News from eRHIC
and advanced cooling schemes
for high energy hadron beams
Vladimir N. Litvinenko for
BNL’S eRHIC team and CAD’s AP group
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.Vogelsang
Inputs on LHC and LHeC from F.Zimmerman, R.Thomas,
O.Brüning
Brookhaven National Laboratory, Upton, NY, USA, Stony Brook University, Stony Brook, NY,
USA
Center for Accelerator Science and Education
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Content
• News from eRHIC
• Updates on coherent e-cooling
• How it can be applied for LHC/LHeC
• Conclusions
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
2
eRHIC Scope -QCD Factory
RHIC
Electron accelerator
p
Unpolarized and
polarized leptons
4-20 (30) GeV
3
Polarized protons
25 50-250 (325) GeV
eLight ions (d,Si,Cu)
Heavy ions (Au,U)
50-100 (130) GeV/u
e-
e+
Polarized light ions
(He3) 215 GeV/u
70% beam polarization goal
Positrons at low intensities
Center mass energy range: 15-200 GeV
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
2007 Choosing the focus:
ERL or ring for electrons?
4
• 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 10
Natural staging strategy

V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
MeRHIC is a single IP coolider
5
4 GeV e x 250 GeV p – 100 GeV/u Au
2 x 60 m SRF linac
3 passes, 1.3 GeV/pass
Polarized
e-gun
Beam
dump
3 pass 4 GeV ERL
STAR
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
4 GeV e
x 250 GeV p or
100 GeV/u Au
MeRHIC
120m SRF linac
3 passes, 1.3 GeV/pass
M/eRHIC
detector
Beam Polarized
dump e-gun
3 pass
4 GeV ERL
STAR
6
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Integrated low-X IR design, β*=25 to50 cm
33
L=3x10
1T, 3m
dipole
p, Au
Soft
dipole
Soft 1T, 3m
dipoledipole
e
Solenoid, 4 T
40 m
First machine elements 20 m from IP
40 m to detect particles scattered at small angles
MeRHIC IR
To provide
effective SR
protection:
-soft bend
(~0.05T) is
used for final
bending of
electron beam
© E. Aschenauer
© J.Bebee-Wang
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Staging all-in tunnel eRHIC:
energy of electron beam is increasing
from 5 GeV to 30 GeV by building-up the linacs
eRHIC detector
4 to 6 vertically
separated
recirculating
passes.
# of passes will
be chosen
to optimize
eRHIC cost
Gap 5 mm total
0.3 T for 30 GeV
20 GeV
e-beam
RHIC: 325 GeV p
or 130 GeV/u Au
eSTAR
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
16 GeV
e-beam
Common vacuum
chamber
The most
cost
effective
design
2 SRF linac
1 -> 5 GeV per pass
4 (6) passes
12 GeV
e-beam
8 GeV
e-beam
5 mm
5 mm
5 mm
5 mm
eRHIC loop magnets: LDRD project
•
Small
•
•
•
gap provides for low current, low power consumption magnets
-> low cost eRHIC
©, G. Mahler, W. Meng,
Dipole prototype is under tests
A. Jain, P. He, Y.Hao
Quad and vacuum chamber are in advanced stage
Gap 5 mm total
0.3 T for 30 GeV
20 GeV
e-beam
16 GeV
e-beam
12 GeV
e-beam
8 GeV
e-beam
1.40E-01
245Ampere, Transverse scan at center of the
dipole
1.20E-01
Magnetic Field [Tesla]
5 mm
Magnetic Field [Tesla]
25 cm
Common vacuum chamber
eRHIC
0.1175
0.117
0.1165
0.116
0.1155
0.115
0.1145
0.114
0.1135
0.113
0.1125
30
32
34
36
38
Transverse position [mm]
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
40
42
1.00E-01
8.00E-02
6.00E-02
dx=0mm
4.00E-02
2.00E-02
0.00E+00At pole center, longitudinal scan
0
100
200
300
400
500
Longitudinal Position [mm]
600
ARC
30 GeV e+ ring
1.27 m beam high
30 GeV ERL
6 passes
HE ERL passes
LE ERL passes
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
30 GeV
25 GeV
20 GeV
15 GeV
10 GeV
5 GeV
Linac
SS
200 m ERL Linac
e+ ring
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
1.27 m beam high
eRHIC Linac Design
703.75 MHz
1.6 m long
Drift
1.5 m long
Total linac length depend on energy
All cold: no warm-to-cold transition
©I. Ben Zvi
Based on BNL SRF cavity with fully suppressed HOMs
Critical for high current multi-pass ERL
Injection
©George Mahler
Energy of electron beam is increased in stages
by increasing the length of the linacs
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
E max
to Dump
TBBU stability (©E. Pozdeyev)
• HOMs based on R. Calaga’s simulations and on
recent 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
Excitation process of transverse HOM
Simulated BBU
threshold (GBBU)
vs. HOM frequency
spread.
x 
m11 m12 0 

 

   
x return m21 m22 x comming
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
R&D ERL
Test-bed for
eRHIC technology
© I. Ben Zvi
20
Vertical scale is increased 100 fold
10
0.32878 m
0.25573 m
eRHIC – Geometry high-lumi IR
with β*=5 cm, l*=4.5 m
and 10 mrad crossing angle
30 GeV e-
30
60.0559 m
90.08703 m
© D.Trbojevic
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
© D.Trbojevic
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
20
30 GeV e-
30
60.0 m
90.0 m
© D.Trbojevic
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Vertical scale is increased 100 fold
10
0.328 m
0.255 m
0.448 m
eRHIC – Geometry of low-x IR
with β*=25 cm, l*=15 m
and 10 mrad crossing angle
Quads for β*=5 cm
© B.Parker
Luminosity in eRHIC
eRHIC IR1
eRHIC IR2
p /A
e
p /A
e
Energy (max), GeV
325/130
20
325/130
20
Number of bunches
166
74
nsec
166
74
nsec
Bunch intensity (u) , 1011
2.0
0.24
2.0
0.24
Bunch charge, nC
32
4
32
4
Beam current, mA
420
50
420
50
Normalized emittance, 1e-6 m,
95% for p / rms for e
1.2
25
1.2
25
Polarization, %
70
80
70
80
rms bunch length, cm
4.9
0.2
4.9
0.2
β*, cm
25
25
5
5
Luminosity, cm-2s-1
2.8x 1033
1.4 x 1034
Luminosity for 30 GeV e-beam operation will be at 20% level
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
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
Recent studies proved our early assumption (ZDR Appendix A) that
using simple feed-back on electron beam suppress kink instability
completely for all eRHIC parameter ranges
Key ingredients:
RHIC with all its species
ERL technology
50 mA polarized electron gun
Coherent electron cooling
Crab-crossing
High gradient SM magnets
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Main technical challenge is 50 mA
CW polarized gun:
we are building two versions
Gatling gun
Single large size cathode
©J.Skaritka
© E.Tsentalovich, MIT
the Gatling gun is the first successful machine gun,
invented by Dr. Richard Jordan Gatling.
*
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Coherent Electron Cooling (CeC)
Dispersion
At a half of plasma oscillation
qFEL 
 (z) cosk zdz
FEL
0
k  kq(1 ); n k 
k
2
E < Eh

Dispersion section
( for hadrons)

Modulator
Hadrons

E  E o 
E h  e  E o  l2  sin k FEL D

E o 

sin  2   1 2

 sin   Z  X; E o  2Goe o / n
  2   2 
  o
L
ct  D
; Dfree  2 ; Dchicane  lchicane   2 .......
o

FEL
l1
Eh
E > Eh
Kicker

High gain FEL (for electrons)
l2
Electrons
FEL
2 RD
vh
RD  RD //
RD 
2 RD//

A 
ce
E > E0
 p
Ez

FEL
kFEL  2 / FEL; kcm  kFEL /2 o
q/Ze


 pt
1   p l
1 /c
q peak  2Ze
r

 fel  w 1 aw2 /2 o 2
r
r
aw  eAw / mc2
LG  LGo (1 )
q  Ze  (1 cos1 )
 pt
E0
2n /  o
p
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
Debay radii

GFEL  e L FEL / LG

LGo 
w
4 3


L
  FEL
3LG
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
namp  Go  nk coskcm z
  4en     0  coskcm z
r
r
E    zˆEo  X sin kcm z
Eo  2Go o

e
n
X  q/ e  Z(1 cos1) ~ Z
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
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Modulator for Yellow
Gains from coherent e-cooling:
Coherent Electron Cooling vs. IBS
   

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
2
Dynamics:
Takes 12 mins
to reach
stationary
point
2
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


a)
b)
c)
d)
This allows
keep the luminosity as it is
reduce polarized beam current down to 50
mA (10 mA for e-I)
increase electron beam energy to 20 GeV
(30 GeV for e-I)
increase luminosity by reducing * from 25
cm down to 5 cm
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Layout for Coherent Electron Cooling
proof-of-principle experiment in RHIC IR
26
Collaboration is opened for all interested labs/people
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
Train
5 bunches
Rep-rate
78.3 kHz
e-beam current
0.39 mA
e-beam power
8.5 kW
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
DX
Polarizing Hadron Beams
with Coherent Electron Cooling
New LDRD proposal at BNL: VL & V.Ptitsyn
Hadrons
Delay for hadrons
Modulator
HW1
left helicity
High gain FEL (for electrons)
HW2
right helicity
Electrons

Kicker
l2
r
dn / d
Modulation of the electron
beam density around a hadron is
caused by value of spin
component
along
the
longitudinal axis, z. Hardons
with spin projection onto z-axis
will attract electrons while
traveling through helical wiggler
with left helicity and repel
them in the helical wiggler with
right helicity.
The high gain FEL
amplify the 
imprinted
modulation.
Hadrons with z-component
of spin will have an energy
kick proportional to the
value and the sigh if the
projection. Placing the
kicker in spin dispersion will
result in reduction of zcomponent of the spin and
in the increase of the
vertical one.
This process will polarize the hadron beam
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Polarizing Hadron Beams
with Coherent Electron Cooling
• It is very provocative proposal and requires very high gain FELs for
attaining reasonable spin-cooling times – no time to go into many
details
• For LHC this technique could an unique opportunity to operate with
polarized hadrons
• in RHIC, bringing polarization of proton beams close to 100% would
provide for a nearly eight-fold boost of the observables and could
be of critical for solving long-standing proton spin crisis
• The methods can be used for polarizing other hadrons, such as
deuterons – polarization of which is considered to be impossible in
RHIC, He3 and other ions
• The technique can open a unique possibility of getting polarized
antiprotons
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Coherent-electron-Cooling would
provide following for linac-ring LHeC
• Smaller proton beam emittance down to 0.2 mm mrad
• Can provide shorted bunches down to 1 cm (if needed)
• Allows to reduce electron beam current 20-fold to
achieve of e-p luminosity above 1034 level with 60 GeV
electrons and 7 TeV protons
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Sample of CeC for LHeC
LHC
Circumference
Cooling time
26658.883 m
Full bunch
0.346
hrs
Local
176.27
sec
Main Parameters
CeC
Modulator Length
70
m Length of the system
153.70
m
Kicker length
35
m
FEL length
48.70
m
Peak current, e
100.0
A
FEL gain length
3.08
m
Amplification
1000.00
Wavelength
10
nm
FEL formula
TRUE
w
FEL bandwidth
5
cm
Checks
TRUE
0.02
I will use conservative 0.8 hrs cooling time
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Evolution of beam in LHC at 7 TeV
(assuming nominal LHC bunch intensity 1.15e11 p/bunch and 40% of CeC cooling capability)
2
f  m 
 2
Nrc c
 5 3 3/2
;
 IBS // 2  x  s  yv
x
 IBS

2
Nrc c
H
2 5  3x 3 / 2 s  y1/ 2
f  m  ;  1
d     
rc m 2c 4
e2
1/ 3
f  m   
ln  e ;  m 
; rc 
; (e  Ze;m  Am)
2 ;bmax  n
mc 2
bmax  E
 m 
m 

   

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 1/ 2
dt  IBS // X S
 CeC X
2
J.LeDuff, "Single and Multiple Touschek effects",
Proceedings of CERN Accelerator School,
Rhodes, Greece, 20 September - 1 October, 1993,
Editor: S.Turner, CERN 95-06, 22 November 1995,
Vol. II, p. 573
2
IBS rates in LHC from
xn 0  3.75 m;  s0  7.55cm
 IBS  80 hrs;  IBS // 61 hrs

Stationary solution for τCeC = 0.8 hrs
X
 CeC
 IBS // IBS 
1
  1 2  
; S

 CeC
 IBS  
 IBS //  IBS //

3
1 2  
x n  0.19 m;  s  0.87 cm

V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Table 2.2
Layout for ERL based LHC
10 GeV linac
R=700m
R=700m
• Hadrons
– 1.15e11 per bunch
– Cooled by CeC
10 GeV linac
• Electron
– Accelerated in the ERL - 60 GeV
– Polarized electron beam current - 8 mA
•
•
•
•
•
Dump
Gun
Number of passes – 3
AC power consumption – 100 MW
Crab-crossing
β*=12 cm
L = 2.1034 cm-2 sec-1
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
0.5 GeV
ERL-injector
Conclusions
• We focused again of all-in-the-tunnel staging of
eRHIC
• 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
crab-crossing
• We aggressively pursue development of polarized
Gatling gun and develop specific plans for testing
Coherent Electron Cooling at RHIC
• Using eRHIC-style ERL and CeC for 60 GeV x 7
TeV LHeC promises providing L >1034 with power
consumption below 100 MW and modest size of
facility
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Back-up
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
LHeC
LHC protons
Energy
_p
N_p
No Cooling
Emittance, norm
Emittance
Allowable tune shift
Maximum # of e
Rep-rate
I max
Realistic
N real
Room for improvement
*
4
L/h
7
7.46E+03
1.70E+11
TeV
3.75
5.03E-01
0.01
3.07E+11
2.00E+07
9.84E-01
0.008
2.50E+09
1.23E+02
0.12
7.58E-10
1.12E+33
mm mrad
nm rad
Radius, 
500.00
2 x 7.5 GeV linacs
2 x10 GeV linacs
2 x 15 GeV linacs
30 GeV linac, dogbone
Cryo
RF main
RF SR
Magnets
18.56
24.75
37.13
37.13
16.67
22.22
33.33
33.33
60.25
46.08
32.40
48.17
4
3
2
3
With cooling
Emittance, norm
Emittance
Allowable tune shift
Maximum # of e
Rep-rate
I max
Beam current
N real
Room for improvement
*
4
L/h
Hz
A
A
m
m^2
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Total
MW
99.48
96.05
104.86
121.63
0.2
2.68E-02
0.01
1.64E+10
2.00E+07
5.25E-02
0.008
2.50E+09
6.56E+00
0.12
4.04E-11
2.10E+34
Passes
4
3
2
DGBN
mm mrad
nm rad
Hz
A
A
m
m^2
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Integrated high-Q IR design, β*=5cm
First quadrupole is 4.5 m from IP
34
L=1.4x10
Nb3Sn
©Dejan Trbojevic
Plan to use newly commissioned
(last month!) LARP SC quads with
200 T/m gradient
May be used for luminosity
hungry experiments
Will work with the
Alan Caldwell detector
Or a JLab type one
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Additional advantage of linac-ring –
removing systematic errors
protons
electrons
© D. Lowenstein
It is built-in feature of the linac-ring eRHIC: we can
arbitrary select polarization of individual bunches
a) In RHIC this is already implemented by injection
scheme (ion source) for protons
b) In eRHIC ERL electron polarization is reversible by
switching helicity of the laser photons
It is impossible in ring-ring EIC
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
Disruption for eRHIC
Optimization
β*= 1m
Emittance:
1nm-rad
β*= 0.2m
Emittance:
5nm-rad
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010
e-Beam Disruption – used bunches are discarded
protons
e
©Y. Hao
MeRHIC
eRHIC
Incorporating eSTAR and ePHENIX
•
Without changing DX-D0 both the energy and luminosity will be low in
electron-hadron collisions
•
Parallel operation of hadron-hadron and electron-hadron collisions does
not allow cooling of hadron beam, hence 10-fold lower luminosity for
e-p and e-A
•
Sequential operation of RHIC as a hadron collider and as an electronhadron collider allows to have both full energy and full luminosities in
al modes of operation, including coherent electron cooling
•
Coherent Electron Cooling would provide 10-fold increases in e-p amd
e-A luminosities (and 6-fold increase in polarized p-p luminosity)
•
We have designs of two IR: low-x (L~3.1033) and high-lumi (L~2.1034)
•
We suggest using crossing angle and ±5 mrad crab-cavities to have
identical energy-independent geometry of IRs and no synchrotron
radiation in detectors
V.N. Litvinenko, ABP Forum, CERN, April 9, 2010