General Parameters
| Parameter | Value |
| Beam particle |
electron |
| Beam energy |
1.9 GeV (1.0–1.9 GeV possible) |
| Injection energy |
1.9 GeV (1.0–1.9 GeV possible) |
| Beam current (all operation is in top-off with ΔI/I ≤ 0.3%) |
500 mA in multibunch mode
2 x 17.5 mA in two-bunch mode |
| Filling pattern (multibunch mode) |
256–320 bunches; possibility of one or two 5- to 6-mA "camshaft" bunches in filling gaps |
|
Bunch spacing: multibunch mode
|
2 ns |
|
Bunch spacing: two-bunch mode
|
328 ns |
| Circumference |
196.8 m |
| Number of straight sections |
12 |
| Number of insertion devices |
12 |
| Radio frequency |
499.642 MHz (± 6 kHz) |
| Beam size in straight sections, rms (1.9 GeV multibunch mode) |
251 µm x 8 µm (horizontal x vertical) |
| Parameter | Value at 1.9 GeV |
|
Top-off injection rate: multibunch mode
|
1–1.5 mA/shot every 25–50 seconds |
|
Top-off injection rate: two-bunch mode*
|
0.4–0.5 mA/shot every 25–30 seconds |
| Horizontal emittance |
2.0 nm-rad |
| Vertical emittance |
0.04 nm-rad |
| Energy spread (ΔE/E, rms) |
0.95 x 10-3† |
| Pulse Length (FWHM) |
60 p‡ |
* Bunch cleaning is performed after every injection.
† Above 8 mA per bunch in two-bunch mode, the energy spread increases because of the microwave instability.
‡ In multibunch mode, the bunch length is deliberately increased using harmonic cavities to improve the beam lifetime. In two-bunch mode, the bunch length is current dependent. For 2 x 17.7 mA in top-off mode, it is about 55 ps.
The ALS has 12 straight sections and 12 arc-shaped sections, like the one shown above, containing bend magnets (B) with a defocusing gradient, quadrupoles (QFA, QDA, QF, and QD), and sextupoles (SF, SD,SHF, and SHD). Three of the arc sections contain superconducting bend magnets (superbends) and therefore have a modified lattice as shown in the lower image.
Horizontal and Vertical Lattice Functions (α β, γ), Horizontal Dispersion Functions (ηx and ηx '), and 1-σ Beam Sizes (σ) and Divergences (σ') at Photon Source Points*
|
Beam Port
|
Angle**
[degrees]
|
Device
|
Axis
|
α
|
β [m]
|
γ [m-1]
|
ηx [m]
|
ηx '
|
σ [µm]
|
σ' [µrad]
|
|
BL x.0
|
0.0
|
Insertion device
|
x
|
0.000
|
21.27
|
0.047
|
0.15
|
0.000
|
251
|
9.7
|
|
BL x.0
|
0.0
|
Insertion device
|
y
|
0.000
|
1.72
|
0.581
|
|
|
8.3
|
4.8
|
|
BL x.0.1
|
0.0
|
Upstream insertion device
|
x
|
0.061
|
21.35
|
0.047
|
0.15
|
0.000
|
251
|
9.7
|
|
BL x.0.1
|
0.0
|
Upstream insertion device
|
y
|
0.756
|
2.7
|
0.581
|
|
|
10.4
|
4.8
|
|
BL x.0.2
|
0.0
|
Downstream insertion device
|
x
|
-0.06
|
21.35
|
0.047
|
0.15
|
0.000
|
251
|
9.7
|
|
BL x.0.2
|
0.0
|
Downstream insertion device
|
y
|
-0.76
|
2.7
|
0.581
|
|
|
10.4
|
4.8
|
|
BL x.1
|
6.3
|
Bending magnet
|
x
|
-0.34
|
0.23
|
4.841
|
0.026
|
0.043
|
32.7
|
106.4
|
|
BL x.1
|
6.3
|
Bending magnet
|
y
|
9.177
|
26.55
|
3.209
|
|
|
32.6
|
11.3
|
|
BL x.2
|
12.6
|
Bending magnet
|
x
|
0.685
|
0.48
|
3.085
|
0.027
|
-0.05
|
40.3
|
89.7
|
|
BL x.2
|
12.6
|
Bending magnet
|
y
|
-0.05
|
1.28
|
0.786
|
|
|
7.1
|
5.6
|
|
SB BL x.2
|
12.6
|
Superbend magnet
|
x
|
0.226
|
0.28
|
3.811
|
0.012
|
-0.04
|
26.2
|
95.8
|
|
SB BL x.2
|
12.6
|
Superbend magnet
|
y
|
0.027
|
2.28
|
0.439
|
|
|
9.5
|
4.2
|
|
BL x.3
|
17.4
|
Bending magnet
|
x
|
-0.69
|
0.48
|
3.085
|
0.027
|
0.046
|
40.3
|
89.7
|
|
BL x.3
|
17.4
|
Bending magnet
|
y
|
0.045
|
1.28
|
0.786
|
|
|
7.1
|
5.6
|
| SB BL x.3 |
17.4 |
Superbend magnet |
x |
-0.23 |
0.28 |
3.811 |
0.012 |
0.042 |
26.2 |
95.8 |
| SB BL x.3 |
17.4 |
Superbend magnet |
y |
-0.03 |
2.28 |
0.439 |
|
|
9.5 |
4.2 |
| BL x.4 |
22.6 |
Bending magnet |
x |
0.827 |
0.34 |
4.923 |
0.031 |
-0.06 |
39.4 |
116.2 |
| BL x.4 |
22.6 |
Bending magnet |
y |
-10.7 |
24.66 |
4.685 |
|
|
31.4 |
13.7 |
*These are generic lattice functions. There are small sector-to-sector variations in the parameters for a given source angle because of the distortion in the lattice functions of the superbends and the insertion devices. For more precise information, contact Christoph Steier (
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).
**Angle refers to the direction of the radiation from the source point, as shown below.
Normal Arc Lattice Function Plot
Superbend Arc Lattice Function Plot
|
