Low Emittance Tuning Tests at the Diamond Light Source (Rutherford Labs) Dec. 2010 R. Bartolini, S. Liuzzo, P. Raimondi SuperB XV Meeting Caltech, CA, Dec. 14-17 2010

Courtesy R. Bartolini

Courtesy R. Bartolini

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

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

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]

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.

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

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

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

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

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

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

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.