Circular e+e- Colliders

John Seeman

SLAC

Snowmass: Lepton Colliders

April 10, 2013

2

Collider Topics

Brief: Existing e+e- colliders

DAFNE

BEPC-II

VEPP-4

VEPP-2000

Brief: Proposed low energy colliders

Charm Tau at Cabibbo-Lab, Tor Vergata, Italy

Charm Tau in Novosibirsk,

Medium energy e+e- collider under construction

SuperKEKB

Potential new high energy colliders

LHeC

Circular Z

Circular Higgs

Circular Top

R&D on technologies and beam dynamics

Potential US Roles

3

Thanks for inputs:

M. Biagini, A. Blondel, A. Bogomyagkov, A. Butterworth, Y.

Cai, J. Fox, Y. Funakoshi, M. Giorgi, E. Jensen, M. Kikuchi,

E. Levichev, K. Ohmi, K. Oide, P. Piminov, P. Raimondi, M.

Ross, M. Sato, D. Schulte, D. Shatilov, D. Shwartz, Y.

Suetsugu, M. Sullivan, T. Suwada, S. Tomassini, U.

Wienands, M. Zanetti, Y. Zhang, F. Zimmermann, M. Zobov

e+e- Collider: New Collision Concepts at Low Energies

1.Round Beams

2.Crab Crossing

3.Large Piwinski Angle

4.Strong RF Focusing

5.Traveling Waist

6.Crab Waist

Tested at VEPP2000, CESR

Tested at KEKB

Tested at DAFNE

[M. Zobov]

SuperKEKB, DAFNE

5

Frascati: DAFNE: Large Piwinski angle and crab waist

DAFNE will run for luminosity for at least the next two to three years.

6

IHEP: BEPC-II: Crossing angle and new sextupole families

BEPC-II will run for luminosity for the next ~five years, then look at upgrades.

7

Novosibirsk: VEPP-4: New injector soon.

VEPP-4 will run for luminosityfor the foreseeable future.

8

Novosibirsk: VEPP-2000: round beams & larger tune shifts

VEPP-2000 will continue to increaseluminosity and data collection.

9

Super Charm-Tau Novosibirsk: Overall Layout

Status CDR is completed. Seeking funding.

Longitudinally polarized e- at IP.by* < 1 mm.

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Tau-Charm Factory at Tor Vergata-Frascati, Italy

Design being finalized. Design meeting on Elba in May. Government will decide in Fall 2013.

Luminosity aim is 1035.

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Tsukuba: SuperKEKB: Large crossing angle & small by*

Funded and in construction.

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SuperKEKB Tsukuba: Parameters

Project funded and under construction. First beam in January 2015.

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SuperKEKB Construction

After TiN coatingbefore baking

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Key Facility Features for these e+e- Colliders

Two rings with a single interaction point

Crossing angle at the IP with very flat beams (emittance ratio = ~300)

Need low detector backgrounds

Crab waist collisions

Wigglers to reduce damping times and emittances

Picometer-vertical and nanometer-horizontal emittances

Longitudinal polarized e- beams at the IP with spin rotators

Low emittance beam with beam-beam effects

Polarized beam with strong beam-beam effects

High currents:

Coherent Synchrotron Radiation (CSR)

Electron Cloud Instability ECI

Fast Ion Instability FII

Low impedance vacuum chambers

High power vacuum chambers

15

CERN: LHeC-ERL: Three passes: 60 GeV e- at IP

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CERN: LEP3, TLEP, VHE-LHC: Expanding CERN’s complex

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Luminosity Scaling (M. Zanetti)

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Circular e+e- Higgs factories LEP3 & TLEP

luminosity formulae & constraints

𝐿=𝑓 𝑟𝑒𝑣𝑛𝑏𝑁 𝑏

2

4𝜋 𝜎𝑥𝜎 𝑦

=( 𝑓 𝑟𝑒𝑣𝑛𝑏𝑁 𝑏)(𝑁 𝑏

𝜀𝑥) 14𝜋 1

√𝛽𝑥 𝛽𝑦

1

√𝜀𝑦 /𝜀𝑥

𝑁𝑏

𝜀𝑥=𝜉 𝑥2𝜋𝛾 (1+𝜅𝜎 )

𝑟 𝑒

( 𝑓 𝑟𝑒𝑣𝑛𝑏𝑁 𝑏)=𝑃𝑆𝑅𝜌

8.8575×10−5mGeV−3

𝐸4

𝑁 𝑏

𝜎 𝑥𝜎𝑧

30𝛾𝑟𝑒2

𝛿𝑎𝑐𝑐𝛼<1

SR radiation power limit

beam-beam limit

>30 min beamstrahlung lifetime (Telnov) → Nb,bx

→minimize ke=ey/ex, by~bx(ey/ex) and respect by≈sz

F. Zimmermann

Comparison of Emittances of Colliders

Existing colliders

Future colliders

From Beam Dynamics Newsletter No. 31Courtesy of F. Zimmermann, H. Burkhardt and Q. Qin

LEP3

TLEP-H

Κ ε=100

Κ ε=500

Κ ε=1000

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TLEP Parameters

Zimmermann et al

22

TLEP Parameters (Cont) Zimmermann et al

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Luminosity and Beam-Beam Parameters (Cornell)

R. Talman

Vertical rms IP spot sizes in nm

LEP2 3500

KEKB 940SLC 500 LEP3 320 TLEP-H 220ATF2, FFTB 73 (35), 77SuperKEKB 50ILC 5 – 8CLIC 1 – 2

LEP3/TLEPwill learn from ATF2 &SuperKEKB

by*:

5 cm→1 mm

TLEP:• with L~5x1034 cm−2s−1 at each of four IPs:

tbeam,TLEP~16 minutes from rad. Bhabha • additional lifetime limit due to

beamstrahlung.

Beam Lifetime

SuperKEKB: t~6 minutes!

Full energy Top-Up Injection.

RF: Top-up injector ring

VRF ≥ 9.7 GV

• (only for quantum lifetime)

SR power very small

• (beam current ~ 1% of collider ring)

Average cryogenic heat load very small

• (duty cycle < 10%)

Power is dominated by ramp acceleration:

• for a 1.6 second ramp length:

TLEP-t

Beam current [mA] 0.054

Energy swing [GeV] 155

Max. SR power/cavity [kW] 6.2

Acceleration power [kW] 18

Max. power per cavity [kW]

24

Well within the 200 kW budget

Butterworth,Jensen

9.00 10 9 9.50 10 9 1.00 10 10 1.05 10 10 1.10 10 10 1.15 10 10 1.20 10 100

1

2

3

4

5

6

VRF V

max,RF

RF voltage requirement is defined by:

Accelerator ring: acceptable quantum

lifetime (very steep function of VRF)

Collider ring: momentum acceptance

needed to cope with beamstrahlung

• 3.0% for TLEP @ 120 GeV

• 4.5% for TLEP @ 175 GeV

RF voltage needed for TLEP (704 MHz)

U0 = 9.3 GeVp = 1.0 x 10-5

E0 = 175 GeVJz = 1.0fRF = 704 MHz

Energy [GeV]

VRF [GV]for τq = 100h

VRF [GV]for δmax,RF

120 2.2 2.7

175 9.7 11.2

||max,RF vs VRF

M. Zanetti (MIT)

4.5% gives some margin

4.5%

RF Parameters LHeC TLEP collider

TLEP inj.

Beam energy [GeV] 60 175 175Frequency [MHz] 720 or 800Total voltage [GV] 20 12 12Av gradient [MV/m] 20 20 20Eff. RF length [km] 1 0.6 0.6#cavities 1000 600 600RF efficiency (wall→beam)

55% 55% 55%

Power throughput [MW]

17 110 10 (peak)

Power / cavity [kW] 17 183 17

Energy efficiency

High voltage power converter

• thyristor 6 pulse: 95%- AC power quality, DC ripple @ multiples of 50 and 300 Hz

• switched mode: 90%- lower ripple on the output, and/or smaller size

Klystron: 65%

• if run at saturation as in LEP2

• i.e. no headroom for RF feedback

RF distribution losses: 5 to 7%

• waveguides, circulators

Overall RF efficiency (wall to beam) between 54% and 58%

without margin for RF feedback

Power consumption for TLEP* at 120 GeV (MW)

TLEP

Wall-plug RF power 44 (1)

RF cryo power 6 (2)

Magnet system power 6 (3)

Cooling and ventilation 30 (4)

Experiments 25 (5)

General services 15 (5)

SPS & PS as pre-injectors (20 & 3.5 GeV)

5 (6)

e-/e+ source & pre-pre-injector 1(7)

Total 132

Mike Koratzinos & F.Z.

Power Consumption for TLEP at 175 GeV (MW)

TLEP

Wall-plug RF power 218 (1) [181 w/o RF feedback]

RF cryo power 24 (2)

Magnet system power 6 (3)

Cooling and ventilation 60 (4)

Experiments 25 (5)

General services 15 (5)

SPS & PS as pre-injectors (20 & 3.5 GeV)

5 (6)

e-/e+ source & pre-pre-injector 1(7)

Total 354 [318 w/o RF feedback]

(1

Mike Koratzinos & F.Z.

Need to add 80 km synchrotron power.

RF System Overall

An RF system based on 700 MHz SC cavity technology such

as being developed for eRHIC, SPS, ESS seems to be a good

choice.

• ongoing R&D at BNL, CERN, ESS for 704 MHz cavities and

components

• RF wall-plug to beam efficiency around 54 – 58% (w/o cryo)

• total power consumption for 175 GeV around 220 MW including

cryogenics, resulting in efficiency around 48 – 51%.

Open questions and R&D necessary

• fundamental power couplers: R&D ongoing

• HOM damping scheme: study needed

• low level RF & feedback requirements: study needed

• construction cost?

Butterworth, Jensen

TLEP Overall Components

tunnel SRF system cryoplants magnets injector ring detectors

The tunnel is main costThe RF is main system

Zimmermann

34

Tunnel costs: 80 km

Zimmermann

TLEP cost breakdown – extremely rough (GEuro)TLEP

Bare tunnel 3.1 (1)

Services & Additional infrastructure (electricity, cooling, ventilation, service cavern, RP, surface structure, access roads)

1.0(2)

RF system 1.0 (3)

Cryo system 1.0 (4)

Vacuum system & RP 0.5(5)

Magnet system for collider & injector ring 0.8(6)

Pre-injector complex SPS reinforcements 0.5

Total 7.9

(1): J. Osborne, Amrup study(2): very rough guess, conservative escalated extrapolation from LEP(3): B. Rimmer, SRF cost per GeV or per Watt for CEBAF upgrade, 2010(4): ½ LHC system [also, possibly some refurbished LHC plants could be reused](5): factor 2.5 higher than KEK (K. Oide) estimate for 80 km ring(6): 24,000 magnets for collider & injector; cost per magnet 30 kCHF (LHeC); 10% added; no cost saving from mass production assumedNote: detector costs not included

preliminary – not endorsed by anybody(F. Zimmermann)

TLEP/LEP3 key beam issues (Zimmermann)

SR handling and radiation shielding optics effect of energy sawtooth

[separate arcs?! (K. Oide)] beam-beam interaction for large Qs

and significant hourglass effect by*=1 mm IR with large acceptance TERA-Z operation (impedance effects

& parasitic collisions)

→ Conceptual Design Study by 2014/15!

1980 1990 2000 2010 2020 2030

LHC Constr. PhysicsProto.Design, R&D

HL-LHC Constr. PhysicsDesign, R&D

VHE-LHC Constr.Design, R&D

tentative time line

2040

TLEP Constr. PhysicsDesign, R&D

Physics

LHeC& SAPPHiRE?

Constr. PhysicsDesign, R&D

Draft work topics: TLEP accelerator (Zimmermann)

parameter optimization with regard to lifetime and luminosity, at different energies, & different tunnels

RF system design, prototyping & integration for collider and accelerator ring

optics design for collider ring including low-beta IRs, off-momentum dynamic aperture, different energies

beamstrahlung: lifetime, steady state beam distribution, dependence on tune etc.

beam-beam interaction with large hourglass effect

emittance tuning studies, errors, tolerances, etc.

optics design and beam dynamics for the accelerator ring, ramping speed etc

impedance budget, CSR, instabilities cryogenics system design

magnets design: collider ring dipole, accelerator ring dipole, low-beta quadrupole

radiation, shielding, cooling for 100 MW SR power

vacuum system design engineering study of 80-km tunnel design of injector complex including e+

source, and polarized e- source machine detector interface, integration of

accelerator ring at detector (s), low-beta quadrupoles, shielding (e.g. against beamstrahlung)?

injection scheme polarization, Siberian snakes, spin

matching, acceleration & storage, polarized sources

(19 September 2012)

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F. Zimmermann comments April 4, 2013:

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Seeman: Interaction Point Design

Key issues: 1 mm to 300 micron scale by*, large betas in IR quadrupoles,

quadrupoles inside the detector, collision feedback, vacuum chamber design,

magnet tolerances, alignment and jitter tolerances, crab cavities, crab waist,

US relevance: LHC, Muon collider, ILC, Higgs factory

Test accelerators/facilities: SuperKEKB, CESR-TA, PETRA-3, vibration

stabilization facility

Technologies:

100+ Hz IP dither feedback on luminosity

Superconducting magnets

Permanent magnets

Power supply stability

Vibration control

Non-linear optics

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Seeman: Machine Detector Interface

Key issue: Synchrotron radiation backgrounds, lost particle

backgrounds, SR heating of vacuum chambers, radiation

damage/lifetime of detectors, sensor occupancy, luminosity

measurement.

US relevance: LHC, Muon collider, ILC, Higgs factory

Test accelerators/facilities: SuperKEKB, LHC, lab tests of

high power vacuum chambers, lab tests of detector lifetime

Technologies:

IP vacuum pumping

Advanced masking

Rapid luminosity feedback

Detector design

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Seeman: Low Emittances

Key issue: Component tolerances, vibration control, emittance measuring

hardware, active feedbacks, field nonlinearities.

US relevance: ILC, Ultimate Storage Ring

Test accelerators/facilities: SuperKEKB, PETRA-3, CESR-TA, NSLS-II, lab tests

of x-ray size monitors

Technologies:

300 to1 emittance tuning techniques

Coherent Synchrotron Radiation CSR simulations and

measurements

Fast Ion Instability FII simulations and measurements

Intra-Beam Scattering IBS simulations and measurements

Electron Cloud Instability ECI simulations and measurements

Effects of spin rotators.

Effects of beam-beam interaction

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Seeman: High Current Effects

Key issues: Beam stability, high power RF, high power vacuum

components, AC wall efficiency, injector capabilities, I> 1 A.

US relevance: LHC, muon collider, muon storage ring, Project X, Ultimate

Storage Ring

Test accelerators/facilities: SuperKEKB, CESR-TA

Technologies:

Better bunch feedbacks

ECI control

IBS mitigations

FII mitigations

More efficient klystrons

High power cavities

Longitudinal beam feedback

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Seeman: Longitudinally Polarized e- Beam at the Interaction Point

Key issue: Injected polarization, beam lifetime, polarization

lifetime, spin rotators, polarization measurements, effect on IP

optics, beam-beam effect on polarization.

US relevance: ILC

Test accelerators/facilities: SuperKEKB?, VLEPP-2000?

Technologies:

Siberian snakes

Solenoidal rotators

Beam-beam depolarization diagnostics

Spin manipulation in the Damping Ring and Linac.

e- polarized source

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Seeman: General Observations Lepton e+e- Colliders

Lattices:

x-y chromatic coupling in the IR is important: skew

sextupoles.

Sextupole and skew quadrupole coupling corrections in IR

More studies of IR error tolerances needed.

Instabilities:

More work on e-cloud to allow more bunches.

Beam-Beam Calculations:

Need mores studies of non-linear beam dynamics.

Parasitic crossing studies

Beam lifetimes:

Short beam lifetimes expected in the next collider (~10

minutes) with continuous top-off needed.

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Seeman: Personal View

-Each region should follow their desires and strengths.

-Any new large accelerator should have a viable additional

energy or physics reach.

-Every region could build all these machines, but likely:

Asia: 250 GeV ILC capable of going to 1 TeV.

Europe: 250 GeV TLEP with a VHE-LHC add-on.

Americas: Muon Collider or PWFA Collider (equal for now)

with reach to several TeV.