Results Up to Run 51 (March 2009)
Beam currents up to 300 mA have safely injected and stored in the storage ring. A variety of beam currents have been used to run experiments on the VLS-PGM, SGM, HXMA, CMCF, SM, Mid IR and Far IR beamlines. Phase 2 beamlines are in various stages of installation and commissioning.
The storage ring is set up for low-By operation (see: http://www.lightsource.ca/machine/techdocuments.php - Document 5.2.69.2 ).
Stored electron current: |
300 mA (max) |
|
Lifetime(1/e) @ 100/200/300mA |
16 / 14 / 10 hours Jan 07 |
29 / 19 / 10 hours March 09 |
MACHINE PARAMETERS |
Model |
Measured |
Horizontal tune: |
10.22 |
10.22 |
Vertical tune: |
4.32 |
4.32 |
Horizontal Chromaticity: |
2 |
2 |
Vertical Chromaticity: |
4 |
4 |
Horizontal emittance (εx): |
20.5 nm-rad |
22.70 |
Vertical emittance (εy): |
0.0923 nm-rad (0.45 % coupling) |
0.1017 (0.45% coupling) |
Energy spread (δ = ΔE/E): |
0.0011 |
~0.0011 (from beam size) |
Bunch length (1 σ) |
35 ps |
34 ps (normal) / 8 ps (CSR mode) |
Straight functions: |
|
|
ηx |
0.15 m |
0.15 m (also see Fig. 2) |
ηy |
0 |
see Fig. 2 at bottom of page |
βx |
9.5 m |
see Fig. 1 at bottom of page |
βy |
2.6 m |
see Fig. 1 at bottom of page |
Horizontal beam size (1 σ) (in straight) |
456 μm |
485 μm ** |
Vertical beam size (1 σ) (in straight) |
15.4 μm (0.45 % coupling) |
16.1 μm ** |
RMS horizontal orbit position: |
~ 5 μm |
~ 5 μm |
RMS vertical orbit position |
~ 5 μm |
~ 5 μm |
RMS horizontal stability |
|
~ 3 μm |
RMS vertical stability |
|
~ 3 μm |
*** bold: latest results
Stored current and lifetime
250 mA is the normal operations maximum current.
300 mA was safely stored in January 2007. This is the maximum current that can be reached with the single SRF cavity.
Beam lifetime will improve as more beam is circulated and the vacuum chamber is conditioned.
Tunes
Horizontal and vertical tunes are adjusted with the three quadrupole families.
The tunes establish the relative electron beam size throughout the storage ring.
The design tunes establish the source sizes for which the photon beamlines have been designed.
Small adjustments to the design tunes have been made to find the best combination of maximum brightness, beam lifetime, stability and dynamic aperture.
Chromaticity
Horizontal and vertical chromaticities are adjusted with the two sextupole families.
Chromaticity is a measure of the change of tune for off-energy electrons.
To keep all electrons at the same tune the chromaticity would need to be zero.
For stability reasons the chromaticities are both adjusted to a slightly positive value, cx=2 and cy=4.
Emittance
At the design tunes the horizontal emittance should be < 20 nm-rad.
The emittance measured using the X-Ray Synchrotron Radiation (XSR) beamline indicate that the emittance is now about 22 nm-rad. (A lower emittance (~15) is possible with higher dispersion, but no advantage in beam size in the straights.) The vertical emittance is determined by the amount of coupling between the horizontal and vertical motion. The planes are decoupled by skew quadrupoles in the ring. No coupling correction is currently used, and the natural coupling for this lattice is ~ 0.45%, vertical emittance ~ 0.1 nm-rad. It is possible to reduce this to about 0.2 nm-rad (coupling 0.1%).
Beam size and position stability
Beam size is given by sqrt(ε*β+(ηδ)2) where β is a measure of the relative beam size. With the emittances and machine functions given above the beam sizes are X = 480 microns and Y = 13 microns. (These are 1 σ of a Gaussian distribution). Our 2005 design goal was to have the beam stability to be less than 10% of the beam size. With 3 micron stability, both horizontal and vertical motion meet this goal. As we go to smaller coupling and the vertical size is reduced the vertical stability will have to be improved. Stability numbers are over hours of operation and include active orbit correction. Stability at frequencies from 1 to 100 Hz have yet to be investigated.
Improvements to orbit stability have been made. The BPM feedback was originally from a Unix-based acquisition system which averaged the raw BPM data for only ~ 0.1 s per update. The four quadrants of BPMs in the ring were acquired in series and the data posted to the EPICS once per second. The upgrade consisted of switching to a different operating system (RTEMS) capable of acquiring data from each quadrant in parallel and averaging each channel for > 0.5 s before posting the data to EPICS.
Bunch length is typically 35 ps. A short bunch mode has been developed to create coherent synchrotron THz radiation. Bunch lengths < 10 ps are created by decreasing the momentum compaction (see Accelerator Activities).
Brightness
In our storage ring the brightness of the beam is proportional to the stored current and inversely proportional to the beam sizes. In the future brightness will be increased by increasing the current to (eventually) 500 mA and reducing the vertical beam size by reducing the vertical coupling.
Model and measurements
The model (DIMAD) uses magnet field measurements and power supply calibrations to calculate the beam optics. The model agrees with the measurements for the tunes, chromaticities and corrector responses. As well, RMS orbits are consistent with model calculations which assume 150 micron random misalignments on the magnetic elements.
Figure 1. Machine β functions: First two cells are shown. The other cells are similar. Functions are measured at the quadrupoles. The theory is for the complete cell. The centers of the straights are at the edges and in the middle of the plot.
Figure 2. Machine dispersion functions: First two cells are shown. The other cells are similar. Functions are measured at the BPMs. The theory is for the complete cell. The centers of the straights are at the edges and in the middle of the plot.
Last modified: 2009-04-01 13:04:19
