Transcript Document

Planning and Realization of
an Electron-Ion Collider
Steve Vigdor
Hawaii DNP Meeting
October 13, 2009
“An EIC with polarized beams
has been embraced by the
U.S. nuclear science community as embodying the
vision for reaching the
next QCD frontier.”
How can we
realize this
vision?
Articulate the Basic Science
Themes More Clearly
 Which parts of the program are “discovery”, which
parts “characterization”?
 How does EIC go beyond the QCD programs at RHIC,
JLab, LHC, HERA (EIC will have much higher
luminosity, polarized ion and heavy ion beams)?
 What new aspects of QCD matter will be revealed/
explored?
Note INT workshops on EIC science, Fall ’09 and ’10.
EIC Science: Gluon-Dominated Cold Matter in e+A
Search for supersymmetry @
LHC, ILC (?): seeking to unify
matter and forces
Electron-Ion Collider: reveal
that Nature blurs the distinction
Deep inelastic scattering @ HERA 
Gluons dominate the
soft constituents of
hadrons! But density
must saturate…
EIC probes weak coupling regime of very
high gluon density, where gauge boson
occupancy >> 1. All ordinary matter has
at its heart an intense, semi-classical
force field -- can we demonstrate its
universal behavior? Track the transition
from dilute parton gas to CGC? “See”
confinement reflected in soft-gluon
spatial distributions inside nuclei?
EIC Science II: Polarized e + N
 Polarized DIS,  -gluon fusion  gluon
polarization to x ~ few  104
 Bjorken sum rule test to ≲  2%
 SIDIS for low-x sea-quark polarization
and transverse spin studies
More luminosity-hungry:
 Polarized DVCS, exclusive reactions +
LQCD  GPD’s  map low-x transverse
position-dep. PDF’s; Jq from Ji sum rule
 High-Q2 e+p,d parity viol’n  weak
coupling running below Z-pole
Proton
tomography
via exclusive
reactions
x < 0.1
x ~ 0.3
x ~ 0.8
Choose “Golden” Experiments That
Set Machine/Detector Performance
Requirements
e.g.,
 inclusive DIS for indirect (F2) determination of gluon
densities in heavy nuclei, extension of spin structure (g1)
 direct determination of gluon densities by FL (emphasis
on energy variability of machine, detector)
 diffractive measurements to probe spatial distribution
of gluons in e+A
 deep exclusive reactions to map GPD’s
 parity-violating asymmetries at high Q2
Detailed simulations needed to demonstrate feasibility,
determine requirements
Minimum luminosities
The √s vs. luminosity landscape
to “get in the game” -Diffraction
from Elke Aschenauer
exclusive DIS (PS & VM)
electro-weak
exclusive DIS (DVCS)
semi-inclusive DIS
HERA
inclusive DIS
4x100 10x100 20x100
4x250
20x250
30x325
6
Detector Requirements (E. Aschenauer)
 ep-physics
• the detector needs to cover inclusive (ep -> e’X)  semi-inclusive (ep ->
e’X hadron(s))  exclusive reactions (ep -> e’pp)
- large acceptance absolutely crucial
- particle identification (p,K,p,n) over wide momentum
range
- excellent vertex resolution (charm)
- particle detection for very low scattering angle
• small systematic uncertainty for e/p polarization measurements
• very small systematic uncertainty for luminosity measurement
 eA-physics
• requirements very similar to ep
- most challenging get information on recoiling heavy ion
from exclusive and diffractive reactions.
Settle on Preliminary Machine &
Detector Designs, Staging and Cost
Estimates
 Machine designs further along than detector designs
 Two quite distinct designs from BNL and JLab, each
with well-defined staging plan
 Bottoms-up cost estimates in progress at each lab,
with emphasis now on 1st-stage machines – likely
several hundred million dollar projects
Is there one affordable machine that can cover
the whole science program? If not, what is
optimal tradeoff of science vs. cost?
 Start with MeRHIC: 4 GeV electron
ERL to  collisions at one IP with
already existing RHIC ion beams
eRHIC @ BNL
 Later add e linac sections in RHIC
tunnel to increase energy & # IP’s
250 GeV p↑
100 GeV/A Au,U
Additional
linac
10 … 30 GeV e↑
Pol. electron
source
Beam
dump
eRHIC
detector
Coherent
e-cooling
MeRHIC
+ detector
eRHIC
PHENIX
2 x 200 m SRF linac
~ 4 GeV per pass







Permits
simultaneous
operation with
RHIC A+A, p+p
STAR
5 vertically separated
recirculation passes in
RHIC tunnel

Full use of MeRHIC
10 GeV electron design energy. Possible
upgrade to 20 – 30 GeV.
Peak luminosity: 3 × 1033 cm-2 s-1
5 recirculation passes in the RHIC tunnel
Multiple electron-hadron IP’s possible
Full polarization transparency at all
energies for the electron beam
Ability to take full advantage of transverse
cooling of the hadron beams
Possible options to include polarized e+ at
lower luminosity: compact storage ring or
ILC-type polarized positron source
Considerable FY09 Progress on Design of
Possible 1st (Medium Energy, MeRHIC) Stage
SRF electron gun
Main ERLs: 6 cryostats x 6
cavities x 18.1 MeV/cav =
0.652 GeV/linac/pass
Stage I e-RHIC with ERL
outside RHIC tunnel @ IP2:
4 GeV e with RT magnets
3 recirculation
passes
ep + eA detector
 Would enable 4 GeV e on 100 GeV/N heavy ions and 250 GeV p, with
most equipment to be reused later in full EIC
 1st look at saturation surface for nuclei in e+A DIS: confirm nuclear
“oomph” factor & measure gluon densities relevant to RHIC initial
state; e+A diffraction tests of high gluon occupancy
 e-p program extending DIS, adding: transverse-spin SIDIS over broad
Q2-range  TMD evolution; detection of boosted target fragments to
probe spin-dependent correlations in nucleon.
 Developing science case, detector design, cost estimate.
eRHIC parameters
MeRHIC
Energy, GeV
eRHIC with CeC
p (A)
e
p (A)
e
250 (100)
4
325 (125)
20 <30>
Number of bunches
111
Bunch intensity (u) , 1011
2.0
0.31
2.0 (3)
0.24
Bunch charge, nC
32
5
32
4
Beam current, mA
320
50
420
50 <10>
Normalized emittance, 1e-6 m,
95% for p / rms for e
15
73
1.2
25
Polarization, %
70
80
70
80
rms bunch length, cm
20
0.2
4.9
0.2
β*, cm
50
50
25
25
Luminosity, x 1033, cm-2s-1
166
0.1 -> 1 with CeC
2.8
< Luminosity for 30 GeV e-beam operation will be at 20%
level>, limited by synchrotron radiation loss rate
11
EIC and MEIC @ JLab
Focus on high
luminosity at
moderate  s ~
30 GeV
Figure 8 lepton & ion rings
ensure spin preservation and
ease of spin manipulation at all
energies.
Simultaneous operation with
CEBAF fixed-target program is
possible.
JLab
 Very strong final focus!
Factor 50 difference in assumed * for colliding beams fully accounts for
difference in projected luminosity between the two designs.
Detector and IR Design Beginning in Earnest
Use soft (~0.05 T) bend for final bending of e beam to IP, to shield
detector from all but the very softest synchrotron radiation
Dipole
3Tm
Solenoid (4T)
FED
//
Dipole
3Tm
FPD
//
r: 8 ft / 2.5m
~15m
ZDC
/ TRD
Delineate Coherent Program of
Essential R&D and Obtain Funding
Priorities:
1)
Proof of principle for large improvements over present state
of the art – needed for technical plausibility by next LRP:

Polarized electron source current (50 mA eRHIC vs. 1 mA at
best present sources)

ERL operation at high energies and 100’s mA @ eRHIC

Hadron beam * in collider (5 mm @ JLab vs. ~25 cm at
existing hadron colliders)

Detector operation at 500 MHz @ JLab
2)
Proof of principle of high-energy hadron beam cooling
techniques (e.g., Coherent electron Cooling – CeC) to
improve luminosity from initial design
3)
Technology developments to reduce costs, e.g., in SRF
cavity fabrication, stability
Accelerator R&D Already Under Way: e- Guns
To relax limitation from ion bombardment
damage of photocathode, increase area:
Large
annular
photocathode
under test by
E. Tsentalovich
@ MIT/Bates –
funded by DOE
E
Dogleg funneling system is spin transparent
“Gatling gun” approach,
using rotating RF field
to recombine
successive pulses from
24 2-mA guns under
design by I. Ben-Zvi @
BNL – 2-gun test funded
by BNL LDRD
Electrostatic kicker
Electrostatic kicker
Rotating field kicker
Accelerator R&D Already Under Way: II
R&D 20 MeV ERL under
construction @ BNL to
demonstrate high-current
performance. Utilizes 704
MHz SRF cavity designed for
this purpose – Q=1  1010 @
20 MV/m demonstrated,
exceeding required
performance.
Funded by DOE, Navy, BNL
Compact (5 mm gap) dipoles, to allow
multiple vertical passes within single
vacuum enclosure around RHIC tunnel,
under development via BNL LDRD funds.
Extensive R&D Needed on HighEnergy Hadron Beam Cooling
JLab proposes SRF ERL-based electron cooler.
Present state of the art from FNAL:
4.34 MeV e @ 0.5 A DC
MEIC requires up to 33 MeV e, EIC up to 136
MeV e @ up to 3A CW !
BNL proposes novel Coherent e-Cooling, with proof of
principle test to be performed on RHIC 40 GeV/A Au beam
Modulator: hadron
beam structure introduces density modulation in e-beam
Wiggler: FEL amplification (x 102-3)
of e-beam modulations, while
chicane adds dispersion to h beam
Kicker: attraction to ebeam density peak reduces ion-beam E spread.
CeC of high-energy hadron beams: high-gain FEL based on high-brightness
ERL  potential to boost EIC ( and LHC? RHIC p+p?) luminosities.
R&D Needed on Crab Crossing to Boost Luminosity
of Collisions at Non-Zero Crossing Angle
Joint EIC R&D plan (to be updated)
 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)
• Crab cavities
[20 FTE-yrs; M&S: $4.5 M Total: $8.5M]
[ 8 FTE-yrs; M&S: $1.2M Total: $2.8M]
 R&D activities specific to eRHIC
• High current polarized electron source (MIT)
• Energy recovery technology for
[7.5 FTE-yrs; M&S: $ 2.0 M Total: $3.5M]
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]
 Breakdown between Laboratories
• BNL – $19.0M
JLab – $15.4M
MIT - $3.5M
Get Good Advice
EIC Advisory Committee
Joachim Bartels (Universitait Hamburg, DESY)
Allen Caldwell (Max-Planck Institute for Physics, Munich)
Albert De Roeck (CERN)
Walter Henning (ANL, Chair)
David Hertzog (University of Illinois)
Xiangdong Ji (University of Maryland)
Robert Klanner (DESY)
Al Mueller (University of Columbia)
Katsunobu Oide (KEK)
Naohito Saito (JPARC)
Uli Wienands (SLAC)
1st meeting 2/16/09. 2nd meeting 11/02/09 – will recommend
coherent R&D plan, hopefully to be funded by DOE starting FY10.
EICAC Advice from Feb. 09
Meeting Forms Basis of This Talk!
EICAC requested next meeting on Fall ’09 schedule, for 2 days to
allow deeper discussion, and with following major deliverables:
 Coherent R&D plan, timeline,
 Short list of “golden measure-
milestones & resource needs
ments” & what will be learned
 Initial cost-performancescience reach matrix
 Implications of golden exp’ts
for detector requirements + R&D
Other EICAC recommendations:
 Further develop the schedule including approximate resource-loading,
to provide a timeline for major decisions (including, if at all possible, site
decision), technical developments, and (staged) realization
 In particular, strive for a timeline (under reasonable assumptions) that
provides for data taking before 2020
Other Recent Developments at BNL & JLab
 Set up BNL EIC Task Force led by Elke Aschenauer & Thomas Ullrich,
comprising ~15 nuclear/particle physicists in addition to accelerator team
 JLab Users Group forming EIC development team
 BNL targeted LDRD program funds a number of EIC efforts starting
FY10:
I. Ben-Zvi et al., EIC Polarized Electron Gun
T. Rao and T. Tsang, Development of a laser system for driving the
photocathode of the polarized electron source for the EIC
V. Litvinenko et al., Simulation, design and prototyping of an FEL for proof-ofprinciple of Coherent Electron Cooling
T. Ullrich and R. Venugopalan, Realization of an e+A Physics Event Generator
for the EIC
R. Venugopalan et al., Exploring signatures of saturation and universality in e+A
collisions at eRHIC
W. Marciano et al., Electroweak Physics with an Electron Ion Collider
Higher- and lower-energy electron-ion
colliders now under consideration in Europe:
 LHeC @ CERN:
S. Brodsky
Divonne LHeC
Workshop,
Sept. 2008
at Conceptual Design Report stage

sep ~ 1 TeV @ Lep ~ 2  10 32 cm 2s 1
Main LHeC focus on “new physics”
(e.g., SUSY, lepto-quarks, lepton
and quark substructure) and
precision SM physics. Overlaps
EIC focus on high-density QCD @
low-x end of reach.
Question: how fits with SLHC, CLIC?
 ENC @ FAIR: 3 GeV e  15 GeV p @ L ~ 1033 in HighEnergy Storage Ring  polarized parton distributions with
higher precision in kinematic region scanned in fixed-target
experiments. Case at preliminary stage.
Opportunities abound for joint accelerator & detector R&D
Summary
 Activity on delineating science case, machine design and
costing for EIC and 1st medium-energy stage is ramping up.
 Substantial accelerator R&D programs already under way
with some DOE + some laboratory funding. Anticipate
competitive DOE-funded R&D program to be launched soon.
 Upcoming INT workshops should help to lay out scientific
impact in more detail.
 Great deal of work remains to be done, especially on
detector concepts, simulations and R&D !
 Now is the time to join the effort if we are to make
compelling case at next Nuclear Physics Long Range Plan!
Backup Slides
Suggested Framing Questions for EIC Science Case
1) Is main goal of EIC “discovery” or “characterization”? If latter,
what is transformational (as opposed to incremental)? How are we
likely to fundamentally alter understanding of QCD and/or QCD
matter? Are there likely to be implications beyond QCD? What
facility features not available at HERA (N, A-beams, higher L )
enable transformational measurements? Not doable in p-A?
2) Why should scientists not directly involved in QCD studies care
about dense gluonic matter? If we find, or don’t find, clear
evidence that gluon field strength saturates, what do we conclude
about QCD or nuclei? Are there general implications of transition
from dilute parton gas to high gauge boson occupancy?
3) Are gluon degrees of freedom important for understanding
nuclear structure? Should soft gluon distributions in nuclei
exhibit evidence of confinement, or should saturated gluonic
matter look identical in nucleons and nuclei? Can we measure
gluon spatial distributions in nuclei with sufficient resolution to
see nucleon-scale “clumps”?
Suggested Framing Questions, continued…
4) If we can’t solve the nucleon spin puzzle without EIC, can we
solve the puzzle with EIC? Do we have a clear strategy for
completing a full measurement of the spin sum rule in either
target rest frame (Ji sum rule) or on light front (G sum rule)?
5) What features do we hope to unravel with 3D maps from GPDs
at low x (more than x-dependence of overall transverse size)?
Do we have the transverse spatial resolution to see “fine”
structure? Is there a viable strategy to Jq by combining DES
with LQCD constraints on moments of GPD’s?
6) Will the running of sin2W below the Z-pole, at sensitivity levels
accessible with PVES @ EIC still be a significant question on
the timescale of EIC measurements? Are there other unique EW
symmetry opportunities with EIC?
7) What fraction of above science goals could be accomplished, or
at least started, with 1st lower-energy stage of EIC? In what
ways can experience gained at 1st stage inform accelerator /
detector design and cost-effectiveness for a full EIC?
MeRHIC in IR 2: 3D layout
© J.C.Brutus, J. Tuozzolo, D. Trbojevic,
G. Mahler, B. Parker, W. Meng
V.N. Litvinenko, Internal cost review of MeRHIC/eRHIC, October 2009
30
31
Switchyard at the linac
1.4GeV
2.7GeV
4GeV
0.2458 m
0.136 m 0.16 m 0.16 m
0.702 m
0.1GeV
0.55 m
1.25 m
1.866 m
2.8423 m
V.N. Litvinenko, EINN 2009, Milos, Greece, September 27, 2009
First ideas for
a detector
concept
Solenoid
(4T)
Dipole
3Tm
Dipole
3Tm
FED
//
FPD
//
ZDC
/ TRD
r: 8 ft / 2.5m
~15m
E.C. Aschenauer
BNL S&T-Review, July 2009
32
 no synchrotron shielding included
 allows p and heavy ion decay product tagging
IR-Design for MeRHIC II
E.C. Aschenauer
BNL S&T-Review, July 2009
33
FT (GPD) : momentum space  impact parameter space:
[M. Burkardt, M. Diehl 2002]
Proton Tomography
u-quark
polarized nucleon:
[x=0]
T
probing partons with specified long. momentum @transverse position b
d-quark
from
lattice
E.C. Aschenauer
BNL S&T-Review, July 2009
35