The FCC study:
synergies and constraints of FCC-ee and FCC-hh
Philippe Lebrun, CERN
FCC-ee Physics Workshop (TLEP8)
LPNHE, Paris, 27-29 October 2014
Scope of FCC study
•
The main emphasis of the conceptual design study shall be the long-term goal
of a hadron collider with a centre-of-mass energy of the order of 100 TeV in a
new tunnel of 80 - 100 km circumference for the purposes of studying physics
at the highest energies.
•
The conceptual design study shall also include a lepton collider and its
detectors, as a potential intermediate step towards realization of the hadron
facility. Potential synergies with linear collider detector designs should be
considered.
•
Options for e-p scenarios and their impact on the infrastructure shall be
examined at conceptual level.
•
The study shall include cost and energy optimisation, industrialisation aspects
and provide implementation scenarios, including schedule and cost profiles
Note 1: FCC-ee and FCC-hh not simultaneously housed in the tunnel
Note 2: FCC-he not considered at this stage
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
2
Organization of FCC study
Study Coordination
Hadron Collider Physics and Experiments
F. Gianotti, A. Ball, M. Mangano
Lepton Collider Physics and Experiments
A. Blondel, J. Ellis, P. Janot
e-p Physics, Experiments, IP Integration
M. Klein, O. Bruning
Hadron Injectors
B. Goddard
Hadron Collider
D. Schulte, M. Syphers, J.M. Jimenez
Lepton Injectors
Y. Papaphilippou (tbc)
Lepton Collider
J. Wenninger, U. Wienands, J.M. Jimenez
Accelerator R & D and Technologies
Infrastructure and Operation
CostingM.Planning
Benedikt
Ph. Lebrun
M. Benedikt, F. Zimmermann
M. Benedikt, F. Zimmermann
P. Lebrun, P. Collier
F. Sonnemann, P. Lebrun
FCC-ee Workshop Paris Oct 2014
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3
FCC-hh baseline parameters
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
4
FCC-ee design targets

highest possible luminosity for a wide physics program ranging from
the Z pole to the 𝑡𝑡 production threshold


beam energy range from 45 GeV to 175 GeV
main physics programs / energies:

Z (45.5 GeV): Z pole, ‘TeraZ’ and high precision MZ & GZ,

W (80 GeV): W pair production threshold,

H (120 GeV): ZH production (maximum rate of H’s),

t (175 GeV): 𝑡𝑡 threshold

some polarization up to ≥80 GeV for beam energy calibration

optimized for operation at 120 GeV
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
5
FCC-ee baseline parameters
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
6
Tunnel footprint
•
4 values of perimeter considered, rational multiples of LHC taken as highenergy booster for FCC-hh
–
–
–
–
•
80.0 km
86.6 km
93.3 km
100.0 km
Arc radius of curvature maximized
– FCC-hh: to reach maximum beam energy at achievable magnetic field
– FCC-ee: to reach maximum luminosity at 50 MW/beam synchrotron power
•
Geometry
– Experimental areas “clustered” and separated by short arcs, away from injection
and collimation regions
– Long straight sections for IRs and RF
– Distribute RF in LSS to limit energy sawtoothing (FCC-ee)
– Extended short straight sections for FCC-hh collimation and extraction
– Dispersion suppressors on either side of LSS and ESS
– Very short technical straight sections between long arcs (FCC-hh)
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
7
Functional Sections of FCC-hh
LSS
LARC
SARC LSS
DS DS
SARC
DS DS
DS
LSS
DS
LARC
TSS
TSS
LARC
LARC
DS
DS
ESS
ESS
DS
DS
LARC
LARC
TSS
TSS
LARC
DS
LSS
Ph. Lebrun
DS DS
SARC
DS DS
LSS SARC
DS
LARC
LSS
FCC-ee Workshop Paris Oct 2014
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Allocation of Straight Sections FCC-hh
INJ
EXP
INJ
FEED/RETURN
FEED/RETURN
COLL + EXTR
COLL + EXTR
FEED/RETURN
FEED/RETURN
EXP
Ph. Lebrun
EXP
EXP
FCC-ee Workshop Paris Oct 2014
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Functional Sections of FCC-ee
LSS
LARC
SARC LSS
DS DS
SARC
DS DS
DS
LSS
DS
LARC
LARC
LARC
DS
DS
ESS
ESS
DS
DS
LARC
LARC
LARC
DS
LSS
Ph. Lebrun
DS DS
SARC
DS DS
LSS SARC
DS
LARC
LSS
FCC-ee Workshop Paris Oct 2014
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Allocation of Straight Sections FCC-ee
EXP + RF
INJ + RF
INJ + RF
RF?
RF?
COLL + EXTR
+ RF
COLL + EXTR
+ RF
RF?
RF?
EXP + RF
Ph. Lebrun
EXP + RF
EXP + RF
FCC-ee Workshop Paris Oct 2014
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Lengths of arcs and straight sections
Abbreviation
Generic name
Number
Length [km]
LSS
Long straight section
6
1.4
ESS
Extended straight section
2
4.2
TSS
Technical straight section
4
e
DS
Dispersion suppressor
16
0.4
SARC
Short arc
4
3.2
LARC
Long arc
8
see table below
Perimeter
[km]
LARC length
[km]
SARC length
[km]
L/SARC avg.
radius [km]
DS avg. radius
[km]
80.0
5.50
3.20
9.80
13.07
86.6
6.33
3.20
10.85
14.47
93.3
7.16
3.20
11.92
15.89
100.0
8.00
3.20
12.99
17.32
Note 1: the cumulated length of TSS is taken as negligible
Note 2: the average bending strength of DISP is taken as 0.75 that of SARC/LARC
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
12
Lattice
•
FCC-hh
– Cell length ~ 200 m
– Short TSS between LARCs
•
FCC-ee
– Cell lengths from ~50 m to ~300 m, depending on the energy & phase advance
– No TSS unless one needs to add RF stations between LARCS
 Relative transverse positions of machines in tunnel to be checked
B. Holzer
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
13
Experiments
•
FCC-hh
– Very large detectors (L>50 m, D~30 m)
– Sets the size of caverns and installation shafts
•
FCC-ee
– No preliminary design available
– ILC-type detectors would be much smaller than FCC-hh detectors
– Unconventional ideas of detectors making use of large cavern volume of FCC-hh
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Interaction regions
•
FCC-hh
–
–
–
–
•
Small crossing angle 11 mrad
Moderate b* = 1.1 m
Very large detectors  L* = 46 m
Length of IR ~1 km  LSS = 1.4 km
FCC-ee
–
–
–
–
Large crossing angle 30 mrad
Small b* = 1 mm
Small L* = 2 m
Length of IR may require LSS > 1.4 km
 work in progress
β (m)
J. Wenninger
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Tunnel location: topography [1/3]
•
Minimize ground coverage
– Hydrostatic pressure for TBM tunnelling
– Shaft depth/cost
Lac Léman
300 – 372 m/mer
Plaine du
genevois
Vallée du Rhône 350 – 550 m/mer
330 m/mer
Pré-Alpes du
Chablais
600 – 2500 m/mer
Plateau du Mont
Sion
550 – 860 m/mer
Vallon des Usses
380 – 500 m/mer
Mandallaz
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
Bornes – Aravis
600 – 2500 m/mer
16
Tunnel location: topography [2/3]
•
Low points imposed by crossing lake and Rhône canyon
– Avoid crossing too far in Petit Lac
– Staying in molasse practically requires not more than ~200 m ASL
– Alternative options for tunnel across the lake could relax this constraint
mASL
370
Riverbed
320
210
Molasse Rockhead
J. Osborne
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Tunnelling options for crossing the lake
Superficial sediments
Immersed Tube Tunnel
Moraine
Slurry TBM
Molasse
Open Shield TBM
J. Osborne
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Tunnel location: topography [3/3]
•
High-energy booster (FCC-hh) in LHC tunnel
– Minimize horizontal bending strength of injection lines
– Limit vertical distance d to reduce length of injection lines (max slope ~5%)
– Lengths of few km seem feasible
LHC
d
FCC
L
 It appears that these constraints can be met by a planar tunnel, with a slope
< 1 % w.r. to horizontal
 Weak diedral option (change of slope < 1 %) kept as reserve in case of
geological difficulties
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Tunnel location: geology
•
Stay in sedimentary Geneva basin
– Limit underground works in Jura limestone (karst)
– Avoid sedimentary layers displaced by alpine thrust (Prealps)
•
•
•
•
•
Maximize tunnel length in molasse  3-D model of cretaceous-molasse and
molasse-quaternary transitions
Minimize rock transitions along perimeter
Avoid main fault lines
Avoid aquifers
Avoid man-made hazards
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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93km “optimised” racetrack
PRELIMINARY
J. Osborne & C. Cook
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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100km “optimised” racetrack
PRELIMINARY
20,800m
J. Osborne & C. Cook
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Possible tunnel cross-section (Arc)
Single tunnel, longitudinal ventilation
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Possible tunnel cross-section (Arc)
Double tunnel
 in all cases, consider that transverse space requirement in machine tunnel is set
by FCC-hh high-field magnet cryostat (installed position & transport)
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Superconducting RF
•
FCC-ee – very large RF system
–
–
–
𝑓 < 400 MHz: large cavities, mechanically less stable, high He content, smaller impedance
𝑓 > 800 MHz: multi-cell cavities, more wakefield effects, larger impedance
Going to 400 MHz would have several advantages:
1.
2.
3.
4.
•
Operate at 4 K and provocatively argue for coated cavities (more advantages). Requires investment into
R&D to push to higher 𝑄0 at high gradient.
Fairly confident we can aim at 12 ÷ 15 MV/m, so SS will be slightly longer than for sheet Nb cavities.
Use LHC power coupler (tuneable for better matching) – 300 kW CW
HOM power would be much less. LHC type damping system could be used with warm ferrites outside.
FCC-hh – beam dynamics considerations
–
–




Combining a 200 MHz system with a 400 MHz system looks like a good starting point, allowing
for both long bunches and short bunch spacings.
Limiting bunch lengths to 10 cm, a combination 400 MHz & 800 MHz would be a better choice
(stability)
Choice of frequency still open, among harmonics of 200 MHz
Consider combination of 200 MHz, 400 MHz and 800 MHz systems
Choice of frequency will drive choice of operating temperature
RF system much larger for FCC-ee, similar components could be used for FCC-hh
E. Jensen
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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•
FCC-ee will need klystron galleries paralleling the main tunnel in the straight
sections equipped with RF
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
26
Cryogenics: refrigeration
Preliminary discussion: choice of operating temperatures of SCRF cavities and
SC magnets is prerequisite to proper analysis
FCC-hh, per arc (1/12 of total)
Beam screen
Arc equivalent refrigeration capacity [kW @ 4.5 K]
•
Thermal shield
Cold mass
CL
FCC-ee, per RF section (1/12 of total)
•
80
•
70
60
50
40
30
State-of-the-art cryoplant
20
LHC cryoplant
10
> 150 m of RF cavities per
cryoplant
> 4.2 kW @ 1.9 K (?) of RF
heating per cryoplant, equivalent
to 16 kW @ 4.5 K, not counting
– Static losses of cryomodules
– Static and dynamic losses of
couplers
– Cryogenic distribution losses
– Operation overhead
 12 cryoplants of ~ LHC size
0
Tcm = 4.5 K Tcm = 1.9 K Tcm = 4.5 K Tcm = 1.9 K
FCC-hh 100 km
Ph. Lebrun
FCC-hh 83 km
FCC-ee Workshop Paris Oct 2014
L. Tavian
27
Cryogenics: possible layouts
•
FCC-ee and FCC-hh cryoplants could share the same sites, but many
differences in
– Unit capacity
– Supply temperatures, driving possible choice of alternative refrigerants (Ne-He)
– Refrigeration vs liquefaction loads, driving possible split in installation layout (ground
level vs underground) to limit hydrostatic heads
•
Other cryogenic insfrastructure could probably be shared/reused
FCC-hh
½ arc cooling
12 cryoplants
12 technical sites
FCC-ee
Cooling of RF sections
12 cryoplants
12 technical sites
L. Tavian
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
28
Powering FCC-ee and FCC-hh
•
•
•
Both FCC-ee and FCC-hh will consume a few 100 MW nominal
Dense network of HV lines (400 kV and 225 kV) in FCC area
3 main nodes (Génissiat, Cornier, Bois-Tollot) well distributed around
perimeter
 Specific substations and local distribution lines can be shared/reused
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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Summary
•
Present knowledge leads to quasi-circular planar tunnel on slope < 1% with
12 sectors of unequal length, uneven distribution of FCC-ee RF around ring
– Option for non-planar (weakly diedral) geometry kept as back-up in case of
geological difficulties
•
Sizing in tunnel transverse cross-section, experimental caverns and
infrastructure essentially given by FCC-hh, with some specificities for FCC-ee
– Technical galleries for housing RF power sources
– IR design may need longer LSS
•
SC RF
– Choice of frequencies open, multiples of 200 MHz for FCC-ee and FCC-hh
– Acceptable energy sawtoothing and spacing of RF sections to be defined
•
Operating temperatures of SC RF and SC magnets still open, prerequisiste for
further work on cryogenics
– Cryogenic refrigeration to be distributed around the perimeter for reasons of unit
capacity of cryoplants (FCC-hh) and for feeding distributed RF (FCC-ee)
•
Some synergy between FCC-ee and FCC-hh appears possible
– Evidently on civil engineering and infrastructure
– Further analysis requires refining studies and establishing sequential scenarios
Ph. Lebrun
FCC-ee Workshop Paris Oct 2014
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