1. Low Emittance Tuning Tests at the Diamond Light Source (Rutherford Labs) Dec R. Bartolini, S. Liuzzo, P. Raimondi SuperB XV Meeting Caltech, CA, Dec

2. Courtesy R. Bartolini

3. Courtesy R. Bartolini

4. SuperB Tests in progress at Diamond Light Source for the
new correction schemes suggested for SuperB.
Short term goal: to compare with LOCO
Long term goal: reduce V emittance below 2 pm

5. Coupling and Beta-Beating Free Steering
New correction scheme:
Orbit and Dispersion Free Steering +
Coupling and Beta-Beating Free Steering
Measured at BPM
Pseudo Inversion (SVD) of the matrix M provides a set of correctors that should set to zero all the measured quantities. Model matrices are used and so reiteration is necessary. α and ω are relative weights.
Same is done in horizontal plane with different matrix sensible to the effect of β-beating

6. BEFORE AFTER Simulations On Diamond Lattice Vertical Emittance [m rad]
70μm rms horizontal misalignment Quadrupoles and Sextupoles
40μm rms vertical misalignment Quadrupoles and Sextupoles
50 μm rms vertical and horizontal Monitor offsets
Vertical Emittance [m rad]
DISPERSION FREE STEERING
+ Coupling and beta-beating FREE STEERING
BEFORE AFTER
<εy>=7.1*10-12 [m rad]
<εy>=7.1*10-12 [m rad]
<εy>=3.3*10-13 [m rad]
<εy>=5.3*10-12 [m rad]

7. TESTS at Diamond Light Source (UK)
(23rd Nov and 7th Dec 2010)
Tested:
CFS using vertical steerers
CFS using skew quadrupoles
Different correctors for the calculation of coupling vectors.
Monitor tilts (previously measured by LOCO) are taken into account in all measurements.

8. CFS Correction with vertical correctors
Correction reiteration
converges
first for dispersion
then for coupling
and for orbit.
1 mm rms vertical dispersion
10 μm rms vertical orbit
0.24% coupling measured
At end of reiterations

9. Test of the choice of ORM columns used for correction.
Red line shows which
corrector is being
used for calculations.
Changing the corrector
used to evaluate coupling,
And then
reiterating correction,
Does not improve
orbit and dispersion.
May be correctors tilts

10. CFS Correction with Skew Quadrupoles
DY ≈ 600 μm
Coupling 0.23%

11. Beam sizes at the two pinhole cameras
During correction with skew quadrupoles X1 X2
preliminary correction Y1
Decrease in beam size
corresponds to Minimum dispersion measurements (30 and 39-40).
LOCO correction Y2

12. 10 μm orbit and 0.24% coupling.
H Emittance measurement not ok due to change in optics

13. Comparison with LOCO Vertical dispersion very small (Diamond record)
Best seen emittance about 2.5 times larger than LOCO record
Tried LOCO correction on the same machine and obtained slightly (20%) worst performances.
To be investigated what is limiting the present performances (e.g. Vertical tune much closer to the integer now (Qy=0.1) w.r.t the past one (Qy=0.37))
In addition predicted emittance from simulated data (with realistic errors) much lower (about factor 10) than achieved

14. Conclusions
Vertical correction or Skew Quadrupoles correction using Coupling Free Steering provide 0.23%-0.24% emittance coupling and rms vertical Dispersion of 600 μm - 1mm after few reiterations.
NEXT STEPS
Evaluation of coupling with different correctors spoils preceding correction. May be tilted correctors. Next we will consider more coupling vectors at the same time to average tilts effects.
Simultaneous correction with skew quadrupole and vertical correctors.
Test horizontal correction (also beta-beating constrained)
Monitor tilt detection from measurements introduced but not tested.