Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 1
An Electron-Ion Collider for JLabAn Electron-Ion Collider for JLab
Antje Bruell
Lia Merminga
(Kees de Jager)
Jefferson Lab
QCD-N’06
June 15, 2006
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 2
CHL-2CHL-2
Upgrade magnets Upgrade magnets and power and power suppliessupplies
Enhance equipment in Enhance equipment in existing hallsexisting halls
6 GeV CEBAF1112Add new hallAdd new hall
• JLab Upgrade only present construction project in DOE-NP
• First 12 GeV beam expected in ~2012
• However, plans for next upgrade already being developed now
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 3
Why Electron-Ion Collider?
• Polarized DIS and e-A physics: in past only in fixed-target mode• Collider geometry allows complete reconstruction of final state• Better angular resolution between beam and target fragments
• Lepton probe provides precision but requires high luminosity to be effective
• High Ecm large range of x, Q2 Qmax2= ECM
2•x
x range: valence, sea quarks, glueQ2 range: utilize evolution equations of QCD
• High polarization of lepton, nucleon achievable
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 4
com
pass
herm
es JLab (upgraded)
clas
Q2
Kinematic coverage of ELIC
EIC
• Luminosity of up to 8x1034 cm-2 sec-1 (one-day life time)
• One day 4,000 events/pb• Supports Precision
Experiments
Lower value of x scales as s-1
• DIS Limit for Q2 > 1 GeV2 implies x down to 2.5 times 10-4
• Significant results for 200 events/pb for inclusive scattering
• If Q2 > 10 GeV2 required for Deep Exclusive Processes can reach x down to 2.5 times 10-3
• Typical cross sections factor 100-1,000 smaller than inclusive scattering high luminosity essential
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 5
EIC Monte Carlo Group•Antje Bruell (JLab)•Abhay Deshpande (SBU)•Rolf Ent (JLab)•Ed Kinney (Colorado)•Naomi Makins (UIUC)•Christoph Montag (BNL)•Joe Seele (Colorado)•Ernst Sichtermann (LBL)•Bernd Surrow (MIT)
+ Several “one-timers”: Harut Avakian,
Dave Gaskell,
Andy Miller, …
GRSV
ELIC projection (~10 days)
Examples: g1p,Transversity, Bjorken SR
Can determine the Bjorken Sum Rule to better than 2% (presently 10%)
EIC Monte Carlo work by Antje Bruell + Mindy Kohler
EIC Monte Carlo work by Naomi Makins
Examples: g1p
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 6
Exclusive 0 production on transverse target
2 (Im(AB*))/ T
t/4m2) - ReUT
A ~ 2Hu + Hd
B ~ 2Eu + Ed0
K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001
Q2=5 GeV2
Eu, Ed needed forangular momentum sum rule. 0
B
A ~ Hu - Hd
B ~ Eu - Ed+
EIC
Higher Q2 of EIC may be crucial
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 7
Sivers function extraction from AUT (0) does not require information on fragmentation function. It is free of HT and diffractive contributions.
F1T=∑qeq2f1T
┴q
AUT (0) on proton and neutron will allow flavor decomposition w/o info on FF.
In large Nc limit:
f1Tu = -f1T
d
Efremov et al(large xB behavior of
f1T from GPD E)
CLAS12projected
CLAS12projected
From CLAS12 to ELIC: Sivers effect projections
EIC
Thomas Jefferson National Accelerator Facility
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Nonperturbative TMD Perturbative region
PT-dependence of beam SSA
sinLU(UL) ~FLU(UL)~ 1/Q (Twist-3)
In the perturbative limit 1/PT
behavior expected (F.Yuan SIR-2005)
Study for SSA transition from non-perturbative to perturbative regime.
ELIC will significantly increase the PT range.
2.0
EIC
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 9
From CLAS12 to ELIC: Transversity projections
AUT ~Collins
Simultaneous measurement of, exclusive with a transversely polarized target
The background from vector mesons very different for CLAS12 and EIC.
EIC
10-3
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 10
From CLAS12 to ELIC: Mulders TMD projections
Simultaneous measurement of, exclusive with a longitudinally polarized target important to control the background.
UL ~KM
EIC
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 11
Ion Linac and pre-booster
IR IR
Beam Dump
Snake
CEBAF with Energy Recovery
3-7 GeV electrons 30- 150 GeV light ions
Solenoid
Ion Linac and pre-booster
IR IR
Beam Dump
Snake
CEBAF with Energy Recovery
3-7 GeV electrons 30- 150 GeV light ions
Solenoid
Ion Linac and pre-booster
IR IR
Beam Dump
Snake
CEBAF with Energy Recovery
3 -7 GeV electrons 30 -150 GeV light ions
Solenoid
Electron Injector
Electron Cooling
ERL-based ELIC DesignERL-based ELIC Design
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 12
• Polarized electron current of 10’s of mA is required for ERL-based ELIC with circulator ring. Present state of art ~0.3 mA.
• A fast kicker with sub-nanosecond rise/fall time is required to fill the circulator ring. Present state of art is ~10 ns.
• Substantial upgrades of CEBAF and the CHL (beyond the 12 GeV Upgrade) are required. Integration with the existing 12 GeV CEBAF accelerator is challenging.
• Exclusion of physics experiments with positron beam.
• Electron cooling of the high-energy ion beam is required.
• All these challenges led to the design of a new Ring-Ring Concept
Challenges of ERL-based ELICChallenges of ERL-based ELIC
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 13
Ring-Ring Concept
Use present CEBAF as injector to electron storage ringAdd light-ion complex
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 14
Polarized Electron Injection & Stacking
J Storage ring
t
J
t
3000 pulses5 s
Injector
4 ms*1 mA
*4 ms is the radiation damping time at 7 GeV
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 15
Ion Complex
“Figure-8” boosters and storage rings• Zero spin tune avoids intrinsic spin resonances• No spin rotators required around the IR• Ensure simultaneous longitudinal polarization for
deuterons at 2 IPs, at all energies
Linac 200 MeV
Ion Collider Ring
Pre-Booster3 GeV/c
C≈75-100 mIon Large Booster 20 GeV(Electron Storage Ring)
spin
Thomas Jefferson National Accelerator Facility
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Positrons!
Generation of positrons: (based on CESR experience)• Electron beam at 200 MeV yields unpolarized positron accumulation
of ~100 mA/min• ½ hr to accumulate 3 A of positron current• Polarization time 2 hrs at 7 GeV (Sokolov-Ternov polarization)• Equilibrium polarization ~90%
Possible applications:• e+i colliding beams (longitudinally polarized)• e+e- colliding beams (longitudinally polarized up to 7x7 GeV)• …..
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 17
Achieving the Luminosity of ELIC
For 150 GeV protons on 7 GeV electrons, L~ 8 x 1034 cm-2 s-1 is compatible with realistic Interaction Region design.
Beam Physics Issues
• High energy electron cooling
• Beam – beam interaction between electron and ion beams
(i ~ 0.01 per IP; 0.025 is presently utilized in Tevatron)
• Interaction Region
High bunch collision frequency (f = 1.5 GHz)
Short ion bunches (z ~ 5 mm)
Very strong focus (* ~ 5 mm)
Crab crossing
*24i e
b
N NL f
=
Thomas Jefferson National Accelerator Facility
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Polarization of Electrons
• Spin injected vertical in arcs (using Wien filter) • Self-polarization in arcs to support injected polarization • Spin rotators matched with the cross bends of IPs
spin rotator
spin rotator
spin rotator
spin rotator
collision point
spin rotator with 90º
solenoid snake
collision point
collision point
collision point
spin rotator with 90º
solenoid snake
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 19
Polarization for Positrons
• Sokolov-Ternov polarization for positrons• Vertical spin in arcs • 4 IPs with longitudinal spin• Polarization time is 2 hrs at 7 GeV – varies as E-5 (can be accelerated
by introduction of wigglers).• Quantum depolarization in IP bends -> equilibrium polarization ≈ 90%
spin rotator
spin rotator
spin rotator
spin rotator
collision point
spin rotator with 90º
solenoid snake
collision point
collision point
collision point
spin rotator with 90º
solenoid snake
Thomas Jefferson National Accelerator Facility
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Polarization of Ions
Protons and 3He: Two snakes are required to ensure longitudinal polarization at 4 IP’s simultaneously.Two IP’s (along straight section) with simultaneous longitudinal polarization with no snakes.
collision point
collision point
collision point
collision point
Snake
P, He3
Protons and 3He
Deuterons: Two IP’s with simultaneous longitudinal polarization with no snakes. Solenoid (or snake for protons) to stabilize spin near longitudinal direction for all species.
collision point
collision point
collision point
collision point
Solenoid
d
Deuterons
Thomas Jefferson National Accelerator Facility
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ELIC Interaction Region Concept
Focal Points
2 m
spin detectorCrab cavity
Crab cavity
focusing triplet
focusing triplet
80 MV
focusing doublet
focusing doublet
Crab cavity
Crab cavity
spin tune solenoid
spin tune solenoid
cross bend
cross bend
α
0.1 rad
4 m
i
e
i
4 m
0.1 rad
Thomas Jefferson National Accelerator Facility
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Short bunches make Crab Crossing feasible.
SRF deflectors at 1.5 GHz can be used to create a proper bunch tilt.
SRF dipole
Final lens FF
Crab CrossingCrab Crossing
Parasitic collisions are avoided without loss of luminosity.
Thomas Jefferson National Accelerator Facility
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ELIC, June 15, 2006, 23
ELIC ParametersParameter Unit ERL Ring-Ring Beam ener gy GeV 150/ 7 150/ 7 100/ 5 30/ 3
Bunch collisi on r ate GHz 1.5
Number of
par ticles / bunch
1010 0.4/ 1.0 0.4/ 1.0 0.4/ 1.1 0.12/1 .7
Beam curr ent A 1/ 2.4 1/ 2.4 1/ 2.7 0.3/4 .1
Cooling beam energ y MeV 75 75 50 15
Cooling beam curre nt A 2 2 2 .6
Ener gy spr ead, rms 10-4 3/ 3
Bunch length, rms mm 5/ 5
Beta -sta r mm 5/ 5
Hor izontal emit tance
(nor m)
m 1/ 86 1/ 86 0.7/7 0 0.2/4 3
Ver tical emitt ance (nor m) m 0.04/ 3.4 0.04/ 3.4 0.06/ 6 0.2/4 3
Beam-beam t une shif t
(vert ical) per IP
0.01/ 0.086 0.01/ 0.086 0.01/0. 073 0.01/0. 007
Laslet t t une shif t (p -
beam)
0.015 0.015 0.03 0.06
Luminosity pe r IP , 1034 cm-2 s-1 7.7 7.7 5.6 0.8
Number of inte r act ion
point s
4
Cor e & luminosit y IBS
life t ime
h 24 24 24 >4
Thomas Jefferson National Accelerator Facility
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Summary
Design studies at JLab have led to an approach that promises
luminosities up to nearly 1035 cm-2 s-1, for electron-light ion collisions at
a center-of-mass energy between 20 and 65 GeV.
A fundamentally new approach has led to a design that can be realized
on the JLab site using CEBAF as a full-energy injector into an electron
storage ring and that can be integrated with the 12 GeV fixed-target
physics program.
Understanding the structure of the nucleon requires measurements of
the Generalised Parton Distributions over the full x range and
at high Q2 necessary for a full flavor decomposition
Measurements of both DVCS and exclusive meson production at EIC
will allow the determination of the quark and gluon orbital momenta
Extend single-spin asymmetry measurements in semi-inclusive
scattering to much lower x-values and over large pT-range