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Accelerator R&D towards eRHIC Yue Hao, C-AD For the eRHIC Team Slide 2 eRHIC, linac-ring EIC Linac=ERL, or the luminosity is negligible The first proposed linac-ring collider 250GeV (p) *15.9 (e) @1.5e33 cm-2 s-1 Why linac-ring Luminosity, remove the limitation of b-b parameter of e-beam High spin polarization (e-beam) Easy to upgrade Easier synchronization with various ion energy. I. Ben-Zvi, J. Kewisch, J. Murphy and S. Peggs, Accelerator Physics Issues in eRHIC, NIM A463, 94 (2001), C-A/AP/14 (2000). Slide 3 eRHIC Layout Slide 4 Luminosity Defined by P SR = 12 MW Defined by p = 0.015 Defined by Q sp = 0.035 Slide 5 Beam Synchronization, Detail Ion at sub-TeV energies is not ultra- relativistic, Change in energy velocity frequency Linac-ring scheme enable a trick to adjust the frequency of RF to sychronize electron and ion at discrete ion energies Reduces the need of path lengthening. Ring-ring scheme can not take the trick. Slide 6 eRHIC R&D efforts IR design, crab cavity and dynamic aperture Beam cooling major R&D efforts, high priority R&D Polarization and Polarimetry (including electron polarimetry) Polarized 3 He production and acceleration Polarized electron source Superconducting RF system Multipass ERL and related beam dynamics FFAG energy recovery pass Linac-ring beam-beam interaction...... Slide 7 NS-FFAG Layout of the eRHIC Arc #2 #1 7.944 GeV #2 9.266 GeV #3 10.588 GeV #4 11.910 GeV #5 13.232 GeV #6 14.554 GeV #7 15.876 GeV #8 17.198 GeV #9 18.520 GeV #10 19.842 GeV #11 21.164 GeV Injector 0.012 GeV Linac 1.322 GeV Arc #1 #1 1.334 GeV #2 2.565 GeV #3 3.978 GeV #4 5.300 GeV #5 6.622 GeV 7.944 15.876 GeV * 21GeV Design, Jan'14 Slide 8 Trajectory in FFAG 2.5819 m 0.90805 m Half of 1.09855 m 21.164 GeV 19.824 GeV 18.520 GeV 17.198 GeV 15.876 GeV 14.554 GeV 13.232 GeV 11.910 GeV 10.588 GeV 9.266 GeV 7.944 GeV D =3.057567mrad B D =0.1932 T, G d =-49.515 T/m D =296.985 m x(mm) F =3.699017 mrad F =296.984 m B f = 0.1932 T, G f =49.515 T/m 5.02 - 7.5 B max [-0.178, 0.442 T] B max [-0.013, 0.4215 T] Other half of QF magnet 28.764 cm - 4.61 4.17 28.764 cm Half of 1.09855 m QFBD Slide 9 Magnet for FFAG arcs Slide 10 Two alternative magnets Permanent Magnet Iron (steel) Slide 11 Bunch-by-Bunch BPM With fewer BPMs than magnets, the space between some FFAG magnets could be used entirely by a BPM; this design produces stretched output pulses (from 13 ps rms bunches) intrinsically in the BPM in-vacuum hardware 1.0 ns 1.18 ns = 422 MHz rf wavelength = minimum FFAG bunch spacing long sampling platforms signal processing: use pair of 2 GSPS ADCs triggered ~ 200 ps apart Slide 12 Multi-pass FFAG Prototype There is on-going plan to build a multi- pass FFAG Energy Recovery Linac prototype to prove the principle and the method of detecting and correcting the beam. Energy of linac ~100MeV # of passes: ~4 Slide 13 IR design Crab-cavities p e Forward detector components SC magnets Slide 14 IR and DA 10 mrad crossing angle and crab-crossing 90 degree lattice and beta-beat in adjacent arcs (ATS) to reach beta* of 5 cm Combined function triplet with large aperture for forward collision products and with field-free passage for electron beam Only soft bends of electron beam within 60 m upstream of IP Slide 15 Beam cooling, CEC PoP oTraditional stochastic cooling does not have enough bandwidth to cool intense proton beams (~ 310 11 /nsec). Efficiency of traditional electron cooling falls as a high power of hadrons energy. Coherent Electron Cooling has a potential for high intensity beams including heavy ions. oResearch Goals: Develop complete package of computer simulation tools for the coherent electron cooling Demonstrate cooling of the ion beam Validate developed model Develop experimental experience with CeC system Slide 16 Gun Beam Dump FEL Section Helical Wigglers Low Power Beam Dump Flag ICT Flag Linac Bunching Cavities Pepper Pot Modulator Section Kicker Section ParameterUnitsValue Electron EnergyMeV21.9 R.M.S. normalized emittancemm mrad5 Peak current in FELA60-100 R.M.S. momentum spread1.010 -3 Charge per bunchnC1-5 ParameterUnitsValue Ions EnergyGeV/u40 R.M.S. normalized emittance mm mrad2 R.M.S bunch lengthns1.5 R.M.S. momentum spread3.510 -4 Repetition ratekHz78.3 CEC PoP, contd Slide 17 CEC PoP, anticipated results Ion bunch 2 nsec Electron bunch 10 psec After 60 sec After 250 sec After 650 sec r.m.s. length of the cooled part 80-120 ps. The cooling effects can be observed with oscilloscope 2 GHz or more bandwidth or spectrum analyzer with similar upper frequency Modeling of cooling is performed with betacool by A. Fedotov Slide 18 CEC timeline CEC PoP RHIC ramp is developed Injection system (112 MHz gun, 500 MHz buncher) were installed. Main cavity (704MHz) is fabricated. Commission injector system in July 2014 Experiment starts 2015 Slide 19 Polarized e-source We are aiming at a high-current (50 mA), high- polarization electron gun for eRHIC. The principle we are aiming to prove is funneling multiple independent beams from 20 cathodes. External review was carried out in 2012. Next week, first HV conditioning and possibly first beam! Slide 20 eRHIC will utilize five-cell 422 MHz cavities, scaled versions of the BNL3 704 MHz cavity developed for high current linac applications. Stability considerations require cavities with highly damped HOMs. The HOM power is estimated at 12 kW per cavity at a beam current of 50 mA and 12 ERL passes. Apply funding to build prototype. 5-cell SRF cavity HOM ports FPC port HOM high-pass filter Slide 21 Crab Cavity Development of a highly compact Double Quarter Wave Crab Cavity at 400 MHz. Prototype to be tested in the CERN SPS in 2016- 2017. Helium vessel Cavity FPC Input power waveguid es Tuning system Cryo jumper Thermal shielding (80K nitrogen) Magnetic shielding Slide 22 ERL test facility The BNL ERL objectives 20 MeV at >100 mA (500 mA capability). Experiment in progress, will see first photo-emission soon. Loop in Oct, 2014, project completes in 2016. All hardware in house, most installed Slide 23 Electron beam disruption Ion Beam e Slide 24 Summary There are many on-going simulation and experiment aiming on the challenge port of eRHIC. The design now is based on extensive simulations. R&D experiments are on-going, need few years to finish. Slide 25 THANK YOU FOR YOUR ATTENTION!