potential CERN facilities to study proton-driven plasma acceleration

Frank ZimmermannMunich MPI, 9 December 2008

CTF-3

existing accelerator chain (LHC beam)

PS booster

PS SPS LHC

final momentum [GeV/c] 2.1 26 450 7000protons/bunch [1011] 17 1.3 1.15 1.15rms longitudinal emittance [eVs] 0.11 0.03 0.06 0.2 (0.08*)rms bunch length [ns] 143 1 <0.5 0.25 (0.16*) relative rms energy spread [10-3] 0.32 1 0.3 0.11 (0.07*)rms transverse emittance [mm] 2.5 3.0 3.5 3.75bunch spacing [ns] N/A 25 25 25 # bunches / cycle 4 (4 rings) 72 288 2808cycle time 1.2 s 3.6 s ~22 s 5-10 h?

* w/o longitudinal blow up in the LHC1 ns = 30 cm, 3x10-4 ns = 100 mm

PSB

SPSSPS+

Linac4

(LP)SPL

PS

LHC / SLHC DLHC

Ou

tpu

t en

ergy

160 MeV

1.4 GeV4 GeV

26 GeV50 GeV

450 GeV1 TeV

7 TeV~ 14 TeV

Linac250 MeV

(LP)SPL: (Low Power) Superconducting Proton Linac (4-5 GeV)

PS2: High Energy PS(~ 5 to 50 GeV – 0.3 Hz)

SPS+: Superconducting SPS(50 to1000 GeV)

SLHC: “Superluminosity” LHC(up to 1035 cm-2s-1)

DLHC: “Double energy” LHC(1 to ~14 TeV)

Proton flux / Beam power

present and future LHC injectors

PS2

Roland Garoby, LHCC 1July ‘08

layout of new LHC injectorsSPS

PS2, ~2017

SPL,~2017

Linac4~2012

PS

R. Garoby, CARE-HHH BEAM07, October’07; L. Evans, LHCC, 20 Feb ‘08

R. Garoby, LHCC 1 July 2008

ID WBS Task Name

1 Linac4 project start

2 2 Linac systems

3 2.1 Source and LEBT construction, test

4 Drawings, material procurement

5 2.2 RFQ construction, test

6 2.4 Accelerating structures construction

7 Klystron prototypying

8 2.6.2 Klystrons construction

9 2.6.1 LLRF construction

10 2.7 Beam Instrumentation construction

11 2.8 Transfer line construction

12 2.9 Magnets construction

13 2.10 Power converters construction

14 5 Building and infrastructure

15 5.1 Building design and construction

16 5.2,3,4 Infrastructure installation

17 3 PS Booster systems

18 3.1 PSB injection elements construction

19 3.2 PSB beam dynamics analysis

20 4 Installation and commissioning

21 4.1 Test stand operation (3 + 10 MeV)

22 4.2 Cavities testing, conditioning

23 Cabling, waveguides installation

24 Accelerator installation

25 Klystrons, modulators installation

26 Hardware tests

27 Front-end commissioning

28 4.5 Linac accelerator commissioning

29 Transfer line commissioning

30 PSB modifications

31 4.6 PSB commissioning with Linac4

32 Start physics run with Linac4

01/01

01/05

Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q12007 2008 2009 2010 2011 2012 2013 2014

injector upgrade schedulesynchronized with LHC IR upgrades

LHC IR phase 1

LHC IR phase 2

2013: PSB with linac4

2017: SPL+PS2

upgraded accelerator chain (LHC beam)

SPL PS2 SPS LHCfinal momentum [GeV/c] 5 50 450 7000protons/bunch [1011] 2.5x10-4 4 4 4rms longitudinal emittance [eVs] 7.3x10-7 0.05 0.06 0.2 (0.08*)rms bunch length [ns] 1.9x10-4 1 <0.5 0.25 (0.16*) relative rms energy spread [10-3] 0.18 1 0.3 0.11 (0.07*)rms transverse emittance [mm] 0.35 3.0 3.5 3.75bunch spacing [ns] 2.8 25 25 25 # bunches / cycle 200,000 144 288 2808cycle time 20 ms 2.4 s ~13 s 5-10 h?

* w/o longitudinal blow up in the LHC1 ns = 30 cm, 3x10-4 ns = 100 mm

phase space at SPL exit

M. EshraqiA. Lombardi

intermediate conclusions the only proton beam which is naturally “short” is the one

from the SPL, ~60 micron rms length, with 2.5x107 protons / bunch and available at the earliest in 2017 the beam from the SPS must be compressed by a factor

10,000 to obtain rms bunch lengths of 100-200 mm equilibrium bunch length scales with the inverse 4th root

of RF voltage and with the 4th root of the momentum compaction factor

four other possibilities come to mind: rapid change in momentum compaction factor

followed by bunch rotation in mismatched bucket or transverse deflecting cavity?! damping by intrabeam scattering below transition?! coherent electron cooling?!

mismatch

pulse fast quadrupolesto changemomentum compaction, and quickly raise RF voltage

bunch

shape of linear rf bucket

z

d

extract after ¼ synchrotron oscillation when bunch length is minimum

bunch length scales with the square root of pulsed momentum compaction factor

initial momentum compaction ac,initial ~ 0.01 we may hope for ac,new ~ 10-6

initial RF voltage ~ few MVwe may hope for final RF voltage ~ 10x higher

→ expect compression by factor 2 x 10-2 /Sqrt(10) ~ 0.006 ~ 1/160

transverse deflecting cavity+bending system

transverse deflecting cavity

drift

bendingsystem?

can something like this work?

idea is to convert transverse size into longitudinal size

(above schematic ignores x-dependent energy change fromcrab cavity)

can the plasmawave excited by crabbed beam be used for e- acceleration?

shortbunch!

or transverse crab cavity followed by “slit”?

coherent e- cooling

CeC proof-of-Principle experiment at RHIC in 2012

damping times in hours:

promise of 1-hr damping time at 7 TeV!

V. Litvinenko, Y. Derbenev

interesting, but still too small for our purpose

final conclusion

to get “high-energy” proton bunch lengths below 1 mm,

we can use the beam from the SPL, or we need strong cooling or bunch compression or an x(y)-z 4/6-D emittance exchange transformation or a combination thereof

appendix: thoughts on scattering limits and chances

• scattering limits and maximum energy reach of plasma accelerators

• the return of fixed target experiments?

scattering limits and energy reach• at the plasma-acceleration WG of CLIC08 Andrei

Seryi and Tor Raubenheimer reported that 500 GeV acceleration in a plasma was possible, but that 1.5 TeV was excluded by Coulomb scattering – this seemed odd at first glance since Coulomb scattering gets weaker at higher energy

• scattering limits were previously looked at by Montague & Schnell (1985) and Katsouleas & Dawson (1987)

A. SeryiCLIC08 workshop, Plasma wakefield acceleration working group, CERN, Oct. 2008

B.W. Montague, W. SchnellMultiple scattering and synchrotron radiation in the plasma beat wave accelerator.2nd Int. Workshop on Laser Acceleration of Particles, Los Angeles, CA, Jan 7-18 Jan 1985, AIP Conf.Proc.130:146-155,1985.

T. Katsouleas, J.M. Dawson Plasma acceleration of particle beams. 1987. AIP Conf.Proc.184:1798-1828,1989.

22/1

2 1

ds

d

ds

d

2/1

22/3 1

final

d

d

multiple scattering from my memory

indeed the normalized emittance grows as the square root of the finalenergy, but no hard limit in energy reach

to avoid this limit the b function must increase less than with the the square root of energy (e.g. tapered plasma density)

scaling of the multiple scattering limit

bremsstrahlung

most important vacuum limit at high energy e+ or e- machines

this effect would suggest that the total distancetravelled through the plasma cannot be more than one or a few radiation lengths

for example X0~10 m for 4x1022 e/cm3

using the rough estimate of 30 GV/m for 1x1017e/cm3 this gives an ultimate energy of ~200 TeV

0

2ln

0X

X

eEE

nuclear interaction of protons with plasma?

similar magnitude as radiation length

variation with beam energy?

return of fixed target experiments

since extremely high gradients are feasible with plasmas but the collision of two such beams may be difficult to achieve, could fixed target experiments become attractive again? Pantaleo Raimondi

in particular they could be interesting for proton driven plasma accelerators with a single proton beam, a single stage, and very high proton and electron energy;possibly high luminosity

experiment might be different from present colliders