ATF2 as a test bench for CLIC BDS tuning, also R. Toms and A. Latina - PowerPoint PPT Presentation

ATF2 as a test bench for CLIC BDS tuning, also R. Tomás and A. Latina (CERN) Thanks to P. Bambade and G. White ATF2 project meeting 2007 Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.1/12

Contents • Motivation: • Beam based alignment in the CLIC BDS • FFS? • ATF2 case • Tuning approach • Simulation ingredients • Results from ATF2 tuning simulations. Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.2/12

Aligning the CLIC collimation section test beam 98% nominal energy, ω 1 / ω 0 =1e5, σ bpm =0.1 µ m, misalignment 10 µ m 100 1-to-1 correction, no multipoles DFS correction, no multipoles 90 1-to-1 correction, multipoles DFS correction, multipoles nominal 80 70 ε y [nm] 60 50 40 30 20 0 20 40 60 80 100 quadrupole index 5% emittance growth after aligning only the collima- tion section. Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.3/12

Aligning the full BDS? test beam 98% nominal energy, ω 1 / ω 0 =1e5, σ bpm =0.1 µ m, misalignment 10 µ m 100 1-to-1 correction, no multipoles DFS correction, no multipoles 90 1-to-1 correction, multipoles DFS correction, multipoles nominal 80 70 ε y [nm] 60 50 40 30 20 0 20 40 60 80 100 quadrupole index Does not work. The FFS corrupts the correction in the collimation section. Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.4/12

Looking into the CLIC FFS 3 FFS BPM readings (with and without radiation) 0.2 Vertical BPM reading [ µ m] 0.1 0 -0.1 -0.2 -0.3 -0.4 0.98 0.985 0.99 0.995 1 Relative Energy (E/E 0 ) Large error due to radiation Apparent linear and non-linear vertical dispersion Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.5/12

The ATF2 FFS 3 ATF2 FFS BPMs 0 bpm1 QF1 -0.2 Vertical BPM reading [ µ m] QD0 -0.4 -0.6 -0.8 -1 -1.2 -1.4 -0.02 -0.015 -0.01 -0.005 0 0.005 dp/p Apparent linear and non-linear vertical dispersion due to the transverse particle distribution. Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.6/12

Tuning approach A 0-th order tuning algorithm based on the Simplex: • Observables: σ x and σ y at IP. • Variables: Magnet strengths, x, y and tilt displacements. First test via ATF2 simulations: • Code: PLACET-Octave • Ingredients: realistic errors but no ground motion (yet) Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.7/12

Simulation ingredients: errors • H & V misalignments with σ = 30 µ m. • Transverse roll with σ = 30 µ rad. • Relative strength error with σ = 10 − 4 . • Measurement error of σ y , σ =1nm. Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.8/12

Initial σ y for 150 seeds 16 14 12 10 Counts 8 6 4 2 0 0 0.5 1 1.5 2 2.5 3 3.5 4 Initial σ y [ µ m] Up to 4 µ m of initial σ y . Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.9/12

Number of Simplex iterations 12 10 8 Counts 6 4 2 0 500 1000 1500 2000 2500 3000 3500 Number of iterations Below 4000 iterations required (without ground mo- tion). Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.10/12

Final σ y 35 30 25 20 Counts 15 10 5 0 36 37 38 39 40 41 42 43 44 Final σ y [nm] Final σ y between 37 and 44nm. Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.11/12

Summary and such • ATF2 tuning experience is extremely valuable for CLIC. • A 0-th order tuning algorithm has been simulated with ATF2 based on the Simplex. • Initial σ y < 4 µ m gets below 44nm in less than 4000 iterations • Consistent with Glenn’s previous results • Ground motion to be included in future studies • “Realism” studies from SLAC colleagues to be observed (even more dramatic for CLIC!). Rogelio Tom´ as Garc´ ıa ATF2 as a test bench for CLIC BDS tuning, also – p.12/12