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Storage Ring Parameters Print

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 ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).

**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