JLEIC Forward Ion Detection Region Machine Parameters V.S. Morozov JLEIC Forward Ion Detection Region October 28, 2016 F. Lin

JLEIC Layout 2015 Electron complex CEBAF Electron collider ring Ion complex Ion source SRF linac (285 MeV/u for protons) Booster Ion collider ring Optimum detector location for minimizing background 3-10 GeV 8-100 GeV 8 GeV 2015 arXiv:1504.07961

JLEIC Layout & Detector Location Cold Ion Collider Ring (8 to 100 GeV) Two IP locations: One has a new detector, fully instrumented Second is a straight-through, minor additional magnets needed to turn into IP Ion Source Booster Linac Warm Electron Collider Ring (3 to 10 GeV) Considerations: Minimize synchrotron radiation IP far from arc where electrons exit Electron beam bending minimized in the straight before the IP Minimize hadronic background IP close to arc where protons/ions exit

Beam Parameters p e Beam energy GeV 100 5 Collision frequency MHz 476 Particles per bunch 1010 0.98 3.7 Beam current A 0.75 2.82 Polarization >70% Bunch length, rms cm 1.2 Norm. emittance, x/y m 0.5/0.1 70/14 x/y * 6/1.2 4/0.8 Vert. beam-beam param. 0.015 0.053 Laslett tune shift 0.048 Small Detector space, up/down m 3.6/7 2.4/1.6 Hourglass (HG) reduction 0.80 Lumi./IP, w/HG, 1033 cm-2s-1 19.5

e-p Collision Luminosity Design point (CM) p energy (GeV) e- energy (GeV) Main luminosity limitation low 30 4 space charge medium 100 5 beam-beam high 10 synchrotron radiation

Detector Region Design Ingredients Detector requirements Acceptance Large detector space Forward tagging Emittance Background Dynamic requirements Magnet strengths Optical integration Magnet multipoles Non-linear dynamics Chromaticity compensation Dynamic aperture Geometric integration Crossing angle Matched beam-line footprints IR magnet dimensions Ring geometry decoupled from IR design

IR & Detector Concept Ion beamline Electron beamline Possible to get ~100% acceptance for the whole event Central Detector/Solenoid Dipole Forward (Ion) Detector Scattered Electron Particles Associated with Initial Ion Particles Associated with struck parton

Full-Acceptance Detector 50 mrad crossing angle Improved detection, no parasitic collisions, fast beam separation Forward hadron detection in three stages Endcap Small dipole covering angles up to a few degrees Far forward, up to one degree, for particles passing through accelerator quads Low-Q2 tagger Small-angle electron detection

Detector Region IP e ions p e Integrated detector region design developed satisfying the requirements of Detection – Beam dynamics – Geometric match GEANT4 detector model developed, simulations in progress IP e Compton polarimetry ions forward ion detection forward e detection dispersion suppressor/ geometric match spectrometers p (top view in GEANT4) e low-Q2 electron detection and Compton polarimeter Forward hadron spectrometer ZDC

Detector Region Geometry Overall geometry fixed: the beam position and angle at the end point are fixed e beam i beam 2nd spectrometer dipole 56 mrad (4.7 T @ 100 GeV) “3rd” spectrometer dipole -56 mrad (4.7 T @ 100 GeV) length of this straight controls overall length controls overall height Three dispersion-suppression/ geometry-control dipoles |56 mrad| (4.7 T @ 100 GeV) cannot be much smaller geometrically fixed point

Ion IR *x,y = 10 / 2 cm, D* = D* = 0 Three spectrometer dipoles (SD) Large-aperture final focusing quadrupoles (FFQ) Secondary focus with large D and small D Dispersion suppressor geometric match geom. match/ disp. suppression IP SD1 SD2 SD3 FFQ ~14.4 m 4 m D = 0, D’ = 0 D’ ~ 0 forward detection x , y < ~0.6 m middle of straight limit x and y

Downstream Ion IR Layout Blue – dipoles, green – vertically focusing quads, red – horizontally focusing quads, grey – corrector packages Element sizes, center coordinates, and angular orientations are specified in the Excel file All elements are approximately cylindrical Detector and anti solenoids are not shown rbffb sp. dip. #1 sbffb sp. dip. #2 bxspds01r sp. dip. #3 qffb1 x  = 50 mrad qffb2 qffb3 e- QSPDS01 1st machine element z IP 1.5 m ions FF quads 14.4 m

IR Ion Magnet Parameters Assuming 100 GeV/c Parameters are determined primarily by detection requirements rather than beam dynamics Bottom-up study of multipole requirements in progress Note: parameters are still being fine-tune but no major changes Name Type Length [m] Good-field radius [cm] Inner radius [cm] Outer radius [cm] Min. beam separation [cm] Strength [T or T/m] Pole-tip field [T] QFFB3_US Quad [T/m] 1 3 4 12 36.0 -116 -4.6 QFFB2_US 1.5 26.5 149 6 QFFB1_US 1.2 2 10 18.0 -141 -4.2 SB1 Dipole [T] 17 24 25.0 -2 QFFB1 6.8 17.1 35.9 -88 -6 QFFB2 2.4 11.8 24.7 48.2 51 QFFB3 26.7 67.2 -35 SB2 40 90 102 4.7 -4.7

Ion Beam Envelope & 99%p Trajectory Assuming beam momentum of 100 GeV/c, ultimate normalized x/y emittances xN/yN of 0.35/0.07 m, and ultimate momentum spread p/p of 310-4 The horizontal size includes both betatron and dispersive components 2nd focus IP

Far-Forward Acceptance for Charged Fragments Δp/p = -0.5 Δp/p = 0.0 Δp/p = 0.5 (protons rich fragments) (exclusive / diffractive recoil protons) (tritons from N=Z nuclei) (spectator protons from deuterium) (neutron rich fragments) 15

Far-Forward Ion Acceptance Transmission of particles with initial angular and p/p spread Quad apertures = B max / (fixed field gradient @ 100 GeV/c) Uniform particle distribution of 0.7 in p/p and 1 in horizontal angle originating at IP Transmitted particles are indicated in blue (the box outlines acceptance of interest) More accurate simulations are in progress 6 T max  electron beam 16

Far-Forward Ion Acceptance for Neutrals Transmission of neutrals with initial x and y angular spread Quad apertures = B max / (fixed field gradient @ 100 GeV/c) Uniform neutral particle distribution of 1 in x and y angles around proton beam at IP Transmitted particles are indicated in blue (the circle outlines 0.5 cone) 6 T max  electron beam 17

Ion Momentum & Angular Resolution Protons with p/p spread are launched at different angles to nominal trajectory Resulting deflection is observed at the second focal point Particles with large deflections can be detected closer to the dipole  electron beam ±10 @ 60 GeV/c |p/p| > 0.005 @ x,y = 0 18

Ion Momentum & Angular Resolution Protons with different p/p launched with x spread around nominal trajectory Resulting deflection is observed 12 m downstream of the dipole Particles with large deflections can be detected closer to the dipole |x| > 3 mrad @ p/p = 0  electron beam  electron beam ±10 @ 60 GeV/c 19

Parameter Choice Impact of * and  on luminosity and detector acceptance Luminosity Smaller * and   higher luminosity nx,y = 1 / 0.5 m  0.5 / 0.1 m  a factor of 3 increase in L *x,y = 10 / 2 cm  6 / 1.2 cm  another factor of 1.7 increase in L Fundamental limit on detector angular acceptance nx,y = 1 / 0.5 m, *x,y = 10 / 2 cm  min > 3-5 mrad at 100 GeV/c nx,y = 1 / 0.5 m  0.5 / 0.1 m  a factor of 0.5-0.7 reduction in min *x,y = 10 / 2 cm  6 / 1.2 cm  a factor of 1.3 increase in min

Parameter Choice Fundamental limit on momentum acceptance at the secondary focus Roman pot at the secondary focus has finite length l , therefore where sx is the  function at the secondary focus Smaller x  smaller (p/p)min Optimum is when sx = l / 2 (similar to the hour-glass effect) Currently, sx ~ 0.6 m, it changes proportionally to *x In our case, the beam size is dominated by Dx , changes in *x and sx have very little effect Assume l = 2 m, nx = 1 m, sx = 0.6 m, Dx = 1 m,  = 5 10-4  (p/p)min > 510-3

Summary & Outlook Detector region design is fairly complete from the accelerator integration point of view Most detector optimization does not affect the beam dynamics significantly Ongoing work Quantification of detector performance Background simulations Need to better define Solenoid compensation elements Orbit diagnostics and correction elements in the detector region Engineering parameters of detector region magnets