1. Summary Accelerator Workshop 18 July
Afternoon Session
F. Willeke
BNL

2. Agenda
Overview of the JLEIC Design, Vasiliy Morozov Overview of the eRHIC Design Christoph Montag EIC Beam Dynamics, F. Willeke (for Michael Blaskiewicz) Advanced Hadron Cooling Concepts Vadim Ptitsyn Bunched Beam Electron Cooling Yuhong Zhang Superconducting Magnet Technology, Gianluca Sabbi Superconductng RF for EIC, Jiquan Guo

3. EIC Design Comparison
eRHIC
JLEIC
3-12 GeV
8-100(400) GeV
8 GeV

4. Different Designs – Many Common Elements
Despite the fact that the two designs are based on different boundary conditions and that they differ in shape and size
There are many common challenges and R&D items
Layout of the interaction region and machine-detector integration
Large aperture superconducting IR septum quadrupoles and dipoles
Superconducting RF cavities
Similar beam dynamic challenges: beam-beam effects, high beam current, many bunches
Crossing angle geometry and crab cavities
Need for strong hadron cooling using electron beams
Spin Polarized electron- and ion-sources
 There is plenty og opportunity for collaboration between BNL and JLAB on EIC R&D

5. Complementary Expertise
BNL Expertise:
Ion/proton beam sources
Ion acceleration
Ion Spin preservation
Hadron beam dynamics
RF for hadron beams
Hadron beam instrumentation
Superconducting Magnets
Storage Ring Beam Physics
Electron Cooling
JLAB Expertise:
Polarized Electron Sources
Superconducting RF development
Superconducting RF production and industrialization
Superconducting LINAC technology
Superconducting LINAC beam physics
Acceleration and transport of polarized
Electron beams
Strong BNL-JLAB collaboration will help to make EIC designs
more compelling and thus will make an EIC project more likely,
… But will have little impact on the site decision

6. Ongoing Collaboration JLAB/BNL
Superconducting IR magnets using Nb3Sn technology (starting up, dedicated DOE funding)
Polarized electron guns
Beam-Dynamics Simulations (in particular beam-beam interaction)
Crab Cavity development
Ist planned common collaboration meeting (at BNL October 9-12, 2017)
Includes collaboration with FNAL, ANL, LBL, SLAC, TAMU
Welcome potential collaborators from Europe, …

7. EIC Beam Dynamics
Combines the challenges of high performance e+e- colliders and hadron colliders
Adds EIC specific beam dynamic aspects
JLEIC and eRHIC have common beam dynamic challenges
Topics Discussed
Electron cloud effect (eRHIC) (also important for SuperKEK-B, LHC HL, ….)
Coherent single bunch instabilities (eRHIC, JLEIC) mostly for eRHIC
Electron beam heating (eRHIC, JLEIC) mostly for eRHIC
Coupled bunch instabilities (eRHIC, JLEIC)
Electron-Ion Beam-beam effects (eRHIC, JLEIC), EIC specific aspect
Beam dynamics with Crab Cavities (eRHIC, JLEIC), also relevant for LHC
Dynamic aperture (eRHIC, JLEIC) relevant for all high performance colliders and light sources
Polarized beam storage (eRHIC, JLEIC)
Acceleration of polarized beams (eRHIC, JLEIC)
Intrabeam Scattering and electron cooling (JLEIC, eRHIC)
This suggests strong collaboration between the accelerator labs on beam dynamcs, in particular, but not limited to BNL-JLAB collaborations, collaborations with other labs including European labs expted to be mutually beneficial
Planned Meetings
ICFA Miniworkshop on dynamic aperture, Beijing, September 2017
Beam-Beam Workshop LBL, Spring 2018

8. Electron Cooling of HADRON Beams
Two presentations:
Overview of Hadron Cooling techniques by Vadim Ptitsyn
Specific presentation on Bunched Electron Cooling (Choice for JEIC design) by Yuhong Zhang
Need for Cooling
EIC hadron beam are subject to Intrabeam-scattering (Lorentz boosted bunch internal Coulomb scattering)
This does not allow to reduce the beam size (beam emittance) to the extend required for high luminosity
 There is consensus that high luminosity in an EIC collider depends on the feasibility of strong hadron cooling
Strong means: Cooling times < 1h
“Classical” methods such as microwave stochastic cooling are insufficient (cooling times ~5- 10 hours)

9. Cooling Overview Standard methods:
Classical electron cooling with DC electron beam from an electro-static accelerato
is useful only at low energy of a few GeV (gamma<10), may be used for precooling of EIC beam
Cooling rates greatly improved by solenoidal fields in cooling channel
Microwave stochastic cooling, works at all energies, but cooling rated limited by bandwidth of pickups, amplifiers and kickers of <30 GHz
Bunched Beam Electron Cooling
Electrons accelerated in RF structures, reach larger energies (multi MeVs electron multi GeV hadron beam)
Is implemented and will be used in RHIC FY18/19 low energy run
Solenoidal fields make cooling more powerful, but need to produce fields in solenoidal fields, but accelerations is without solenoid complicated beam transport, extreme alignment requirement on solenoid
Cooling rate still scales with g-5/2  need very large electron (amps) currents to cool EIC hadron beam
requires multi-turn cooler rings and ERL for energy recovery to make it affortable (JLEIC Cooling Scheme)
Novel techniques:
Coherent Electron cooling, Like stochastic cooling, but use electron beam as pick-up and amplifier, FEL based amplifier, so far exists only on paper and in simulation, demonstration experiment underway
Microbunching cooling, same principle, but use space charge and wakefields and amplifying mechanism (eRHIC Cooling Scheme)
Optical stochastic cooling (use photons as pick-ups and kickers)
Lively discussions on Hadron Cooling feasibility R&D Efforts for EIC

10. Technology Part
Superconducting Magnets
Superconducting RF

11. Superconducting Magnet Technology
Superconducting magnet technology is vital for feasibility of EIC designs:
Superconducting long dipoles for JLEIC (energy range)
Superconducting large aperture, high gradient quadrupoles for IR design

12. Superconducting Magnet Technology State of the Art
Nb Ti Alloy
require temperatures below 10 K (usually 4.5 K)
Is very mature technology (large magnet systems like Tevatron, HERA, RHIC, LHC …..)
Current density limiting Jc 4.2 K , B <~5T
Strong Dependence of Jc on external magnetic Field
 Field strength for accelerator magnets practically limited at around 7 T (LHC)
New techniques such as direct winding (developed for HERA, used at BEPC-II, SuperKEKB..) allows for large aperture, very high field quality but moderately high fields

13. Nb3Sn
similar maximum current density but shifted to higher values of magnetic field B<15 T
Allows in principle magnets up to 15 T (FCC magnet concept)
Technology very cumbersome (accelerator community spent 4 decades in developing the techniques)
Material is pulverized or in thin wire form, needs to be cured at high temperature after which is become brittle and extremely hard to handle
Jc depends on pressure: sophistocated mechanical design to manage pre-pressure and operating pressure, quench propagation critical
Technology is well developed now, should be well suited for EIC IR magnet (prototype in Collaboration JLAB/BNL, dedicated DOE funding underway)

14. HL-LHC IR Quadrupole Development

15. High Temperature Superconductors (HTS)

16. HTS
Available since end of the 80-ties, Bi and Yttrium compounds are best suited
Jc very insensible to external magnetic fields: allows in principle magnets with B>20T
Even more difficult to wind coils (Bi in thin layers on tape YBCO in power form)
 needs decades of development to go

17. HTS Technology Challenges
Bi2Ca2CuSr2O8+x (Bi-2212)
YBa2Cu3O7- (YBCO)
Process
W&R (900C, pure Oxygen)
Sensitive temperature variations; high pressure requires for high Jc
W (pre-reacted tape)
Scalability
(current)
Can use Rutherford cables
(routinely fabricated since ~2000)
Difficult; “Roebel” cable under investigation
Winding
Can use existing processes
Challenge: minimum bend radius, no hard-way bends
Dep. on field orientation
Isotropic
Highly anisotropic; being addressed
Strain dependence
Degradation starts at 60 Mpa in present wires; little reversible regime expected
Reversibility improving; transverse pressure limitations

18. Superconducting RF
A large number of different superconducting RF is required for each of the EIC solutions
Systems being developed are benefitting from the SRF development of the linear collider development (TESLA, ILC)
Both eRHIC (ring-ring design) and JLab EIC (JLEIC) are electron-ion colliders designed to deliver high luminosities up to above 1034/cm2/s for meeting the requirements of the EIC science program
To achieve this luminosity goal, both designs chose ampere level high beam current electron/ion collider rings, with short bunch length, high bunch reprate, and low emittance (hadron cooling needed).
The beam current in the electron ring of both designs is mainly set by the 10MW administrative limit in synchrotron radiation power. The parameters will be similar to the B-factory storage rings (PEP-II and super KEKB), with more challenges from wide electron energy range.
Short bunch length (cm level) is unprecedented in the ion ring and will be a challenge for the RF system. Strong hadron cooling requires high current (Ampere level) low energy (20-140MeV) electron beam.
Crabbing in hadron collider requires a strong crabbing RF voltage and is unproven. Both EIC teams collaborate closely with HiLumi LHC crab cavity development.
Both designs need to inherit some real estates from existing accelerators.
Both designs are still evolving and becoming more self-consistent

19. Introduction: RF Cavities for JLEIC
952.6 MHz i-ring
(SCRF) IP
Future IP
Ion Source
Booster
JLEIC
Collider
Rings
12 GeV 1497MHz CEBAF
Halls A, B, C
Electron Injector
Hall D
SRF Linac
e-RF
i-SRF +
NCRF
Crab
BB cooler
952.6 MHz cooler ERL (SCRF)
476.3 MHz e-ring
(NCRF PEP-II)
952.6 MHz cooler booster (SCRF)
ODU
952.6 MHz crab
(SCRF)
Harmonic Fast kicker for cooling ring
Not including ion acceleration and bunch formation

20. Introduction: eRHIC RF Cavities
5-cell injector linac cavity with ridged waveguide HOM damper
Two-cell 563MHz SRF cavity for e-ring, under development
DQW SRF crab cavity, 337.8MHz, under development
28MHz accelerating cavities
56MHz QWR SRF storage cavity, newly developed

21. Conclusion
Results presented and discussed at Accelerator workshop demonstrate considerable maturing of EIC designs
There are many communalities in design feature and in required accelerator technology
JLAB and BNL are agreeing that it will be mutually beneficial to collaborate on common aspects of both designs
There are many synergies with accelerator projects elsewhere
Collaboration with other US and non-US institutions are highly encouraged and will be very welcome