

25 ns 50 ns 50 ns

50 ns

where Qbb = total beam-beam tune shift

(the change of Fh-g due to hourglass effect is neglected above)

Luminosity at the beam-beam limit

€

L ≈ πγ nb

γε( ) frev

rp2β *

ΔQbb2 1+ Θ2 FprofileFh − g



luminosity reduction factor from

crossing angle

R 0.85 (nominal LHC)

x

zcR

2 ;

1

12

≡ΘΘ+

=

Piwinski angle



25-ns ultra-low-25-ns ultra-low- upgrade upgrade scenarioscenario stay with ultimate LHC beam stay with ultimate LHC beam

(1.7x10(1.7x101111 protons/bunch, 25 protons/bunch, 25 spacing)spacing)

squeeze squeeze * below ~10 cm in ATLAS & * below ~10 cm in ATLAS & CMS CMS

add early-separation dipoles in add early-separation dipoles in detectors, one at ~ 3 m, the other detectors, one at ~ 3 m, the other at ~ 8 m from IPat ~ 8 m from IP

possibly also add quadrupole-possibly also add quadrupole-doublet inside detector at ~13 m doublet inside detector at ~13 m from IP from IP

and add crab cavities (and add crab cavities (ffPiwinskiPiwinski~ 0), ~ 0), and/or shorten bunches with and/or shorten bunches with massive addt’l RFmassive addt’l RF

new hardware inside ATLAS & CMS, new hardware inside ATLAS & CMS,

first hadron-beam crab cavities first hadron-beam crab cavities

(J.-P. Koutchouk et al)


CMS & ATLAS IR layout for 25-ns option

ultimate bunch intensity & near head-on collision (RΘ1)

stronger triplet magnetsD0 dipole

small-

angle

crab c

avity

Q0 quad’s

l* = 22 m

Magnets

embedded

in the e

xpt.

apparatu

s


challenges: •D0 dipole deep inside detector (~3 m from IP),

•Q0 doublet inside detector (~13 m from IP & slim magnet technology),

•crab cavity for hadron beams (emittance growth ?),

•4 parasitic collisions at 4-5 separation,•“chromatic beam-beam” Q’eff ~ z/(4*),

•poor beam and luminosity lifetime ~ *

merits:•negligible long-range collisions,

•reduced geometric luminosity loss,

•no increase in beam current beyond ultimate

25-ns scenario assessment (accelerator

view point)



50-ns high intensity upgrade 50-ns high intensity upgrade scenarioscenario

double bunch spacingdouble bunch spacing

longer & more intense bunches with longer & more intense bunches with ffPiwinskiPiwinski~ 2~ 2

keep keep *~25 cm (achieved by stronger *~25 cm (achieved by stronger low-low- quads alone) quads alone)

do not add any elements inside do not add any elements inside detectorsdetectors

long-range beam-beam wire long-range beam-beam wire compensation compensation

novel operating regime for hadron novel operating regime for hadron colliderscolliders

(W. Scandale, F.Zimmermann & PAF)

add early-separation dipoles, one at ~ 5 m, the other at ~ 9 add early-separation dipoles, one at ~ 5 m, the other at ~ 9 m from IPm from IP Reduce the current Reduce the current Almost head-on crossing angleAlmost head-on crossing angle

Variant (not yet studied)


CMS & ATLAS IR layout for 50-ns option

long bunches & nonzero crossing angle & wire compensation

wire

compensator

stronger triplet magnets

l* = 22 m


merits:• no elements in detector, no crab cavities,

• lower chromaticity,

• less demand on IR quadrupoles (NbTi possible)challenges:

• operation with large Piwinski parameter unproven for hadron beams,

• high bunch charge,

• beam production and acceleration through SPS,

• “chromatic beam-beam” Q’eff ~ z/(4*),

• larger beam current,

• wire compensation (established last validation in RHIC)

50-ns scenario assessment (accelerator view point)


IR upgrade optics“compact low-gradient” NbTi, *=25 cm

<75 T/m (Riccardo De Maria, Oliver Bruning)

“modular low gradient” NbTi, *=25 cm <90 T/m (Riccardo De Maria, Oliver Bruning)

“low max low-gradient” NbTi, *=25 cm <125 T/m (Riccardo De Maria, Oliver Bruning)

standard Nb3Sn upgrade, *=25 cm ~200 T/m, 2 versions with different magnet parameters(Tanaji Sen et al, Emmanuel Laface, Walter Scandale)

+ crab-waist sextupole insertions? (LNF/FP7)include sextupoles to compansate the glass-hours effect

early separation with *=8 cm, Nb3Sn includes D0; either triplet closer to IP; being prepared for PAC’07 (Jean-Pierre Koutchouk et al)

Use of Q0being finalized for PAC’07 (E. Laface, W.Scandale)

compatiblewith50-nsupgradepath


crab waist scheme

⎟⎟⎠

⎞⎜⎜⎝

⎛−=

cyI

xpH

θ

2

4

1 2

minimizes at s=x/c

focal plane

realization:add sextupoles at right phase distance from IP

initiated and led by LNF in the frame of FP7;first beam tests at DAFNE later in 2007

Hamiltonian


25 ns spacing

50 ns spacing

IP1& 5 luminosity evolution for 25-ns & 50-ns spacing

averageluminosity

initial luminosity peakmay not be useful for physics

Turnaround time 10hOptimized run duration


25 ns spacing

50 ns spacing

IP1& 5 event pile up for 25-ns and 50-ns spacing


new upgrade bunch structures

25 ns

50 ns

nominal

25 ns

ultimate& 25-ns upgrade

50-ns upgrade,no collisions @S-LHCb!

50 ns

50-ns upgradewith 25-ns collisionsin LHCb

25 ns

new altern

ative!

new baseli

ne!

PAF/POFPA Meeting 20 November 2006LHC Upgrade Beam Parameters, Frank ZimmermannF. Zimmermann, W. Scandale, 19.03.2007

S-LHCb collision parametersparameter symbol 25 ns, offset 25 ns, late collision 50 ns, satellites

collision spacing Tcoll 25 ns 25 ns 25 ns

protons per bunch Nb [1011] 1.7 1.7 4.9 & 0.3

longitudinal profile Gaussian Gaussian flat

rms bunch length z [cm] 7.55 7.55 11.8

beta* at LHCb [m] 0.08 3 3

rms beam size x,y* [m] 6 40 40

rms divergence x’,y’* [rad] 80 13 13

full crossing angle c [urad] 550 180 180

Piwinski parameter cz/(2*x*) 3.3 0.18 0.28

peak luminosity L [1033 cm-2s-1] 1.13 2.1 2.4

effective luminosity (5 h turnaround time) Leff [1033 cm-2s-1] 0.25 0.35 0.67

initial lumi lifetime L [h] 1.8 2.8 9

length of lum. region l [cm] 1.6 5.3 8.0

rms length of luminous region:

€

1

σ l2

≈2

σ z2

+θ c

2

2σ *x,y2

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟


luminosity leveling in IP1&5

experiments prefer more constant luminosity, less pile up at the start of run, higher luminosity at end

how could we achieve this?

50-ns higher- scheme:dynamic squeeze, and/ordynamic reduction in bunch length (less invasive)

25-ns low- scheme: dynamic squeeze orNovel proposal under investigation based on the change the crossing angle (G. Sterbini)


constLL ≈= 0constn

LXingevents

b

inel ≈=0/

beam intensitydecays linearly

length of run average luminosity

leveling equations

€

N = N 0 −L0σ totnIP

nb

t

€

trun =ΔN maxnb

Lσ tot nIP

€

Lave =L0

1+L0σ tot nIP

ΔN maxnb

Tturn−around


25 ns, low *,with leveling

50 ns, long bunches, with leveling

events/crossing 300 300

run time N/A 2.5 h

av. luminosity N/A 2.6x1034s-1cm-2


run time 2.5 h 14.8 h

av. luminosity 2.6x1034s-1cm-2 2.9x1034s-1cm-2


run time 9.9 h 26.4 h

av. luminosity 2.6x1034s-1cm-2 1.7x1034s-1cm-2

assuming 5 h turn-around time


25 ns spacing

50 ns spacing

IP1& 5 luminosity evolution for 25-ns & 50-ns spacingwith leveling

averageluminosity


25 ns spacing

50 ns spacing

IP1& 5 event pile up for 25-ns and 50-ns spacingwith leveling



summary summary • two scenarios of L~10two scenarios of L~103535 cm cm-2-2ss-1-1 for which for which heat load and #events/crossing are heat load and #events/crossing are acceptableacceptable

• 25-ns option25-ns option: pushes : pushes *; requires slim *; requires slim magnets inside detector, crab cavities, magnets inside detector, crab cavities, & high gradient large aperture (Nb& high gradient large aperture (Nb33Sn) Sn) quadrupolesquadrupoles and/or Q0 doublet; and/or Q0 doublet; attractive if total beam current is attractive if total beam current is limited; transformed to a 50-ns spacing limited; transformed to a 50-ns spacing by keeping only 1/2 the number of by keeping only 1/2 the number of bunches bunches

• 50-ns option:50-ns option: has fewer longer bunches has fewer longer bunches of higher charge ; can be realized with of higher charge ; can be realized with NbTi technologyNbTi technology if needed ; compatible if needed ; compatible with LHCb ; open issues are with LHCb ; open issues are SPS upgrade SPS upgrade & beam-beam effects at large Piwinski & beam-beam effects at large Piwinski angleangle; luminosity leveling may be done ; luminosity leveling may be done via bunch length and via via bunch length and via * tuning* tuning



recommendationsrecommendations•luminosity levelingluminosity leveling should be should be seriously considered in all cases: seriously considered in all cases: • more regular flow of eventsmore regular flow of events• moderate decrease in average moderate decrease in average

luminosityluminosity

•long-bunch 50-ns option entails long-bunch 50-ns option entails less riskless risk and less uncertainties; and less uncertainties; however with the drawback of the however with the drawback of the larger bunch populationlarger bunch population

•25-ns option is an optimal back up25-ns option is an optimal back up until we have gained some until we have gained some experience with the real LHC experience with the real LHC

•concrete optics solutionsconcrete optics solutions, , beam-beam-beam tracking studiesbeam tracking studies, and , and beam-beam-beam machine experimentsbeam machine experiments are needed are needed for both scenarios for both scenarios

The VLHC versus the LHC energy upgrade

LHC VLHC (20 01)

nominal dou bler tr ipler Sta ge 1 Sta ge 2

Peri me te r , km 26. 7 233

CM Ener gy, TeV 14 28 42 40 175

Dipole f ie ld, T 8 .4 16.8 25. 2 2 10

S upercon ductor Nb Ti Nb 3Sn HTS Nb Ti Nb 3Sn

Fermilab-TM-2149June 11, 2001

www.vlhc.org

Design Study for a Staged Very Large Hadron Collider

Build a long tunnel.Fill it with a “cheap” 40 TeV collider.Later, upgrade to a 200 TeV collider in the same tunnel.– Spreads the cost – Produces exciting energy-frontier physics sooner & cheaper

– Allows time to develop cost-reducing technologies for Stage 2

– vigorous R&D program in magnets and underground construction required.

•This is a time-tested formula for success

Main Ring TevatronLEP LHC

The two Stages of the VLHC

Stage 1 Stage 2

Total Circumference (km) 233 233

Center- of- Mass Energy (TeV) 40 200

Number of interaction regions 2 2

Peak luminosity (cm- 2s- 1) 1 x 1034 2.0 x 1034

Dipole field at collision energy (T) 2 11.2

Average arc bend radius (km) 35.0 35.0

I nitial Number of Protons per Bunch 2.6 x 1010 5.4 x 109

Bunch Spacing (ns) 18.8 18.8

* at collision (m) 0.3 0.5

Free space in the interaction region (m) ± 20 ± 30

Interactions per bunch crossing at Lpeak 21 55

Debris power per IR (kW) 6 94

Synchrotron radiation power (W/m/beam) 0.03 5.7

Average power use (MW) for collider ring 25 100

Parameters of the VLHC

Cost estimate ~ 4 G$o no detectors (2 halls included), o no EDI, o no indirect costs, o no escalation, o no contingency

2001 prices and c.a. 2001 technology. o No cost reduction assumed from R&D o Cost almost independent of the

choice of the B-field

Stage-1 at 40 TeV and 1034 luminosityo large tunnel to be build in the Fermilab area

o total construction time ~ 10 years

o Logistics and management complex

o only 20 MW of refrigeration power, comparable to the Tevatron.

o significant money and time saving by building the VLHC at FNAL

Cost drivers for the stage-1 (at FNAL)

30cm support tube/ vacuum jacketCryo-lines

100kA return bus

vacuum chambers

SC transmission line(100 kA)

2-in-1 warm iron

Superferric: 2T B- field

100kA Transmission Line

Combined function dipole (no quadrupoles needed)

65m Length

Self-contained including Cryogenic System and Electronics Cabling

Warm Vacuum System

Transmission line magnet for Stage-1

The Stage-2 VLHC can reach 200 TeV and 2x1034 or possibly significantly more in the 233 km tunnel. o A large-circumference ring is a great advantage for Stage-2

o A high-energy, high B-field (B > 12 T) VLHC in a small-circumference ring may not be realistic (too much synchrotron radiation).

o To demonstrate feasibility and to reduce cost, there is the need for R&D in the following items

high-field magnet,

vacuum in presence of large radiated power

efficient tunneling

photon stopper.

Stage-2

Superconducting magnets based on Nb3Sn

Stage-2 Dipole Single-layer common coil

Stage-2 Dipole Warm-iron Cosine Q

Magnets for Stage-2

Synchrotron radiation

Beam screen

There is an optimal size of the coolant pipe and of the beam screen temperature for a given synchrotron emission regime

€

Eturn =e2

3ε 0

β 3

r

E

m0c2

⎛

⎝ ⎜

⎞

⎠ ⎟

4

Synchrotron radiation masks look promising.

Preliminary tests already performed at FNAL.

They will decrease refrigerator power and permit higher energy and luminosity.

They are practical only in a large-circumference tunnel.

BEAM SCREEN

SLOT

GAP

PHOTON-STOP

Photon stoppers

PSR<10 W/m/beam peak

tL > 2 tsr

Interaction per cross < 60

L units 1034 cm-2s-1

Optimum Dipole Field

€

Eturn =e2

3ε 0

β 3

r

E

m0c2

⎛

⎝ ⎜

⎞

⎠ ⎟

4

The cutoffs are field too low, not enough damping, field too high, too much synchrad power so required aperture too large.

Luminosity scale

LHC energy doubler 14*14 TeV dipole field Bnom = 16.8 T, Bdesign = 18.5-19.3 T

(10-15% margin)

o superconductor - Nb3Sn

o 10-13 T field demonstrated in several 1-m long Nb3Sn dipole models

o DLHC magnet parameters well above the demonstrated Nb3Sn magnet technology

R&D and construction time and cost estimates o 10+ years for magnet technology development and demonstration

o Magnet production by industry ~ 8-10 years

o High cost for R&D and construction (cost of dipoles > 3GCHF ?)

LHC energy tripler 21*21 TeV

dipole field Bnom = 25 T, Bdesign = 28-29 T (10-15% margin)

o superconductor - HTS-BSCCO (low demand) or Nb3Sn

o Magnet technology to be fully demonstrated

o DLHC magnet parameters well above the demonstrated Nb3Sn magnet technology

Large aperture dipole to accommodate an efficient beam screen

R&D and construction time and cost/risk estimates o 20++ years for magnet technology development and

demonstrationo Extremely high R&D and construction cost and risk

SC cable to be developed, Magnetic coil stress requires innovative dipole cross section

o Magnet production by industry (?) ?? years

LHC, sLHC, DLHC perspective

VLHC perspective

Documents

Scenarios for the sLHC and the vLHC Walter Scandale, Frank Zimmermann CERN HCP2007 We acknowledge the support of the European Community-Research Infrastructure