1. V. Ptitsyn on behalf of eRHIC Design team: E. Aschenauer, M. Bai, J. Beebe-Wang, S. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, R. Calaga, X. Chang, A.Fedotov, D. Gassner, L. Hammons, H. Hahn, Y. Hao, P. He, W.Jackson, A. Jain, E. C. Johnson, D. Kayran, J. Kewisch, V. N. Litvinenko, Y. Luo, G. Mahler, G. McIntyre, W. Meng, M. Minty, B. Parker, I. Pinayev, T. Rao, T. Roser, J. Skaritka, B. Sheehy, S. Tepikian, Y. Than, D. Trbojevic, N. Tsoupas, J. Tuozzolo, G. Wang, S. Webb, Q. Wu, Wencan Xu, A.Zelenski (BNL), E. Pozdeyev (FRIB, MSU), E. Tsentalovich (MIT-Bates) V. Ptitsyn on behalf of eRHIC Design team: E. Aschenauer, M. Bai, J. Beebe-Wang, S. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, R. Calaga, X. Chang, A.Fedotov, D. Gassner, L. Hammons, H. Hahn, Y. Hao, P. He, W.Jackson, A. Jain, E. C. Johnson, D. Kayran, J. Kewisch, V. N. Litvinenko, Y. Luo, G. Mahler, G. McIntyre, W. Meng, M. Minty, B. Parker, I. Pinayev, T. Rao, T. Roser, J. Skaritka, B. Sheehy, S. Tepikian, Y. Than, D. Trbojevic, N. Tsoupas, J. Tuozzolo, G. Wang, S. Webb, Q. Wu, Wencan Xu, A.Zelenski (BNL), E. Pozdeyev (FRIB, MSU), E. Tsentalovich (MIT-Bates) Accelerator Design of High Luminosity Electron-Hadron Collider eRHIC 3/28/12

2. From RHIC to eRHIC RHIC + Electron accelerator = eRHIC eRHIC Quark splits into gluon splits into quarks … Gluon splits into quarks Increasing resolution High precision microscope for the nucleons and nuclei: resolving nucleon spin puzzle 3-D tomography of nucleons non-linear QCD regime of high gluon densities (saturation) High precision microscope for the nucleons and nuclei: resolving nucleon spin puzzle 3-D tomography of nucleons non-linear QCD regime of high gluon densities (saturation) 3/28/12

3. eRHIC: QCD Facility at BNL e-e- e+e+ p Unpolarized and 80% polarized leptons, 5-30 GeV Polarized light ions (He 3 ) 167 ( 215* ) GeV/u Light ions (d,Si,Cu) Heavy ions (Au,U) 50-100 ( 130* ) GeV/u 70% polarized protons 100-250 ( 325* ) GeV Center of mass energy range: 30-175 GeV Any polarization direction in lepton-hadrons collisions e-e- protons electrons 3/28/12

4. Design choices Compared with HERA eRHIC will have: Polarized proton and 3 He Heavy ion beams Wide variable center-of mass energy range Considerably higher luminosity Compared with HERA eRHIC will have: Polarized proton and 3 He Heavy ion beams Wide variable center-of mass energy range Considerably higher luminosity L peak, cm -2 s -1 ~5 10 31 HERA 10 GeV storage ring ZDR in 2004 Fundamental luminosity limits: o Beam-beam o SR power loss (total and per m) 10 GeV storage ring ZDR in 2004 Fundamental luminosity limits: o Beam-beam o SR power loss (total and per m) RHIC ~4 10 32 eRHIC ring-ring Large allowed beam-beam on electrons Electron energy beyond 10 GeV Simple energy staging by increasing the linac length No e-polarization issues with spin resonances Large allowed beam-beam on electrons Electron energy beyond 10 GeV Simple energy staging by increasing the linac length No e-polarization issues with spin resonances RHIC up to 1.5 10 34 eRHIC linac-ring 3/28/12

5. All-in tunnel staging approach uses two energy recovery linacs and 6 recirculation passes to accelerate the electron beam. Staging: the electron energy will be increased in stages, from 5 to 30 GeV, by increasing the linac lengths. Up to 3 experimental locations All-in tunnel staging approach uses two energy recovery linacs and 6 recirculation passes to accelerate the electron beam. Staging: the electron energy will be increased in stages, from 5 to 30 GeV, by increasing the linac lengths. Up to 3 experimental locations ERL-based eRHIC is multiple IP collider Beam dump Polarized e-gun 0.6 GeV eSTAR ePHENIX Coherent e-cooler New detector 0.6 GeV 30 GeV 27.55 GeV 22.65 GeV 17.75 GeV 12.85 GeV 3.05 GeV 7.95 GeV Linac 2.45 GeV 25.1 GeV 20.2 GeV 15.3 GeV 10.4 GeV 30.0 GeV 5.50 GeV 27.55 GeV 0.60 GeV 3/28/12

6. eRHIC luminosity Hourglass effect is included Luminosity falls as the cube of hadron energy E h 3 because of space charge limit Luminosity is the same at at energy of electrons from 5GeV to 20 GeV e-beam current and luminosity fall as E e -4 at electron energy >20 GeV ep 2 He 379 Au 19792 U 238 Energy, GeV20250167100 CM energy, GeV 14111589 Number of bunches/distance between bunches74 nsec166 Bunch intensity (nucleons),10 11 0.2421.30.790.83 Bunch charge, nC3.832105.2 Beam current, mA5042014067 Normalized emittance of hadrons, 95%, mm mrad 1.2 Normalized emittance of electrons, rms, mm mrad 324880 Polarization, %8070 none rms bunch length, cm0.28.3 β*, cm55555 Luminosity per nucleon, x 10 34 cm -2 s -1 0.970.650.390.41

7. Luminosity Reaching high luminosity: high average electron current (50 mA = 3.5 nC * 14 MHz): energy recovery linacs; SRF technology high current polarized electron source cooling of the high energy hadron beams (Coherent Electron Cooling)  *=5 cm IR with crab-crossing Reaching high luminosity: high average electron current (50 mA = 3.5 nC * 14 MHz): energy recovery linacs; SRF technology high current polarized electron source cooling of the high energy hadron beams (Coherent Electron Cooling)  *=5 cm IR with crab-crossing Protons Electrons E, GeV5075100130250325 5 0.0770.260.621.49.715 10 0.0770.260.621.49.715 20 0.0770.260.621.49.715 30 0.0190.060.150.352.43.8 Polarized e-p luminosities in 10 33 cm -2 s -1 units Limiting factors: -hadron space charge  Q sp ≤ 0.035 -hadron beam-beam  ≤ 0.015 -polarized e current ≤ 50 mA -SR power loss ≤ 8 MW Limiting factors: -hadron space charge  Q sp ≤ 0.035 -hadron beam-beam  ≤ 0.015 -polarized e current ≤ 50 mA -SR power loss ≤ 8 MW 3/28/12

8. Main Accelerator Challenges In red –increase/reduction beyond the state of the art eRHIC at BNL Polarized electron gun – 10x increase Coherent Electron Cooling – New concept Multi-pass SRF ERL 5x increase in current 30x increase in energy Crab crossing New for hadrons Polarized 3 He production Understanding of beam-beam affects New type of collider β*=5 cm 5x reduction Multi-pass SRF ERL 3-4x in # of passes Feedback for kink instability suppression Novel concept 3/28/12

9. eRHIC SRF Linac Based on BNL SRF cavity with fully suppressed HOMs This is critical for high current multi-pass ERL eRHIC cavity & cryostat designs are still evolving E max Injection Total linac length -> 200 m Two warm-to-cold transition only at the ends Maximum energy gain per pass –> 2.45 GeV Accelerating gradient – 19.2 MV/m 3/28/12

10. Energy recovery facility Cryo-module e - 15 – 20 MeV SC RF Gun e - 4-5MeV Beam dump 50 kW 700 MHz transmitter Magnets, vacuum Controls & Diagnostics Laser 1 MW 700 MHz Klystron e - 4-5 MeV 3/28/12 Accelerating bunches Decelerating bunches

11. Principle of Coherent Electron Cooling Modulator Kicker Dispersion section ( for hadrons) Electrons Hadrons l2l2 l1l1 High gain FEL (for electrons) EhEh E < E h E > E h vhvh 2 R D// 2 R D  Debye radii Amplifier of the e-beam modulation in an FEL with gain G FEL ~10 2 -10 3 FEL EzEz E0E0 E < E 0 E > E 0 The bandwidth 10 2 -10 3 times larger than in conventional stochastic cooling The bandwidth 10 2 -10 3 times larger than in conventional stochastic cooling Ya. Derbenev, V. Litvinenko 3/28/12

12. Proof-of-principle CeC Experiment in RHIC IP2 Helical Wiggler Kicker Section Modulator Section Beam Dump Accelerator Section Buncher Cavities Gun @ A. Fedotov Expected deformation of Au beam longitudinal signal due to the cooling @ I. Pinayev PoP experiment in RHIC by the collaboration: BNL, Jefferson Lab, Tech-X Corporation Projected dates: 2014-2016 Aim : demonstration of (partial) cooling of 40 GeV Au ion beam PoP experiment in RHIC by the collaboration: BNL, Jefferson Lab, Tech-X Corporation Projected dates: 2014-2016 Aim : demonstration of (partial) cooling of 40 GeV Au ion beam 3/28/12

13. 50 mA polarized electron source R&D 3/28/12  Detailed mechanical design been done  All critical parts been purchased  Ready for prototype construction  Detailed mechanical design been done  All critical parts been purchased  Ready for prototype construction BNL Gatling Gun: the current from multiple cathodes is merged BNL Gatling Gun: the current from multiple cathodes is merged I. Ben-Zvi X. Chang Alternative development by MIT: large cathode gun (E. Tsentalovich).

14. eRHIC R&D: Development of compact magnets More than 14000 magnets in electron beam lines Small gap -> efficient and inexpensive- > low cost eRHIC Designed and manufactured two prototypes of dipole and quadrupole – We used EDM for initial prototypes – Later we started using grinding We built magnetic measurement system and measured prototypes – Dipole field performance is close to specs – Quadrupole field requires major improving Ordered mini-series of prototypes at BINP (Novosibirsk) Yue Hao, Ping He, Animesh Kumar Jain, Vladimir N. Litvinenko, George Mahler, Wuzheng Meng, Joseph Tuozzolo 3/28/12 Gap 5 mm total 0.3 T for 30 GeV

15. Beam-Beam Simulations 325 GeV Proton beam & 20 GeV Electron beam disruption parameter (d=27). The electron beam finishes 1 full oscillation in the opposing beam. Long tail is formed due to the nonlinearity. The resulting luminosity is 2.2e34 cm -2 s -1. Here and below, the simulation results come from ERL beam-beam code EPIC. 3/28/12 @Y.Hao

16. eRHIC high-luminosity IR with  *=5 cm 10 mrad crossing angle and crab-crossing High gradient (200 T/m) large aperture Nb 3 Sn focusing magnets Arranged free-field electron pass through the hadron triplet magnets Integration with the detector: efficient separation and registration of low angle collision products Gentle bending of the electrons to avoid SR impact in the detector © D.Trbojevic, B.Parker, S. Tepikian, J. Beebe-Wang 3/28/12 e p 0.44843 m Q5 D5 Q4 90.08703 m 60.0559 m 10 3 m 4.5  =4 mrad 8.18 m  =9.82 mrad 10 mrad 5.475 m 30 20 40 50 15.1 m 0.316 m  =3.6745 mrad

17. IR Magnets 3/28/12 Peak field is 6.2 TPlot of |B| (Tesla) for the Coil Structure Low field region for e-beam Region used by circulating hadron beam Neutrons Large aperture for passage of neutrons and gammas, circulating beam and off-momentum charged particle. Based on NB 3 Sn magnet technology developed for LHC IR upgrade Magnetic Yoke Nb 3 Sn 200 T/m G.Ambrosio et al., IPAC’10 LHC IR magnet prototype eRHIC Q1 @B. Parker

18. Crab-crossing 3/28/12 Idea Introduced by R. B. Palmer SLAC PUB 4832 Used at KEK B-factory For eRHIC: 250 GeV p/ 100 GeV/u Au, M12=16.7 m Fundamental +3 rd + 5 th, f fund = 183 MHz, V fund = 24 MV, V 3rd =1.3 MV, V 5th =0.09 MV OR Fundamental +2 nd + 3 rd f fund = 244 MHz, V fund = 22 MV, V 2nd =4.4 MV, V 3th =0.5 MV Crab-cavity design on the basis of the quarter wave SRF cavities has been developed For eRHIC: 250 GeV p/ 100 GeV/u Au, M12=16.7 m Fundamental +3 rd + 5 th, f fund = 183 MHz, V fund = 24 MV, V 3rd =1.3 MV, V 5th =0.09 MV OR Fundamental +2 nd + 3 rd f fund = 244 MHz, V fund = 22 MV, V 2nd =4.4 MV, V 3th =0.5 MV Crab-cavity design on the basis of the quarter wave SRF cavities has been developed @ V. Litvinenko, I. Ben-Zvi, S. Belomestnykh, Q. Wu

19. Electron polarization in eRHIC High polarized beam current produced by the e-gun. (DC gun with strained-layer super-lattice GaAs- photocathode) Direction of polarization are switch by changing helicity of laser photons in and arbitrary bunch-by- bunch pattern Linac accelerator -> No depolarizing resonances! Only longitudinal polarization is needed in the experimental detector(s) High polarized beam current produced by the e-gun. (DC gun with strained-layer super-lattice GaAs- photocathode) Direction of polarization are switch by changing helicity of laser photons in and arbitrary bunch-by- bunch pattern Linac accelerator -> No depolarizing resonances! Only longitudinal polarization is needed in the experimental detector(s) Beam polarization vector rotates in the horizontal plane during the acceleration. The conditions for the longitudinal polarization orientation in possible experimental points: IP8: E e =N*0.077922 GeV IP6: E e = N*0.075690 GeV Both IP6 and IP8: E e = N*1.321 GeV Beam polarization vector rotates in the horizontal plane during the acceleration. The conditions for the longitudinal polarization orientation in possible experimental points: IP8: E e =N*0.077922 GeV IP6: E e = N*0.075690 GeV Both IP6 and IP8: E e = N*1.321 GeV Polarized e-gun  d,  d  0,  0  stays in horizontal plane and rotates in arcs around vertical direction 3/28/12 protons electrons

20. Main Milestones – Finish eRHIC cost estimate Spring of 2012 – External review of the estimateSpring of 2012 – Address concerns of the reviewsEnd of 2012 – Complete start-to-end eRHIC ERL simulations2013 – Complete beam-beam simulations2014 – Complete magnet prototyping2015 – Demonstrate coherent e-cooling2016 3/28/12

21. Summary eRHIC accelerator design progresses well – The design is well advanced and went through the External review – Cost estimate is underway Physics of the collider is well understood – No show-stoppers were found Number of novel approached require extensive R&D Considerable progress on crucial R&D items has been achieved: polarized source; compact magnets; cavities and cryo-module; beam-beam simulations Next 3-4 years will be critical for completing R&D and be ready for full eRHIC design 3/28/12