FCC-he Parameters Daniel Schulte, O. Brüning, M. Klein, F. Zimmermann Rome, April 2016

Basis for FCC-he Design Infrastructure does not aim for FCC-ee and FCC-hh being in the tunnel at the same time FCC-he will be based on using the LHeC recirculating energy recovery electron linacs with the FCC-hh collider ring FCC-he will operate at the same time as the two main FCC experiments and potentially more experiments It must not significantly compromise the main experiments D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 FCC-hh Parameters House two main and two additional experiments For baseline will run all experiments For ultimate parameters may run main experiments only Use dipole magnets of up to 16T Assuming 80% dipole filling factor in arcs we need about 82km of arcs Current baseline of 3.75 corresponds to C=99.971km Baseline Ultimate CMS energy [TeV] 100 Luminosity [1034cm-2s-1] 5 20 Bunch distance [ns] 25 (5) Background events/bx 170 (34) 680 (136) Bunch charge [1011] 1 (0.2) Norm. emitt. [mm] 2.2(0.44) RMS bunch length [cm] 8 IP beta-function [m] 1.1 0.3 IP beam size [mm] 6.8 (3) 3.5 (1.6) Max ξ for 2 IPs 0.01 (0.02) 0.03 D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Luminosity Evolution Example of ultimate parameters shown 1.5 years shutdown, 1 year of MDs and stops, 2.5 years of luminosity operation at 70% efficiency Can reach >8fb-1 with ultimate for ξ=0.03 5000fb-1 per 5 year run Beam is burned quickly Another reason to have enough charge stored Ultimate example, 25ns, no luminosity levelling 8fb-1/day Turn-around time D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Baseline ERL Layout Circumference will have to be adapted to the FCC circumference C=CFCC/n Reasonable choice could be n=11 About 2% larger circumference than LHeC D. Schulte FCC-he parameters, Rome, April 2016

Parameter Choice for FCC-he For matched electron and proton beam sizes: Electron beam current Fill pattern matching Proton beam brilliance Proton ring design Hourglass effect Beam-beam effect D. Schulte FCC-he parameters, Rome, April 2016

Proton Beamsize Evolution Assumed 15cm beta-function for proton beam Agressive number because of high energy May be a bit tight for the aperture hh beta-function is 1.1m-0.3m But can gain some factor to be studied in detail The beam emittance varies strongly during run (baseline parameters) Try to follow with electron beam Luminosity is almost constant σ=2.5μm σ=1.7μm D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Electron Current Can likely tolerate 4x109 electrons per bunch (LHeC review 2014) Corresponds to maximum of 26mA About 100MW, only for injectors and synchrotron radiation compensation Use 15mA, 2.3x109 FCC-hh ring beam filling factor is only 80% Will lose 20% luminosity Could avoid accelerating these bunches (RF fluctuates a tiny bit or use beam with 11-fold symmetry in FCC-hh) Need to have ion clearing gaps May lose 1/3 of the bunches Could add the charge in other buckets Need to review single bunch limitation LHC circumference D. Schulte FCC-he parameters, Rome, April 2016

Note: Electron Beam Emittance Initial emittances could be of the order of a few μm (e.g. typical for TTF) Synchrotron radiation in arcs: Δεx≈7.4μm and Δεy≈0.8μm (agrees with theory) Other sources to be added Emittance goals: 20μm appears reasonable 10μm appears aggressive D. Pellegrini A. Latina Questions to address: Could we consider flat beams to collide with the protons? Is there an advantage by making the beam round at collision using a small horizontal and a large vertical beta-function? Could we couple the planes to share the growth? D. Schulte FCC-he parameters, Rome, April 2016

Scaling LHeC to FCC-eh Parameters protons electrons beam energy [GeV] 7000 50000 60 Luminosity [1033cm-2s-1] 1 6.8/8.2 normalized emittance gex,y [mm] 3.75 2.2 50->20/10 IP beta function b*x,y [mm] 100 150 120 -> 36/72 rms IP beam size s*x,y [mm] 7 2.5 7 2.5 beam current [mA] 860 500 6.5 15 bunch spacing [ns] 25 (50) 25 bunch population [1010] 17 10 0.1 (0.2) 0.23 Effective crossing angle 0.0 Beam-beam not included, no gap for ions assumed, Hcoll=0.8 D. Schulte FCC-he parameters, Rome, April 2016

Including Beam-beam Effect protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] 6.8/8.2 8.4/11.7 normalized emittance gex,y [mm] 2.2 20/10 IP beta function b*x,y [mm] 150 36/72 rms IP beam size s*x,y [mm] 2.5 beam current [mA] 500 15 bunch spacing [ns] 25 bunch population [1010] 10 0.23 Effective crossing angle 0.0 Beam-beam not included, no gap for ions assumed, Hcoll=0.8 D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 End of the Run protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] 8.4/11.7 -> 4.7/8.3 normalized emittance gex,y [mm] 2.2 -> 1.1 20/10 IP beta function b*x,y [mm] 150 36/72-> 18/36 rms IP beam size s*x,y [mm] 2.5 -> 1.7 2.5 ->1.7 beam current [mA] 500 -> 250 15 bunch spacing [ns] 25 bunch population [1010] 10->5 0.23 Effective crossing angle 0.0 D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Effective Beam Size Do the electron and proton transverse beam sizes have to be matched? In LHeC the sizes are not matched along the collision Strong pinching of electrons Not obvious why beam sizes do need to match Scan for optimum electron beam size and waist position Electron beam shrinks during collision Increases beam-beam tune shift for protons D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Scan Results E. Nissen Scans performed with GUINEA-PIG Strong-strong simulation Waist [μm] Start of a run End of a run Waist [μm] β [mm] Identified optimum beta-function and waist shift for perfect head-on collisions β [mm] D. Schulte FCC-he parameters, Rome, April 2016

Optimised Beam-beam Effect protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] (8.4/11.7) 10.8/13.7 normalized emittance gex,y [mm] 2.2 -> 1.1 20/10 IP beta function b*x,y [mm] 150 (36/72) 44/42 rms IP beam size s*x,y [mm] 2.5 (2.5/2.5) 2.7/1.9 Waist shift [mm] (0/0) 65/65 beam current [mA] 500-> 250 15 bunch spacing [ns] 25 bunch population [1010] 10 -> 5 0.23 Smaller electron emittance is helpfull D. Schulte FCC-he parameters, Rome, April 2016

Including Beam-beam Effect protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] 10.8/13.7->7.3/10.7 normalized emittance gex,y [mm] 2.2 -> 1.1 20/10 IP beta function b*x,y [mm] 150 44/42 -> 48/52 rms IP beam size s*x,y [mm] 2.5 2.7/1.9 -> 2.9/2.1 Waist shift [mm] 65/65 -> 60/70 beam current [mA] 500-> 250 15 bunch spacing [ns] 25 bunch population [1010] 10 -> 5 0.23 O(320-450fb-1) per 5-year period Assuming no Ion gaps D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Baseline Summary An integrated luminosity of O(250-380fb-1) per 5-year period of operation appears potentially possible What is the electron bunch charge limit? Could lose 1/3 of the luminosity due to ion clearing Electron current depends on Hcoll and clearing gaps Is the proton beta-function of 30cm possible without making the proton-electron experiment the tightest spot for the proton beam? Can the electron beta-function be achieved? Is the impact of the beam-beam effects on both beams acceptable? … D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 FCC-hh Ultimate Run σ=2.5μm Same beta-function in main and proton-electron experiments Could attempt to push proton beta-function in eh Very difficult to reach <1μm with electron beam σ=0.7μm For 5ns spacing sizes can go down to about 0.35μm D. Schulte FCC-he parameters, Rome, April 2016

Ultimate Parameters, 25ns protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] 14.1 (-> 22.4) -> 11.1 normalized emittance gex,y [mm] 2.2 -> 0.15 10 IP beta function b*x,y [mm] 150 45 -> 45 rms IP beam size s*x,y [mm] 2.5 -> 0.7 1.9 -> 1.9 beam current [mA] 500 -> 100 15 bunch spacing [ns] 25 bunch population [1010] 10 -> 2 0.23 Effective crossing angle 0.0 O(>320fb-1) per 5-year period Assuming no Ion gaps D. Schulte FCC-he parameters, Rome, April 2016

Ultimate Parameters, 5ns protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] 6.1 -> 2.6 normalized emittance gex,y [mm] 0.44->0.044 10 IP beta function b*x,y [mm] 150 40 -> 40 rms IP beam size s*x,y [mm] 1.1-> 0.35 1.6 -> 1.6 beam current [mA] 500-> 150 15 bunch spacing [ns] 5 25 bunch population [1010] 2->0.6 0.23 Effective crossing angle 0.0 O(>110fb-1) per 5-year period Assuming no Ion gaps D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Conclusion Target parameter sets for FCC-he presented Need to take into account emittance damping during luminosity run The operation mode of FCC might change … Uncertainties from gaps in both beams, … Parameters appear reasonable for FCC-hh baseline But need to verify beta-functions for protons and electrons More difficult for the ultimate parameters 25ns are probably OK (O(320fb-1/5years)) 5ns spacing most difficult (O(110fb-1/5years)) Explore limits for the electron emittance (flat beams?) and proton beta-function More work is needed to verify parameter sets Interaction region layout Ion studies Electron beam gaps and RF … D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Reserve D. Schulte FCC-he parameters, Rome, April 2016

Machine Protection and Friends 8GJ kinetic energy per beam Airbus A380 at 720km/h 2000kg TNT per beam O(20) times LHC Machine protection This machine protection risk must not be increased by FCC-he Do not create a new bottleneck High risk at injection and extraction Instrumentation to detect failures Interlock system Passive protection and collimation system Machine protection strategy O(160GJ) in magnets O(20) times LHC Serious protection issue D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Collimation System S. Redaelli Efficiency is important Robustness in case of fast beam loss (in a few minutes) Materials, … Main impedance at collision energy => Optics, materials, … D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Power Consumption Luminosity is limited by allowed power consumption (100MW) Synchrotron radiation loss compensation RF 20 MW -> 40MW Can be calculated reliably Include cryogenics etc for this part of the linacs Cryo power of linacs 21 MW -> ? Depends on cavity (Q0) and gradient RF power to control linacs 24 MW -> ? QL due to microphonics, phase stability, … Injector and other consumers are less important Depends on injection energy, hence wakefields etc. D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Interaction Region Will not discuss detail here Integration of machine and detector is challenging Proton optics design focus has been on b=10cm Chromatic correction studied Achieved b=8cm with L*=10m Achieved b=10cm with L*=18m Had a design for CDR Significant design work is required for new design Can relax electron beta-function if we aim for smaller emittance E. Cruz-Alaniz, M. Korostelev, D. Newton (Cockcroft), R. Tomás D. Schulte FCC-he parameters, Rome, April 2016

Beam Pulse and Fast Beam-ion Instability Fast beam-ion instability may require a long gap All ions are trapped in continuous beam (fc<flimit) Beam will become unstable before neutralisation is reached Gaps of different turns need to overlap Fix LHeC circumference to be 1/n of LHC Each LHC bunch always or never collides with electron bunches Would increase bunch charge by 50% to 3x109 Needs to be reviewed CDR Stronger trapping with high luminosity parameters But better clearing in gap LHC circumference D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 FBII Rise Length Rise length in linacs for 10-11hPa: CH4+: 14km -> 2.5km H2+: 25km -> 4km Total distance in linacs 12km Measured 1x10-11 (HERA, B. Holzer), 0.05x10-11 hPa (LHC, V. Baglin) In arcs for p=10-9hPa H2+: 70km -> 12km N2+,CO+:50km -> 8km CO2+: 60km -> 10km Total distance traveled 33km Probably OK But simulations will be required Tool is under development Use a few shorter gaps? D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Impact on Proton Beam Strong variation of tune shift along the bunch ->time dependent quadrupole Also position changes with time Calculate tune shift for each slice of proton beam at the location of the collision with the electron beam Effective tune shift in worst slice is about 5 10-4 strong variation along the bunch -> Smaller than in LHC collision points -> opposite sign -> small linear region D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Beam-beam Effect The proton beam emittance growth due to beam-beam effects is of concern Change of normalised emittance at the end of the ultimate run is O(-1a/s) Aim for growth of <O(0.1a/s) Growth rate Δϵxn (x10-10)(m) Turn Number Predicted rate 9.470x10-14 Mean calculated rate 4.046x10-14 Δϵxn/Δt=7.095x10-9(σjitter/σx)²m/s Doubling time 1 day σjitter/σx=5.99% D. Schulte FCC-he parameters, Rome, April 2016

High-luminosity Insertions The allocated length is consistent with the required performance Achieve beta-function goal Provide less beam stay clear than HL-LHC Pushed beta-function More shielding in magnet Collimation system Hopeful to be able to handle radiation into the final triplet Enough space for the detector Do currently not expect large variations of the required length D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 Betatron Collimation Need to adapt to smaller beam stay clear in experiment triplets Secondaries from showers in primary collimators will be much harder to catch smaller scattering angles more energy in showers Optics scaling from HL-LHC: rC =(50TeV/7TeV)1/2 x 0.4m/0.3m x (59mm/49mm)2 => rC ≈ 5.2 ≈ 2 r => LC=2.8km Normal scaling (r) IP beta-function (increases beta-function in triplets) Aperture reduction due to shielding Have a scaled lattice of 2.7km seems to give adequate inefficiencies gaps are consistent with experimental insertion beam stay clear Now need to verify the performance In particular for secondaries D. Schulte FCC-he parameters, Rome, April 2016

First Collimation Studies First betatron collimation system scaled from LHC Gaps as in HL-LHC But 2.7km long Starting point for exploration Fix issues from LHC design R. Tomas LHC M. Fiascari, S. Redaelli D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 5 ns Spacing protons electrons beam energy [GeV] 50000 60 Luminosity [1033cm-2s-1] 2.3->0.97 (1.06) normalized emittance gex,y [mm] 0.44->0.044 10 IP beta function b*x,y [m] 0.30 0.036-> 0.003 (0.009) rms IP beam size s*x,y [mm] 1.56-> 0.5 beam current [mA] 500-> 150 6.5 bunch spacing [ns] 5 25 bunch population [1010] 2->0.6 0.125/1.875 Effective crossing angle 0.0 D. Schulte FCC-he parameters, Rome, April 2016

FCC-he parameters, Rome, April 2016 LHeC Parameters protons electrons beam energy [GeV] 7000 60 Luminosity [1033cm-2s-1] 1 normalized emittance gex,y [mm] 3.75 50 IP beta function b*x,y [m] 0.10 0.12 rms IP beam size s*x,y [mm] 7 beam current [mA] (860) 430 6.5 bunch spacing [ns] (25) 50 bunch population 1.7x1011 (1x109) 2x109 Effective crossing angle 0.0 D. Schulte FCC-he parameters, Rome, April 2016

Parameter Choice for FCC-he For matched electron and proton beam sizes: Note: CDR electron current is 6.5mA Corresponds to 1.0-1.875x109 particles per bunch at 25ns spacing (filling pattern) Could be doubled adding 23MW of power consumption Further increase remains to be studied LHC circumference D. Schulte FCC-he parameters, Rome, April 2016