1. Possibility of MEIC Arc Cell Using PEP-II Dipole
Fanglei Lin, Andrew Hutton, Vasiliy S. Morozov, Yuhong Zhang
MEIC R&D Meeting, JLab, August 7, 2014
F. Lin

2. PEP-II HER vs. MEIC Arc Cell
Parameters
Unit
PEP-II HER
MEIC FODO cell
MEIC TME-like cell
Energy
GeV 9 12 5
Dipole length m
5.4
Bending angle
deg
1.875
4.272
5.34
Bending radius
165.0
72.4 (57.9)
72.4
57.9 (57.9)
57.9
Magnetic field T
0.1819
0.5527
0.4145
0.2303
0.6908
0.2878
Quad length
0.45
0.35
0.5/0.6/0.6
Field gradient
T/m
9.79 29 22
27/28/26
11/12/11
Aperture radius cm
3.6 (?)
4.5
FODO length
15.2
13.74
17.16
Number of FODO
16*6 50 40
Arc length
243.2*6
687 (673.92)
687
686.4
Normalized emittance um
845
3478 (438)
1446 (184.8)
252 (31.7)
951 (438)
69 (31.7)
SR power density
kW/m
7.23 (11.31)
7.04 (11.01)
5.03 (7.87)
11.31
7.87
Total SR power MW
4.39 (5.49)
4.28 (5.35)
3.05 (3.82)
5.49
3.82
* The current values are given in parenthesis

3. MEIC FODO & TME-like Cell
MEIC FODO cell
MEIC TME-like cell

4. Some Practical Considerations
Orbit curvature changes inside the dipoles  limit maximum sagitta R
PEP-II FODO cell
MEIC FODO cell
MEIC TME-like cell
optimal curvature   4

5. Back Up

6. MEIC’s e-Ring Current FODO Cell
Aperture radius 33 mm (CEBAF quads radius 14 – 27 mm mostly)
Dipoles
Magnetic length 2 m
Bending angle 34.5 mrad (1.98)
Bending radius 57.9 m
Field at 12 GeV T
Quadrupoles
Magnetic length 0.4 m
Field gradients at 12 GeV/c and T/m for 120 betatron phase advance/cell
Fields at 33 mm radius and T
Drift
Length 0.36 m
Complete FODO
Length 6.24 m (FODO * 2 = 12.48m)
Average bending radius 90.4 m
Chromaticity (H) and (V)
Normalized horizontal equilibrium emittance
438 um at 12 GeV
Problems: strong quads, short drift,
missing BPMs, correctors and
sextupoles, no physical lengths,
large equilibrium emittance.
0.36 m 6

7. MEIC’s e-Ring Current Equilibrium Emittance
Normalized Equilibrium Horizontal Emittance εxN (μm)
Energy (GeV) 3 5 6 7 8 9 10 11 12
Arc FODO (120 phase advance)
6.8
31.7
54.7
86.9
129.8
184.8
253.5
337.4
438.2
Arc (FODO + spin rotators)
11.8
54.5
94.2
149.6
223.2
317.8
435.9
580.4
753.4
Whole ring (Arc + IR)
15.4
71.3
123.2
195.7
292.1
415.8
570.4
759.2
985.7
Beam energy
Gev 3 5 6 7 8 9 10 11 12
Beam current A
2.0
1.1
0.65
0.4
0.26
0.18
0.13
Total SR power MW
0.49
3.82
5.28
5.38
5.43
5.35
5.37
5.49
Linear SR power density
kW/m
1.02
7.87
10.88
11.08
11.10
11.01
11.06
11.31
Energy loss per turn
MeV
0.17
1.27
2.64
4.89
13.37
29.84
Energy spread
10-3
0.34
0.56
0.68
0.79
1.01
1.24
Longitudinal damping time ms
83.6
18.1
10.4
6.6
3.1
1.7