Lattice Design Choices for
LHeC ERL
Alex Bogacz
Jefferson Lab
March 17-20, 2014
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
EIC14 Workshop, Jefferson Lab, March 20, 2014
1
Linac-Ring Option - LHeC ERL Recirculator
tune-up dump
10-GeV linac
0.12 km
comp. RF
comp. RF
injector
0.17 km
1.0 km
20, 40, 60 GeV
total circumference ~ 8.9 km
2.0 km
LHC p
10, 30, 50 GeV
dump
10-GeV linac
0.03 km
0.26 km
IP
F. Zimmermann
e- final focus
The baseline 60 GeV ERL option proposed can give an e-p luminosity of 1033 cm-2s-1 (extensions to 1034 cm-2s-1 and beyond are being considered)
Thomas Jefferson National Accelerator Facility
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EIC14 Workshop, Jefferson Lab, March 20, 2014
2
Why Energy Recovering RLA?
High energy (60 GeV), high current (6.4 mA) beams: (384 MW beam power) would
require sub GW (0.8 GW)-class RF systems in conventional linacs .
Invoking Energy Recovery alleviates extreme RF power demand (power reduced by
factor (1 - hERL) ⇨ Required RF power becomes nearly independent of beam current.
Energy Recovering Linacs promise efficiencies of storage rings, while maintaining
beam quality of linacs: superior emittance and energy spread and short bunches
(sub-pico sec.).
GeV scale Energy Recovery demonstration with high ER ratio (hERL = 0.98) was
carried out in a large scale SRF Recirculating Linac (CEBAF ER Exp. in 2003)
No adverse effects of ER on beam quality or RF performance: gradients, Q, cryoload observed – mature and reliable technology (next generation light sources)
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EIC14 Workshop, Jefferson Lab, March 20, 2014
3
LHeC Recirculator with ER
injector
Linac 1
0.5 GeV
10 GeV/pass
Arc1, 3, 5
dump
Linac 2
0.5 GeV
10 GeV/pass
Arc 2, 4, 6 + l/2
IP
60 GeV
LHC
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EIC14 Workshop, Jefferson Lab, March 20, 2014
4
LHeC Recirculator with ER
injector
Linac 1
0.5 GeV
10 GeV/pass
Arc1, 3, 5
dump
Linac 2
0.5 GeV
10 GeV/pass
Arc 2, 4, 6 + l/2
IP
60 GeV
LHC
Thomas Jefferson National Accelerator Facility
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EIC14 Workshop, Jefferson Lab, March 20, 2014
5
LHeC Recirculator with ER
injector
Linac 1
0.5 GeV
10 GeV/pass
Arc1, 3, 5
dump
Linac 2
0.5 GeV
10 GeV/pass
Arc 2, 4, 6 + l/2
IP
60 GeV
LHC
Thomas Jefferson National Accelerator Facility
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EIC14 Workshop, Jefferson Lab, March 20, 2014
6
ERL–Ring: Dimensions/Layout
J. Osborne
IP
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EIC14 Workshop, Jefferson Lab, March 20, 2014
7
Beam Dynamics Challenges/Mitigations
Incoherent and coherent synchrotron radiation related effects
on the electron beam
energy losses
Size/Layout
longitudinal emittance increase
Size/Layout
transverse emittance increase
Lattice
Beam Breakup Instability (BBU)
single beam
Lattice
multi-pass
Lattice
Depolarization effects
Lattice
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EIC14 Workshop, Jefferson Lab, March 20, 2014
8
BETA_X&Y[m]
160
5
Cryo Unit Layout/Optics - Half-Cell 1300 FODO
×3
8
0
BETA_X
quad
BETA_Y
DISP_X
0
0
Lc
DISP_Y
Cavity Cryo: 8 RF cavities
29.6
Cavity Cryo: 8 RF cavities
802 MHz RF, 5-cell cavity:
D. Schulte
l = 37.38 cm
Lc = 5l/2 = 93.45 cm
Grad = 18 MeV/m (16.8 MeV per cavity)
DE= 269.14 MV per Cryo Unit
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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10 GeV Linac - Focusing profile
5
200
E = 0.5 - 10.5 GeV
0
0
DISP_X&Y[m]
BETA_X&Y[m]
quad gradient
0
BETA_X
BETA_Y
DISP_X
DISP_Y
1008
19 FODO cells (19 × 2 × 16 = 608 RF cavities)

1 

=   ds 
E
L E
min
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EIC14 Workshop, Jefferson Lab, March 20, 2014
10
Linac 1 - Multi-pass ER Optics
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EIC14 Workshop, Jefferson Lab, March 20, 2014
11
Linac 1 and 2 - Multi-pass ER Optics
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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Arc Optics – Beam Dynamics Issues
Natural momentum spread due to quantum excitations:
Ds E2
E2
55a æ c ö 5
=
ç 2 ÷ g I3
24 3 è mc ø
2
I3 =
ò
1
L
r
0
ds =
3
q
,
2
r
Emittance dilution due to quantum excitations:
55 r0
c 6
De N =
g I5
2
48 3 mc
I5 =
L
ò
0
H
r
3
ds =
q H
r
2
,
H = g D 2 + 2a DD '+ b D '2
Momentum Compaction – synchronous acceleration in the linacs:
1
M 56 = I1
C
L
I1 = 
0
D

ds
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EIC14 Workshop, Jefferson Lab, March 20, 2014
13
0
-1.5
DISP_X&Y[m]
BETA_X&Y[m]
1.5
150
1350 FODO Cell
0
D
N
BETA_X
c 6

=

H
2
2
48 3 mc
55 r0
BETA_Y
DISP_X
DISP_Y
52.3599
at 50.5 GeV
H = 2.2  10-2 m
D N = 82 micron rad
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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150
0.3
BETA_X&Y[m]
DISP_X&Y[m]
Flexible Momentum Compaction (FMC) Cell
Emittance dispersion
Momentum compaction
0
-0.3
〈H〉avereged over bends
0
BETA_X
H =  D2  2 DD '  D '2
BETA_Y
DISP_X
DISP_Y
52.3599
M 56 = - 
H = 8.8  10-3 m
factor of 2.5 smaller than 1350 FODO
D

ds = -bend D
M 56 = 1.16  10-3 m
factor of 27 smaller than 1350 FODO
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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Arc Optics – Emittance preserving FMC cell
c 6


H
2
2
48 3 mc
55 r0
BETA_X
BETA_Y
DISP_X
52.3599
DISP_Y
H = 8.8  10-3 m
0
BETA_X
BETA_Y
DISP_X
52.3599
DISP_Y
0
H = 2.2  10-3 m
DISP_X&Y[m]
TME-like Optics
-0.5
0.5
DISP_X&Y[m]
BETA_X&Y[m]
-0.5
DBA-like Optics
500
Arc5, Arc 6
0
500
BETA_X&Y[m]
0
0
0
DISP_X&Y[m]
Imaginary t Optics
-0.5
0.5
Arc 3, Arc 4
BETA_X&Y[m]
500
Arc 1 , Arc2
H = g D2 + 2a DD'+ b D'2
0.5
D N =
BETA_X
BETA_Y
DISP_X
DISP_Y
52.3599
H = 1.2  10-3 m
factor of 18 smaller than FODO
total emittance increase in Arc 5: DxN = 4.268 mm rad
Thomas Jefferson National Accelerator Facility
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EIC14 Workshop, Jefferson Lab, March 20, 2014
16
Energy Loss and Emittance Dilution in Arcs
A. Valloni
Thomas Jefferson National Accelerator Facility
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EIC14 Workshop, Jefferson Lab, March 20, 2014
17
Vertical Separation of Arcs
y [cm]
Spreader 1, 3 and 5
150
Arc 1 (10 GeV)
100
Arc 3 (30 GeV)
50
Arc 5 (50 GeV)
0
-50
0
1000
2000
3000
4000
5000
6000
7000
8000
z [cm]
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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-0.6
0
Spr. 1
DISP_X&Y[m]
BETA_X&Y[m]
0.6
600
Vertical Spreaders - Optics
0
BETA_X
BETA_Y
DISP_X
DISP_Y
vertical step I
76
path-length adjustment
‘doglegs’
-0.6
DISP_X&Y[m]
BETA_X&Y[m]
0
Spr. 3
0.6
600
vertical step II
0
BETA_X
BETA_Y
DISP_X
DISP_Y
vertical step I
76
path-length adjustment
‘doglegs’
-0.6
DISP_X&Y[m]
BETA_X&Y[m]
0
Spr. 5
0.6
600
vertical step II
0
BETA_X
BETA_Y
vertical chicane
DISP_X
DISP_Y
76
path-length adjustment
‘doglegs’
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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Vertical Separation of Arcs
Arc 1 (10 GeV)
Arc 3 (30 GeV)
Arc 5 (50 GeV)
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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0
BETA_X
BETA_Y
DISP_X
DISP_Y
vert. 2-step doglegs dis. sup. cell
spreader
230
3060
0.6
DISP_X&Y[m]
-0.6
BETA_X&Y[m]
0
600
DISP_X&Y[m]
-0.6
0
BETA_X&Y[m]
0.6
600
Arc 1 Optics (10 GeV)
BETA_X
BETA_Y
DISP_X
58 FMC cells
DISP_Y
dis. sup. cell
3292.61
doglegs
vert. 2-step
recombiner
180 deg. Arc
Arc dipoles:
$Lb=400 cm
$B=0.47 kGauss
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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0
BETA_X
BETA_Y
DISP_X
DISP_Y
vert. 2-step doglegs dis. sup. cell
spreader
230
0.6
DISP_X&Y[m]
600
BETA_X&Y[m]
0
3060
-0.6
0.6
DISP_X&Y[m]
-0.6
0
BETA_X&Y[m]
600
Arc 3 Optics (30 GeV)
BETA_X
BETA_Y
DISP_X
58 FMC cells
DISP_Y
dis. sup. cell
3292.58
doglegs
vert. 2-step
recombiner
180 deg. Arc
Arc dipoles:
$Lb=400 cm
$B=1.37 kGauss
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EIC14 Workshop, Jefferson Lab, March 20, 2014
22
Vertical Stack - Combined Aperture Arc Dipole
∙
∙
×
×
0.264 T
60 GeV
×
0.176 T
40 GeV
∙
∙
×
0.088 T
20 GeV
A. Milanese
Thomas Jefferson National Accelerator Facility
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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Summary
High luminosity Linac-Ring option - ERL
RF power nearly independent of beam current.
Multi-pass linac Optics in ER mode
Choice of linac RF and Optics - 802 MHz SRF and 1300 FODO
Linear lattice: 3-pass ‘up’ + 3-pass ‘down’
Arc Optics Choice - Emittance preserving lattices
Quasi-isochronous lattices
Flexible Momentum Compaction Optics
Balanced emittance dilution & momentum compaction
Complete Arc Architecture
Vertical switchyard
Matching sections & path-length correcting ‘doglegs’
Alternative ERL Topology - ‘Dogbone’ Option?
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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Special Thanks to:
Frank Zimmermann
Daniel Schulte
Erk Jensen
Oliver Brüning
and
Max Klein
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EIC14 Workshop, Jefferson Lab, March 20, 2014
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‘Racetrack’ vs ‘Dogbone’ RLA
Twice the acceleration efficiency for the ‘Dogbone’ topology
DE/2
1.5 DE
DE/2
DE
3 DE
Challenge: traversing linac in both directions while accelerating
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‘Dogbone’ vs ‘Racetrack’ – Arc-length
9×DE/2
9×DE/2
=
n×

n(p  4)R
2n×
=
2npR

Net arc-length break even: if  = p/4
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Future Muon Facilities - Muon Acceleration
n to Homestake
Neutrino Factory
LBNE
NF Decay Ring
Higgs Factory
RLA to 63 GeV
Linac + RLA to 4 GeV
Fermilab
J.-P. Delahaye, MASS
(Muon Accelerator Staging Studies)
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Droplet Arcs - Layout
top view
1.2 GeV
side view
2.4 GeV
1.2 GeV

1m
2.4 GeV
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‘Racetrack’ vs ‘Dogbone’ ERL for LHeC
3-pass RLA
Baseline
0.5 GeV
10 GeV
30 GeV
g5
De0 » H 2
r
20 GeV
10 GeV linac
40 GeV
0.5 GeV
50 GeV
10 GeV linac
60 GeV
IP
60 GeV
5-pass RLA
‘Dogbone’
24GeV
12 GeV
0.5 GeV
48 GeV
0.5 GeV
36 GeV
60 GeV
12 GeV linac
IP
60 GeV
5 æ 48 ö
De = De0 ç ÷ = 1.36 De0
3 è 50 ø
5
 = p /6
5 300
=
3 180
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‘Dogbone’ RLA - Multi-pass Linac Optics
Acceleration
Deceleration
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Pros and Cons of a ‘Dogbone’ RLA
High acceleration efficiency (≤2) –
Beams of different energies moving
traversing the linac in both directions
in the opposite direction through
while accelerating
the linac – orbit separation needed
Better orbit separation at linac’s end
to avoid parasitic collisions.
~ energy difference between
As linac length and number of
consecutive passes (2DE) vs (DE) in
passes are increased, the BBU
case of the ‘Racetrack’
threshold can be a problem.
Suppression of depolarization effects
Travelling ‘clearing gaps’ to
Beam trajectory can be made to follow
alleviate ion trapping - No practical
a Figure-8 path (by reversing field
solution found
directions in opposing droplet arcs)
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