1. 3.2 km FODO lattice for 10 Hz operation (DMC4)
ILC Damping Rings Lattice Evaluation Meeting
3.2 km FODO lattice for 10 Hz operation (DMC4)
Dou Wang, Jie Gao (IHEP)
Tuesday, June 28, 2011

2. Main updates The momentum compaction is reduced.
Damping time is decreased according to 10 Hz repetition rate (storage time=100ms).
23 ms → 13.9 ms
60°
75°
90°
MDC3(5Hz)
6.19×10-4
4.04×10-4
2.77×10-4
MDC4(10Hz)
4.17×10-4
3.31×10-4
2.11×10-4

3. Damping ring layout Arcs consist of a total of 166 FODO cells
11% radiation in arcs
Straights are similar to 6 km DCO4
89% radiation in wigglers

4. 90°arc cell Reduce p Shorten the arc cell to reduce the dispersion
DMC4
(10 Hz)
DMC3
(5 Hz)
Shorten the arc cell to reduce the dispersion
Shorten the dipole length
Reduce p

5. Major parameters of DMC4
Beam energy
5.0 GeV
Circumference m
RF frequency
650 MHz
Transverse damping time
13.9 ms
Natural bunch length
6 mm
Natural energy spread
0.13%
Phase advance per FODO cell
65°
75°
90°
Momentum compaction factor
4.17×10-4
3.31×10-4
2.11×10-4
Normalized natural emittance
6.34 um
5.27 um
3.76 um
RF voltage
24.48 MV
20.04 MV
14.07 MV
RF acceptance
2.42%
2.26%
1.87%
Synchrotron tune
0.047
0.037
0.024
Working point x/y
44.52/41.88
48.02/45.55
56.06/54.15
Natural chromaticity x/y
-49.2/-48.1
-54.7/-53.5
-69.6/-67.7

6. Magnet parameters DMC4 (10Hz) DMC3(5Hz) DSB3 DCO4 Arc dipole length
Arc dipole field
0.26T
0.154T
0.26/0.36T
0.27 T
Number of arc dipoles
344
128
200
Chicane dipole length
1.50 m
1.0 m
Number of chicane dipoles 32 48
Quadrupole length
0.40 m
0.6/0.3 m
0.3 m
Total number of quadrupoles
474
590
692
Maximum quadrupole gradient
10.9T/m
11.3T/m
7.5 T/m
12.0 T/m
Wiggler peak field
1.7 T
1.6 T
Wiggler period length
0.4 m
Wiggler total length
142 m
98 m
78.4 m
215.6 m

7. summary
Machine flexibility is kept with FODO lattice. The momentum compaction can be adjusted from 2.1×10-4 to 4.1×10-4.
The damping time is reduced from 23ms to 13.9ms so that 10 Hz operation can be realized.
The range of RF voltage for 10 Hz case (14.07MV～24.48MV) is similar, even smaller than 5 Hz case.
The linear lattice for 10 Hz case satisfies all the principal requirements for the 3.2 km ring. The next work will be inserting sextupoles and check its dynamic aperture.