1. MEIC Alternative Design Part V
Using PEP-II RF Stations (476 MHz)
Damping Wiggler
Mismatching Beam Spot size at IP
MEIC Accelerator R&D Meeting
Oct. 30, 2014

2. A New Baseline for MEIC (?!)
Main components
Electron collider ring (PEP-II magnets, vacuum, and possibly RF stations)
Ion linac (could its energy be lower?)
(single!) Booster ring (up to 8 GeV/c, Fermilab cooler, plus a 150 KeV cooler, super-ferric magnets?)
Ion collider ring (super-ferric, other existing rings?, imaginary gamma-t, or crossing?)
Outstanding issues in the electron ring based on PEP-II magnets
Magnets (quad strength, dipole saggitts, good field, vacuum pump)
Beam emittance (particularly at 9 GeV and above)
Injection scheme and beam loss/background if using PEP-II RF station (over 10 MW)

3. MEIC Luminosity w/ PEP-II RF Station (476 MHz)
Proton
25 GeV
60 GeV
100 GeV
748.5 MHz
476 MHz
GeV
1033 /cm2/s 3
0.25
3.8
9.5
9.0 4
7.0 5
3.0
4.5
4.7 6
2.1
3.1
3.3 7
0.24
1.5
2.3
2.4 8
0.14
0.18
0.86
1.2
1.3
1.8 9
0.07
0.10
0.43
0.65
0.64
1.0 10
0.04
0.06
0.22
0.32
0.34
0.53 11
0.02
0.03
0.20
0.19
0.30 12
0.01
0.08
0.11
0.21

4. Damping Wiggler
Synchrotron radiation power from the bending magnets and wigglers
Wigglers must be placed in the (external) dispersion-free area in order to suppress the quantum fluctuation

5. CLIC Damping

6. A (very primary) Damping Wiggler for MEIC
No wiggler
Circumference m
2200
Dipole bending radius
113.5
Lattice
deg
135/60
Wiggler period length M
0.05
Wiggler period
600
Total length of wiggler
30 (two?)
Magnetic field T
2.5 K
11.7
Energy (GeV)
Current (A)
Energy loss per turn (MeV)
Radiation Power (MW) 3
0.092
0.28 4
0.29
0.87 5
0.71
2.13 6
1.47
4.41 7
2.72
8.17 8
2.23
4.65
10.37 9
1.4
7.45
10.42 10
0.91
11.4
10.33 11
0.63
16.6
10.39 12
0.44
23.5
10.35

7. Electron Current with A Damping Wiggler
Energy (GeV)
Current
(A)
Energy loss per turn (MeV)
Radiation Power (MW)
Energy loss over wiggler (MeV)
Total Rad. power
(MW) 3
0.092
0.28
1.07
3.20
3.48 4
0.29
0.87
1.90
5.70
6.57 5
2.8 (3)
0.71
2.00
2.97
8.31
10.30 6
1.8 (3)
1.47
2.65
4.27
7.69
10.34 7
1.23 (3)
2.72
3.35
5.82
7.15
10.51 8
0.84 (2.23)
4.65
3.91
7.60
6.38
10.29 9
0.61 (1.4)
7.45
4.55
9.62
5.86
10.41 10
0.45 (0.91)
11.4
5.1
11.87
5.34
10.45 11
0.33 (0.63)
16.6
5.49
14.36
4.74
10.23 12
0.26 (0.44)
23.5
6.00
17.09
4.36
10.37

8. Electron Beam Emittance with A Damping Wiggler
Energy (GeV)
Horizontal emittance without wiggler
Horizontal emittance with wiggler
Emittance reduction factor
mm mrad 3
14.7
1.07
0.07 4
34.8
3.54
0.1 5 68
9.81
0.14 6
117.5
22.7
0.19 7
186.6
45.6
0.24 8
82.6
0.3 9
396.6
137.8
0.35 10
544.0
215.7
0.4 11
724.1
320.6
0.44 12
940.0
456.8
0.49

9. MEIC Luminosity wo/w Wiggler (proton 25 GeV)
750 MHz,
no wiggler
476 MHz,
with wiggler
Energy
Normalized emittance (x)
Luminosity
GeV
mm mrad
1033 /cm2/s 3
14.7
0.25
1.07 4
34.8
3.54 5
68,0
9.81 6
117.5
22.7
0.21 7
186.6
0.24
45.6 8
278.5
0.14
0.18
82.6
0.13 9
396.6
0.07
0.10
137.8
0.08 10
544.0
0.04
0.06
215.7 11
724.1
0.02
0.03
320.6 12
940.0
0.01
456.8

10. MEIC Luminosity WO/W Wiggler (proton 60 GeV)
750 MHz,
no wiggler
476 MHz,
with wiggler
Energy (GeV)
Normalized emittance (x)
Luminosity
mm mrad
1033 /cm2/s 3
14.7
3.8
1.07
0.36 4
34.8
3.54
1.3 5
68,0
3.0
9.81 6
117.5
2.1
22.7
3.4 7
186.6
1.5
45.6
2.3 8
278.5
0.86
1.2
82.6
1.6 9
396.6
0.43
0.65
137.8
0.81 10
544.0
0.22
0.32
215.7
0.40 11
724.1
0.20
0.18
320.6 12
940.0
0.08
0.11
456.8
0.13

11. MEIC Luminosity WO/W Wiggler (proton 100 GeV)
750 MHz, no wiggler
476 MHz, no wiggler
476 MHz, with wiggler
Energy (GeV)
Normalized emittance (x)
Luminosity
mm mrad
1033 /cm2/s 3
14.7
9.5
9.0
1.07
0.6 4
34.8
7.0
3.54
2.0 5
68,0
4.5
4.7
9.81
6.0 6
117.5
3.1
3.3
22.7
8.9 7
186.6
2.3
2.4
45.6
6.1 8
278.5
1.3
1.8
82.6
6.2 9
396.6
0.64
1.0
137.8 10
544.0
0.34
0.53
215.7
0.67 11
724.1
0.19
0.30
320.6
0.36 12
940.0
0.14
0.21
456.8

12. Beam-Beam and Spot Size Matching at IP
The conventional wisdom is to match the spot sizes of the colliding beam for optimization of beam-beam effect
Otherwise, the “fatter” beam is not happy due to sampling more nonlinear beam-beam effect while the “thinner” beam is more stable.
These are all for strong-strong beam-beam cases while the parameters for both beams are closed to the beam-beam limits
One idea I am proposing is, in a strong-weak case, the “weak” beam whose beam-beam parameters are much smaller than the beam-beam limit, can be a “fatter” beam
In that case, we purposely over-focus the strong beam without matching it to the weak beam spot size, thus gains some additional luminosity