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Storage Ring Parameters Print
Friday, 18 June 2010 19:33

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