High-energy high-luminosity
electron-ion collider eRHIC
Vladimir N. Litvinenko for eRHIC team
Brookhaven National Laboratory, Upton, NY, USA
Stony Brook University, Stony Brook, NY, USA
Center for Accelerator Science and Education
V.N. Litvinenko, “The Science Case for an EIC” INT workshop, Seattle, WA, Nov , 2010
Acknowledgements
•
All members of eRHIC team and BNL task force for their
numerous contributions, especially Joanne Beebe-Wang,
Ilan Ben-Zvi, Xiangyun Chang, Yue Hao, Animesh Jai,
Dmitry Kayran, George Mahler, Wuzheng Meng, Brett
Parker, Vadim Ptitsyn, Thomas Roser, John Skaritka,
Dejan Trbojevic, Nicholaos Tsoupas, Joseph Tuozzolo,
Gang Wang, an ex-BNLer Eduard Pozdeyev and Genya
Tsentalovich from MIT
•
Inputs on Physics from BNL EIC task force,
E.-C.Aschenauer, T.Ulrich A.Cadwell,
A.Deshpande, R.Ent, W.Gurin, T.Horn,
H.Kowalsky, M.Lamont, T.W.Ludlam,
R.Milner, B.Surrow, S.Vigdor,
R.Venugopalan, W.Vogelsan
•
Ourcollaborators on CeC PoP experiment from
Jlab: M.Poelker, R,Rimmer, G.Krafft,
A.Hutton, and Tech X: D.Bruhwiler,
G.Bell,B.Schwartz
•
Supported by Brookhaven Science Associates under Contract No. DEAC02-98CH10886 with the U.S. Department of Energy
Content
• Why electron-hadron collider?
• What world has to offer?
• eRHIC @ BNL: brief review
• Recent developments and plans
• Accelerator R&D for eRHIC
• Conclusions
3
Why electron-hadron collider?
– High Energy ep/eA colliders are the perfect instrument for high precision studies.
They are the ultimate QCD microscope.
© E. Aschenauer & T. Ulrich
Quark splits
into gluon
splits
into quarks …
Gluon splits
into quarks
10-16m
10-19m
higher √s
increases resolution
–
Over decades they have been the cornerstone of High Energy and High Energy Nuclear Physics
–
Next Generation:
• High energy eA collisions
• Polarized beams: e↑p↑
• Substantially higher √s and/or L
•
Proposed Facilities
‣ LHeC (CERN)
‣ EIC (BNL/JLAB)
‣ ENC (FAIR)
The Science of Electron-Hadron Colliders
© E. Aschenauer & T. Ulrich
High density parton matter, gluon
saturation/non-linear QCD, Color-GlassCondensate?
eA
e↑p↑
Spin structure of the nucleon
3D Spatial Landscape of the nucleon:
valence quarks → gluons and sea
Lepton Flavor Number Violation
ep
Formation of color neutral hadrons from quarks
and gluons
10
100
Higgs physics, Supersymmetry,
Beyond the Standard
Model,
Tera-scale physics,
Substructure of quarks
and leptons?
1000
√s (GeV)
Energy Reach and
Luminosities of future
electron-hadron colliders
eRHIC
MEIC/
ELIC
ENC
LHeC
ECM  4E e E h
Luminosity in e-A case
is per nucleon, i.e. it is
the RHIC style
“equivalent e-p
luminosity”

ELIC parameters are in next talk
eRHIC: QCD Factory at BNL
12 o’clock proposed
Add electron accelerator to the existing
$2B RHIC
RHIC
PHENIX
e-
3.8 km in circumference
STAR
Unpolarized and
e80% polarized
leptons, 2-30 GeV
BOOSTER
70% polarized protons
50-250 (325) GeV
RF
Light ions (d,Si,Cu)
Heavy ions (Au,U)
50-100 (130) GeV/u
ERL Test Facility
Polarized light ions
(He3) 215 GeV/u
e+
EBIS
p
AGS
Center of mass energy range: 20-200 GeV
Any polarization direction in lepton-hadrons collisions
electrons
protons
TANDEMS
Brief history of eRHIC
•
First eRHIC paper, 2000, I. Ben. Zvi
et al., ~300 papers after that, 138
@JACoW, 26 Phys. Revs, 54 NIMs….
•
First White Paper on eRHIC/EIC, 2002
Appendix A of the eRHIC ZDR
•
•
•
2003, eRHIC appears in DoE’s “Facilities
for the Future Sciences. A TwentyYear Outlook”
“eRHIC Zeroth-Order Design Report”
with cost estimate for Ring-Ring, 2004
2007 – after detailed studies we found
that linac-ring (LR) has ~10-fold higher
luminosity – LR became the main option
•
2008 – first staging option of eRHIC
•
In 2009 – completed technical design,
dynamics studies and cost estimate for
MeRHIC with 4 GeV ERL
•
Present - returned to the costeffective (green) all in tunnel highluminosity eRHIC design with staging
electron energy from 5 GeV to 30 GeV
Linac-Ring eRHIC.
Daniel Anderson, Ilan Ben-Zvi1, Rama Ca laga1, Xiangyun Chang1,
Manouchehr Farkhondeh2, Alexei Fedotov1, Jšrg Kewisch1, Vladimir Litvinenko1,
William Mackay1, Christoph Montag1, Thomas Roser1, Vitaly Ya kimenko3
(1)
Electron
e ~ 0.1 storage ring
eRHIC
C-AD, BNL (2) Bates, MIT (3) Physics Department, BNL
Content
page
detector 173
181
Main beam parame ters and lumin osity
183
2
x
200
m
SRF
linac
Layout of the Linac-ring eRHIC
186
a. Energy recovery L inac 4 (5) GeV per pass188
b. Polarized electron g un
204
c. Laser source for the polarized
gun passes
209
5 (4)
1. Introduction to the Linac- Ring collider
1.1 Advantages of the ERL-based eRHIC
2.
3.
d. The e-beam polarizat ion and
✔
polarization transpare ncy of the ERL lattice
e. Electro n cooling
f. Integration with IP
g. Considerations of the experiments
214
219
ERL
223
231
h. Adjustment of collision frequency for variable hadron energies
232
4. Cost
235
5. R&D items
236
6. Future energy upgra des
240
7. Summary
242
8. Acknowledgements
243
Lumi x 10
-
STAR
2007 Choosing the focus:
ERL or ring for electrons?
• Two main design options for eRHIC:
– Ring-ring:
4  h  e 
'
'
L  
 h e  h e f
 rh re 
Electron storage ring
RHIC
e ~ 0.1

– Linac-ring:
Z
L   h f N h h* h
 h rh
RHIC
Electron linear accelerator
 e 1
L x 50
Natural staging strategy

✔
MeRHIC – 2007/2008
•
Completed 2 technical designs of 3pass 4 GeV ERL – selected a
racetrack over a dog-bone
•
Developed injector concept
•
Completed isochronous achromatic
lattice
for the ERL including
90 MeV Linac
10 MeV Injector
spreaders and combiners
11 m
•
Completed development of IR with
detector
Gatling Gun
10 MeV Booster Linac
Ek=200keV)
•
•
•
Studied in details all aspects of
MeRHIC
11 m





Linac 1
from
MeRHIC
beam
dynamics – no showstoppers
arcs
1.4, 2.7, 4 GeV









Longitudinal dynamics
Transverse dynamics
Energy loss & compensation
Emittances growth
Wake-fields:
CSR, cavity, resistive wall…
Beam losses
Touschek, residual gas
10 MeV x 50 mA
Ion accumulation
0.5 MW Beam Dump
Transverse Solenoid
Beam Break-Up
Magnet errors
(4T)
Dipole
Beam-Beam effect on protons
~3Tm
MeRHIC
vertical
Noise in electrontobeam
combiner
Electron beam disruption
Effect of clearing gap
Kink instability…….
Finally went through a lengthy
30 m 2
Linac
bottoms-up
cost
estimate
and
Beam losses: Collisions with residual gas
internal review
1T, 3m
dipole
DX
LearnedScattering
a lot and
shelved it
1T, 3m
Bremsstrahlung
dipole
(April
Solenoid, 4 T
09)
p, Au
e
DX
Staging of all-in-tunnel e-RHIC
30 GeV
25 GeV
20 GeV
Polarized e-gun
eRHIC detector
Beam-dump
15 GeV
10 GeV
Common vacuum chamber
ARC’s
e- energy increases from 5 to 30 GeV by building-up SRF linacs
5 GeV
30 GeV e+ ring
Gap 5 mm total
0.3 T for 30 GeV
Common vacuum chamber
27.5 GeV
22.5 GeV
30 GeV ERL
17.5GeV
HE ERL passes
12.5 GeV
LE ERL passes
7.5 GeV
2.5 GeV
100m
|--------|
1.27 m beam
high
6 passes
30 GeV
25 GeV
20 GeV
RHIC: 325 GeV p
or 130 GeV/u Au
15 GeV
10 GeV
5 GeV
STAR
The most
cost effective
design
eRHIC Linac Design developments
•Energy of electron beam is increased in stages by increasing the length of the
linacs, up to maximum length of 200m of each linac
•Acceleration gain per cavity: 18 MV for 26.5 Gev, 20.4 MV for 30 GeV
•Several variants of lattice have been considered, including the lattice without
quadrupoles inside the linac.
•BBU simulations for different lattices are underway
© I. Ben-Zvi, G.Mahler
New design of 704 MHz cavity (BNL III):
-reduced peak surface magnet field
-reduced cryogenic load
12
Recirculating arc lattice
© D.Trbojevic
•Principle inherited from MeRHIC lattice
•M56 ~0 and can be varied
•Two options has been developed:
-separated function magnets
-combined function magnets
•Combined function magnets lattice has
minimized effect of synchrotron radiation
but the design of compact magnets
is more challenging
MW
Synchrotron radiation power
for separated function magnet lattice
Emittance and momentum spread
increases are acceptable
passes
13
eRHIC IRs, β*=5cm, l*=4.5 m
Star detector
Plan to use newly commissioned
LARP Ni3Sn SC quads with 200
T/m gradient
0.45 m
©Dejan Trbojevic
30 GeV e- beam
90.m
L = 1 . 4 x 1 0 34c m -2s -1, 2 0 0 T / m g r a d i e n t
A detector integrated into IR
ZDC
FPD
FED
 Dipoles needed to have good forward momentum resolution
 Solenoid no magnetic field @ r ~ 0
 DIRC, RICH hadron identification  π, K, p
 high-threshold Cerenkov  fast trigger for scattered
lepton
 radiation length very critical  low lepton energies
RHIC interaction region “4.5 m” with *= 5 cm
L triplet=4.5 m
Dx
x
y
7/20/2
016
Dejan Trbojevic EICC meeting- the Catholic University of America, 29-31 July,
2010
16
eRHIC luminosity at top energy
Energy, GeV
2
He3
79
Au197
92
U238
e
p
20 (30)
325
215
130
130
161
131
102
102
(197)
(161)
(125)
(125)
CM energy, GeV
Number of bunches/distance between bunches
74 nsec
166
166
166
166
Bunch intensity (nucleons) ,1011
0.24 (.05)
2
3
5
5
Bunch charge, nC
3.8 (0.4)
32
32
32
32
Beam current, mA
50 (10)
420
420
420
420
Normalized emittance of hadrons , 95% , mm mrad
1.2
1.2
1.2
1.2
Normalized emittance of electrons, rms, mm mrad
23 (34)
35 (52)
57 (85)
57 (85)
Polarization, %
80
70
70
none
none
rms bunch length, cm
0.2
4.9
4.9
4.9
4.9
β*, cm
5
5
5
5
5
Luminosity per nucleon, cm-2s-1
1.46 x 1034
(0.29 x 1034)
Hourglass effect is included: h  s / *   0.851
October 20, 2010, New IP configuration for eRHIC
© D.Trbojevic
4.5 cm
pc/2.5
neutrons
11.2 cm
q=10 mrad
IP
2
4
6
Dipole:
2.5 m, 6 T
q=18 mrad
8
10
12
14
16
Estimated β*≈ 8 cm
6T is mostly likely tooooo aggressive – 3.5 T is more likely – opinion of B.Parker
Will need longer magnet.
Seems to be favorite of our EIC team… so far.
© D.Trbojevic
5.75 cm
10
17.65 m
20
30
60.0559 m
90.08703 m
7/20/201
6
0.44843 m
0.39065 m
0.333 m
D5
Brand New Idea - Correction Coil in Split
Dipole 06-Oct-2010, B. Parker
Super-ferric design
HTC coil in its own
cryostat, warm steel
© B.Parker
eRHIC R&D highlights
• Polarized gun for e-p program – LDRD
at BNL + MIT
• Development of compact magnets LDRD at BNL, ongoing
• SRF R&D ERL – ongoing
• Beam-beam effects, beam disruption,
kink instability suppression, etc.
• Polarized He3 source
• Coherent Electron Cooling including
PoP – plan to pursue
©Y. Hao
Main technical challenge for eRHIC
is 50 mA CW polarized gun:
we are building two versions
Gatling gun : LDRD @ BNL
Single large size cathode @ MIT
©J.Skaritka
© E.Tsentalovich, MIT
the Gatling gun is the first successful machine gun,
invented by Dr. Richard Jordan Gatling.
*
Electron polarization in eRHIC
The polarization benefits greatly from the linac acceleration
geometry
 No coherent buildup of small depolarizing errors -> No problem with
depolarizing resonances
jd, d
 No depolarization due to synchrotron radiation
 Simple control of spin orientation at the collision point
eRHIC
detector
The polarization orientation at the eRHIC detector:
d
jd  j0  G     d
Pe
j
0
Adjusted by Wien filter
rotator after the source

Adjusted by modifications
of energy gains in the linacs
Pe
stays in horizontal plane
and rotates in arcs around
vertical direction
j0, 0
Polarized
e-gun
eRHIC Linac Design
703.75 MHz
1.6 m long
Drift
1.5 m long
©I. Ben Zvi
Total linac length depend on energy
All cold: no warm-to-cold transition
Based on BNL SRF cavity with fully suppressed HOMs
Critical for high current multi-pass ERL
Injection
E max
Beam Optics Calculations
in progress
to Dump
Transverse Beam BreakUp (TBBU) instability
(©E. Pozdeyev)
Higher Order Modes (HOM)
• HOMs based on R. Calaga’s
simulations/measurements
• 70 dipole HOM’s to 2.7 GHz in each
cavity
• Polarization either 0 or 90°
• 6 different random seeds
• HOM Frequency spread 0-0.001
Simulated BBU
threshold (GBBU)
vs. HOM frequency
spread.
Excitation process of transverse HOM
 m11 m12   0 
 x


m21 m22   x
 

   comming  x return
F (GHz)
R/Q (Ω)
Q
(R/Q)Q
0.8892
57.2
600
3.4e4
0.8916
57.2
750
4.3e4
1.7773
3.4
7084
2.4e4
1.7774
3.4
7167
2.4e4
1.7827
1.7
9899
1.7e4
1.7828
1.7
8967
1.5e4
1.7847
5.1
4200
2.1e4
1.7848
5.1
4200
2.1e4
eRHIC
Threshold significantly exceeds the beam current,
especially for the scaled gradient solution.
50 mA
25
Electron beam disruption for eRHIC. Optimization of beam parameters
protons
e
©Y. Hao
β*= 1m
Emittance:
1nm-rad
Parameters
with minimal
disruption:
β*= 0.2m
Emittance:
5nm-rad
Gains from coherent e-cooling:
Coherent Electron Cooling vs. IBS
2
2
   

X  x ; S   s    E  ;
xo
 so   sE 
dX
1
1
 1

  ;
3 / 2 1/ 2
dt  IBS  X S
 CeC S
dS
1
1
1 2  1


;
3/2
dt  IBS // X Y
 CeC X
Dynamics:
Takes 12 mins
to reach
stationary
point
X


 CeC
 IBS // IBS 
1
  1 2  
; S

 CeC
 IBS  
 IBS //  IBS //
xn 0  2 m;  s0  13 cm;  0  4 104
 IBS  4.6 hrs;  IBS // 1.6 hrs

3
1 2  
IBS in RHIC for
eRHIC, 250 GeV, Np=2.1011
Beta-cool, A.Fedotov
x n  0.2 m;  s  4.9 cm
This allows
a)  keep the luminosity as it is
b) reduce polarized beam current down
to 50 mA
c) increase electron beam energy to 20
GeV (30 GeV for e-I)
d) increase luminosity by reducing *
from 25 cm down to 5 cm
Coherent Electron Cooling proof-of-principle experiment
in RHIC IR 2: aim to demonstrate cooling within 3-4 years
Collaboration between BNL, Jlab and Tech X
DoE funded year 1
19.6 m
DX
Kicker, 3 m
Wiggler 7m
Modulator, 4 m
Parameter
Species in RHIC
Au ions, 40 GeV/u
Electron energy
21.8 MeV
Charge per bunch
1 nC
Rep-rate
78.3 kHz
e-beam current
0.078 mA
©G.Mahler e-beam power
1.7 kW
V.N. Litvinenko, IPAC’11, Kyoto, May 26, 2010
DX
Recent and continuing developments
(very important for completion of the design and the cost
estimates, by mostly boring for this audience…)
• Detailing layout of every straight section and arc,
including linacs sections, splitters, combiners, passes
around detectors…..
• Developing clear models/prototypes for magnets,
vacuum chambers
• Identifying beam diagnostics..
• Details of beam dynamics, timing, synchronization…
• Defining need for additional utilities, structures…
• Putting all parts together (early 2011)
• This is a random sample of things we are doing now…
Splitter/Combiner in Relation to the RHIC
Ring
RHIC Ring Location at 2 o’clock
ARCS
Tunnel Wall
Top View
ARCS
Blue Yellow
Combiner LINAC at 2 o’clock
L=202 m E=2.45 GeV
Splitter
ARCS
ARCS
Side View
© N.Tsoupas
Blue Yellow
Schematic diagram of the
Combiner/Splitter
1st LINAC at 10 o’clock (Acceleration cycle)
It is the system of the beam lines which Combines the beams of the ARCS
into the LINAC or Splits the beams exiting the LINAC into the ARCS
From pre accelerator 0.6 GeV Injection
3.05 GeV
5.5 GeV
10.4 GeV
Combiner
Splitter
15.3 GeV
20.2 GeV
12.85 GeV
1st 2.45 GeV LINAC
25.1 GeV
17.75 GeV
22.65 GeV
27.55 GeV
30. GeV
ARCS
7.95 GeV
Acceleration cycle
© N.Tsoupas
Splitters/Combiners will also be employed at the IR Regions
ARCS
Schematic diagram of the Combiner/Splitter
2nd LINAC at 2 o’ clock (Acceleration cycle)
It is the system of the beam lines which Combines the beams of the ARCS
into the LINAC or Splits the beams exiting the LINAC into the ARCS
5.5 GeV
3.05 GeV
7.95 GeV
Combiner
Splitter
12.85 GeV
17.75 GeV
15.3 GeV
2nd 2.45 GeV LINAC
22.65 GeV
20.2 GeV
25.1 GeV
27.55 GeV
ARCS
10.4 GeV
30.0 GeV
Acceleration cycle
© N.Tsoupas
Splitters/Combiners will also be employed at the IR Regions
ARCS
Layouts and engineering drawings: all 3.8 km of them…..
IP10
IP12
IP2
Beam power losses due to synchrotron radiation
Rmag = 234.2m
Power loss, MW
IR12
Collision
© V.Ptitsyn
Acceleration
Deceleration
Turns
This is a calculation for separated function magnet lattice.
Combined function magnet lattice (Dejan) reduces the loss to ~5 MW
Resistive wall
6 pass scheme
One turn: 3440 m
Bunch length: 2 mm
Bunch charge: 3.54 nC
Beam current: 50 mA
Reasonable choice : Al or Cu pipe,
5 mm radius (or half-gap)
© V.Ptitsyn
Characterizes also
resulting energy spread
Cavity loss
Bunch length: 2mm
Kloss = 3.5 V/pC
Kloss_adj = 3 V/pC
Pozdeyev’s calculation for
MeRHIC =1.8 mm, Gauss
© V.Ptitsyn
At eRHIC:
Bunch charge, nC =
3.54
Beam current = 50
Using
mA Kloss_adj:
Power
per cavity per pass = 0.53 kW
6 passloss
scheme
Total power loss per cavity = 6.32 kW
Number of cavities = 120x 2 =240
Total power loss = 1.52 MW
Resulting energy spread ~ 30 MeV !
Total power loss, MW
Loss budget for 6 pass scheme
© V.Ptitsyn
5 10
15
20
25
30
Top energy, GeV
How decrease losses?:
-Combined function magnet lattice (SR losses -> 5 MW)
-Use 4 passes for acceleration up to 20 GeV (modification of splitter design)
-Reduce bunch charge (paying the luminosity price)
Electron-hadron frequency matching
Proton revolution
frequency, kHz
Electron pass circumference
lengthening, cm
ΔCe(50 GeV) ~ 66 cm
ΔCe(20GeV)~ 420 cm
Hadron energy per nucleon, GeV
Electron pass circumference
lengthening, cm
Using the RF harmonic
switching the required
lengthening of the electron
circumference is reduced to
43 cm even for the proton
energies down to 20 GeV.
Proton energy, GeV
Electron bunch frequency should match the proton bunch frequency in wide energy range.
Present eRHIC design: 50-325 GeV proton energy. Here we consider down to 20 GeV.
Harmonic relations
This condition is not
required ERL !
One can change the relation between bunch frequencies using he
Protons:
RF harmonic
Bunch harmonic
RF to bunch
harmonic
frf_p = hp frev_p
fb_p = np frev_p
frf_p = mp fb_p
np = 180
Electrons:
frf_e = he frev_e
fb_e = fb_p
frf_e = me fb_p
he ~ 8980-9020
fb_e = ne frev_e
me = 50
Depends on the design
circumference length
Electron effective
revolution frequency, kHz
Collision
synchronization
From this:
f rev _ e 
me n p
he
h = 9011
h = 9012
f rev _ p 
9000
f rev _ p
he
h = 9013
h = 9014
h = 9015
Switching the RF harmonic
number allows to reduce the
variation of the electron
revolution frequency
Shown only for 50-325 GeV proton energy range
h = 9016
Proton revolution frequency, kHz
Plans, plans
• And hundreds more of all important details
should be finalized in two-three months for
completing eRHIC design
• It will follow by the bottoms-up engineering
cost estimate of all eRHIC stages, including
subsystems such as coherent electron cooling
• Plan to complete this exercise by Fall of 2011
Conclusions
• eRHIC is future electron-hadron collider at BNL
• In addition to previous solid design of low-X IR, we
had developed high luminosity IR with L >1034 using
advances in the SM quad technology and in the crabcrossing
• We continue working in close collaboration with BNL
EIC Task force and others from the EIC community in
developing eRHIC IRs
• We aggressively pursue development of polarized
Gatling gun and push forward the test of Coherent
Electron Cooling at RHIC
© S.Vigdor
Back-up slides
Schematic diagram of the Combiner/Splitter at the
2nd LINAC at 10 o’clock
(Deceleration cycle)
0.6 GeV PreDecelerator
5.50 GeV
3.05 GeV
7.95 GeV
Combiner
Splitter
12.85 GeV
17.75 GeV
22.65 GeV
15.3 GeV
2nd 2.45 GeV
LINAC
27.55 GeV
ARCS
10.4 GeV
20.2 GeV
25.1 GeV
30.0 GeV
Deceleration cycle
© N.Tsoupas
Splitters/Combiners will also be employed at the IR Regions
ARCS
Possible layout in RHIC IP
of CeC driven by a single linac
for RHIC and eRHIC
Kicker for Yellow
Kicker for Blue
FEL for Yellow
Modulator for Blue
FEL for Blue
Beam dump 1
ERL dual-way electron linac
2 Standard eRHIC modules
Beam dump 2
Gun 1
Gun 2
Ep, GeV
100
250
325

106.58
266.45
346.38
Ee, MeV
54.46
136.15
177.00
Modulator for Yellow
High gradient Nb3Sn quadrupoles
-developed for the LHC luminosity upgrade
-demonstrated gradients more than 220 T/m
© B.Parker
Large enough aperture to pass the forward products
+-5mrad around the beam direction
proton
beam
electron beam
passes through the
field free region in the
iron core of the magnet
© D.Trbojevic
Linac
SS
V.N. Litvinenko, talk Duke University, Durham NC, April 27, 2010
200 m ERL Linac
e+ ring
1.27 m beam high
© V. Litvinenko
Suppression of kink instability
© Y. Hao
ERL
BPM
Nonlinear force model
with Hourglass effect
With rms proton
energy spread =1e-3
By chromaticity:  ~ +4
Feedback
kicker
IP
RHIC
By feedback
Kink instability – a possible instability of the proton beam caused by
its interaction with the electrons. Specific for linac-ring scheme.
Simple feed-back on electron beam suppress kink instability
completely for all eRHIC parameter ranges.
48
Coherent Electron Cooling (CeC)
Dispersion
At a half of plasma oscillation
qFEL 
 (z) cosk zdz
FEL
0
 k  kq(j1 ); n k 
k
2
E < Eh

Modulator
Hadrons


E  E o 
E h  e  E o  l2  sin kFEL D

E o 

sin j 2   j1 2

 sin   Z  X; E o  2Goe o / n
 j 2   2 
  o
L
ct  D
; Dfree  2 ; Dchicane  lchicane   2 .......
o

FEL
l1
Dispersion section
( for hadrons)
Eh
Kicker
E > Eh

High gain FEL (for electrons)
l2
Electrons
FEL
Debay radii
2 RD
vh
RD  RD //
RD 
2 RD//

 pt
A 
2n /  o
ce
p
E0
E > E0
 p
Ez

FEL
p  4 ne e2 /  ome

FEL
E < E0

c
RD //,lab  2   FEL

Density
Amplifier of the e-beam modulation
in an FEL with gain GFEL~102-103
kFEL  2 / FEL; kcm  kFEL /2 o
q/Ze


 pt
q  Ze  (1 cosj1 )
j1   p l
1 /c

q peak  2Ze
r

 fel  w 1 aw2 /2 o 2
r
r
aw  eAw / mc2
LG  LGo (1 )
GFEL  e L FEL / LG

LGo 
w
4 3


L
j  FEL
3LG
namp  Go  nk coskcm z
j  4en  j  j 0  coskcm z
r
r
E  j  zˆEo  X sin kcm z
Eo  2Go o

e
n
X  q/ e  Z(1 cosj1) ~ Z
Major IEC Accelerator R&D in the US
Common R&D activities for eRHIC and ELIC

Polarized 3He production and acceleration (BNL)
[ 5 FTE-yrs; M&S: $ 1.0 M Total: $2M]

Coherent Electron Cooling (BNL)
[15 FTE-yrs; M&S: $ 5.0 M Total: $8M]

Energy recovery technology for
100 MeV level electron beam. (JLab)
[20 FTE-yrs; M&S: $4.5 M Total: $8.5M]

Crab cavities
[ 8 FTE-yrs; M&S: $1.2M Total: $2.8M]
R&D activities specific to eRHIC

High current polarized electron source (MIT)
[7.5 FTE-yrs; M&S: $ 2.0 M Total: $3.5M]

Energy recovery technology for
high energy and high current beams (BNL) [10 FTE-yrs; M&S: $ 3.0 M Total: $5M]

Development of eRHIC-type SRF cavity (BNL)
[10 FTE-yrs; M&S: $ 2.0 M Total: $4M]
R&D activities specific to ELIC

Ion space charge sim. (JLab in collab. with SNS)
[ 2 FTE-yrs; M&S: $0.5M Total: $0.9M]

Spin track studies for ELIC (JLab)
[ 8 FTE-yrs;
Total: $1.6M]

Studies traveling focus scheme (JLab)
[ 3 FTE-yrs;
Total: $0.6M]

Simulation studies supporting ELIC project (JLab) [ 5 FTE-yrs;
Total: $1.0M]
Main Accelerator Challenges
In red –increase/reduction beyond the state of the art
ENC at FAIR
ELIC at JLaB
eRHIC at BNL
β*=0.5 cm
50x reduction
Polarized electron gun –
50x increase
Depolarization at the
top energy
Polarized e- source
8 MV, 3 A magnetized
electrostatic
(Voltage*2, Current*6)
HE Electron Cooling –
100x increase in the
rate of cooling
Coherent Electron
Cooling – New concept
Energy reach beyond 70
GeV for leptons
Potential 10x gains from
cooling, but need special
CeC
Investigation of large
beam-beam tune shift in
space charge dominated
regimes
High current
recirculating ring with
ERL-injector
New concept
Multi-pass SRF ERL
5x increase in current
30x increase in energy
Synchrotron radiation
losses in the arcs
Multi-pass SRF ERL
5x increase in current
30x increase in energy
3-4x in # of passes
Crab crossing
(compliance with
acceptance of PANDA)
Crab crossing
5x the angle
New for hadrons
Crab crossing
New for hadrons
Crab crossing
New for hadrons
Crab crossing
New for hadrons
By-passes
Totally new tunnel
Complexity of the
sharing tunnel with LHC
Very challenging to have
e+ source
Polarized 3He production
LHeC at CERN
Ring-Ring
Linac-Ring
Limited space for
electron ring
Never explored beambeam parameter range
3-4x in ξ
Understanding of beambeam affects
New type of collider
Polarization life time in
electron ring
(lattice considerations)
Dispersive crab crossing
Traveling focus
New concepts
β*=5 cm
5x reduction
Space charge limits
beam dynamics,
Bunching (1200)
Sub-nsec kicker with
MHz rep-rate
50x shorter pulses
Multi-pass SRF ERL
3-4x in # of passes
Need new injector
Figure-8 ring spin
dynamics
New concept
Feedback for kink
instability suppression
Novel concept
Synchrotron radiation in
the IR
Using crossing angle to
avoid SR in IR
V.N. Litvinenko, IPAC’11, Kyoto, May 26, 2010
eRHIC Linac Design developments
•Energy of electron beam is increased in stages by increasing the length of the
linacs, up to maximum length of 200m of each linac
•Acceleration gain per cavity: 18 MV for 26.5 Gev, 20.4 MV for 30 GeV
•Several variants of lattice have been considered, including the lattice without
quadrupoles inside the linac.
•BBU simulations for different lattices are underway
© I. Ben-Zvi, G.Mahler
New design of 704 MHz cavity (BNL III):
-reduced peak surface magnet field
-reduced cryogenic load
52