1. MEIC IR Design Yuhong Zhang EIC Generic R&D Advisory Committee Meeting December 13, 2012

2. Y. Zhang ---2--- Outline Introduction MEIC Accelerator Design overview Interaction Region Design Optimization for detector capability Optimization for chromaticity Compensation Machine Background Summary

3. Acknowledgement The work reported in this presentation are done primarily by Vasiliy Morozov and Fanglei Lin, CASA, Jefferson Lab Pawel Nadel-Turonski, Physics Division, Jefferson Lab Charles Hyde, Jefferson Lab/Old Dominion University Michael Sullivan, SLAC I would also like to thank members of the JLab EIC design study group and our external collaborators Y. Zhang --3--

4. Introduction JLab’s fixed target program after the 12 GeV CEBAF upgrade will be world- leading for at least a decade. A Medium energy Electron-Ion Collider (MEIC) at JLab will open new frontiers in nuclear science. The timing of MEIC construction can be tailored to match available DOE-ONP funding while the 12 GeV physics program continues. MEIC parameters are chosen to optimize science, technology development, and project cost. We maintain a well defined path for future upgrade to higher energies and luminosities. A conceptual machine design has been completed recently, providing a base for performance evaluation, cost estimation, and technical risk assessment. Y. Zhang --4--

5. Pre- booster Ion linac IP MEIC Full Energy EIC CEBAF

6. Y. Zhang ---6--- MEIC is The Stage 1 at JLab Energy (bridging the gap of 12 GeV CEBAF & HERA/LHeC) –Full coverage of s from a few 100 to a few 1000 GeV 2 –Electrons 3-12 GeV, protons 20-100 GeV, ions 12-40 GeV/u Ion species –Polarized light ions: p, d, 3 He, and possibly Li, and polarized heavier ions –Un-polarized light to heavy ions up to A above 200 (Au, Pb) Up to 2 detectors Luminosity –Greater than 10 34 cm -2 s -1 per interaction point –Maximum luminosity should optimally be around √s=45 GeV Polarization –At IP: longitudinal for both beams, transverse for ions only –All polarizations >70% desirable Upgradeable to higher energies and luminosity –20 GeV electron, 250 GeV proton, and 100 GeV/u ion

7. MEIC Design Report Released! Y. Zhang --7-- arXiv:1209.0757 Table of Contents Executive Summary 1.Introduction 2.Nuclear Physics with MEIC 3.Baseline Design and Luminosity Concept 4.Electron Complex 5.Ion Complex 6.Electron Cooling 7.Interaction Regions 7.1 MEIC Primary Detector 7.2 Interaction Region Design Considerations 7.3 Interaction Region Layout and Detector Acceptance 7.4 Linear Optics Design 7.5 Chromaticity Compensation 7.6 Momentum Acceptance and Dynamic Aperture 7.7 Crab Crossing 7.8 Synchrotron Radiation and Detector Background 7.9 Beam-Beam Interactions. 8.Outlook

8. Interaction Region Requirements Detector requirements Hermeticity  allows for the detection of scattered electrons, mesons and (full acceptance)baryons without holes in the acceptance, even in forward directions High luminosity  operates in a high-luminosity environment with moderate event multiplicities and acceptable background conditions Accelerator/beam dynamics requirements (& considerations) High luminosity  pushing final focusing of the beams (squeezing down β*)  not so demanding machine elements (e.g., max. field & gradient)  crab crossing for high bunch repetition rate colliding beams Nonlinear dynamics  chromaticity compensation  momentum acceptance and dynamic aperture Collective effect limit  beam-beam (flat beam, etc.) Y. Zhang --8-- Interaction region design rules #1: Detector requirements & accelerator requirements, though they usually conflict, must coexist #.2: Compromises must be made on both sides without jeopardizing either side’s design goals

9. JLab MEIC Detector-IR Workshops MEIC Detector & Interaction Region Design Mini-Workshop ( Oct. 31, 2011) http://casa.jlab.org/meic/workshops/detector_2011/detector_ir_workshop_2011.shtml The 2 nd MEIC Detector & Interaction Region Design Mini-Workshop (Nov. 2, 2012) http://casa.jlab.org/meic/workshops/detector2012/detector_ir_workshop2012.shtml Y. Zhang --9-- 1:00 PM -- 1:15 PMOpening Remark and Workshop ChargeRolf Ent 1:15 PM -- 1:40 PMMEIC Detector DesignPawel Nadel-Turonski 1:40 PM -- 2:05 PMMEIC Interaction Region Design & Detector IntegrationVasiliy Morozov 2:05 PM -- 2:30 PMMEIC Optics and Nonlinear Beam DynamicsFanglei Lin 2:30 PM -- 2:55 PMSynchrotron Radiation and Detector BackgroundsMichael Sullivan 2:55 PM -- 3:15 PMCoffee Break 3:15 PM -- 3.45 PMDiscussion Session I: MEIC Primary Detector 3:45 PM -- 4:15 PMDiscussion Session II: MEIC Secondary Detector 4:15 PM -- 4:25 PMLEIC LuminosityYuhong Zhang 4:25 PM -- 4:55 PMDiscussion Session III: LEIC 4:55 PM -- 5:00 PMWorkshop SummaryAndrew Hutton P. Nadel-Turonski’ talk at “EIC Generic Detector R&D Advisory Committee Meeting” May 2012 “IR design and Critical Machine Parameters for Detector Design and Simulation (Stage I): JLab MEIC”

10. Interaction Region w/ Integration of Detector Y. Zhang --10-- ultra forward hadron detection low-Q 2 electron detection large aperture electron quads small diameter electron quads central detector with endcaps ion quads 50 mrad crab crossing angle n, g e p p small angle hadron detection 60 mrad bend Tracking detectors No other magnets or apertures between IP and FP! ions 3000 2000 1000 0 1 0.5 0 V. Morozov’s talk at the 2 nd Detector/IR Mini-workshop V. Morozov, et al, IPAC2012 paper A major victory for producing a preliminary optics design which satisfies all the requirements element location, size and apertures maximum fields or field gradients Beam stay-clear Small beta final focusing, crab crossing Make use of crab crossing for enhancing detector acceptance Adopted permanent magnets for smaller sizes of electron FFQs

11. n p e achievable field strengths 100 GeV maximum ion energy allows using large- aperture magnets with achievable field strengths resolution < 3x10 -4Momentum resolution < 3x10 -4 – limited by beam momentum spread all ion fragmentsExcellent acceptance for all ion fragments Neutrondown to zero degreesNeutron detection in a 25 mrad cone down to zero degrees Recoil baryonRecoil baryon acceptance: 99.5%all angles – up to 99.5% of beam energy for all angles 2-3 mradall momenta – down to 2-3 mrad for all momenta A 3D View of Detector & Summary of Small-angle Ion Detection Y. Zhang ---11--- e p n 20 Tm dipole 2 Tm dipole solenoid

12. Y. Zhang ---12--- (Small Angle) Hadron Detection Prior to Ion FFQs Large crossing angle (50 mrad) – Moves spot of poor resolution along solenoid axis into the periphery – Minimizes shadow from electron FFQs Large-acceptance dipole further improves resolution in the few-degree range Crossing angle 2 Tm dipole Ion quadrupoles Electron quadrupoles trackingcalorimetry 1 m electron 1.2 m, 89 T/m, 9 T 2.4 m, 51 T/m, 9 T, 1.2 m, 36 T/m, 7 T 46 T/m 38 T/m 34 T/m Permanent magnets 2x34 T/m

13. Proton Acceptance at Downstream Ion FFB Y. Zhang ---13--- Quad apertures = B max / (field gradient @ 100 GeV/c) 6 T max9 T max12 T max  electron beam Red: Detection between the 2 Tm upstream dipole and ion quadrupoles Blue: Detection after the 20 Tm downstream dipole G4Beamline/GEANT4 Model V. Morozov’s talk at the 2 nd Detector/IR Mini-workshop V. Morozov, et al, IPAC2012 paper

14. Forward Ion Momentum & Angle Resolution at Focal Point Y. Zhang --14--  electron beam  electron beam |  x | > 3 mrad @  p/p = 0 Protons with different  p/p launched with  x spread around nominal trajectory

15. Y. Zhang ---15--- Nonlinear Beam Dynamics MEIC chromaticity compensation scheme Local compensation scheme: dedicated chromaticity compensation blocks (CCB) near an IP Using families of sextupoles and octupoles simultaneous compensation of chromatic tune-shift and beam smear at IP Symmetric CCB (with respect to its center) –u x is anti-symmetric, u y is symmetric –D is symmetric –n and n s are symmetric Chromaticity is an issue in MEIC design, particularly due to the low-β insertions Chromatic turn spread Chromatic beta-smear at IP Ion ring (ξ x /ξ y )Electron ring (ξ x /ξ y ) Contribution from whole arc17.4 / 16.168.8 / 70. 1 Contribution per IR130 / 12647.3 / 54.0 Whole ring (2IP+arc)278 / 268188 / 202 MEIC design report Section 7.4

16. Y. Zhang --16-- IR Optics Optimized for Chromaticity Compensation Ion beam Electron beam FFBCCBBES

17. Y. Zhang ---17--- Momentum Acceptance & Dynamic Aperture Compensation of chromaticity with 2 sextupole families only using symmetry Nonlinear dynamic studies (aperture optimization and error impact) under way  p/p = 0.3  10 -3 at 60 GeV/c  5  p/p Ions  p/p = 0.7  10 -3 at 5 GeV/c  5  p/p Electrons w/o Octupole with Octupole Ions F. Lin’s talk at the 2 nd Detector/IR Mini-workshop F, Lin, et al, IPAC2012 paper

18. Y. Zhang ---18--- Crab Crossing Scheme Incoming At IPOutgoing Tracking Simulations Integration of crab crossing into IR Required for supporting high bunch repetition rate (small bunch spacing) Local crab scheme Two cavities are placed at (n+1)π/2 phase advance relative to IP. Large β x at location of crab cavities for minimizing the required kicking voltage. π/23π/2 Location of crab cavities SRF crab cavity R&D @ ODU MEIC design report Section 7.6

19. Beam Synchronization at IP & Collision Pattern Path length difference in collider rings Electrons travel at the speed of light, protons/ions are slower Slower proton/ ion bunches will not meet the electron bunch again at the IP after one revolution Synchronization must be achieved at every IP in the collider ring simultaneously Y. Zhang --19-- Present conceptual solution Varying number of bunches (harmonic number) in the ion collider ring would synchronize beams at IPs for a set of ion energies (harmonic energies) To cover the energies between the harmonic values –varying electron orbit up to half bunch spacing –varying RF frequency (less than 0.01%) Bunches in ion ring Energy (GeV/u) ProtonLead 3370100 337135.9 337226.3 337321.7 337418.9 337517.0 Collision pattern at IP Each time it returns to the IP, an Ion bunch will collide with a different electron bunch (Specifically, If n is the difference of ion and electron harmonic numbers, then an ion bunch will always collide the n-th bunch in the electron bunch train) An ion bunch will collider all or a subset (eg. all even numbers) electron bunches Number of bunch in the electron ring is always 3370 Assuming electron and ion have a same circumference (1350 m) at 100 GeV proton energy MEIC design report section 5.9

20. Suppressing Synchrotron Radiation at IR Y. Zhang --20-- MEIC Design optimized for suppressing synchrotron radiation at IR Flat electron ring  ions travels to the plane of the electron ring for horizontal crab crossing at collision points Detector solenoid is along the electron beamline Gentle bending of electrons at end of each arcs Minimizing bending of electrons in long straights of figure-8 Keep bending angles of dipoles in chromaticity compensation blocks small (Place IP close to the end of arc where ion beam comes from) More synchrotron radiation issues A high forward detector design requires carefully tracing synchrotron radiation fans from bend magnets to see where the power goes how this interacts with the beam pipe design in front of the detector Local forward and back scattering rates from nearby beam pipe surface

21. Initial SR background calculations 240 3080 4.6x10 4 8.5x10 5 2.5W 38 2 Synchrotron radiation photons incident on various surfaces from the last 4 electron quads Rate per bunch incident on the surface > 10 keV Rate per bunch incident on the detector beam pipe, assuming 1% reflection coefficient and 4.4% solid angle acceptance M. Sullivan July 20, 2010 F$JLAB_E_3_5M_1A Beam current = 2.32 A 2.9x10 10 particles/bunch X P+P+ e-e- Z Electron energy = 11 GeV  x /  y = 1.0/0.2 nm-rad Y. Zhang --21-- M. Sullivan’s talk at the 2 nd Detector/IR Mini-workshop

22. Summary The 1 st design of MEIC is completed and a comprehensive design report has been released The MEIC interaction region has been designed to support a full-acceptance detector and also optimized for achieving good chromaticity compensation The MEIC design is optimized for suppressing synchrotron radiation in the interaction regions and at the detectors. Lots of interaction region design studies are still in progress –integration of detector-interaction-region –optimization of dynamic aperture and studies of impact of magnet errors –Synchrotron radiation and background We plan to study interaction region design for the 2 nd MEIC detector and also a low energy (up to 25 GeV proton) EIC detector Y. Zhang --22--

23. Backup slides Y. Zhang --23--

24. Y. Zhang ---24--- MEIC Schematic Layout Cross sections of MEIC tunnels

25. Y. Zhang ---25--- ProtonElectron Beam energyGeV605 Collision frequencyMHz750 Particles per bunch10 0.4162.5 Beam CurrentA0.53 Polarization%> 70~ 80 Energy spread10 -4 ~ 37.1 RMS bunch lengthmm107.5 Horizontal emittance, normalizedµm rad0.3554 Vertical emittance, normalizedµm rad0.0711 Horizontal β*cm10 Vertical β*cm22 Vertical beam-beam tune shift0.0140.03 Laslett tune shift0.06Very small Distance from IP to 1 st FF quadm73 Luminosity per IP, 10 33 cm -2 s -1 5.6 Parameters for Full Acceptance Interaction Point

26. MEIC Design Features & accelerator R&D Y. Zhang --26-- High luminosity Very high bunch repetition rate Very small bunch charge Very short bunch length Very small β* Crab crossing Small transverse emittance Electron cooling A proved concept: KEK-B@2x10 34 /cm 2 /s JLab will replicate the same success in colliders w/ hadron beams The electron beam from CEBAF possesses a high bunch repetition rate Ion beams from a new ion complex can match the electron beam High Polarization All rings have a figure-8 shape Spin precessions in the left & right parts of the ring are exactly cancelled Net spin precession (spin tune) is zero, thus energy independent The only practical way to accommodate polarized deuterons Accelerator R&D we now focus on Electron cooling simulation ERL-circulator cooler and its test facility, and a Proof-of-Principle experiment IR design optimization (dynamic aperture) Spin matching/tracking

27. Another View of MEIC Interaction Region --27-- 0 25 50 75 100 cm 051015 m M. Sullivan JLAB_EP_3M_4R July 30, 2012 Q1P D1P Q1e Q2e Q3e Q4e Q5e e- P+ Q2P Q3P Y. Zhang

28. ---28--- IR Optics Optimized for Detector Integration Upstream FFB is much closer to the IP  lower betatron functions  smaller contribution to the chromaticity Downstream FFB has larger apertures and distance from the IP  maximizing acceptance to the forward- scattered hadrons Focusing in the downstream allows to place the detectors close to the beam center. Combining with ~1 m dispersion, it can detect particles with small momentum offset Δp/p Similar optics to ion beam two permanent magnetic quadrupoles are used in the upstream FFB and vey close to the IP to maximize the ion detector acceptance by reducing the solid angle blocked by the final focusing quadrupoles. Changing of their focusing strengths with energy can be compensated by adjusting the upstream electric quadruples.

29. Y. Zhang ---29--- Ion Interaction Region Optics Optimized for Both Detector and Chromaticity Compensation FFB (up)CCBBESFFB (down) D1 D2 Ion beams DSB BES: Beam Extension Section FFB: Final Focusing Block D1,D2: Spectrometer Dipoles DSB: Dispersion Suppression Block Two sextupole families are inserted symmetrically in the CCB for the chromaticity compensation

30. Y. Zhang --30-- Ion Ring Parameters Optics design optimized forChromaticity compensation Detector integration IP  * functions cm10/2 Proton beam momentumGeV/c60 Circumferencem1340.921394.47 Arc’s net benddeg240 Straights’ crossing angledeg60 Arc lengthm391.0 Maximum  functions (hori. / vert.) m2225 / 24502300/2450 Maximum horizontal dispersion D x m1.78 betatron tunes  x,y 23.273/ 21. 28523.223/22.371 chromaticities  x,y (2 IPs) -278 / -268-207/-191 Momentum compaction factor  5.12  10 -3 Transition energy  tr 13.97 Normalized emittance  x,y µm rad0.35 / 0.07 Maximum RMS beam size  x,y mm3.5 / 1.63.6/1.6