Accelerator and Interaction Region Alex Bogacz Center for Advanced Studies of Accelerators EIC Detector Workshop at Jefferson Lab June 4-5, 2010

EIC Efforts at JLab For over a year… We have explored a staged approach to EIC, focusing on science cases and accelerator designs for a low-to-medium energy EIC with similar design features (high luminosity (>1034), polarization (>80%), multiple detectors) We have developed a conceptual design of a low-to-medium energy EIC based on CEBAF, and have therefore reduced the detector and accelerator technology R&D significantly, yielding a large cost saving compared to the full energy collider. We are now engaged in accelerator design, optimizations and staged R&D for enabling technologies.

Design Goals Energy Luminosity Ion Species Polarization Electrons: 3 to 11 GeV Ions: 20-60+ GeV protons, ~30 GeV/A ions Luminosity a few1034 cm-2 s-1 per interaction point over a wide range of s values Multiple interaction points Ion Species Polarized H, D, 3He, possibly Li Up to A = 208, all fully stripped Polarization Longitudinal at the IP for both beams, transverse for ions Spin-flip for the electron beam: All polarizations >80% desirable Positron Beam desirable

Collider Parameters

Design Features High luminosity at medium energy range Enabled by short ion bunches, low β*, high rep. rate Require crab crossing colliding beams Electron cooling is an essential part of MEIC Multiple IPs (detectors) “Figure-8” electron and ion collider rings Ensure spin preservation & ease spin manipulations No spin sensitivity to energy for all species. 12 GeV CEBAF injector meets storage-ring polarized beam requirements, can serve as a full energy injector

Conceptual Layout Three compact rings: 3 to 11 GeV electron Up to 12 GeV/c proton (warm) Up to 60 GeV/c proton (cold)

Collider Rings with ‘Relaxed’ IR Optics Larger Figure-8 Rings (~1000 m circumference) 5 Tesla bends for ions at 60 GeV Additional straights to accommodate spin rotators and RF Horizontal IR crossing, dispersion free straights ‘Relaxed’ IR Design: Chromaticity Compensating Optics Uncompensated dispersion in the straights Anti-symmetric dispersion pattern across the IR Dedicated Symmetric Inserts around the IR Electron Collider Ring based on emittance preserving Optics

Figure-8 Collider Ring Collider Ring design is a compromise between: total ring circumference: 1000 m 64 deg. crossing Collider Ring design is a compromise between: Minimizing synchrotron radiation effects  prefers a large size ring Space charge effect of ion beam  prefers a compact ring

Ion Ring – 900 FODO Cell phase adv/cell: Dfx,y= 900 Arc quadrupoles: $Lb=40 cm $G= 14.4 kGauss/cm Arc dipoles: $Lb=180 cm $B=60.0 kGauss $ang=3.09 deg. $rho = 33.4 meter Arc quadrupoles $Lb=40 cm $G= 10.1kG/cm beta chromaticity perturbation wave propagates with twice the betatron frequency – intrinsic cell-to-cell cancellation of chromatic terms (after two cells)

Ion Ring - Arc Optics 248 deg. Arc Arc – 120 meter Arc – 120 meter Straight – 20 meter

Electron Ring – 1350 FODO Cell Synchrotron radiation power per meter less than 20 kW/m phase adv/cell: Dfx,y= 1350 Arc dipoles, 9 GeV: $Lb=100 cm $B=16.2 kGauss $ang=3.09 deg. $rho = 18.4 meter emittance preserving optics Quadrupoles $Lq=50 cm $G= ±4.5 kG/cm <H> minimum 1350 FODO

Electron Ring - Arc Optics 248 deg. Arc Arc – 120 meter Arc – 120 meter Straight – 20 meter

IR Detector - Layout

IR Optics (electrons) Natural Chromaticity: x = -47 y = -66 IP f 19 800 5 BETA_X&Y[m] DISP_X&Y[m] BETA_X BETA_Y DISP_X DISP_Y l * = 3.5m IP FF doublets f Natural Chromaticity: x = -47 y = -66

IR Optics (electrons at 5 GeV) IP 19 800 5 BETA_X&Y[m] DISP_X&Y[m] BETA_X BETA_Y DISP_X DISP_Y 19 0.15 Size_X[cm] Size_Y[cm] Ax_bet Ay_bet Ax_disp Ay_disp IP Q4 Q3 Q2 Q1 Q1 G[kG/cm] = -2.8 Q2 G[kG/cm] = 3.1 Q3 G[kG/cm] = -2.0 Q4 G[kG/cm] = 2.0

IR Optics (ions) Natural Chromaticity: x = -88 y = -141 IP f 50 3000 5 BETA_X&Y[m] DISP_X&Y[m] BETA_X BETA_Y DISP_X DISP_Y l * = 7m IP FF triplet : Q3 Q2 Q1 f Natural Chromaticity: x = -88 y = -141

IR Optics (ions) at 60 GeV IP IP FF triplet : Q3 Q2 Q1 50 3000 5 BETA_X&Y[m] DISP_X&Y[m] BETA_X BETA_Y DISP_X DISP_Y 50 0.25 Size_X[cm] Size_Y[cm] Ax_bet Ay_bet Ax_disp Ay_disp IP FF triplet : Q3 Q2 Q1 Q1 G[kG/cm] = -9.7 Q2 G[kG/cm] = 6.9 Q3 G[kG/cm] = -6.8

Chromaticity Compensation uncompensated dispersion from the Arc Dfx = 2 Dfy Dfx = p Pairs of sextupoles ‘minus identity’ apart – cancelation of spherical aberrations Cancelation of higher order chromatic terms due to symmetry imposed correlations

IR Chromaticity Compensation ions Dfx = p Dfx,y = p Dfy = 3p IP Arc end Chromaticity Compensation with four families of sextupoles

Chromaticity Compensation electrons Dfx = p Dfx,y = p IP Arc end Chromaticity Compensation with four families of sextupoles

Collider Ring – Tune Diagram Working point above half integer a la KEKB: Qx=36.506 Qy=31.531 37 36 32 31 5 4 3 2 1

Tune Chromaticity Correction Large momentum acceptance and dynamic aperture

Figure-8 Collider Rings total ring circumference: 1000 m

Figure-8 Collider Rings total ring circumference: 1000 m

Summary MEIC EIC at JLab promises to accelerate and store a wide variety of polarized light ions and un-polarized heavy ions in collision with polarized electron or positron beam enabling a unique physics program. The project covers a wide CM energy range (10 to 100 GeV) in a coherent way. In the immediate future, a low-to-medium energy collider (CM energy 10 to 50 GeV) is our immediate goal & R&D focus. The collider luminosity for e-p collisions should reach ~1034 cm-2s-1 at (60x3~52 GeV2) The project is now based on mostly proven accelerator technologies. Making a high intensity ion beam with high repetition rate, small emittance and short bunch length is a key to reaching the luminosity goals (advanced cooling techniques are required). We have identified critical accelerator R&D topics for the project, We are currently pursuing staged accelerator design studies to validate and further optimize our design.