1. Update on JLEIC Electron Ring Design
Fanglei Lin

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

3. Design Tasks for Electron Collider Ring
Finish dynamic aperture study (in progress)
Retune the lattice:
Reserve enough space for BPMs (existing drift-bpm-drift ( )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)

4. 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 m, with a figure-8 crossing angle of 69. Each arc is m long and each straight is 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

5. Arc FODO Cell Arc FODO cell (each arc has 45 such normal FODO cells)
Length 11.4 m (arc bending radius 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
GeV, GeV
Sagitta 1.65 cm
Quadrupole
Magnetic/physical length 0.56/0.62 m
Field gradient GeV, GeV
4.5 cm 10 GeV
Sextupole (for linear chromaticity compensation)
Magnetic/physical length 0.25/0.31 m
325 and -151 T/m2 field 5 GeV, 650 and GeV
0.66 and cm 10 GeV
BPM and Corrector
Physical length 0.05 and 0.3 m

6. 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 GeV, 0.2 and 10 GeV
Sagitta 1.02 and 0.63 cm
Quadrupole
Magnetic/physical length 0.56/0.62 m
Maximum field gradient GeV,
GeV
4.5 cm 10 GeV
BPM and Corrector
Physical length 0.05 and 0.3 m

7. 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 / m
Bending angle 1.05, bending radius 174 m
0.1 5 GeV, GeV
Sagitta 0.73 cm
Quadrupole
Magnetic/physical length 0.56/0.62 m
Field gradient in 1 and 2 regions is less
than GeV,15.4 GeV.
Field gradient in 3 region reaches 35 T/m
@ 10 GeV (can be further optimized)
0.7 and cm 10 GeV
Two CCBs are reserved in the straight for the 2nd IP, but with low beta functions 1 2 3
Crab cavities

8. 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 GeV, ~ 4 and 7 10 GeV
Dipole
Magnetic/physical length 4 (2) / 4.2 (2.2) m
Bending angle 4.4 (2.2), bending radius m (local strong SR linear density )
GeV, 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
( 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

9. 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.

10. Upstream of the IP e- ion SB1 IP: (10,2)cm
2.4 m det. sol m 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 = ;
qffus2 = ;
qffus3 = ;
qffus1->k1s = ; (skew)
qffus2->k1s = ; (skew)
qffus3->k1s = ; (skew)
IP: (10,2)cm

11. 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 = ;
qffds2 = ;
qffds3 = ;
qffds1->k1s = ; (skew)
qffds2->k1s = ; (skew)
qffds3->k1s = ; (skew)
Three 0.6m-long FFQs

12. 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-

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

14. 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

15. Complete Electron Ring Optics
Ring circumference m, arc length m, straight length m e- IP

16. Electron Ring Footprint
310m
1000 m IP e-

17. Electron Collider Ring Parameter
Beam energy
GeV 5
Circumference m
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

18. 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
-98.52
-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

19. 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

20. 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
BXSP1
BXSP2
0.5
AASOLEDS
anti-solenoid (T)
1.2
2.2 -4
QFFDS3
quadrupole
0.6
2.4 10
QFFDS2
2.8
8.5
QFFDS1
1.7 8
SOLDETDS
detector solenoid (T)
1.6
Upstream elements
SOLDETUS
QFFUS1 2
QFFUS2
3.2
QFFUS3
1.5
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)

21. Element Count
Dipoles:
Quadrupoles:
Sextupoles:

22. 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

23. Back Up

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

25. 2. At the ends of each cryostat1 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

26. 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