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LEP3 Machine Design Options Frank Zimmermann LEP3 Day, 18 June 2012 work supported by the European...

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LEP3 Machine Design Options Frank Zimmermann LEP3 Day, 18 June 2012 work supported by the European Commission under the FP7 Research Infrastructures project EuCARD, grant agreement no. 227579 cern.ch/accnet
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LEP3 Machine Design Options

Frank ZimmermannLEP3 Day, 18 June 2012

work supported by the European Commission under the FP7 Research Infrastructures project EuCARD, grant agreement no. 227579

cern.ch/accnet

LEP3 history in a nutshell• “LEP3” idea raised by Alain Blondel at Grenoble

EPS-HEP ECFA session in July 2011 • LEP3 paper with beam parameters submitted to

arXiv on Christmas’ Eve 2011• “SuperTRISTAN” proposals by Katsunobu Oide in

January/February 2012• LEP3 was a parenthesis at Chamonix’12 • Lots of interest in LEP3 poster at IPAC’12 • 18 June 2012: first LEP3 day

LEP3 at IPAC’12

key parameters

beam energy: ≥120 GeV luminosity in each of two experiments:≥ 1034 cm-2s-1 at the ‘Higgs energy’ (~240 GeV c.m.)≥ 1035 cm-2s-1 at 2xMW (~160 GeV c.m.)

≥ 5x1035 cm-2s-1 at the Z pole (~90 GeV c.m.)

LEP3 circular Higgs factory (ee-> ZH)

• installation in the LHC tunnel “LEP3” + inexpensive (<0.1xLC)+ tunnel exists+ reusing ATLAS and CMS detectors+ reusing LHC cryoplants- interference with LHC and HL-LHC

• new larger tunnel “DLEP” or “TLEP”+ higher energy reach+ decoupled from LHC and HL-LHC operation and construction+ tunnel can later serve for HE-LHC (factor 2-3 in energy from

tunnel alone) with LHC remaining as injector- 3-4x more expensive (new tunnel, cryoplants, detectors?)

two options

LEP3 double ring

Sketch of LEP3 double ring [1]: a first ring accelerates electrons and positrons up to operating energy (120 GeV) and injects them at a few minutes interval into the low-emittance collider ring, which includes high luminosity 1034 cm-2 s-1 interaction points.

A. Blondel

LHC tunnel cross section with space reserved for a future lepton machine like LEP3 [blue box above the LHC magnet] and with the presently proposed location of the LHeC ring [red]

arc optics• same as for LHeC: ex,LHeC<1/3 ex,LEP1.5 at equal beam energy,• optical structure compatible with present LHC machine• small momentum compaction (short bunch length)• assume ey/ex ~5x10-3 similar to LEP (ultimate limit ey ~ 1 fm from opening angle)

RF • RF freqeuncy 1.3 GHz• ILC-type RF cavities high gradient (20 MV/m assumed, 2.5 times LEP gradient)• total RF length for LEP3 at 120 GeV similar to LEP at 104.5 GeV• short bunch length (small b*

y) • cryo power <1/2 LHC

synchrotron radiation • energy loss / turn: Eloss[GeV]=88.5×10−6 (Eb[GeV])4 /ρ[m]. • higher energy loss than necessary • arc dipole field = 0.153 T• compact magnet • critical photon energy = 1.4 MeV• 50 MW per beam (total wall plug power ~200 MW ~ LHC complex)→4x1012 e±/beam

LEP3 key parameters

LHeC Conceptual Design Report

M. Klein

LEP2 LHeC LEP3 DLEPbeam energy Eb [GeV] circumference [km] beam current [mA] #bunches/beam #e−/beam [1012] horizontal emittance [nm] vertical emittance [nm] bending radius [km] partition number Jε momentum compaction αc [10−5] SR power/beam [MW] β∗

x [m] β∗

y [cm] σ∗

x [μm] σ∗

y [μm] hourglass Fhg

ΔESRloss/turn [GeV]

104.526.7442.3480.253.11.118.5111.552703.50.983.41

6026.710028085652.52.61.58.1440.181030160.990.44

12026.77.244.0250.102.61.58.1500.20.1710.320.676.99

12053.414.46016.0100.055.21.52.0500.20.1450.220.753.5

LEP3/DLEP parameters in comparison -1

LEP2 LHeC LEP3 DLEPESR

loss/turn [GeV] VRF,tot [GV] dmax,RF [%]ξx/IP ξy/IPfs [kHz] Eacc [MV/m] eff. RF length [m] fRF [MHz] δSR

rms [%] σSR

z,rms [cm] L/IP[1032cm−2s−1] number of IPs beam lifetime [min] ϒBS [10−4] nγ/collision DdBS/collision [MeV] DdBS

rms/collision [MeV]

3.413.640.770.0250.065 1.67.54853520.221.611.2543600.20.080.10.3

0.440.50.66N/AN/A0.6511.9427210.120.69N/A1N/A0.050.160.020.07

6.9912.04.20.090.083.912060613000.230.23107216100.603348

3.54.65.00.050.050.9141837613000.160.1714222280.251226

LEP3/DLEP parameters in comparison -2

IR designlarge aspect ratio sx/sy ~200 to limit beamstrahlung

b*y ~ 1 mm:• close to the value giving the maximum geometric luminosity for sz ~ 2-3 mm (hourglass effect);• realized by

o short free length from the IP, l* ~ 4 mo quadrupole length ~ 4 mo quadrupole gradient ~ 17 T/m o and aperture (radius) ~ 5 cm (>20σy)

quadrupoles inside CMS?J. NashCARE-HHHIR’07

Had Barrel: HB

Had Endcaps:HE

Had Forward: HF

HB

HE

HF

HO

The important regions for forward jet tagging are in HE/HF

The important regions for forward jet tagging are in HE/HF

10.8m10.8m14.3 m14.3 m

3.0 m3.0 m6.5 m6.5 m

z=4.0-10.0 mRmax≥40 cm

quadrupoles inside ATLAS?

z=3.49-4.58 mrmax=18 cm

z=6.8-8.66 mrmax=43 cm

z=8.69-12.870 mrmax=87 cm

M. NessiCARE-HHHIR’07

z=12.95-18.60 mrmax=150 cm

bunch intensity limitsbeam-beam tune shift up to ~0.1 OK

(see talk by R. Assmann)

TMCI LEP2: limit of 5x1011 at 22 GeV injectionLEP3: gain factor 5.5 from higher energy;

lose factor (1.3/0.7)3 from wakefield (different RF frequency);gain factor >2 from larger Qs

[other: b functions at RF, bunch length?]

=> Nb~1012 OK; 4 bunches per beam

beam lifetimeLEP2: • beam lifetime ~ 6 h • dominated by radiative Bhahba scattering with

cross section s~0.215 barn [11]

LEP3:• with L~1034 cm−2s−1 at each of two IPs:

tbeam,LEP3~16 minutes • additional beam lifetime limit due to

beamstrahlung > 30 minutes if dmax,RF ≥ 4%(see talk by Marco Zanetti)

Upsilon parameter P. Chen, K. Yokoya [7]

beamstrahlung formulae

photons emitted per collision

average energy loss per collision

for LEP3 the longitudinal damping time is 17 turns and the number of collisions per damping time 34

rms energy spread per collisionK. Yokoya [8]

𝛿BS ,rms ≈𝛿BS, ave√0.1389+ 1.146𝑛𝛾

Ψ ≈56

𝑟 𝑒2𝛾𝑁 𝑏

𝛼𝜎𝑧 (𝜎 𝑥+𝜎 𝑦 )

𝑛𝛾≈2.54 [ 2𝜋𝛼𝜎 𝑧

𝜆𝑐𝛾Ψ

(1+Ψ 2 /3 )1/2 ]𝛿BS ,ave ≈1.24 [ 2𝜋𝛼𝜎 𝑧

𝜆𝑐𝛾Ψ 2

(1+(1.5Ψ )2/3 )2 ]

RF momentum acceptance

synchronous phase

overvoltage

momentum acceptance

e+ production rate

top-up interval << beam lifetime→ average luminosity ≈ peak luminosity!

for the top-up to work: we need about 4×1012 e+ every few minutes, or of order 2×1010 e+ per second

for comparison: LEP injector complex delivered of order 1011 e+ per second [12]

ramping speed of accelerator ring

nominal ramp rate of LEP: 500 MeV/s [13]

at the same speed acceleration to 120 GeV would take less than 4 minutes

this would be sufficient, but faster ramp rate would be even better for maintaining a constant luminosity

two ambitious time schedules

LEP3 robustness & novelties

storage-ring colliders: well-established, robust technology novel features of LEP3: • 15% more energy than LEP2• top-up injection• ultralow vertical b* (but still 3-4 x SuperB)• significant beamstrahlung

LEP3 R&D • 3-D integration in LHC tunnel & cohabitation with HL-LHC and LHeC; RF

integration; • beam dynamics studies and optics design for the collider ring; HOM

heating w. large bunch currents and short bunch lengths; vertical emittance tuning, single-bunch charge limits, longitudinal effects for Qs ~ 0.35, low beta insertion with large momentum acceptance, parameter optimization, beam-beam effects, including beamstrahlung, and top-up scheme

• optics & beam dynamics for accelerator ring• magnets: collider-ring dipole magnet, acc.-ring dipole, and low-beta quad.; • 100 MW SR effects• SRF & cryogenics; optimum RF gradient & RF frequency; • engineering study of new larger tunnel for DLEP or TLEP • cost and performance comparison double vs single ring; • injector complex, including e+ source• dual use LEP3 and LHeC• MDI; integration of warm low-beta quadrupoles inside ATLAS & CMS • detector performance and upgrade studies • LEP3 physics studies

Synergies: LHeC, HP-SPL, XFEL, HE-LHC

conclusions & questions

circular Higgs factory with 240 GeV c.m. and L~1034 cm-2s-1 appears possible in the LHC tunnel or in a larger tunnel

both LEP3 and/or DLEP/TLEP look feasible

is such machine important for particle physics?- going much beyond 120 GeV looks challenging, in

particular in the LHC tunnel- how critical are H-H-Z production & t-t studies?

which of the two options is more realistic/preferred?

can LEP3/DLEP wait until after the HL-LHC (~2035)?

circular Higgs factories become popular around the world

LEP3 2011

SuperTristan 2012LEP3 on LI, 2012

LEP3 in Texas, 2012

References:

[1] A. Blondel, F. Zimmermann, ‘A High Luminosity e+e- Collider in the LHC tunnel to study the Higgs Boson,’ V2.1-V2.7, arXiv:1112.2518v1, 24.12.2011[2] C. Adolphsen et al, ‘LHeC, A Large Hadron Electron Collider at CERN,’ LHeC working group,

LHeC-Note-2011-001 GEN.[3] H. Schopper, The Lord of the Collider Rings at CERN 1980- 2000, Springer-Verlag Berlin Heidelberg 2009[4] K. Oide, ‘SuperTRISTAN - A possibility of ring collider for Higgs factory,’ KEK Seminar, 13

February 2012[5] R.W. Assmann, ‘LEP Operation and Performance with Electron-Positron Collisions at 209

GeV,’ presented at 11th Workshop of the LHC, Chamonix, France, 15 - 19 January 2001[6] A. Butterworth et al, ‘The LEP2 superconducting RF system,’ NIMA Vol. 587, Issues 2-3,

2008, pp. 151[7] K. Yokoya, P. Chen, CERN US PAS 1990, Lect.Notes Phys. 400 (1992) 415-445[8] K. Yokoya, Nucl.Instrum.Meth. A251 (1986) 1[9] K. Yokoya, ‘Scaling of High-Energy e+e- Ring Colliders,’ KEK Accelerator Seminar, 15.03.2012[10] V. Telnov, ‘Restriction on the energy and luminosity of e+e- storage rings due to beamstrahlung,’ arXiv:1203.6563v, 29 March 2012[11] H. Burkhardt, ‘Beam Lifetime and Beam Tails in LEP,’ CERN-SL-99-061-AP (1999)[12] R. Bossart et al, ‘The LEP Injector Linac,’ CERN-PS-90-56-LP (1990)[13] P. Collier and G. Roy, `Removal of the LEP Ramp Rate Limitation,’ SL-MD Note 195 (1995).

thanks to: • Alain Blondel for getting me involved in this exciting

project and for organizing a LEP3 BBQ tonight!• Katsunobu Oide for his interest and excellent ideas• Mike Koratzinos for many stimulating discussions• Kaoru Yokoya and Valery Telnov for pointing out the

importance of beamstrahlung• Marco Zanetti for addressing the beamstrahlung issue • all speakers and participants of the LEP3 day• Andrzej Siemko for lending us a piece of LEP2 beam pipe• Steve Myers and Jean-Pierre Koutchouk for supporting

the initiative

recruiting an SRF expert for LEP3?

thank you for your attention!


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