Update on JLEIC Electron Ring Design Fanglei Lin

Outline Update on the design tasks for pre-CDR Update on the lattice design in detail Plan

Design Tasks for Electron Collider Ring Finish dynamic aperture study (in progress) Retune the lattice: Reserve enough space for BPMs (existing drift-bpm-drift (5+5+7.5)cm space in arc FODO cells should be long enough, based on the experience in PEP-II and SuperB CDR and NSLSII (see more detail in the backup slides)) Replace sbend with rbend in arcs (done) Adjust spin rotator dipoles to reduce the linear density of SR power Reserve realistic space for RF cavities (space in straights is long enough) Make space for crab cavities in the arcs Redesign the detector region optics including the compensation of coupling induced by the detector solenoid (done) Integrated latest detector region design with correcting elements (done) Update the nomenclature (in progress) Reduce * (one version has been done for the beam-beam simulation)

General Information The new electron ring is designed using new magnets. Comparing to PEP-II magnets, short dipoles in arcs have a better control of emittance and sagitta, quads, except for those in the IP region, are slightly stronger, but still warm magnets, sextupoles, bpms and correctors have same lengths, but strengths are different. The ring circumference is 2498.6 m, with a figure-8 crossing angle of 69. Each arc is 956.2 m long and each straight is 293.1 m long. e- R=155m Spin rotator Arc, 249 69 Forward e- detection and polarimetry IP Tune trombone & Straight FODOs Future 2nd IP CCB For illustration only

Arc FODO Cell Arc FODO cell (each arc has 45 such normal FODO cells) Length 11.4 m (arc bending radius 155.5 m) 2 dipoles + 2 quadrupoles + 2 sextupoles 108/108 x/y betatron phase advance Dipole Magnetic/physical length 3.6/3.88 m Bending angle 2.1, bending radius 98.2 m 0.17 T @ 5 GeV, 0.34 T @ 10 GeV Sagitta 1.65 cm Quadrupole Magnetic/physical length 0.56/0.62 m Field gradient 8.7 T/m @ 5 GeV, 17.5 T/m @ 10 GeV 0.79T @ 4.5 cm radius @ 10 GeV Sextupole (for linear chromaticity compensation) Magnetic/physical length 0.25/0.31 m 325 and -151 T/m2 field strengths @ 5 GeV, 650 and -302 T/m2 @ 10 GeV 0.66 and -0.30 T @ 4.5 cm radius @ 10 GeV BPM and Corrector Physical length 0.05 and 0.3 m

Dispersion Suppressor at Ends of FODO Cells Similar to the arc-FODO-cell structure, but total bending angle in this two-cell structure is same as the one in one normal FODO cell Dipole Magnetic/physical length 3.6/3.88 m Bending angle 1.3 and 0.8, bending radius 159 and 257 m 0.1 and 0.06 T @ 5 GeV, 0.2 and 0.12T @ 10 GeV Sagitta 1.02 and 0.63 cm Quadrupole Magnetic/physical length 0.56/0.62 m Maximum field gradient 8.8 T/m @ 5 GeV, 17.6 T/m @ 10 GeV 0.8T @ 4.5 cm radius @ 10 GeV BPM and Corrector Physical length 0.05 and 0.3 m

Chromaticity Compensation Block (CCB) CCB is designed considering minimum emittance contribution, non-interleaved –I pair sextupoles for chromatic correction of FFQs Dipole Magnetic/physical length 3.1941/3.4741 m Bending angle 1.05, bending radius 174 m 0.1 T @ 5 GeV, 0.2 T @ 10 GeV Sagitta 0.73 cm Quadrupole Magnetic/physical length 0.56/0.62 m Field gradient in 1 and 2 regions is less than 7.7 T/m @ 5 GeV,15.4 T/m @10 GeV. Field gradient in 3 region reaches 35 T/m @ 10 GeV (can be further optimized) 0.7 and 1.6 T@ 4.5 cm radius @ 10 GeV Two CCBs are reserved in the straight for the 2nd IP, but with low beta functions 1 2 3 Crab cavities

Spin Rotator Spin rotator is designed to rotate the spin between vertical and longitudinal directions, Composed of dipoles and solenoids, and quadrupoles for optics control Adopted a DBA-like lattice to minimize emittance contribution and suppress spin resonances Solenoid Magnetic/physical length 2.5 (5) / 2.6 (5.1) m 2.2 and 2.9 T @ 5 GeV, ~ 4 and 7 T @ 10 GeV Dipole Magnetic/physical length 4 (2) / 4.2 (2.2) m Bending angle 4.4 (2.2), bending radius 52.1 m (local strong SR linear density ) 0.32 T @ 5 GeV, 0.64 T @ 10 GeV Sagitta 3.8* (0.96) cm Quadrupole Different lengths, a few of quads need to reduce the strength * sagitta at the 4m dipole can be reduced to 0.96 cm by cutting it into two halves E Solenoid 1 (2.5 + 2.5 m) Arc Dipole 1 Solenoid 2 (5 + 5 m) Arc Dipole 2   Spin Rotation BDL GeV rad T·m 3 π/2 15.7 π/3 π/6 4.5 π/4 11.8 23.6 6 0.62 12.3 2π/3 1.91 38.2 9 π 62.8 12 24.6 4π/3 76.4

Redesign of Detector Region Optics Anti-solenoids are 1.2 m long in both up- and downstream of IP They were 1.2 m long in the upstream and 1.6 m long in the downstream in v1 version All FFQs have 60 cm long magnetic length, but different strengths Use FFQs with skew components for coupling compensation of detector solenoid Removed all skew quadrupoles v1 version Move chicane further down by 2.36 m (comparing to that in v1 version) Each side of each magnet (except detector solenoid and anti-solenoids) reserves 10 cm space for coil shaping, coil collars, assembly, etc. Minimum 20 cm for interconnect of magnets for bellows, vacuum pumping, assembly, etc. Each end of each cryostat reserves 30 cm for a warm to cold transition (not all, related to next bullet) Upstream QFFUS2 and QFFUS3 are outside of the ion SB1. But it does not have 30 cm space for a warm to cold transition, but can be solved.

Upstream of the IP e- ion SB1 IP: (10,2)cm 2.4 m det. sol. + 0.56m drift 0.6m 1.85 m 0.4m 1.2m anti. sol. 0.3m ion SB1 Three 0.6m-long FFQs At 10 GeV, strengths of FFQs (T/m) qffus1 = -37.26308053 ; qffus2 = 42.51112874 ; qffus3 = -29.39050179 ; qffus1->k1s = 8.170545513 ; (skew) qffus2->k1s = -9.321266714 ; (skew) qffus3->k1s = 6.444352672 ; (skew) IP: (10,2)cm

Downstream of the IP (FFQs) 1st dipole in the chicane 1.6m det. sol. + 0.6m drift 0.6m 1.2m anti. sol. 3.4m e- At 10 GeV, strengths of FFQs (T/m): qffds1 = -44.78044481 ; qffds2 = 43.46563597 ; qffds3 = -13.62947228 ; qffds1->k1s = -6.488773242 ; (skew) qffds2->k1s = 6.298254893 ; (skew) qffds3->k1s = -1.974936948 ; (skew) Three 0.6m-long FFQs

Downstream of the IP (FFQs + Chicane) Downstream chicane is used for forward low-Q2 detection, suppression of dispersion and compton polarimetry that provides a non-invasive measurement of electron polarization. Dipoles Dipole 1: 3m-long, bending radius 80m, bending angle 2.15, sagitta 1.4cm. Dipole 2: 0.5m-long, bending radius 200m, bending angle 0.14, sagitta 0.016cm. Dipole 3, 3m-long, bending radius 75m, bending angle 2.29, sagitta 1.5cm. Forward e- detection + Compton polarimetry e-

Straight FODO Cell Straight FODO cell (for space holder and tune trombone, 35 cells in total) Length 12.68 m Drift Maximum 5 m (probably long enough for two RF cavities) Quadrupole Magnetic/physical length 0.73/0.79 m 3.8 T/m @ 5 GeV, 7.6 T/m @ 10 GeV BPM and Corrector Physical length 0.05 and 0.3 m

Matching Sections Arc DS to SBCC / SBCC to Arc DS Arc End to Chicane (also used to adjust the phase advance between CCB sextupoles and IP) Upstream FFQ to Tune Trombone (also used to adjust the phase advance between CCB sextupoles and IP) Tune Trombone to Arc End Arc End to Straight FODO Cell Straight FODO to Arc End

Complete Electron Ring Optics Ring circumference 2498.6 m, arc length 956.2 m, straight length 293.1 m e- IP

Electron Ring Footprint 310m 1000 m IP e-

Electron Collider Ring Parameter Beam energy GeV 5 Circumference m 2498.64 Straights’ crossing angle deg 69 Horizontal / vertical beta functions at IP *x,y cm 10 / 2 Maximum horizontal / vertical beta functions x,y max 446 Maximum horizontal dispersion Dx 0.497 Horizontal / vertical betatron tunes x,y 63(.10)/ 61(.81) Horizontal / vertical natural chromaticitiesx,y -167 / -214 Momentum compaction factor  10-4 4.6 Transition energy tr 34.51 Normalized horizontal / vertical emittance x,y µm rad 5.63 / 1.13 Horizontal / vertical rms beam size at IP *x,y µm 24 / 4.8 Maximum horizontal / vertical rms beam size x,y mm 3.2 / 1.5

Electron Ring Operation Parameters Energy 3 4 5 6 6.65 7 8 9 10 GeV Energy Loss per Turn 0.113 0.359 0.875 1.815 2.739 3.363 5.737 9.190 14.007 MeV SRpower/ring (= power to beam) 0.34 1.08 2.63 5.45 8.22 9.15 9.58 MW SR power per unit length 0.38 1.20 2.93 6.07 9.16 10.20 10.68 kW/m Energy Spread 2.77E-04 3.69E-04 4.62E-04 5.54E-04 6.14E-04 6.46E-04 7.39E-04 8.31E-04 9.23E-04 Trans. SR Damping Time 412.13 173.87 89.02 51.52 37.84 32.44 21.73 15.26 11.13 mSec Long. SR Damping Time 206.06 86.93 44.51 25.76 18.92 16.22 10.87 7.63 5.56 Beam Average Current 3.000 2.720 1.669 1.042 0.684 A Bunch Length 10.0 11.6 mm Vpeak, Total 0.53 1.27 2.54 4.51 6.25 7.36 11.33 16.68 19.94 MV Vgap, 1K2C 0.26 0.32 0.28 0.24 0.52 0.69 0.77   Vgap, 1K4C 0.00 Gradient, 1K2C 0.84 1.01 0.89 0.76 0.90 1.64 2.21 2.44 MV/m Gradient, 1K4C Bucket Heigt / Energy Spread 16.79 15.81 14.89 14.04 13.51 13.24 12.50 11.82 8.07 Syn. Phase 12.4 16.4 20.1 23.8 26.0 27.2 30.4 33.4 44.6 degree Syn. Tune 0.010 0.013 0.016 0.020 0.022 0.023 0.026 0.030 0.028 Cavity Number, Total 2 16 26 22 24 Klystron Number 1 13 11 12 Loading Angle ψL 0.0 PowerToBeam per Cavity, 1K2C 170.19 268.93 328.29 340.37 316.07 351.83 435.35 399.07 368.37 kW PowerToBeam per Cavity, 1K4C Cavity Wall Loss Power, 1K2C 9.95 14.48 14.42 8.25 11.45 37.91 68.98 83.99 Cavity Wall Loss Power, 1K4C Reflected Power, 1K2C 16.33 33.18 68.29 125.46 177.33 135.12 5.84 17.82 44.71 Reflected Power, 1K4C Forward Power Per Cavity, 1K2C 196.47 316.60 411.00 477.16 501.65 498.40 479.10 485.86 497.07 Forward Power Per Cavity, 1K4C Total RF Power 0.393 1.266 3.288 7.635 13.043 12.958 10.540 11.661 12.924 Robinson Instability Y, 1K2C 1.45 1.36 1.59 1.22 0.41 0.19 0.11 Robinson Instability Y, 1K4C Tuning Angle ψ, 1K2C -54.7 -49.0 -48.4 -51.1 -55.0 -47.4 -19.6 -9.1 -4.6 Tuning Angle ψ, 1K4C δf 1K2C -123.38 -100.49 -98.52 -108.37 -124.72 -94.98 -31.06 -13.91 -7.05 kHz δf 1K4C Injection Time with 2 ts 24.73 13.91 8.90 6.18 5.03 4.12 1.93 0.95 0.51 min Loop Gain of Direct Feedback 4.00 RF Not Valid Will update

Emittance Beam energy GeV 3 5 6.9 9 10 Beam current A 1.1 0.71 Total SR power MW 0.33 2.51 9.1 9.6 9.5 Energy loss per turn MeV 0.11 0.84 3.1 8.8 13.4 Energy spread 10-4 2.8 4.6 6.4 8.3 9.3 Transverse damping time ms 462 100 38 17 13 Longitudinal damping time 231 49.8 19.0 8.5 6.3 Normalized Emittance um 12 54 141 313 429

Aperture Specifications Detector region electron elements 10 GeV/c electrons Element name Type Length [m] Good field half-aperture [cm] Inner Half-aperture [cm] Outer Radius [cm] Strength [T or T/m] Skew Strength [T/m] Downstream elements (second focusing point approximately in the middle of chicane) BXSPL rectangular bend [T] 3 1.8 4.5 11 0.444722484 BXSP1 -0.416930695 BXSP2 0.5 -0.166782007 AASOLEDS anti-solenoid (T) 1.2 2.2 -4 QFFDS3 quadrupole 0.6 2.4 10 -13.62947239 -1.974936965 QFFDS2 2.8 8.5 43.46563611 6.298254915 QFFDS1 1.7 8 -44.78044515 -6.488773293 SOLDETDS detector solenoid (T) 1.6 Upstream elements SOLDETUS QFFUS1 2 -37.26308052 8.170545512 QFFUS2 3.2 42.51112873 -9.321266715 QFFUS3 1.5 -29.39050179 6.444352672 AASOLEUS -6 10σ Large enough to allow the forward e- detection Smooth beam pipe to reduce the impudence Good enough to apply to all magnets in the ring, considering (maximum 10 σ + 1cm COA + sagitta/2)

Element Count Dipoles: Quadrupoles: Sextupoles:

Plan Focus on dynamic aperture study Update the nomenclature Tune scan Misalignment and orbit correction Multipole effect Update the nomenclature Reduce *, apply the compensation scheme and study the DA

Back Up

BPM PEP-II and SuperB BPM NSLSII BPM between quadrupole and sextupole

2. At the ends of each cryostat 1 2 5 6 3 4 ~32 m i e 2. At the ends of each cryostat 30 cm for Cold bore designs for a warm to cold transition With a bellows this could be less. Need HOM power loss estimates for bellows. 10 cm for Warm bore designs Some of this could be inside of the detector area and SB1, depending on design and installation plan From Mark’s slides on 12/19/17

From Mark’s slides on 12/12/17 QFFUS1 318.02mm QSFFUS2 QFFUS2 QSFFUS3 QFFUS3 SB1 631.93mm 132.03mm 731.93mm 531.93mm From Mark’s slides on 12/12/17 26