potential CERN facilities to study
proton-driven plasma
acceleration
Frank Zimmermann
Munich MPI, 9 December 2008
CTF-3
existing accelerator chain (LHC beam)
final momentum [GeV/c]
protons/bunch [1011]
rms longitudinal emittance [eVs]
rms bunch length [ns]
PS
booster
PS
SPS
LHC
2.1
17
0.11
143
26
1.3
0.03
1
450
1.15
0.06
<0.5
7000
1.15
0.2 (0.08*)
0.25 (0.16*)
1
3.0
25
0.3
3.5
25
0.11 (0.07*)
3.75
25
relative rms energy spread [10-3] 0.32
2.5
rms transverse emittance [mm]
bunch spacing [ns]
N/A
# bunches / cycle
cycle time
1 ns = 30 cm, 3x10-4 ns = 100 mm
4 (4 rings) 72 288 2808
1.2 s
3.6 s ~22 s 5-10 h?
* w/o longitudinal blow up in the LHC
present and future LHC injectors
Proton flux / Beam power
50 MeV
160 MeV
Output energy
1.4 GeV
4 GeV
26 GeV
50 GeV
450 GeV
1 TeV
7 TeV
~ 14 TeV
Linac2
Linac4
PSB
(LP)SPL
PS
PS2
SPS
LHC /
SLHC
SPS+
(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)
DLHC
Roland Garoby, LHCC 1July ‘08
layout of new LHC injectors
SPS
PS2, ~2017
SPL,~2017
PS
Linac4
~2012
R. Garoby, CARE-HHH BEAM07, October’07; L. Evans, LHCC, 20 Feb ‘08
injector upgrade schedule
synchronized with LHC IR upgrades
R. Garoby,
LHCC 1 July 2008
LHC IR phase 1
2013: PSB
with linac4
LHC IR
phase 2
2017:
SPL+PS2
upgraded accelerator chain (LHC beam)
SPL
5
PS2 SPS
50 450
LHC
7000
2.5x10-4
7.3x10-7
1.9x10-4
0.18
4
0.05
1
1
4
0.2 (0.08*)
0.25 (0.16*)
0.11 (0.07*)
rms transverse emittance [mm]
bunch spacing [ns]
# bunches / cycle
0.35
2.8
200,000
3.0 3.5
25 25
144 288
cycle time
20 ms
2.4 s ~13 s 5-10 h?
final momentum [GeV/c]
protons/bunch [1011]
rms longitudinal emittance [eVs]
rms bunch length [ns]
relative rms energy spread [10-3]
1 ns = 30 cm, 3x10-4 ns = 100 mm
4
0.06
<0.5
0.3
3.75
25
2808
* w/o longitudinal blow up in the LHC
phase space at SPL exit
M. Eshraqi
A. 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
d
bunch
shape of
linear rf
bucket
z
pulse fast
quadrupoles
to change
momentum
compaction, and
quickly raise RF voltage
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 MV
we 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
can the plasma
wave excited by
crabbed beam be
used for eacceleration?
drift
transverse deflecting cavity
bending
system?
can something like this work?
idea is to convert transverse size
into longitudinal size
short
bunch!
(above schematic ignores x-dependent energy change from
crab cavity)
or transverse crab cavity followed by “slit”?
coherent ecooling
damping times in hours:
V. Litvinenko, Y. Derbenev
promise of
1-hr damping
time at 7 TeV!
CeC proof-ofPrinciple
experiment at
RHIC in 2012
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. Seryi
CLIC08 workshop, Plasma wakefield acceleration working
group, CERN, Oct. 2008
B.W. Montague, W. Schnell
Multiple 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.130:146155,1985.
T. Katsouleas, J.M. Dawson
Plasma acceleration of particle beams. 1987.
AIP Conf.Proc.184:1798-1828,1989.
scaling of the multiple scattering limit
d
d 2
1/ 2 1


ds
ds
2
d  
3/ 2 1

d
2
/2
    1final
multiple scattering from
my memory
indeed the normalized
emittance grows as the
square root of the final
energy, but no hard limit
in energy reach
to avoid this limit the  function must increase less than with the
the square root of energy (e.g. tapered plasma density)
bremsstrahlung
most important vacuum limit at high energy e+ or emachines
X
 ln 2
E  E0 e
X0
this effect would suggest that the total distance
travelled 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
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