Synchrotron Radiation and Future Colliders Kévin André, February 3Rd 2021

Synchrotron radiation and future colliders Kévin André, February 3rd 2021

For the materials : B. Holzer, the different CDRs, ATLAS & CMS websites as well as JUAS/CAS courses. Mendeleïev (1869) and Standard Model (1950+)

Nucleosynthesis within stars, hydrogen and helium fusion up to iron, neutron and proton captures as well De Broglie : as neutron star fusions to complete the chart

2 StandardModel Integrated luminosity = Cumulative The Higgs discovery number of potential collisions Integrated luminosity Higgs cross section

R = L Σ = 26.1015 x 10.10-12

≅ 260 000 potential Higgs

out of 2.6 billion million collisions

In reality less than 500 Higgs

R = L Σ = 150.1015 x 40.10-12

≅ 6 000 000 potential Higgs

out of 15 billion million collisions

3 The Higgs boson mass has been determined by ATLAS : The Higgs discovery mH = 124.97 ± 0.24 GeV and CMS : mH = 125.35 ± 0.15 GeV

Both detectors have different elements and electronics so that the accuracy of the results depends on their finite statistical and systematic precisions. 4 Luminosity and statistics

In order to double the statistics one needs four times the running time or luminosity.

f0.nb represent the collision frequency : number of bunches x revolution frequency

Ip1,2 represent the current in beam 1 & 2

σx σy represent the horizontal and vertical beam size at collision

In LHC : σ = 17 mm, I = 584 mA, f0.nb = 11.245 x 2808 ℒ = 1.1034 cm-2.s-1

5 Luminosity and statistics

LHC √s - c.o.m Int. Luminosity

Run 1 (2011 - 2012) 7 - 8 TeV 26 fb-1

Run 2 (2015 - 2018) 13 TeV 150 fb-1

Run 3 (2021 - 2024) 14 TeV 300 fb-1

HL-LHC (2027 - ...) 14 TeV 3000 fb-1

HE-LHC (High Energy) 33 TeV 300 (3000) fb-1

Future Circular Collider 80 - 100 TeV 3 - 100 ab-1

There are other particles and physics processes than the Higgs boson; the physics beyond the standard model (BSM), the dark matter & dark energy, the supersymmetry, signs of extra space-time dimensions, etc.. 6 Dark matter ?

Velocity curve of a typical disc galaxy

More mass on the edge of the galaxy : Dark matter ?

A predicted B observed

Andrew Liddle, An introduction to modern cosmology 7 Considered future energy frontier colliders

Circular Colliders : ● Future Circular Collider, electron positron : FCC - ee, 90 - 350 GeV c.o.m ● Future Circular Collider, hadron hadron : FCC - hh, 100 TeV c.o.m Linear colliders : ● International Linear Collider, electron positron : ILC - 500 GeV c.o.m in Japan ● Compact Linear Collider, electron positron, 0.38 - 3 TeV c.o.m at CERN Others : ● Plasma acceleration ● Muon collider, multi-TeV c.o.m ● Large Hadron electron Collider, lepton hadron, TeV c.o.m

8 Future colliders landscape

lepton collider : FCCee, CepC; ILC, CLIC lepton-hadron collider : EIC, LHeC hadron collider : SppC, FCChh

9 Future colliders timescale

10 Circular colliders - LHC upgrade

In order to get a higher luminosity with the existing LHC e.g. HL-LHC : Reduction of the beam size at interaction point with a stronger focusing. Higher gradients and larger aperture are required → new superconducting technology with Nb3Sn

11 Circular colliders - LHC upgrade

In order to get a higher luminosity from the existing LHC e.g. HL-LHC : ● Geometrical loss factor due to the crossing angle between the beams to avoid parasitic interactions.

F = 0.891 for LHC however F=0.31 for HL-LHC

F The objective is to recover the head-on collisions with Crab cavities (transversely deflecting cavities).

12 Circular colliders - LHC upgrade

In order to get a higher luminosity from the existing LHC e.g. HL-LHC : ● Need to reduce the beam size at interaction (stronger focusing) ➢ Higher gradients and larger aperture → new technology with Nb3Sn with 13 T peak field ➢ Achromatic Telescopic Squeeze (ATS) : new optics → focus the beam in the neighboring sectors ● Geometrical loss factor due to the crossing angle between the beams ➢ Crab cavities to compensate the crossing angle ● Increase the number of proton per bunch ➢ LHC Injector Upgrade (LIU): Linac 4 commissioning and the upgrade of the injectors will allow to reach 2.2 1011 protons per bunch or 1.12 A.

13 Considered future energy frontier colliders

14 Hadron collisions or Lepton collisions

Hadron collisions : frontier of physics Lepton collisions : precision physics

Discovery machine : large discovery Elementary particle collision : process range known

Not all nucleon energy available for Well defined c.o.m energy collisions Background limited Huge background Polarization possible

15 Higher energy hadron machine : FCC hh

Increase the ring circumference and use stronger magnets

Maximum beam energy in a storage ring ?

Lorentz force :

Centrifugal force :

16 Higher energy hadron machine : FCC hh

Increase the ring circumference and use stronger magnets

Maximum beam energy in a storage ring ?

Collider B E 2 π ⍴ ratio of C

SPS 2.0 T 450 GeV 4.7 km 68 %

LHC 8.3 T 7 TeV 17.7 km 65 %

FCC hh 16.0 T 50 TeV 65.5 km 65 % 17 Higher energy hadron machine : FCC hh

High field magnets. NbTi is a ductile superconducting material that is convenient when building magnets however Current vs Field at 4.2 K most of the other materials including Nb3Sn foressen for HL-LHC are brittle.

18 source : JUAS Feb 2013 Higher energy hadron machine : FCC hh

Pile up effect = Mean number of interaction per bunch crossing. It requires an improved triggering and it’s challenging for the particle reconstruction. Use of levelling for the luminosity.

LHC pile up = 40

HL-LHC pile up = 204

FCC hh pile up ⋝ 1000 19 Higher energy hadron machine : FCC hh

Technologistical, logistical and geographical challenge for such a large facility.

The ring requires: water & air ventilation, helium cooling for cryogenics, power supply (580 MW), access shafts, etc..

20 Machine protection and safety

Energy stored in one beam of LHC is 362 MJ → melt 0.5 ton of copper.

Energy stored in the magnet system of LHC is 10 GJ.

In a superconducting machine a quench can happen and destroy a magnet.

21 Machine protection and safety

Energy stored in one beam of LHC is 362 MJ → melt 0.5 ton of copper.

Energy stored in the magnet system of LHC is 10 GJ.

Need to be able to dump the beam in less than three turns ~0.27 ms in case of ultra-fast failure or in the milliseconds otherwise.

The dump is a 8m long graphite block

22 Higher energy lepton machine : FCC ee

Limitations ?

● Synchrotron radiation emissions ● Radio Frequency power

23 Beam acceleration in LHC unit LHC

Synchrotron radiation keV 7 losses / turn

RF frequency MHz 400

RF voltage MV 16

Energy gain/turn keV 485

In LHC : Injection energy of 450 GeV Acceleration up to 7 TeV in about 20 min that is roughly 500 keV per turn with 8 RF cavities.

Point 4 of the LHC tunnel, source CERN website About 14 million turns.. 24 Synchrotron radiation - I

Charged particles in a circular accelerator emit photons and therefore lose energy.

Source Wille book

25 Synchrotron radiation - II

Photon mass attenuation coefficient Normalised power distribution with the photon energy from NIST

Half of the power is radiated by photons with less 26 than the critical energy, the other half above. Synchrotron radiation - III

2 effects compete :

1. Emission of radiation in region with dispersion, like in a dipole, that increases the emittance. 2. The emission of photon decreases the electron momentum and the cavity restores longitudinal momentum

Based on equilibrium 27 Synchrotron radiation - IV

In addition to the energy loss, synchrotron radiation increases the beam emittance. Therefore the beam size at collision. To cope with this issue, flat beams at collision are

used such that in the plane of synchrotron beta function [km] radiation emissions (horizontal) the beam size is larger while in the vertical plane very strong focusing is required in order to get a ratio of 1 or more orders of magnitudes. longitudinal distance [m]

CLIC ILC FCCee HL-LHC FCChh

Beam size H/V 40/1 nm 474/6 nm 38.2 µm / 68 nm 7.1 µm 3.5 µm 28 Synchrotron radiation, come back to FCC ee

Maximum beam energy of 182.5 GeV and beam current of 6 mA. Such that a energy loss per turn is 9.8 GeV per beam (5% of the beam energy!), And in power it adds up to 50 MW per beam ! A cavity can replenish around 20 MeV therefore a total of 500 cavities are needed that corresponds to 2 km of straight section filled with cavities to compensate the losses.

29 FCC ee and synchrotron radiation losses compensation

unit LHC

Synchrotron radiation keV 7 losses / turn

RF frequency MHz 400

RF voltage MV 16

Energy gain/turn keV 485

There is an obvious limit for the lepton circular collider due to the synchrotron radiation, a solution could be to use linear collider.

30 FCC ee top-up injection

31 sources : http://accelconf.web.cern.ch/eefact2018/papers/tupab01.pdf, https://accelconf.web.cern.ch/eefact2016/papers/tut2h1.pdf FCCee vs. CepC

32 FCC ee, arc lattice and magnets

In the arc a periodic cell is around 50 m,

with 2900 dipoles of about 50 mT magnetic field with twin apertures.

and 2900 quadrupoles with about 10 T/m gradient with twin apertures as well.

The arc lattice is a FODO cell in order to have the highest dipole filling factor to mitigate the synchrotron radiation.

33 Considered future energy frontier colliders

34 Circular colliders versus linear colliders (for leptons)

Circular collider have reduced luminosity with increasing Ecm

While linear collider do not suffer from a limitation due to synchrotron radiation but only the power delivered to the cavities.

35 Linear colliders - ILC - Energy range of 500 GeV c.o.m

Avoid bending magnet and therefore avoid synchrotron radiation losses however the energy gain has to be achieved in one passage !

Accelerating gradient of about 35 MV/m based on TESLA cavity type

36 Linear colliders - CLIC - 380 GeV to 3 TeV c.o.m

CLIC c.o.m energy 380 GeV 3 TeV

Repetition freq. 50 Hz

Acc. gradient 72 MV/m 72/100 MV/m

Luminosity 1.5 x 1034 5.9 x 1034

H/V beam size 149/2.9 nm 40/1 nm

Cavity at 100 MV/m are at the breakdown limit, impact on beam quality, accelerating structure and accelerator performance (luminosity).

37 Considered future energy frontier colliders

38 In order to go for higher energy: plasma acceleration

The plasma is ionised with a laser or a particle beam (electron or proton) leading to very high gradient of charges in the small distance → extremely high gradient.

39 In order to go for higher energy: plasma & Co. acceleration

Dielectric based Plasma based Crystal channeling

Accelerating media microstructures ionised plasma solid crystals

energy source optical laser & e- optical laser & x-ray laser beam e-/p beam

particles to accelerate any stable e-, µ- p+, µ+

max acc. gradient 1-3 GV/m 30-100 GV/m 0.1-10 TV/m

c.o.m reached in 10 km 3-10 TeV 3-50 TeV 103-105 TeV

Crystal channelling uses the same principle as plasma acceleration in a solid crystals, since the charge density in a solid is much higher than in a gas, one can expect much higher accelerating gradient in the TV/m range. 40 sources https://arxiv.org/ftp/arxiv/papers/1205/1205.3087.pdf, https://arxiv.org/ftp/arxiv/papers/1612/1612.08740.pdf In order to go for higher energy : plasma acceleration

A plasma wake acceleration created with a laser or particle beam (e- or p) create a traveling wave in a low pressure gas.

This method allows to accelerate electrons that surfs the plasma wave.

41 In order to go for higher energy : plasma acceleration

The AWAKE experiment

source publication in Nature 42 Muon collider & Plasma Wake Linear collider

The fundamental nature of leptons (elementary particles) makes lepton-antilepton colliders the ideal candidate to serve at the energy frontier. The large muon mass, 207 times that of the electron, suppresses synchrotron radiation by a factor of 2074 = 109 compared with electron beams of the same energy. However some challenges arise: the lifetime of 2.2 µs for a muon at rest and it is difficult to have a large number of muons in a bunch with a small emittance.

In order to make a plasma wake linear collider, the beam quality still needs to be addressed as well as a way to accelerate positrons.

43 Luminosity versus power consumption

The linear collider have a roughly constant trend over the center of mass energy.

The circular collider have a decreasing slope due to synchrotron radiation.

The muon collider seems to have an increasing slope.

What about LHeC ?

44 Energy Recovery Linac, what is it ? In LHC : Injection energy of 450 GeV Acceleration up to 7 TeV in about 20 min that is roughly In CLIC 380 : 500 keV per turn Injection energy of 9 with 8 RF cavities. GeV Acceleration up to 190 GeV in about 3.5 km. Tens In FCCee: Top-Up of thousand of RF injection at 182.5 cavities of 23cm. GeV with 644 RF cavities in order to replenish with a total of 10.93 GV the energy lost per turn.

In LHeC : Injection energy of 500 MeV and acceleration up to 50 GeV in 3 turns 8.25 GeV per turn per linac of 828 m, 448 RF cavities of 1m per linac. 45 Electron Recirculating Linac, what is it ?

Cavity Voltage Injection

Linac

E = E + ΔE

Dump

46 Experiment Energy Recovery Linac, what is it ?

Cavity Voltage Injection

Linac

Dump E = E ± ΔE

+ 0.5 λRF

Experiment 47 Layout of the Energy Recovery Linac (ERL) for LHeC

Design specificities : ● Continuous Wave (CW) operation. ● Arc 6 shift the RF phase. ● Second harmonic RF to compensate energy loss of accelerating & decelerating bunches. ● Total electrical power consumption of 100 MW.

48 Layout of the Energy Recovery Linac (ERL) for LHeC

Figure from LHeC CDR-2020

49 Power consumption and energy saving

Reuse of the heat lost at CERN point 8 by the accelerator complex to supply an industrial zone.

Un futur réseau de revalorisation de la chaleur perdue au Cern

There is a complete section on energy saving and management and heat waste recovery in the Conceptual Design Report for FCC hh/ee.

It deals with :

● reducing the peak power required by the ramping of the magnets and the collider operation, ● storage of energy in capacitor and battery in order to power the magnets, ● improved klystrons efficiency, ● reduce losses in the cryogenic elements, ● twin apertures in the main dipoles and quadrupoles, ● use of the cooling water at the cryogenic plants to supply nearby consumers, etc..

50 51