Dr. Stewart T. Boogert Accelerator Physicist at the John Adams ... - UCL...

Collider Accelerator Physics

Dr. Stewart T. Boogert

Accelerator Physicist at the John Adams Institute at Royal Holloway, University of London

14 January 2014University of London Post-Graduate Lecture

1

Thursday, 23 January 14

My Research

• Projects: CLIC and ILC

• Diagnostics

• How to measure electron beams

• Laserwire

• Collide 1 μm high power laser (1 GW) with 1 μm electron beam

• Beam Position Monitors

• Measure beam position to 10s of nanometers

• EM radiation for charged particles beams

2Former life : HERA, QCD, top quark, energy spectrometery

Lase

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e at

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at A

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2


Outline

• Historical overview

• Just enough accelerator physics, scaling and UG physics to understand the problems

• Acceleration

• Luminosity production

• Machines to address these problems

• International Linear Collider (ILC)

• Compact Linear Collider (CLIC)

• Muon Collider

• Large Hadron Collider (LHC) and its upgrade (High Energy; HE & High Luminosity; HL)

• Exotic acceleration

3


Recent History

• Tevatron shut down

• LHC moving into large scale data collection with higher energy and luminosity

• International efforts towards:

• High energy or high luminosity LHC

• ILC, CLIC, Muon Collider

• Beam and laser driven plasmas

• Exotics! Dielectric wakefield, meta-materials

4


Particle Physics

• Need events to perform analysis on

• Stays remarkably constant

• Not the entire picture as we need to think about:

• Beam energy

• Polarisation

• Composite nature of colliding beams (e.g., protons)

• Of course complications PDFs etc

5

N = �L = �

ZL dt

Number of events

Cross section Integrated luminosity

N =

Z�(E1, E2, s1, s2, ...)·

L(E1, E2, s1, s2, ...) dt

Instantaneous luminosity

Beam energies Beam polarisation


Cross Sections

• Probe beam wavelength scales as inverse of energy

• Cross section like inverse of energy squared

• Desire to reach high energies based on

• High mass states, SUSY

• Decreasing probe wavelength

6

� = �2

Cross-section [m2]

� =h

p⇠ h

E

Matter wavelength [m]

Ultra-relativisticDe Broigle wavelength

Point-like cross section scales as:

� ⇠ 1

E2

Beam energyBeam momentum


Energy Frontier

• Historical progress has been power law like for most of the last 70 years

• Vast majority of recent machines were synchrotrons

• Notable exceptions

• SLC

• NLC/ILC

• LHC

7

ps > 2MX� =

h

p⇠ h

E


Luminosity Frontier

• Need corresponding rise in luminosity

• Higher luminosity brings all the challenges for detectors

• High event rates

• Pile up

• Beam-beam interactions

• Beamstrahlung

8


Designing a Machine

• Particle species

• Electrons/positrons

• Protons/anti-protons

• Muons/anti-muons

• Beam energy

• Spin

• Luminosity

9

• How do you produce anti-particles?

• Once produced how you does one keep them? (muon collider)

• Once collided what is done with the spent beams?

• Accelerator and detector protection


Accelerator Much More Than Just...

• Particle production

• Damping, cooling, or preparation

• Injection and extraction

• Acceleration

• Collimation (betatron, energy, etc.)

• Diagnostics and controls

• Machine (and detector) protection

• Beam delivery and luminosity production

• Technology spin off

• Lowe energy machines, medical applications, applied physics, materials, blah, blah

10


Acceleration

• 2nd year electromagnetism

• Electric field (either static, or more commonly, time varying) to accelerate, or more appropriately, increase energy of beam

• Magnetic part of Lorentz force used to guide and focus

• Dipole magnets : to bend

• Quadrupole : to focus or defocus

11

F = q (E+ v ⇥B)

Lorentz force law

Electric field Velocity Magnetic field

�E =

Z r2

r1

F · drEnergy change


Synchrotron

• Work horse of modern particle physics

• Huge legacy of discovery

• W/Z, Gluon, Higgs, SUSY?

• Increase energy whilst synchronously increasing bending magnet strength

• Stable storage of high beam current/power

• Magnetic field proportional to momentum

F

ρ

vE

B� = p/q

B

Magnetic field

Velocity

Bending radius

Momentum

qBv =m0v2

⇢


-5 -4 -3 -2 -1 0 1 2 3 4 5

-1.6

-1.2

-0.8

-0.4

0.4

0.8

1.2

1.6

Synchrotron

• Time varying electric field:

13

F

ρ

vE

t

V

n2�

⇥RF

B

Angular frequency of accelerating field

V (t) = V0 sin(!RF t+ �)

• Particle gets a kick every revolution

IntegerRevolution frequency

1

fref= n

2⇡

!RF


Synchrotron Radiation Limits

• Why not just build bigger LEP?

• Reuse accelerating section every revolution of particle bunch

• Power loss due to synchrotron radiation

• LEP2 was practical limit for electron-positron synchrotron

14

P =1

4⇤⇥0

e2v4

c3⌅2�4

W = 8.85⇥ 10�5E4/�

F

ρ

vE

Energy loss per turnBeam energy

Magnetic radius

B

Power


Absolute Limits on Acceleration

• Need to create large on axis electric fields

• Accelerating structures:

• Superconducting (~35 MV/m)

• Normal conducting (~100 MV/m)

• Beyond these values there is high voltage breakdown

15

Machine length [m] Beam energy [MeV]

Accelerating gradient [MV/m]

V

S =E

q dV/ds


Luminosity

• What luminosity is required for measurement?

• Need some knowledge of x-section

• Simple relationship between number of particles, frequency of collision and beam sizes

16

L = fN1N2

4�⇥x

⇥y

Luminosity [s-1 m-2]

Bunch populations

Beam r.m.s. sizes [m]

Frequency of collisions [Hz]

L = fN1N2

4⇤p⇥x

�⇤x

⇥y

�⇤y

� =p

✏�

Emittance [m] Beta function [m]


Emittance

• Emittance is a invariant measure of phase space (spatial) occupied by charged particle beam

• Product of spatial width and angular width

• Normalised emittance invariant under forces due to Lorentz

17

�2 =⌦x2

↵ ⌦x02↵� hxx0i2

particle position particle angle

Distance along accelerator

x0 =�x

�s=

px

ps

Momentumcomponents

x

x

0


Magnets• Quadrupole magnets effectively act as lenses

• Focusing in one plane and defocusing in the other plane

18

x

x

0

x

x

0Magnetx

0

Focus


Accelerator Magnets

• Normal and super-conducting

• Dipoles and quadrupoles

• Beam losses effect super conductors

• Can cause quench (i.e., superconductor becoming normal)

• High energy large momentum, so big magnets, high currents large resistive losses

19

Nor

mal

Con

duct

ing

Qua

drup

ole

Supe

r C

ondu

ctin

g D

ipol

e


Acceleration

• Acceleration only in direction of motion

• Increase longitudinal component of momentum

• Position is untouched

• Overall the emittance is reduced

• Normalised emittance:

20

x

x

0

x

x

0

x

0 =p

x

p

s

+�p

✏n = ��✏Normalised emittance


Accelerating Cavities

• Need to create high electric fields

• LHC has 8 cavities per beam

• 2 MV, so 16 MeV per turn

• 11245 turns/s

• 0.18 TeV/s

• Ramp time?

21

LHC

Cav

ityAT

F C

avity


Optical Functions• Beam phase space

described in 6 dimensions

• Transformation of vector through magnetic elements

• Beta functions tell us about relationship between position and angle

• Dispersion between energy and time etc etc

22

Beam Delivery Systems

0 500 1000 1500 2000!0.2

!0.1

0

0.1

0.2

! (m)

0 500 1000 1500 20000

100

200

300

400

"1/2 (

m1/

2 ), a

pert

ure

S (m)

10*(aperture in mm)

"y1/2

"x1/2

!x

coupling &emittance

polarimeter& extraction

betatroncollimation

energycollimation

matching &spectrometer

finaltransformer

finaldoublet

FIGURE 2.7-4. BDS optics, subsystems and vacuum chamber aperture; S is distance measured from theentrance.

2.7.3.4 IR design and integration to detector

The ILC final focus uses independently adjustable compact superconducting magnets for theincoming and extraction beam lines. The adjustability is needed to accommodate beam en-ergy changes and the separate beamline allows optics suitable for post IP beam diagnostics.The BNL direct wind technology is used to produce closely spaced coil layers of superconduct-ing multi-strand cable. The design is extremely compact and the coils are almost touching inshared cold mass volumes. Cooling is provided by superfluid helium at 2 K. The technologyhas been demonstrated by a series of short prototype multi-pole coils. The schematic layoutof magnets in the IR is shown in Figure 2.7-5 and Figure 2.7-11. The quadrupoles closestto the IP are actually inside the detector solenoidal field and therefore cannot have mag-netic flux return yokes; at the closest coil spacing the magnetic cross talk between the twobeam apertures is controlled by using actively shielded coil configurations and by use of localcorrection coils, dipole, skew-dipole and skew-quadrupole or skew-sextupole, as appropriate.Figure 2.7-6 shows the prototype of QD0 quadrupole and illustrates the principle of activeshielding.

To facilitate a rapid, “push-pull” style exchange of detectors at a shared IP, the super-conducting final focus magnets are arranged into two groups so that they can be housed intwo separate cryostats as shown in Figure 2.7-5, with only warm components and vacuumvalves placed in between. The cryostat on the left in Figure 2.7-5 moves with the detectorduring switchover, while the cryostat on the right remains fixed on the beamline.

Additional optical elements are required in the IR to compensate the e�ects of the detectorsolenoid field interacting with the accelerator IR magnets. The first is a large aperture anti-solenoid in the endcap region to avoid luminosity loss due to beam optics e�ects [71]. Thesecond is a large aperture Detector Integrated Dipole (DID) [72] that is used to reducedetector background at high beam energies or to minimize orbit deflections at low beamenergies.

The vertical position of the incoming beam line quadrupole field center must be stable

ILC Reference Design Report III-95

R. Assmann

Low Low �� Optics for IR1 and IR5Optics for IR1 and IR5

Collisions at IP with small spot size

v = (x, x0, y, y

0, E, t)

v0 = Mv LHC

ILC


Linear Colliders

• Two different options available

• International Linear Collider (ILC)

• 1 TeV : Super conducting

• Compact LInear Collider (CLIC)

• 3 TeV : Normal

• Avoid the problem of SR losses

• ILC problem : No SUSY < 500 GeV

• CLIC problem : Boundary of technological limits

23

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ILC


Linear Collider Accelerator

• Gradients of 35 MV/m required

• ILC uses

• Niobium cavities

• 1.2 GHz RF

• Above this the super conductor quenches

• Type II SC, largest magnetic penetration of any element

• Remember Maxwell’s equations

24

OVERVIEW

1.2 SUPERCONDUCTING RF

The primary cost driver for the ILC is the superconducting RF technology used for the MainLinacs, bunch compressors and injector linacs. In 1992, the TESLA Collaboration beganR&D on 1.3 GHz technology with a goal of reducing the cost per MeV by a factor of 20 overthe then state-of-the-art SCRF installation (CEBAF). This was achieved by increasing theoperating accelerating gradient by a factor of five from 5 MV/m to 25 MV/m, and reducingthe cost per meter of the complete accelerating module by a factor of four for large-scaleproduction.

FIGURE 1.2-1. A TESLA nine-cell 1.3 GHz superconducting niobium cavity.

The TESLA cavity R&D was based on extensive existing experience from CEBAF (Jef-ferson Lab), CERN, Cornell University, KEK, Saclay and Wuppertal. The basic element ofthe technology is a nine-cell 1.3 GHz niobium cavity, shown in Figure 1.2-1. Approximately160 of these cavities have been fabricated by industry as part of the on-going R&D programat DESY; some 17,000 are needed for the ILC.

A single cavity is approximately 1 m long. The cavities must be operated at 2 K to achievetheir performance. Eight or nine cavities are mounted together in a string and assembledinto a common low-temperature cryostat or cryomodule (Figure 1.2-2), the design of which isalready in the third generation. Ten cryomodules have been produced to-date, five of whichare currently installed in the in the VUV free-electron laser (FLASH)3 at DESY, where theyare routinely operated. DESY is currently preparing for the construction of the EuropeanXFEL facility, which will have a � 20 GeV superconducting linac containing 116 cryomodules.

The ILC community has set an aggressive goal of routinely achieving4 35 MV/m in nine-cell cavities, with a minimum production yield of 80%. Several cavities have already achievedthese and higher gradients (see Figure 1.2-3), demonstrating proof of principle. Records ofover 50 MV/m have been achieved in single-cell cavities at KEK and Cornell[7]. However,it is still a challenge to achieve the desired production yield for nine-cell cavities at themass-production levels (�17,000 cavities) required.

The key to high-gradient performance is the ultra-clean and defect-free inner surface ofthe cavity. Both cavity preparation and assembly into cavity strings for the cryomodulesmust be performed in clean-room environments (Figure 1.2-4).

3Originally known as the TESLA Test Facility (TTF).4Acceptance test.

III-4 ILC Reference Design Report

Superconducting RF

FIGURE 1.2-2. SCRF Cryomodules. Left: an 8 cavity TESLA cryomodule is installed into the FLASHlinac at DESY. Right: design for the 4th generation ILC prototype cryomodule, due to be constructed atFermilab National Laboratory.

A7 Second Vertical RF Test

(Degrease, 20 um EP, HPR, Bake 120C)

0 10 20 30 40Eacc [MV/m]

Q0

AC70AC72AC73AC78AC76AC71AC81Z83Z87

1011

109

1010

1011

1010

109

100 20 30 40Accelerating Gradient (MV/m)

Q0

FIGURE 1.2-3. High-performance nine-cell cavities. Left: Examples of DESY nine-cell cavities achieving� 35 MV/m. Right: Recent result from Je�erson Lab of nine-cell cavity achieving 40 MV/m.

The best cavities have been achieved using electropolishing, a common industry practicewhich was first developed for use with superconducting cavities by CERN and KEK. Overthe last few years, research at Cornell, DESY, KEK and Je�erson Lab has led to an agreedstandard procedure for cavity preparation, depicted in Figure 1.2-5. The focus of the R&Dis now to optimize the process to guarantee the required yield. The ILC SCRF communityhas developed an internationally agreed-upon plan to address the priority issues.

The high-gradient SCRF R&D required for ILC is expected to ramp-up world-wide overthe next years. The U.S. is currently investing in new infrastructure for nine-cell cavitypreparation and string and cryomodule assembly. These e�orts are centered at Fermilab (ILCTest Accelerator, or ILCTA), together with ANL, Cornell University, SLAC and Je�ersonLab. In Japan, KEK is developing the Superconducting RF Test Facility (STF). In Europe,the focus of R&D at DESY has shifted to industrial preparation for construction of the XFEL.There is continued R&D to support the high-gradient program, as well as other critical ILC-related R&D such as high-power RF couplers (LAL, Orsay, France) and cavity tuners (CEASaclay, France; INFN Milan, Italy).


ILC Superconducting Cavity


Beam Delivery System

• Major challenge for lepton colliders is the luminosity

25

Beam Delivery Systems

includes the MPS collimation system, skew correction section, emittance diagnostic section,polarimeter with energy diagnostics, fast extraction/tuning system and beta matching sec-tion.

-2200 -2100 -2000 -1900 -1800 -1700 -1600 -1500 -1400 -1300 -1200-2

-1

0

1

2

Z (m)

X (

m)

ILC e- BDS (500 GeV cm)

-1000 -800 -600 -400 -200 0 200-2

-1

0

1

2

Z (m)

X (

m)

MPScoll

skew correction /emittance diagnostics

polarimeterfast

kickers

betatroncollimation

fastsweepers

tuneupdump

energycollimation

energyspectrometer

betamatch

final transformer

final doublet

IP

polarimeter

energyspectrometer

fastsweepers

primarydump

FIGURE 2.7-2. BDS layout showing functional subsystems, starting from the linac exit; X – horizontalposition of elements, Z – distance measured from the IP.

2.7.3.1.1 MPS collimation At the exit of the main linac is a short 90� FODO lattice,composed of large bore quadrupoles, which contains a set of sacrificial collimators of decreas-ing aperture. The purpose of this system is to protect the 12 mm aperture BDS from anybeam which develops an extremely large trajectory in the 7 cm aperture main linac (thee�ective aperture is R/�1/2, which is 3–4 times smaller in the BDS than in the linac). Thissection also contains kickers and cavity BPMs for inter- and intra-train trajectory feedback.

2.7.3.1.2 Skew Correction The skew correction section contains 4 orthonormal skewquadrupoles which provide complete and independent control of the 4 betatron couplingparameters. This scheme allows correction of any arbitrary linearized coupled beam.

2.7.3.1.3 Emittance Diagnostics The emittance diagnostic section contains 4 laserwires which are capable of measuring horizontal and vertical RMS beam sizes down to 1 µm.


ACCELERATOR DESCRIPTION

2.7.3 System DescriptionThe main subsystems of the beam delivery starting from the exit of the main linacs arethe diagnostics region, the fast extraction and tuneup beamline, the betatron and energycollimation, the final focus, the interaction region and the extraction line. The layout of thebeam delivery system is shown in Figures 2.7-1 and 2.7-2. The BDS is designed for 500 GeVcenter of mass but can be upgraded to 1 TeV with additional magnets.

TABLE 2.7-1Key parameters of the BDS. The range of L�, the distance from the final quadrupole to the IP, correspondsto values considered for the existing detector concepts.

Parameter Units Value

Length (linac exit to IP distance)/side m 2226Length of main (tune-up) extraction line m 300 (467)Max Energy/beam (with more magnets) GeV 250 (500)Distance from IP to first quad, L* m 3.5-(4.5)Crossing angle at the IP mrad 14Nominal beam size at IP, ⌅�, x/y nm 639/5.7Nominal beam divergence at IP, ⇥�, x/y µrad 32/14Nominal beta-function at IP, ��, x/y mm 20/0.4Nominal bunch length, ⌅z µm 300Nominal disruption parameters, x/y 0.17/19.4Nominal bunch population, N 2� 1010

Beam power in each beam MW 10.8Preferred entrance train to train jitter ⌅y < 0.5Preferred entrance bunch to bunch jitter ⌅y < 0.1Typical nominal collimation aperture, x/y 8–10/60Vacuum pressure level, near/far from IP nTorr 1/50

There is a single collision point with a 14 mrad crossing angle. To support future energyupgrades, the beam delivery systems are in line with the linacs and the linacs are also orientedat a 14 mrad angle. The 14 mrad geometry provides space for separate extraction lines andrequires crab cavities to rotate the bunches horizontally for head-on collisions. There aretwo detectors in a common IR hall which alternately occupy the single collision point, in aso-called “push-pull” configuration. The detectors are pre-assembled on the surface and thenlowered into the IR hall in large subsections once the hall is ready for occupancy.

2.7.3.1 Diagnostics, Tune-up dump, Machine Protection

The initial part of the BDS, from the end of the main linac to the start of the collimationsystem (known for historical reasons as the Beam Switch Yard or “BSY”), is responsible formeasuring and correcting the properties of the beam before it enters the Collimation andFinal Focus systems. In addition, errant beams must be detected here and safely extractedin order to protect the downstream systems. Starting at the exit of the main linac, the system


L = fN1N2

4�⇥x

⇥y


Interaction Point Focusing

• We need strong foci

• Strong magnets (lenses)

• Short focal length

• Large beam size on input

26

f1 f2f2

M =f1f2

Generally need large demagnification300 ILC

Need small size, set L⇤ = 2 m

Sets optical system length f2 = 600 m

Beam delivery

Detector volume

L⇤


Accelerator Test Facility (ATF) 2

• Facility to test ideas of beam focusing

• Aim to achieve 35 nm vertical beam size

• Using 1.3 GeV electron beam

27

ATF

2


Beam Power

• Another way to look at luminosity

• Look at it in terms of beam power and efficiency

• How do we pay for luminosity?

• Luminosity directly proportional to input power and efficiency

• £££ or $$$ or €€€ or CHF or JPY

28

L = Nb

fN1N2

4�⇥x

⇥y

HD

Pbeam = fENbN1 = �Pgrid

L =N

4⇥⇤x

⇤y

HD

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E

L � Pbeam

ECM=

�Pgrid

ECM

Grid power

Efficiency


Compact Linear Collider

• Getting to TeV

• Super conducting acceleration even with 50 MeV/m

• 60 km in length!

• Cryogenic power, RF power

• Need more efficient method of making beam power

• Novel power transformation systems

29

L � Pbeam

ECM=

�Pgrid

ECM


Muon Collider

• Muons are difficult to:

• Make enough of them

• Accelerate quickly

• 200 times more massive than electron

• No SR losses

30

P =1

4⇤⇥0

e2v4

c3⌅2�4

L � Pbeam

ECM=

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-34


Muon Production

• High power/current proton driver

• Target must take ~4 MW of power

• Mercury jet

• Solid tungsten

• Small tungsten spheres, with cooling

• Powder jet of tungsten??

• Magnetically levitated rotation toroid????

• Transverse momentum of muons?

31

L = fN1N2

4⇤p⇥x

�⇤x

⇥y

�⇤y

rotating toroid

proton beam

solenoid magnet

toroid at 2300 K radiates heat to water-cooled surroundings

toroid magnetically levitated and driven by linear motors

Target

p ⇡± ⌫µ

µ

ISIS at RAL


Muon Emittance and Cooling

• Cooling needed for most facilities ILC, CLIC, LHC, Muon

• Methods differ, radiation damping, stochastic cooling....

• Ionisation

32

L = fN1N2

4⇤p⇥x

�⇤x

⇥y

�⇤y

SC RF acceleratingstructures

Muon tracker

Liquid hydrogen

cell

µ�

dE

dx

V

MICE experiment at RAL


Fast Acceleration of Muons

• Synchrotron does not work for Muon acceleration

• Need to accelerate quickly

• Can’t because

• Typically

33

L = fN1N2

4⇤p⇥x

�⇤x

⇥y

�⇤y

B� = p/q

⌧ = �⌧0

B / I

EMMA at Daresbury Laboratory


LHC

• Options for LHC upgrade

• High luminosity

• High energy

34

the nominal LHC operation one expects an effective approximate exponential luminosity lifetime of 15 hours [2]. Depending on the machine ‘turn around’ time, a physics run should not last longer than the effective luminosity lifetime. The minimum ‘turn around’ time of the LHC machine is defined by the time it takes to bring the LHC magnets back to their injection current settings (ca. 20min [1]) the time needed to fill the LHC (16 min [1]), the time needed to accelerate the beam from 450 GeV to 7 TeV (ca. 20 min) and the time needed to prepare the beams for collisions (ca. 10 min) and amounts in an ideal operation scenario to ca. 70 min. A similar interruption time applies for almost any unforeseen interruption of the machine filling and acceleration process (e.g. equipment failure during the beam acceleration). A high reliability of all LHC components and its injector complex are therefore key ingredients for maximizing the integrated luminosity in the LHC experiments.

3. Summary of the LHC parameters Table 2 summarized the main nominal LHC parameters, together with the initial design parameters of the white book [5] and the ‘ultimate’ parameters. The ‘White book’ parameters still provide reasonable operation margins. The ultimate LHC performance level is only a factor two larger than the nominal value but no longer features any operational margins. The achievement of the nominal LHC parameters is therefore already a challenging task on its own and might require additional upgrades to the LHC infrastructure in order to overcome operational limitations.

Table 2: Initial, nominal and ‘ultimate’

beam parameters for the LHC with 25ns bunch spacing. *: Including contributions from IBS and rest gas collisions

4. Main Upgrade Options In 2002 CERN identified 3 main options for the LHC upgrade and grouped them according to their impact on the LHC infrastructure into three stages [6]. The required R&D efforts have been conducted within the 6th European Framework Program (FP6) on Coordinated Accelerator Research in Europe (CARE) [7] prepared by the European Steering Group on Accelerator R&D (ESGARD) [8]. Additional international collaborations have been started with laboratories in the U.S.A. within the US LHC Accelerator research Program (USLARP) [9]. In 2007 CERN has launched the implementation of the most urgent upgrade options within the ‘White paper’ initiative. The ‘White paper’ initiatives addresses three options: upgrade of the interaction regions (IRs), upgrade of the LHC injector complex [11] and consolidation. The IR upgrade has been divided into 2 sub phases: an initial phase aiming at larger operational margins and an efficient routine operation with ultimate beam parameters and !* = 0.25m (L = 2.5 1034 cm-2 sec-1) and a second phase aiming at a 10 fold increase of the nominal LHC luminosity. The initial phase is based on the development of low gradient, large aperture NbTi magnets using the spare cables of the LHC dipole production and has been launched within a CNI on ‘LHC upgrade options’ of the 7th European Framework Program (FP7). The second upgrade phase addresses the challenges of an extremely high radiation dose near the IPs for a peak luminosity of L = 1035 cm-2 sec-1. Options for the second upgrade phase focus on the development of new magnet technologies which feature higher peak fields and heat margins compared to the established NbTi magnet technology (e.g. Nb3Sn). The current studies include: R&D on Nb3Sn magnet technologies; studies for active absorbers at the transition of the IRs to the machine arcs (integration of a magnetic spectrometer inside an absorber block); and R&D on open mid-plane magnets with dedicated heat and

Parameters ‘white book’ nominal ultimate # bunches 3564 2808 2808 ppb 0.34 1011 1.15 1011 1.7 1011 !* 1 m 0.55 m 0.5 m " / # 1.07 µm 3.75 µm 3.75�µm full crossing angle 100 µrad 285µrad 315µradevents / crossing 1 <-> 4 19.2 44.2 L [cm-2 sec-1] 0.1 1034 1 1034 2.4 1034 luminosity lifetime* 56 h 15 h 10 h stored beam energy 121 MJ 366 MJ 541 MJ

5


-10-7.5

-5-2.5

02.5

57.5

10

-1.2

-0.8

-0.4

0.4

0.8

1.2

Collimation

• Collimation is to remove unwanted particles

• Off position-angle

• Off energy

• Smallest beta functions, beam size at IR regions

• Loose particles into detector

• Worse damage accelerator

35

R. Assmann

Low Low �� Optics for IR1 and IR5Optics for IR1 and IR5

Collisions at IP with small spot size

SC magnet

Absorber Collimator


LHC Upgrades

• What would you do with the LHC?

• Need to start thinking now

• High energy

• Access to heavier states

• Higher luminosity

• More precise measurements

• Need more particles, smaller beam size and higher frequency collisions

36

L = fN1N2

4�⇥x

⇥y

3) Reduce beta functions or emittance4) Crab crossing system

1) Upgrade pre-accelerators2) Injection system

5) Change RF and timingsystems... experimental triggers?


High Energy LHC

37

Linac4'

2"GeV&Booster&

HE#LHC&&&&2030#33&

SPS+,%1.3%TeV,%2030.33%

B� = p/q To reach higher energies require stronger magnetic fields• Research in new SC magnet technology


High Luminosity LHC

38

IR#upgrade#(detectors,#low3�#quad’s,#crab#cavi9es,#etc)##

~2020321#

SPS#enhancements#(an-#e.cloud#coa-ng,RF,##

impedance),#2012.2021#

L = fN1N2

4⇤p⇥x

�⇤x

⇥y

�⇤y

Booster'energy'upgrade'1.4'→'2'GeV,'~2015' Linac4,((

~2015(


IR Upgrade (L* & Crab Crossing)

39

• Squeeze the beta functions at the IR point

• Smaller beam sizes

• Collimation will change

• Larger beam power

• Detector and machine protection

• Interesting point is crab crossing

• Extra luminosity

Quad Quad

L⇤

p bunch


Crab Crossing Angle

• Fraction of nominal luminosity

40

p bunch

L(✓c

)

L0⇡

"1 +

✓�z

�⇤x

tan(✓c

/2)

◆2#1/2

✓cBunch length

Focus beam sizeFractionalluminosity

Crossing angle

• Recover luminosity by rotating bunches

• Much like a grab walkingThursday, 23 January 14

Dielectric Loaded Accelerator structure

Simulations with CST Microwave Studio

Multi-layer DLA structure: reduce H, hence current, at outer metal surface toreduce losses. Operating in TM03 mode reduces losses by a factor of 6 withcomparable shunt impedance (compared to single layer structure in TM01 mode)

Simulation done by CST MS.

outer dielectric: $=10inner dielectric: $=37

See C. Jing et. al., NIM A 594, 132 (2008)and AAC talks: WG3 Wed and Thurs mornings

transmission

reflectionmeasured

simulated

simulated

Differences due to losses (neglected in simulation),and small mismatches in VNA-DLA mode converter.

|H|

Ez

Woodpile Structure

See B. M. Cowan, PRSTAB 11, 011301 (2008).

a self-supporting 3D photonic crystal

Exotic Acceleration

• Compact acceleration

• Need higher gradients

• Plasma

• Dielectric wake-fields

• Photonic crystals

• Direct laser

• Principle is still power transformation need better efficiency and less break-down

41

TM01-like modes in QuasiCrystals

Measured (open symbols) and simulated (closed) Q, near 17 GHz:

Penrose (5-fold sym) Dodecagonal triangular lattice

See E. Di Gennaro et. al., Appl.Phys. Letters 93, 164102 (2008).

using sapphire rods with copper end-plates

Simulations performed withCST Microwave Studio.

Measured and simulated frequencies agree within 2%.

discrepancies due to uncertaintyin copper conductivity


Plasma Wakefield Acceleration

• Break down limits electron acceleration ~few TeV

• Higher efficiency

42

PRST-AB 4 PARTICLE-IN-CELL SIMULATIONS OF PLASMA… 101302 (2001)

f!x, t", where x refers to the coordinate along the emitter.The final relevant parameter is the particle weight w. Thecurrent density is given by

J!x, t" ! f!x, t"I0

A, (4)

where I0 is the specified current and A is the cross-sectionalarea of the emitter. Using these definitions, the total currentas a function of time can be written as

I!t" !Z x2

x1

g!x"J!x, t" dx

!I0

A

Z x2

x1

g!x"f!x, t" dx , (5)

where g!x" is a geometric factor given by g!x" ! 1 forCartesian coordinates and g!x" ! 2pr for axisymmetriccylindrical coordinates. Then the mean current density isJavg!x, t" ! I!t"#A, and the number of particles emittedper time step is N ! DtI!t"#qc, where qc ! qpw is thecharge on a computer particle of weight w.In the XOOPIC implementation for BEAMEMITTER, the func-

tion f!x, t" is integrated each time step (or less when thespatial and temporal dependencies are decoupled). The in-tegration yields the cumulative distribution function,

F!x, t" !

Rxx1

g!x0"f!x0, t" dx0Rx2

x1g!x"f!x, t" dx

, (6)

which maps the probability of a particle position x to auniformly distributed random number 0 # R , 1 by set-ting F ! R.

For the XOOPIC implementation of the VARWEIGHT-BEAMEMITTER, the particle positions are distributed uni-formly in x, and the weight is set according to w!x, t" !w0g!x"f!x, t", where w0 is the user-specified referenceweight. The VARWEIGHTBEAMEMITTER now also acceptsspecification of the number of particles to emit per timestep, adjusting the value of w0 appropriately to achievethe desired result.

IV. LASER-DRIVEN PLASMA ACCELERATORSIMULATIONS

We present two simulations of the standard LWFA, onedriven by a low !5.5 3 1016 W#cm2" and the other a high!3 3 1018 W#cm2" peak intensity laser pulse, both in slabgeometry. These simulations have relevance to ongoingLWFA experiments at the l’OASIS laboratory of LawrenceBerkeley National Laboratory [49–51]. PIC simulationsare necessary to understand the detailed particle trappingmechanisms in these experiments.These results demonstrate the capabilities of XOOPIC.

Preliminary XOOPIC studies of the effects of colliding laserpulses [4,5] were presented in Ref. [52].

A. Modeling the wakefield generated by a low intensitylaser pulse

We first consider the plasma wakefield generated by alow intensity laser pulse. The electron plasma densityis ne ! 3 3 1019 cm23, which corresponds to an EPW

FIG. 2. (Color) Surface plot of the longitudinal electric field Ex generated by the 5.5 3 1016 W#cm2 !a0 ! 0.2" laser pulse (largepeaks to the right) and the resulting plasma wake (smaller peaks, left and center). The structure of the laser pulse is seen clearly inthe contour plot (above) and the surface plot projection (below). Ex is shown in GV#m, while the coordinates x, y are shown in mm.

101302-5 101302-5


Summary

• Many different technologies and ideas

• Talk focused on lepton colliders

• What about proton/ion-electron, what about high-L, low-E lepton like B-factories, g-2, etc

• Ability to decode technical issues with future colliders

• LHC upgrades

• Future lepton colliders (electron and muon)

• Accelerator physics here applies well

• Machines that might be built in the next 2 decades is unclear

• Laser or beam PWA possible, but technically difficult

43


Revision I

44

the nominal LHC operation one expects an effective approximate exponential luminosity lifetime of 15 hours [2]. Depending on the machine ‘turn around’ time, a physics run should not last longer than the effective luminosity lifetime. The minimum ‘turn around’ time of the LHC machine is defined by the time it takes to bring the LHC magnets back to their injection current settings (ca. 20min [1]) the time needed to fill the LHC (16 min [1]), the time needed to accelerate the beam from 450 GeV to 7 TeV (ca. 20 min) and the time needed to prepare the beams for collisions (ca. 10 min) and amounts in an ideal operation scenario to ca. 70 min. A similar interruption time applies for almost any unforeseen interruption of the machine filling and acceleration process (e.g. equipment failure during the beam acceleration). A high reliability of all LHC components and its injector complex are therefore key ingredients for maximizing the integrated luminosity in the LHC experiments.

3. Summary of the LHC parameters Table 2 summarized the main nominal LHC parameters, together with the initial design parameters of the white book [5] and the ‘ultimate’ parameters. The ‘White book’ parameters still provide reasonable operation margins. The ultimate LHC performance level is only a factor two larger than the nominal value but no longer features any operational margins. The achievement of the nominal LHC parameters is therefore already a challenging task on its own and might require additional upgrades to the LHC infrastructure in order to overcome operational limitations.

Table 2: Initial, nominal and ‘ultimate’

beam parameters for the LHC with 25ns bunch spacing. *: Including contributions from IBS and rest gas collisions

4. Main Upgrade Options In 2002 CERN identified 3 main options for the LHC upgrade and grouped them according to their impact on the LHC infrastructure into three stages [6]. The required R&D efforts have been conducted within the 6th European Framework Program (FP6) on Coordinated Accelerator Research in Europe (CARE) [7] prepared by the European Steering Group on Accelerator R&D (ESGARD) [8]. Additional international collaborations have been started with laboratories in the U.S.A. within the US LHC Accelerator research Program (USLARP) [9]. In 2007 CERN has launched the implementation of the most urgent upgrade options within the ‘White paper’ initiative. The ‘White paper’ initiatives addresses three options: upgrade of the interaction regions (IRs), upgrade of the LHC injector complex [11] and consolidation. The IR upgrade has been divided into 2 sub phases: an initial phase aiming at larger operational margins and an efficient routine operation with ultimate beam parameters and !* = 0.25m (L = 2.5 1034 cm-2 sec-1) and a second phase aiming at a 10 fold increase of the nominal LHC luminosity. The initial phase is based on the development of low gradient, large aperture NbTi magnets using the spare cables of the LHC dipole production and has been launched within a CNI on ‘LHC upgrade options’ of the 7th European Framework Program (FP7). The second upgrade phase addresses the challenges of an extremely high radiation dose near the IPs for a peak luminosity of L = 1035 cm-2 sec-1. Options for the second upgrade phase focus on the development of new magnet technologies which feature higher peak fields and heat margins compared to the established NbTi magnet technology (e.g. Nb3Sn). The current studies include: R&D on Nb3Sn magnet technologies; studies for active absorbers at the transition of the IRs to the machine arcs (integration of a magnetic spectrometer inside an absorber block); and R&D on open mid-plane magnets with dedicated heat and

Parameters ‘white book’ nominal ultimate # bunches 3564 2808 2808 ppb 0.34 1011 1.15 1011 1.7 1011 !* 1 m 0.55 m 0.5 m " / # 1.07 µm 3.75 µm 3.75�µm full crossing angle 100 µrad 285µrad 315µradevents / crossing 1 <-> 4 19.2 44.2 L [cm-2 sec-1] 0.1 1034 1 1034 2.4 1034 luminosity lifetime* 56 h 15 h 10 h stored beam energy 121 MJ 366 MJ 541 MJ

5

6

Table 1.3: Main-beam and main-linac parameters for CLIC at 3 TeV c.m.

References

Prospects for physics (Section 1.1)[1.1] J. Ellis, Physics goals of the next century at CERN, CERN-TH-2000–050 (2000).[1.2] The Physics Study Group for CLIC, http://clicphysics.web.cern.ch/CLICphysics/

Overview of the linear collider (Section 1.2)[1.3] J.-P. Delahaye et al., The CLIC study of a multi-TeV e+e– linear collider, Proc. Part. Accel. Conf. (PAC99),

New York, 1999, Eds. A. Luccio and W. MacKay (IEEE Computer Soc. Press, Piscataway, N. J., 1999).http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=ps-99-005

[1.4] International Linear Collider Technical Review Committee Report, Ed. G. Loew, SLAC-R-95–471 (1995).http://www.slac.stanford.edu/pubs/slacreports/slac-r-471.html

[1.5] J. Ellis, E. Keil and G. Rolandi, Options for future colliders at CERN, CERN-EP/98–03, CERN-SL 98–004(AP) and CERN-TH/98–33 (1998).http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=SL-98-004

[1.6] J.-P. Delahaye, G. Guignard, T. Raubenheimer and I. Wilson, Scaling laws for e+/e– linear colliders, Nucl.Instrum. Methods Phys. Res. A 421 (1999) 369–405.http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=PS-97-051

[1.7] V.E. Balakin, A.V. Novokhatsky and V.P. Smirnov, VLEPP: transverse beam dynamics, Proc. 12th Int. Conf.on High Energy Accel., Fermilab, 1983, p. 119.

Main-beam parameters at IP

Luminosity (with pinch)Luminosity (in 1% of energy)Beamstrahlung mom. spreadBeamstrahlung parameterNumber of photons/electronNumber of particles/bunchNumber of bunches/pulseBunch spacing

Transverse emittancesBeta functionsr.m.s. beam size (no pinch)Bunch lengthEnhancement factorBeam power per beam

LL1%δBΥNγNbkbΔbΔtbγεx/yβx/yσx/yσzHDPb

10.0 × 1034 cm–2 s–1

3.0 × 1034 cm–2 s–1

31%8.12.3

4.0 × 109e±

15420 cm

0.666 ns680/20 nm⋅rad

8/0.15 mm43/1 nm30 µm2.24

14.8 MW

Main-linac parameters

Centre-of-mass energyLinac repetition rateRF frequency of linac Acceleration field (loaded)Energy overheadActive length per linacTotal two-linac lengthRF power at structure inputRF pulse durationNumber of drive-beams/linacNumber of structures per linacAC-to-RF efficiencyRF-to-beam efficiencyAC-to-beam efficiencyAC power for RF production

ECMfrepω/2πGa

LALtotPstΔtpND

PAC

3 TeV100 Hz30 GHz

150 MV/m8%

10.74 km27.5 km229 MW102 ns

2221 47040.3%24.4%9.8%

300 MW

ηRFAC

ηbRF

ηbAC

ACCELERATOR DESCRIPTION

2.7.3 System DescriptionThe main subsystems of the beam delivery starting from the exit of the main linacs arethe diagnostics region, the fast extraction and tuneup beamline, the betatron and energycollimation, the final focus, the interaction region and the extraction line. The layout of thebeam delivery system is shown in Figures 2.7-1 and 2.7-2. The BDS is designed for 500 GeVcenter of mass but can be upgraded to 1 TeV with additional magnets.

TABLE 2.7-1Key parameters of the BDS. The range of L�, the distance from the final quadrupole to the IP, correspondsto values considered for the existing detector concepts.

Parameter Units Value

Length (linac exit to IP distance)/side m 2226Length of main (tune-up) extraction line m 300 (467)Max Energy/beam (with more magnets) GeV 250 (500)Distance from IP to first quad, L* m 3.5-(4.5)Crossing angle at the IP mrad 14Nominal beam size at IP, ⌅�, x/y nm 639/5.7Nominal beam divergence at IP, ⇥�, x/y µrad 32/14Nominal beta-function at IP, ��, x/y mm 20/0.4Nominal bunch length, ⌅z µm 300Nominal disruption parameters, x/y 0.17/19.4Nominal bunch population, N 2� 1010

Beam power in each beam MW 10.8Preferred entrance train to train jitter ⌅y < 0.5Preferred entrance bunch to bunch jitter ⌅y < 0.1Typical nominal collimation aperture, x/y 8–10/60Vacuum pressure level, near/far from IP nTorr 1/50

There is a single collision point with a 14 mrad crossing angle. To support future energyupgrades, the beam delivery systems are in line with the linacs and the linacs are also orientedat a 14 mrad angle. The 14 mrad geometry provides space for separate extraction lines andrequires crab cavities to rotate the bunches horizontally for head-on collisions. There aretwo detectors in a common IR hall which alternately occupy the single collision point, in aso-called “push-pull” configuration. The detectors are pre-assembled on the surface and thenlowered into the IR hall in large subsections once the hall is ready for occupancy.

2.7.3.1 Diagnostics, Tune-up dump, Machine Protection

The initial part of the BDS, from the end of the main linac to the start of the collimationsystem (known for historical reasons as the Beam Switch Yard or “BSY”), is responsible formeasuring and correcting the properties of the beam before it enters the Collimation andFinal Focus systems. In addition, errant beams must be detected here and safely extractedin order to protect the downstream systems. Starting at the exit of the main linac, the system


increase in transverse emittance and is thus called emit-tance exchange.

The status report [9] outlines the details of the accel-eration and collider ring for the 0.1 TeV Higgs factory,shown schematically in Fig. 33. Table XIV gives a sum-mary of the parameters of various muon colliders includ-

ing three different modes of running the Higgs colliderthat have varying beam momentum spreads. Additionalinformation about the muon collider can be found in[133,134].

B. Longitudinal cooling

At the time of writing of the status report [9] therewas no satisfactory solution for the emittance exchangeproblem and this remained a major stumbling block to-wards realizing a muon collider. However, ring coolershave been found to hold significant promise in cooling in6D phase space. Another advantage of ring coolers is thatone can circulate the muons many turns, thereby reusingthe cooling-channel elements. Several meetings on emit-tance exchange were held [135] and a successful work-shop [136] was held in 2001, where we explored in somedepth several kinds of ring coolers. These options differprimarily in the type of focusing used to contain thebeam.We describe the current status of our understandingof three types of ring coolers here.

TABLE XIII. Transverse and longitudinal emittances at the end of the decay channel, study-II cooling channel, and the Higgs factory cooling channel.

Emittance at end of Transverse emittance (! mm) Longitudinal emittance (! mm)

Decay channel 17 150Study-II cooler 2.6 30Higgs factory cooler 0.14 9

FIG. 33. (Color) Plan of a 0.1-TeV-CoM muon collider, alsoknown as a Higgs factory.

TABLE XIV. Baseline parameters for high- and low-energy muon colliders. Higgs=year assumes a cross section " ! 5" 104 fb;a Higgs width ! ! 2:7 MeV; 1 yr ! 107 s.

CoM energy (TeV) 3 0.4 0.1p energy (GeV) 16 16 16

p’s=bunch 2:5" 1013 2:5" 1013 5" 1013

Bunches=fill 4 4 2Repetition rate (Hz) 15 15 15

p power (MW) 4 4 4#=bunch 2" 1012 2" 1012 4" 1012

# power (MW) 28 4 1Wall power (MW) 204 120 81

Collider circumference (m) 6000 1000 350Average bending field (T) 5.2 4.7 3

rms "p=p% 0.16 0.14 0.12 0.01 0.003

6D $6;N #!m$3 1:7" 10%10 1:7" 10%10 1:7" 10%10 1:7" 10%10 1:7" 10%10

rms $n (! mm mrad) 50 50 85 195 290%& (cm) 0.3 2.6 4.1 9.4 14.1"z (cm) 0.3 2.6 4.1 9.4 14.1

"r spot (#m) 3.2 26 86 196 294"& IP (mrad) 1.1 1.0 2.1 2.1 2.1

Tune shift 0.044 0.044 0.051 0.022 0.015nturns (effective) 785 700 450 450 450

Luminosity cm%2 s%1 7" 1034 1033 1:2" 1032 2:2" 1031 1031

Higgs=year 1:9" 103 4" 103 3:9" 103

PRST-AB 6 MOHAMMAD M. ALSHARO’A et al. 081001 (2003)

081001-35 081001-35


Revision II

45

increase in transverse emittance and is thus called emit-tance exchange.

The status report [9] outlines the details of the accel-eration and collider ring for the 0.1 TeV Higgs factory,shown schematically in Fig. 33. Table XIV gives a sum-mary of the parameters of various muon colliders includ-

ing three different modes of running the Higgs colliderthat have varying beam momentum spreads. Additionalinformation about the muon collider can be found in[133,134].

B. Longitudinal cooling

At the time of writing of the status report [9] therewas no satisfactory solution for the emittance exchangeproblem and this remained a major stumbling block to-wards realizing a muon collider. However, ring coolershave been found to hold significant promise in cooling in6D phase space. Another advantage of ring coolers is thatone can circulate the muons many turns, thereby reusingthe cooling-channel elements. Several meetings on emit-tance exchange were held [135] and a successful work-shop [136] was held in 2001, where we explored in somedepth several kinds of ring coolers. These options differprimarily in the type of focusing used to contain thebeam.We describe the current status of our understandingof three types of ring coolers here.

TABLE XIII. Transverse and longitudinal emittances at the end of the decay channel, study-II cooling channel, and the Higgs factory cooling channel.

Emittance at end of Transverse emittance (! mm) Longitudinal emittance (! mm)

Decay channel 17 150Study-II cooler 2.6 30Higgs factory cooler 0.14 9

FIG. 33. (Color) Plan of a 0.1-TeV-CoM muon collider, alsoknown as a Higgs factory.

TABLE XIV. Baseline parameters for high- and low-energy muon colliders. Higgs=year assumes a cross section " ! 5" 104 fb;a Higgs width ! ! 2:7 MeV; 1 yr ! 107 s.

CoM energy (TeV) 3 0.4 0.1p energy (GeV) 16 16 16

p’s=bunch 2:5" 1013 2:5" 1013 5" 1013

Bunches=fill 4 4 2Repetition rate (Hz) 15 15 15

p power (MW) 4 4 4#=bunch 2" 1012 2" 1012 4" 1012

# power (MW) 28 4 1Wall power (MW) 204 120 81

Collider circumference (m) 6000 1000 350Average bending field (T) 5.2 4.7 3

rms "p=p% 0.16 0.14 0.12 0.01 0.003

6D $6;N #!m$3 1:7" 10%10 1:7" 10%10 1:7" 10%10 1:7" 10%10 1:7" 10%10

rms $n (! mm mrad) 50 50 85 195 290%& (cm) 0.3 2.6 4.1 9.4 14.1"z (cm) 0.3 2.6 4.1 9.4 14.1

"r spot (#m) 3.2 26 86 196 294"& IP (mrad) 1.1 1.0 2.1 2.1 2.1

Tune shift 0.044 0.044 0.051 0.022 0.015nturns (effective) 785 700 450 450 450

Luminosity cm%2 s%1 7" 1034 1033 1:2" 1032 2:2" 1031 1031

Higgs=year 1:9" 103 4" 103 3:9" 103

PRST-AB 6 MOHAMMAD M. ALSHARO’A et al. 081001 (2003)

081001-35 081001-35


References• ILC

• http://tesla.desy.de/new_pages/TDR_CD/start.html

• http://www.linearcollider.org/about/Publications/Reference-Design-Report

• CLIC

• http://clic-study.web.cern.ch/clic-study/

• Muon collider

• http://mice.iit.edu/

• http://www.fnal.gov/pub/muon_collider/resources.html

• LHC

• Proceedings of LHC-LUMI-05

• Exotic acceleration

• https://slacportal.slac.stanford.edu/sites/ard_public/facet/Pages/Default.aspx/

• http://www.ireap.umd.edu/AAC2010/

46


http://www.linearcollider.org/about/Publications/Reference-Design-Report

http://www.linearcollider.org/about/Publications/Reference-Design-Report

http://clic-study.web.cern.ch/clic-study/

http://clic-study.web.cern.ch/clic-study/

http://mice.iit.edu

http://mice.iit.edu

http://www.fnal.gov/pub/muon_collider/resources.html

http://www.fnal.gov/pub/muon_collider/resources.html

https://slacportal.slac.stanford.edu/sites/ard_public/facet/Pages/Default.aspx/

https://slacportal.slac.stanford.edu/sites/ard_public/facet/Pages/Default.aspx/

http://www.ireap.umd.edu/AAC2010/

http://www.ireap.umd.edu/AAC2010/

Dr. Stewart T. Boogert Accelerator Physicist at the John Adams ... - UCL...

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