FCC-ee Design and PerformanceFrank Zimmermann, for FCC collaboration and FCC-ee design team -

Eleonora Belli, Michael Benedikt, Alain Blondel, Anton Bogomyagkov, Manuela Boscolo, Olivier Brunner, Helmut Burkhardt, Iryna Chaikovska, Tessa Charles, Eliana

Gianfelice, Bastian Harer, Ozgur Itasken, Patrick Janot, Roberto Kersevan, Dima El Khechen, Mike Koratzinos, Eugene Levichev, Marian Luckhof, Pavel Martyshkin,

Mauro Migliorati, Alexander Novokhatski, Salim Ogur, Kazuhito Ohmi, Katsunobu Oide, Dmitry Shatilov, Mike Sullivan, Tobias Tydecks and many more

11th FCC-ee Physics Workshop, CERN, 8 January 2019

Work supported by the European Commission under the HORIZON 2020 projects EuroCirCol, grant agreement 654305; EASITrain, grant agreement no. 764879; ARIES, grant agreement 730871; and E-JADE, contract no. 645479

circular e+e- colliders: 50 year success story

Peak luminosity of circular e+e- colliders as a function of year – for past, operating, and proposed

facilities including the Future Circular Collider[historical data courtesy Y. Funakoshi]

≥ 1 order of magnitude per decade !

KEKB

PEP-II

KEKB design

PEP-II design

source: KEK

Ie+=3.2 A, Ie-=2.1 A

Ie+=1.6 A, Ie-=1.2 A

PSR ~ 5 MW C = 3 km

PSR ~ 8 MW C = 2.2 km

B factories: high current, high luminosity

+ top-up injection

DAFNE Peak Luminosity

CRAB-WAIST Collision Scheme

Des

ign

Go

al

M. Zobov

DAFNE: crab waist collisions

small by*, large beam-beam tune shift

beam commissioning started in 2016

K. Oide et al.

SuperKEKB: the next BIG step

nanobeam collision scheme,design beam lifetime: 5 minutes,by

* ~0. 3 mm

6FCC-ee technologies, time lines, analysis highlights

Frank Zimmermann

KET workshop, Munich, 2 May 2016

FCC-ee

Marica Biagini

DAFNE

VEPP2000

combining recent, novel ingredients → extremely high luminosity at high energies

LEP: high energySR effects

B-factories:KEKB & PEP-II:

high beam currents,top-up injection

DAFNE: crab waist

Super B-factoriesS-KEKB: low by*

KEKB: e+ source

HERA, LEP, RHIC: spin gymnastics

from past successes to new territory

CepC

“An e+-e - storage ring in the range of a few hundred GeV in

the centre of mass can be built with present technology.

...would seem to be ... most useful project on the horizon.”

1976

B. Richter, Very High Energy Electron-Positron Colliding Beams for the Study of Weak Interactions, NIM 136 (1976) 47-60

Burt Richter1976

365 GeV c.m.↔~100 kmcost-optimizedcircumference

feasibility & optimum circumference

double ring e+ e- collider ~100 km

follows footprint of FCC-hh, except

around IPs

asymmetric IR layout & optics

to limit synchrotron radiation

towards the detector

2 IPs, large horizontal

crossing angle 30 mrad,

crab-waist optics

synchrotron radiation

power 50 MW/beam

at all beam energies

top-up injection scheme; requires

booster synchrotron in collider tunnelK. Oide et al.

FCC-ee basic design choices

𝑳 = 𝑪𝒍𝒖𝒎𝑷𝑺𝑹𝝆𝝃𝒚

𝜷𝒚∗𝑬𝟑

x4x4

x1/50

FCC-ee vs LEP:

→ extremely high luminosity

x2

luminosity scaling

parameter FCC-ee CEPC LEP2

energy/beam [GeV] 45 120 182.5 120 105

bunches/beam 16640 328 48 242 4

beam current [mA] 1390 29 5.4 17.4 3

luminosity/IP x 1034 cm-2s-1 230 8.5 1.5 2.9 0.0012

energy loss/turn [GeV] 0.036 1.72 9.2 1.73 3.34

total synchrotron power [MW] 100 60 22

RF voltage [GV] 0.1 2.0 4+6.9 2.2 3.5

rms bunch length (SR,+BS) [mm] 3.5, 12 3.2, 5.3 2.0, 2.5 2.7, 3.3 12, 12

rms emittance ex,y [nm, pm] 0.3, 1.0 0.6, 1.3 1.5, 2.9 1.2, 3.1 22, 250

longit. damping time [turns] 1273 70 20 69 31

crossing angle [mrad] 30 30 30 33 0

beam lifetime (rad.B+BS) [min] 68 12 12 100 434

FCC-ee and CEPC: 2 separate rings LEP: single beam pipe

2018 baseline parameters

total luminosity [1034 cm-2s-1]

ttbar350-365 GeV

tantalizing performance reach till ~400 GeV

ttbar 182.5 GeV

4 sextupoles (a – d) for local vertical chromaticity correction and crab

waist, optimized for each working point;

common arc lattice for all energies, 60 deg for Z, W and 90 deg for ZH,

t-tbar for maximum stability and luminosity

yellow boxes:

dipole magnets

asymmetric IR

optics to

suppress

synchrotron

radiation toward

the IP, Ecritical

<100 keV from

450 m from IP (e)

K. Oide

FCC-ee asymmetric crab-waist IR optics

horizontal emittance

Emittance normalized to beam energy vs. circumference for storage rings in operation (blue dots)

and under construction or being planned (red dots). The ongoing generational change is indicated

by the transition from the blue line to the red line.

R. Bartolini, 2016

SLC HL-LHC

FFTB, ATF-2, S-KEKB, FCC-ee, CEPC

ILCCLIC

ISR

vertical spot size challenge

FCC-ee in the regime of FFTB, ATF-2, and especially SuperKEKB

working point nominal luminosity/IP[1034 cm-2s-1]

total luminosity (2 IPs)/ yr half luminosity in first two years (Z) and first year (ttbar) to account for initial operation

physics goal

run time [years]

Z first 2 years 100 26 ab-1/year150 ab-1 4

Z later 200 48 ab-1/year

W 25 6 ab-1/year 10 ab-1 2

H 7.0 1.7 ab-1/year 5 ab-1 3

machine modification for RF installation & rearrangement: 1 year

top 1st year (350 GeV) 0.8 0.2 ab-1/year 0.2 ab-1 1

top later (365 GeV) 1.4 0.34 ab-1/year 1.5 ab-1 4

total program duration: 15 years - including machine modificationsphase 1 (Z, W, H): 9 years, phase 2 (top): 6 years

FCC-ee physics operation model

FCC-ee luminosity projection

A. Blondel, P. Janot

SR power: RF system tailored for each stage

three sets of RF cavities:

• high intensity (Z, FCC-hh): 400 MHz mono-

cell cavities (4/cryom.), Nb/Cu, 4.5 K

• higher energy (W, H, t): 400 MHz four-cell

cavities (4/cryomodule), Nb/Cu, 4.5 K

• ttbar machine complement: 800 MHz five-

cell cavities (4/cryom.), bulk Nb, 2 K

• installation sequence comparable to LEP ( ≈ 30 CM/shutdown)

WP Vrf [GV] #bunches Ibeam [mA]

Z 0.1 16640 1390

W 0.44 2000 147

H 2.0 393 29

ttbar 10.9 48 5.4

“Ampere-class” machine

“high-gradient” machine

O. Brunner

FCC-ee physics operation model

working point nominal luminosity/IP[1034 cm-2s-1]

total luminosity (2 IPs)/ yr half luminosity in first two years (Z) and first year (ttbar) to account for initial operation

physics goal

run time [years]

Z first 2 years 100 26 ab-1/year150 ab-1 4

Z later 200 48 ab-1/year

W 25 6 ab-1/year 10 ab-1 2

H 7.0 1.7 ab-1/year 5 ab-1 3

machine modification for RF installation & rearrangement: 1 year

top 1st year (350 GeV) 0.8 0.2 ab-1/year 0.2 ab-1 1

top later (365 GeV) 1.4 0.34 ab-1/year 1.5 ab-1 4

total program duration: 15 years - including machine modificationsphase 1 (Z, W, H): 9 years, phase 2 (top): 6 years

𝐿int/year ≈ 𝑇 𝐸 𝐿nominal

integrated luminosity estimate based on

number of days scheduled for physics per year

nominal (design)luminosity

“efficiency”

FCC-ee assumptions:T=185 days, E= 75% (with top-up injection)

days scheduled for physics per year

T =

365 days

– 17 weeks (119 days) winter shutdown

– 30 days commissioning

– 20 days for MDs

– 11 days for technical stops

= 185 days

average value: 11.25 weeks (assumption is 17 weeks!)

O. Brunner

length of winter shutdown?- dominated by RF installation

run lengths of these colliders were often dictated by the availability of financial budget for operation, and not by technical or schedule constraints; this is true in particular for PEP-II and KEKB; in addition, for PEP-II the 2005 run length was severely reduced by a SLAC lab-wideinvestigation, review, remediation of safety concerns, and re-validation of systems & procedures

days of the year dedicated to physics at various past & present e+e− colliders

𝐸 < 𝐴 machine availability

FCC-ee assumption:A ≥ 80% to obtain E ≥ 80% − 5% ~75%

recovery from 3 failures/day ~5% at the Z [filling time: 18 min (Z), 2 min (H)]

availability of various past and present e+e- colliders

CERN SPS efficiency for physics, including the PS chain

Efficiency – PEP-II operation with on-energy top-up injection

2004 2008

Example evolutions of PEP-II beam currents and luminosity.Stored beam current of HER (red curve), LER (green curve), and luminosity (blue curve) of PEP-II over 24 h.

Efficiency – KEKB operation with on-energy top-up injection

2005 2009

Example evolutions of KEKB beam currents and luminosity. Stored beam current of HER (red line in the top figure), LER (red line in the middle figure), and luminosity (yellow line in the bottom figure) of KEKB over 24 h.

FCC-ee assumption

the question is which peak luminosity to take for each year -peak in that year (LEP), peak reduced by ~15% (above SLC, PEP-II above), average peak over the year after removing values <10% (KEKB), design value (easiest, well defined – FCC-ee)

based on “actual” peak luminosity in each year

efficiency of lepton colliders – one definition

based on design peak luminosity

FCC-ee assumption

start of top-up injection at PEP-II and KEKB

efficiency of lepton colliders – a second definition

E > 100% !!

0.57

0.78

KEKB 1999-2003

without top up

KEKB 2003-2010

with top up

daily efficiency

twin-dipole design with 2× power saving

16 MW (at 175 GeV), with Al busbars

first 1 m prototype

twin F/D quad design with 2×

power saving; 25 MW (at 175

GeV), with Cu conductor

first 1 m prototype

A. Milanese

FCC-ee cost-effective, energy-efficient arc magnets

comparison of facility power

K. Oide

comparison of luminosity per facility power

K. Oide

FCC-ee: a sustainable “green” accelerator

electricity cost ~260 euro per Higgs boson.

twin-aperture arc magnets, thin-film SRF, efficient RF power sources, top-up injection

• chambers feature lumped SR absorbers with NEG-pumps placed next to them.

• construction of chamber prototypes in coming months and integration with twin magnets

vacuum chamber cross section: 70 mm ID with ”winglets” in the plane of the

orbit (SuperKEKB-like);

R. Kersevan, C. Garion

FCC-ee vacuum-chamber prototyping and integration

FCC-ee FCC-hh

5.5 m inner diameter

FCC-ee / FCC-hh tunnel integration in collider arcs

V. Mertens

injector complex

SLC/SuperKEKB-like 6 GeV linacaccelerating; 1 or 2 bunches with repetition rate of 100-200 Hz

same linac used for e+ production @ 4.46 GeV e+ beam emittances reduced in DR @ 1.54 GeV

injection @ 6 GeV into of Pre-Booster Ring (SPS or new ring) and accel. to 20 GeV, or 20 GeV linac

injection to main Booster @ 20 GeV and interleaved filling of e+/e- ( <20 min for full filling) and continuous top-up

S. Ogur, K. Oide, O. Itasken, Y. Papaphilippou

FCC-ee

5x10-5 b-1/e+3 b-1/e+

efficiency of e+ usage:

factor 60000 difference!

FCC-ee S-KEKB SLC CLIC380 ILC250 LEMMA

e+ /

second

7x1011

for top-up

on Z pole

3 x 1012 6 x 1012 1014 >2x1014 >1016

worldrecord

high current, top up injection: e+ source requirements

flux concentrator for FCC-ee e+ source

comparison of conventional e+ sources

P. Martyshkin, I. Chaikovska

polarisation and energy calibrationZ pole with polarisation wigglers

WW threshold

orbit correction + harmonic bumps

orbit correction + harmonic bumps

simulated frequency sweep with depolariser

luminosity-

averaged centre-

of-mass

uncertainties:

~100 keV around

the Z pole

~300 keV at the W

pair threshold

E. Gianfelice-Wendt

technique used at LEP

a few conclusionsFCC-ee optics design incorporates many lessons from recent & present

e+e- colliders, and goes further! - excellent off-momentum dynamic

aperture required & achieved

technology for high-energy/luminosity circular collider exists today,

normal&superconducting magnets & RF systems, vacuum system with

SR/e-cloud/impedance mitigation, linac and e+/e production/injection

devices including e+ damping ring

FCC-ee concept includes: power-saving twin-aperture arc magnets,

high-efficiency klystrons, energy staging with optimized RF system

at each energy, top-up injection, and maximum integrated

luminosity

FCC-ee = efficient and sustainable route to discover signs of new

physics beyond the Standard Model: highest luminosity per input

power, highest luminosity per construction cost, most precise energy

calibration, ultimate upgrade potential (FCC-hh)

“in this field, almost everything is already discovered, and all that remains

is to fill a few unimportant holes"

Philipp von Jolly(1809-1884)

advice to the young Max Planck not to go into physics, Munich 1878

… surely great times ahead!