1
eRHIC Design
at
Brookhaven National Laboratory
Vladimir N. Litvinenko for eRHIC team
Stony Brook University, Stony Brook, NY, USA
Brookhaven National Laboratory, Upton, NY, USA
Center for Accelerator Science and Education
V.N. Litvinenko, EIC UG meeting, Stony Brook University , June 25, 2014
eRHIC design & R&D team
BNL: Z. Altinbas, E.C.Aschenauer, S.Belomestnykh, I.Ben-Zvi, D. Beavis, M. Blaskiewicz, S.Brooks,
C.Brutus, T.Burton, A.Fedotov, C.M. Folz, D.Gassner, H. Hahn, Y.Hao, J. Jamilkowski, Y.Jing, F.X. Karl,
D.Kayran, R. Lambiase, C.Liu, Y.Luo, G.Mahler, M.Mapes, G.McIntyre, W.Meng, F.Meot, T.Miller, M.Minty,
P. Orfin, B.Parker, A. Pendzick, I.Pinayev, V.Ptitsyn, T. Rao, T.Roser, , J. Sandberg, B. Sheehy J.Skaritka, K.
Smith, L. Snydstrup, R. Than, O.Tchoubar, P.Thieberger, D.Trbojevic, N.Tsoupas, J.Tuozzolo, E.Wang,
G.Wang, D. Weiss, M. Willinski, Q.Wu, W.Xu, A. Zaltsman
Stony Brook University/CASE: A. Elizarov, V.N. Litvinenko, C.Marques, O.Rahman E. Riehn, M.Ruiz-Oses,
T. Xin, Y. Wu
BINP, Novosibirsk, Russia: V.V. Anashin, T.V. Bedareva, M.A. Kholopov, A. Krasnov, A.M. Semenov, O.
Shevchenko, P. Vobly
Niowave, Lansing, MI: C. Boulware, T. Grimm, R. Jecks, N. Miller
AES, Medford, NY: M.D. Cole, A.J. Favale, D. Holmes, J. Rathke, T. Schultheiss, A.M. Todd
Tech-X, Bolder Co: G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A. Sobol, S.D. Webb
Stangenes Industries, Palo Alto, CA: C. Yeckel, R. Miller, M. Stangenes, K. Thompson
Transfer Engineering, Fremont, CA: M. Ackeret, J. Pietz, L. Neverida
Atlas Technologies, Pt. Townsend, WA: D. Bothel, J. Bothel, T. Casey
Thermionics NW, Pt. Townsend, WA: K. Coates
STFC, Daresbury, Warrington, UK: P. McIntosh, A.Moss, A. Wheelhouse
SLAC: D. Ratner, V. Yakimenko
ANL: P.N. Ostroumov
Jlab: M Pielker
MIT: E. Tsentalovich
CERN: R. Calaga, S. Verdu-Andres
eRHIC History Line
•
I. Ben-Zvi, J. Kewisch, J. Murphy, S.Peggs, “Accelerator Physics Issues in eRHIC”, Nuclear
Instrumentations and Methods in Physics Research A 463 (2001), p.94.
•
-1; ERL linac-ring as backup) (2004).
eRHIC ZDR (the ring-ring design with L~1032 cm-2 seRHIC
Design Study
•
ERL-based eRHIC with separated re-circulating passes
An Electron-Ion Collider at BNL
–
–
L~1034 cm-2 s-, high hadron beam intensity, upgrades in hadron ring, Space Charge Compensation
Energy staging. First stage eRHIC: 4-5 GeV electron machine.
•
•
2012-2013: Work on cost optimized machine design.
Bottom-up cost estimate and optimization: minimal cost first stage (5 GeV) eRHIC with
separated re-circulating passes: $530 mln. (detector(s) not included).
•
ERL with two FFAG re-circulating passes + HOM damped LF SRF cavities + permanent
magnets
–
–
•
construction and operational cost savings
No energy staging. Using FFAG passes quadruple the energy reach at moderate cost.
10 GeV FFAG design has been evaluated by Machine Advisory Committee (Nov. 2013) :
”The MAC congratulates the eRHIC design team for its ingenious and novel use of the FFAG concept.”
eRHIC
•
21.2 GeV full-energy 16-pass ERL
DRAFT
First draft of “eRHIC Design Study” report includes the Accelerator Design Chapter
February 2014
presenting main features of eRHIC FFAG design.
1
(Final report version expected in summer)
eRHIC: QCD Facility at BNL
4
12 o’clock proposed
Add electron accelerator to the existing
$2B RHIC
RHIC
PHENIX
e-
Unpolarized and
80% polarized
leptons, 5-21.2
GeV EBIS
BOOSTER
3.8 km in circumference
STAR
p
70% polarized protons
100-250 GeV
RF
Light ions (d,Si,Cu)
Heavy ions (Au,U)
50-100 GeV/u
ERL Test Facility
Polarized light ions
(He3) 167 GeV/u
ee+
AGS
Center of mass energy range: 30-145 GeV
Any polarization direction in lepton-hadrons collisions
electrons
protons
TANDEMS
eRHIC with 21.2 GeV ERL
5
Conclusion first
• We found at BNL a cost-effective way of building the full-energy
EIC: (21.2 GeV polarized electrons x 255 GeV p) from day one using
and ERL with FFAG arcs for 16 recirculation passes
• The cost of the machine is similar to a that with 5 GeV ERL using
regular arcs
• It is designed to reach day-one high luminosity > 1033 cm-2 s-1 up to
125 GeV CM energy and 145 GeV CM energy at 40% of the
luminosity.
• R&D is under way on high current polarized electron source (Gatling
Gun), effective hadron cooling (Coherent electron Cooling) and high
current ERL.
• We built in head-room for future accelerator improvement projects
(AIPs) to increase luminosity toward 1034 - 1035 cm-2 s-1. In this
sense, we are using RHIC model, where AIPs were used for reaching
luminosity 20-fold above the design value.
eRHIC kinematic reach: light box
Ee, GeV
Ec.m.., GeV
200
175
175
150
150
125
125
100
100
75
75
50
50
25
25
< 25
Ep, GeV
Ultimate eRHIC luminosity as function of beam energies
L., cm-2 sec-1
Ee, GeV
1035
Not
Accessible
1.1034
2.1034
9.1034
8.1034
7.1034
3.1034
6.1034
5.1034
1035
3.1034
4.1034
4.1034
5.1034
6.1034
7.1034
8.1034
9.1034
3.1034
> 1035
Not
Accessible
2.1034
1.1034
Ep, GeV
The box shows eRHIC reach in energy with current FFAG arc design from day one
V.N. Litvinenko, EIC UG meeting, Stony Brook University , June 25, 2014
eRHIC – day one
Luminosities at top hadron beam energy
2He3
79Au197
9.4
p
250
122.5
9.4
167
81.7
9.4
100
63.2
9.4
Bunch intensity (nucleons), 1011
0.33
0.3
0.6
0.6
Bunch charge, nC
Beam current, mA
Hadron rms normalized emittance, 10-6 m
5.3
50
4.8
42
6.4
55
3.9
33
0.27
0.20
0.20
31.6
5
0.015
34.7
5
0.014
57.9
5
0.008
Electron beam disruption
2.8
5.2
1.9
Space charge parameter
0.006
0.016
0.016
5
70
1.5
5
70
2.8
5
none
1.7
Energy, GeV
CM energy, GeV
Bunch frequency, MHz
Electron rms normalized emittance, 10-6 m
b*, cm (both planes)
Hadron beam-beam parameter
rms bunch length, cm
Polarization, %
Peak luminosity, 1033 cm-2s-1
e
15.9
5
0.4
70
We limit ourselves by 12 MW of synchrotron radiation (SR) power – it results in reducing
electron beam current at 21.2 GeV 2.7-fold and operate at luminosity of 1033 cm-2sec-1 in
eA and 0.55x1033 cm-2sec-1 in ep collision. If needed, we increasing SR power and,
therefore, the luminosity.
9
Synchrotron Radiation Effects
SR power loss per recirculation pass
Accumulated energy spread
Ie=50 mA
Ie=18 mA
rms energy spread, MeV
8
7
6
5
4
Top energy 21.2 GeV
3
Top energy 15.9 GeV
2
1
0
0
5
10
15
20
25
Beam energy, GeV
Energy loss compensation schemes :
 2nd harmonic (788 MHz) cavities;
or
 main linac RF phase offset + high
harmonic cavities
© S. Brooks, F. Meot, V. Ptitsyn
0.6
Transverse emittance growth
Norm. Emi ance,
mm mrad
Total SR power 12 MW:
operation at 15.9 GeV top energy -> 50 mA
operation at 21.2 GeV top energy -> 18 mA
0.5
0.4
0.3
0.2
0.1
0.0
5
10
15
Beam energy, GeV
20
25
11
Luminosity depends on the hadron beam energy
Electron-HI
1.4"
Defin d by xp=0.015
1.2"
1"
0.8"
Defin d by
e
DQsp = 0.035
0.6"
0.4"
0.2"
Space charge effect
0"
0"
50"
100"
150"
200"
e
250"
e-nucleon Luminosity, 1033 cm-2s-1
Electron-proton
300"
1.4
1.2
1
0.8
0.6
0.4
0.2
Space charge effect
0
0
20
40
60
80
100
Au ion energy, GeV/n
The electron energy is 15.9 GeV or below; 40% at 21.1 GeV
Going on the red curve requires space charge effect compensators – one of future AIPs
Luminosity enhancement – in contrast with energy increases - can be done without
interapting physics program
120
RHIC Integrated Luminosity and Polarization
Polarized proton runs
Integrated luminosity L [pb-1]
Integrated nucleon-pair luminosity LNN [pb-1]
Heavy ion runs
• C-AD has well established record of continuously increasing
luminosity
Interaction Region with * = 5 cm
Forward detector components
SC magnets
Crab-cavities
p
e
® Bret Parker
We are bending electron beam gently
towards the IR and use 10 mrad
crossing angle to separate the beam
without bending electron beam ….
*15-fold reduction compared with RHIC
Why crab-crossing?
•
We have to separate colliding beams.
•
To avoid synchrotron radiation by 30 GeV electrons in the IR – one of serious
backgrounds at HERA, we can not use separating dipoles.
•
To separate beams without applying magnetic field, we need a crossing angle
This also allows bringing the hadron triplet closer to the IR – hence lower β*
•
•
Crossing angle reduces luminosity ~100-fold
•
The crabbing (tail up, nose up) is needed to restore luminosity
Idea Introduced by R. B. Palmer SLAC PUB 4832
B
D
D
M left
M right
F/B
F/B D
Lr = 9.48 m
325 GeV p or 130 GeV/u Au
F
B
Lr = 9.48 m
Courtesy of
I. Ben-Zvi,
S.
Belomestnykh,
D.
Trbojevic and Q. Wu
Original BNL crab-cavity
design (I. Ben-Zvi)
14
POETIC 2013, Chile
V.N.Litvinenko
Detailed studies of background in
eRHIC IP – here is just one sample
Photon flux @ IP (cont’d)
Total power is about 40 W and practically all photons will propagate through IR without hitting the
walls of vacuum chamber. It should be absorbed as far as possible from the detector to reduce the
back-scattered photons and neutrons.
Detailed design of the detector and SR absorbers are needed for GEANT4 simulations.
© Y.Jing, O. Tchubar
Main elements of eRHIC concept
 Use for electrons to reach high luminosity at high energy.
 Using fresh electron beam from ERL boosts luminosity 50-fold and
allows attaining high luminosity with collision rep-rate compatible
with modern hadron detectors (start from 9 MHz)
 Use combination of our previous design (multi-pass ERL with arcs +
splitters/combiners) with cost effective FFAG arcs (idea of
D.Trbojevic)
 Use 2 FFAG arcs with 16-pass ERL linac to reach 21.16 GeV
 Reduce SRF frequency to improve HOM damping and beam stability
 Use splitters and combiners to match optics functions to linac (βx,y,
αx,y, Dx,y, D’x,y, R56) and time of flight – 10 parameters for each
energy (160 parameter for eRHIC). This can not be done otherwise
 ERL proved full spin transparency. 1.322 GeV linac provides for
longitudinal polarization in both IRs: IP6 & IP8
 …...
17
Beam Spreader and Combiner
© N. Tsoupas
•
Placed on either side of the linac to
separate/combine the 16 beams
with different energies between
FFAG arcs and CW Linac
•
Match optical function from the arc
to the linac
•
Ensure isochronous one turn
transport:
path length and R56 corrections
•
Linac
Arcs
 15 cm horizontal separation between individual lines
 Some of the lines are folded into the vertical plane to reduce
path length difference
 Vertical magnet chicanes are used for pathlength correction
Betatron phase advance adjusters
eRHIC FFAG arcs as a bent FODO beam-line
•
•
•
•
An ideal eRHIC FFAG cell is comprised of two quadrupoles (F & D) whose magnetic axis
are shifted horizontally with respect to each other by Δ
The structure has a natural bilateral symmetry, e.g. all extrema (min and max) are in the
centers of the quadrupoles (independently of any approximation!)
Orbit dependence on the energy can be easily found in paraxial approximation
Everything can be done accurately and analytically – no doubt that proposed FFAG
lattice would work!
z
f
zd
d d
L=2(lF+lD+2d)
F
20
D
F
lf
D
Orbit
F
xf = -
axdq + cxd ( D + dq )
axf cxd + axd cxf + 2dcxd cxf
xd = -
axf q - cxf ( D - dq )
axf cxd + axd cxf + 2dcxd cxf
θ θ
wd = -
eG f
eGd
;w f =
.
pc
pc
2d
Δ
ld
sin j f
axf = cosj f ; bxf =
wf
axd = cosh j d ; bxd =
;cxf = -w f sin j f
sinh j d
;cxd = w d sinh j d
wd
sinh j f
ayf = cosh j f ; byf =
;cyf = w f sinh j f
wf
ayd = cosj d ; byd =
sin j d
j f ,d = w f ,d l f ,d
wd
;cyd = -w d sinh j d
Orbits Exaggerated 100x
© Stephen Brooks
21
Important features
 You can bend and turn the FODO line, or make it straight
– the βx,y and αx,y stay unchanged;
 This string must be continuous from the linac splitters to
linac combiners;
 By moving quads horizontally (or moving their axis using
dipole trims) one can adjust all orbits to a desirable
pattern, including separating a single energy beam from
the rest of the pack.
® S. Brooks
10 (6)beams
21.2 GeV or 15.9 GeV or any…
V.N. Litvinenko, EIC UG meeting, Stony Brook University , June 25, 2014
Important R&D towards eRHIC
Polarized electron gun
Coherent Electron Cooling
Beam-beam affects in linac-ring collider
Multi-pass SRF ERL with FFAG arcs
Crab cavities
Polarized 3He production
Dynamic aperture with β*=5 cm
5x reduction
23
eRHIC R&D highlights: Gatling gun
24
CeC Proof-of-Principle Experiment
40 GeV/u Au ions cooled by 22 MeV electrons
Under contraction
Commissioning/test should start in 2015
V.N. Litvinenko, EIC UG meeting, Stony Brook University , June 25, 2014
R&D ERL – under commissioning
Short Summary
• We are pursuing all necessary R&D to ensure
eRHIC would deliver promised performance
• We are cost conscious and will fully utilize
$2B investment in RHIC hadron complex
• eRHIC design was reviewed by an external
review committee, MAC and EICAC.
• Quote from latest report: ”The MAC
congratulates the eRHIC design team for its
ingenious and novel use of the FFAG concept.”
28
eRHIC Schedule
© T. Roser
Conclusion Last
• We found at BNL a cost-effective way of building the full-energy
EIC: (21.2 GeV polarized electrons x 255 GeV p) from day one using
and ERL with FFAG arcs for 16 recirculation passes
• The cost of the machine is similar to a that with 5 GeV ERL using
regular arcs. Bottoms-up costing is underway at BNL.
• It is designed to reach day-on high luminosity (> 1033 cm-2 s-1) up to
125 GeV CM energy and 145 GeV CM energy at 40% of the
luminosity.
• R&D is under way on high current polarized electron source (Gatling
Gun), effective hadron cooling (Coherent electron Cooling) and high
current ERL.
• We built in head-room for future accelerator improvement projects
(AIPs) to increase luminosity toward 1034 - 1035 cm-2 s-1. In this
sense, we are using RHIC model, where AIPs were used for reaching
luminosity 20-fold above the design value.