The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.

HL-LHC Optics Configuration vs. Experiment Desiderata

Bernhard Holzer for the WP2, Task2.2 Team

B. Dalena, A. Bogomyagkov, R. Appleby, A. Fauss-Golfe, J. Payet, A. Chance’, K. Hock, M. Korostelev, R. deMaria, J. Resta, C. Milardi, L. Thompson, M.

Thomas, A. Wolski

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HL-LHC Parameter List

Parameter nominal 25ns 50nsNb 1.15E+11 2.20E+11 3.50E+11

nb 2808 2808 1404

Ntot 3.2E+14 6.2E+14 4.9E+14

beamcurrent[A] 0.58 1.12 0.89

x-ingangle[mrad] 300 590 590

beamseparation[σ] 9.9 12.5 11.4

β*[m] 0.55 0.15 0.15

εn[μm] 3.75 2.50 3

εL[eVs] 2.51 2.51 2.51

energyspread 1.20E-04 1.20E-04 1.20E-04

bunchlength[m] 7.50E-02 7.50E-02 7.50E-02

IBShorizontal[h] 80->106 18.5 17.2

IBSlongitudinal[h] 61->60 20.4 16.1

Piwinskiparameter 0.68 3.12 2.85

geom.Reductionfactor'R' 0.83 0.305 0.331

beam-beam/IPwithoutCrabCavity 3.10E-03 3.28E-03 4.72E-03

beam-beam/IPwithCrabcavity 3.75E-03 1.08E-02 1.43E-02

PeakLuminositywithoutleveling[cm-2s-1] 1.0E+34 7.4E+34 8.5E+34

VirtualLuminosity:Lpeak/R[cm-2s-1] 1.2E+34 24E+34 26E+34

Events/crossingwithoutleveling 19->28 210 475

LevelledLuminosity[cm-2s-1] - 5E+34 2.50E+34

Events/crossingwithleveling *19->28 140 140

x-angle

β*ε

L0

ideal luminosity formula

loss factor due to crossing with an angle(pure geometric effect ... but large)

★★★★★★

* R

≈ 0.33

Luminosity & Loss Factor

R * H

Luminosity & Beam Optics

The HL-LHC Lattice & Optic has to establish β* at IP1 & 5 to reach a “virtual luminosity” of

and for the given bunch intensities this means

to small for the IR1 / 5 matching section squeeze starts at neighboring sectors (“ATS”) .

€

ˆ L (25ns) = 24 *1034 cm−2s−1

ˆ L (50ns) = 26*1034 cm−2s−1

€

βx* = β y

* ≈15cm

IP2IP8 IP1

HL-LHC Wish-List of the Experiments

5

present Luminosity HL-max Luminosity HL-leveled Luminosity

IR 1 / 5 0.7*1034 2.4 ... 2.6*1035 2.5 ... 5 *1034

IR 2 6*1030 1 *1033 1 *1031

IR 8 2*1032 1 *1034 1 ... 2 *1033

Establish a set of different beam optics (i.e. β*) that combines the HL-LHC options in IR1,5 with the boundary conditions for IR2, IR8.

set up four baseline opticsbased on assumptions on aperture & magnet technique

170

HL-LHC Wish-List of the Experiments

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to be discussed ... within WP2 & Experiments

Lmax β* Llev β*

IR1,5 25ns 2.4*1035 0.15 5.0*1034 0.65

50ns 2.6*1035 0.15 2.5*1034 1.35

IR8 1.1*1034 3 1-2*1033 15-30

IR2 1.1*1033 30 1.1*1031 - ? -

HL-LHC Beam Optics... and as latest version: 150mm Triplet Aperture / 140T/m Gradient

Problem & Solution: ATS combines the different LHC Interaction Regions.a large variety of beam optics studied & optimised in IP8 / IP2bog_150_0100_0100_3000_3000.madx β*(IP8) = 3m standard ATS, roundbog_150_0050_0200_3000_3000.madx β*(IP8) = 3m standard ATS, flat_xybog_150_0050_0200hv_3000_3000.madx β*(IP8) = 3m standard ATS, flat_yxbog_150_5500_5500_10000_10000.madx β*(IP8) = 10m ATS_injectionbog_150_0400_0400_0500_0500.madx β*(IP8) = 50cm ATS ions

each optics has to be „implemented“ into the overall LHC lattice & optics.

court. A. Bogomyagkov

the “ATS Squeece Optics (15cm/15cm/10m/10m)

IP3, Standard FoDo Optics IP1, ATS Optics

Find an otpics solution that is feasible for the Luminosity upgrade and guarantees adequate conditions for the ALICS and LHCb experiment at the same time.

HL-LHC Optics in IR2

IP2

HL-LHC optics: injection to proton collisions

IR8b*=10 m

IR1b*=5.5 m

IR2b*=10 m

IR4 IR5b*=5.5 m

IR6

IR8b*=3 m

IR1b*=0.4 m

IR2b*=10 m

IR4 IR5b*=0.4 m

IR6

IR8b*=3 m

IR1b*=0.15 m

IR2b*=10 m

IR4 IR5b*=0.15 m

IR6

Injection optics

Transition topre-squeeze optics

ATS tocollision optics

250 - 300 fb-1 per year

find a smooth transition without (too many) hysteresis problems

5.5m injection optics

40cm pre-squeeze optics

15cm ATS optics

HL-LHC Optics in IR1, 5

Standard low-beta-Squeeze

ATS-Squeeze

HL-LHC Optics in IR1, 5

Optics Transition via ATS is “smooth by definition”.

Optics Transition Injection – Pre-Squeeze needs TLC optimisation

court. M. Korostelev

* F

Lattice, Loss Factor & Crab Cavities

F

Optimse the lattice (i.e. quad positions) to gain crab effectiveness.

Study of additional quadrupoles at Q5 / Q6 / Q7 ...

Q4 / Q5 / Q6 in triplet configuration & add. Q7 ... allows for much larger βs at the Crab Cavities

add. Quad at Q5: no big change

additional k-strength needed at Q7

Lattice Optimisation for Crab Cavitiescourt. B. Dalena

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space needed for crab cavity installation enhanced β function needed for crab cavity effectivenessre-shuffling the matching quads, strengthening Q7(170T/m, 15cm Otpics)

Lattice & Crab Cavities

increase the beta function at the location of the crab cavities

CRAB side and beamHL-LHC baseline [MV]

Best optimization [MV]

Horizontal L5 Beam 1 11.8 8.0

Horizontal R5 Beam 1 13.4 8.2

Horizontal L5 Beam 2 13.4 8.2

Horizontal R5 Beam 2 11.8 8.0

court. B. Dalena et al

Lattice & Crab Cavities

Standard Bump for Crossing angle & beam separation closes at Q5 ... and leads to (varying) orbit offsets at the crab cavity location.-> bump closure by strong dipole magnet at D2.-> Alternative: transverse cavity positioning feedback following the beam orbits

court. R. DeMaria

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Crossing Angles & Apertures

2

00

( )s

sβ ββ

Increasing β-function in the mini-beta drift leads to large crossing angles ... to avoid parasitic bunch encounters.

*

s s

β0

crossing angle bump for the case:β=15 cm, ε=3.0μm, +/- 10σ

crossing angle bump for the case:β=15 cm, ε=3.0μm, +/- 10σwith location of parasitic 25ns encounters

Aperture need determined by optics, emittance, orbit tolerances, crossing angleWORK IN PROGRES, LEB-MeetingsM.Gallilee

Crossing Angles & Apertures IR1 & 5

eff crossing angle = -2.27 mrad

collisions at IP, separation at all paras. encounters

Special Problem: 25ns at IR8Injection: horizontal crossing-angle

LHCb = “good”(... negative kick on beam 1)LHCb = -15.5 ... -2.1mrad b1on_x8 = +1.0 .. -170μrad

separation at IP via vert. 2mm sep bump

horizontal plane vertical plane

Injection: vertical crossing-angle

LHCb = “bad”(... positive kick on beam 1)LHCb = +15.5 ... +2.1mrad on_sep8 = +1.0 ... Δx=2.0mmon_x8vi = 0.8 ...... y’ = 125 μrad

optimisation of crossing angle (keep it SMALL) y’=107μrad emittance (keep it SMALL) εn =2.5closed orbit tolerance (keep it SMALL) 3.0mm

collisions at IP avoided via hor. sep bumpseparation ok at paras. encounters 2...4

avoids crossing at IP and paras. encounters 1,2,3

separates the beams from paras. encounters 4

horizontal plane vertical plane

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Open Questions

• Which baseline optics to choose ... hardware R&D will tell

• Follow up of magnet development

• Do we need a 1km Optics ??

• Finally ... the leveling Problem:

β* leveling in IP 1 & 5 ...but then a synchronous β* leveling in IR2 & IR8 will be DIFFICULT

IP2

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Open Questions

Finally ... the leveling Problem:

β* leveling via crab cavity voltage (i.e. crossing angle)

changing the crossingangle reduces the luminositybut does NOT reduce the density of vertices inside the “luminous region”.

β* leveling via closed Orbit Bumps-> special magnets needed (orbit in Crab Cavities)-> beam beam problem ? 20 vertices

2 vertices