ALS Storage Ring Parameters
1. General Parameters
| Parameter | Value |
|---|---|
| Beam particle | electron |
| Beam energy | 1.0-1.9 GeV |
| Injection energy | 1.0-1.5 GeV |
| Beam current | 400 mA in multibunch mode 2 x 25 mA in two-bunch mode |
| Filling pattern (multibunch mode) | 276-320 bunches; possibility of 10-mA "camshaft" bunch in filling gap |
| Bunch spacing: multibunch mode |
2 ns |
| Bunch spacing: two-bunch mode |
328 ns |
| Circumference | 196.8 m |
| Number of straight sections | 12 |
| Current number of insertion devices | 10 |
| Radio frequency | 499.642 MHz |
| Beam size in straight sections, rms (1.9 GeV multibunch mode) | 310 microns horiz. x 16 microns vert. |
| Parameter | Value at 1.5 GeV | Value at 1.9 GeV |
|---|---|---|
| Beam lifetime: multibunch mode |
~3.5 hrs at 400 mA | ~8 hrs at 400 mA |
| Beam lifetime: two-bunch mode |
not used | ~60 min. at 40 mA |
| Horizontal emittance | 4.2 nm-rad | 6.3 nm-rad |
| Vertical emittance* | 0.2 nm-rad | 0.13 nm-rad |
| Energy spread (ΔE/E, rms) | 8 x 10-4 | 1 x 10-3† |
| Pulse Length (FWHM) | 65 ps | 70 ps‡ |
*Vertical emittance deliberately increased to improve Touschek lifetime.
† 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 and decreases from about 70 ps at high bunch current
to below 40 ps at small current.
The ALS has 12 straight sections and 12 arc-shaped sections, like the one shown above, containing bend magnets (B), quadrupoles (QFA, QDA, QF, and QD), and sextupoles (SF and SD). Three of the arc sections contain superconducting bend magnets (superbends) and therefore have a modified lattice as shown in the lower image.
2. 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*
| Angle and Source** | Axis | α | β(m) | γ(m-1) | ηx (m) | ηx' | σ (µm, 1.5 GeV) | σ' (µrad, 1.5 GeV) | σ (µm, 1.9 GeV) | σ' (µrad, 1.9 GeV) |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.0 degrees, insertion device | x | 0.0 | 13.6 | 0.075 | 0.06 | 0.0 | 240 | 18 | 310 | 23 |
| 0.0 degrees, insertion device | y | 0.0 | 3.6 | 0.28 | 27 | 7.5 | 23 | 6.5 | ||
| 6.3 degrees, bending magnet | x | -0.03 | 0.35 | 2.8 | 0.03 | 0.09 | 45 | 130 | 57 | 160 |
| 6.3 degrees, bending magnet | y | 6.36 | 19.4 | 2.15 | 62 | 21 | 54 | 18 | ||
| 12.6 degrees, bending magnet | x | 0.39 | 0.9 | 1.3 | 0.07 | -0.05 | 83 | 84 | 100 | 110 |
| 12.6 degrees, bending magnet | y | -0.13 | 1.6 | 0.63 | 18 | 11 | 15 | 9.7 | ||
| 12.6 degrees, superbend magnet | x | 0.035 | 0.95 | 1.05 | 0.057 | -0.04 | 78 | 74 | 98 | 93 |
| 12.6 degrees, superbend magnet | y | 0.04 | 1.50 | 0.68 | 17 | 12 | 15 | 10 | ||
| 17.4 degrees, bending magnet | x | -0.39 | 0.88 | 1.3 | 0.07 | 0.05 | 83 | 84 | 100 | 110 |
| 17.4 degrees, bending magnet | y | 0.13 | 1.6 | 0.63 | 18 | 11 | 15 | 9.7 | ||
| 17.4 degrees, superbend magnet |
x | -0.035 | 0.95 | 1.05 | 0.057 | 0.04 | 78 | 74 | 98 | 93 |
| 17.4 degrees, superbend magnet | y | -0.04 | 1.50 | 0.68 | 17 | 12 | 15 | 10 | ||
| 22.6 degrees, bending magnet | x | 0.34 | 0.39 | 2.8 | 0.04 | -0.12 | 52 | 140 | 65 | 180 |
| 22.6 degrees, bending magnet | y | -7.50 | 18.1 | 3.15 | 60 | 25 | 52 | 22 |
*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 Cristoph
Steier (csteier@lbl.gov).
**Angle refers to the direction of the radiation from the source point,
as shown below.
