Beam Based Optics Measurements CTF 3 Collaboration meeting

Beam Based Optics Measurements CTF 3 Collaboration meeting 21. 1. - 23. 1. 2008 CERN Yu-Chiu Chao, TJNAF

Objectives Ø Suite of systematic tools for validation, monitoring, and troubleshooting Ø Efficient & Reliable Characterization of Transport Optics Ø Efficient & Reliable Characterization of Beam Phase Space Ø Identifying & Resolving Discrepancy with Design Y. Chao 2008 CTF 3 Collaboration Meeting

Importance of Ensuring Model Agreement with Reality Ø Meeting beam quality/stability requirements to a higher degree Ø Predictable and tractable tuning procedures away from baseline ØOrbit ØLinear and higher order transport ØMultiple pass tuning Y. Chao 2008 CTF 3 Collaboration Meeting

Characterizing Transport Optics Difference orbit measurement with high precision and rigorous error analysis Ø Complete & even coverage of phase space Ø Observability of the monitoring configuration Ø Customized optics to enhance signal observability, corrector orthogonality, and isolate sources of error Ø Y. Chao 2008 CTF 3 Collaboration Meeting

Transport Optics Ø Ø Suite of correctors generating difference orbits forming even, complete coverage of phase space Initial orbit coordinates determined by BPM’s immediately following correctors Advantages X’ X’ § Don’t care about corrector detail (calibration, hysteresis, location, alignment, ……) XX § Don’t care about incoming orbit jitter Correctors BPMs M § Can perform rigorous error analysis Y. Chao 2008 CTF 3 Collaboration Meeting

Transport Optics Emittance of macro-beam is exactly preserved. Deviation from decoupled symplectic transport can be detected. Ø Ø X Ø Ø Y Emittance should be the same for any subset of BPM’s. Deviation from constant 4 D emittance signifies further problems. Y. Chao 2008 CTF 3 Collaboration Meeting

Transport Optics Ø Ø Courant Snyder mismatch factor of macro-beam w. r. t. Design Optics Constant CS implies correct transport of Design beam. Deviation indicates optical error. X Ø Ø Y Good phase space coverage is critical. Together with betatron phase (tune) measurement, this forms sufficient and Y. Chao necessary condition for exactly correct transport as design. 2008 CTF 3 local Collaboration Meeting

Transport Optics Ø Ø Ø Global transfer matrix determination Orbits on both ends determined on equal footing Rigorous error analysis Orthogonal phase space coverage Large signal-to-noise ratio Symplectification M P Correctors BPMs Error Covariance between Measured Matrix Elements Number of Orbits Orbit Orthogonality Noise to Signal Ratio Number of BPMs Q Trajectory Resolution Y. Chao 2008 CTF 3 Collaboration Meeting

Transport Optics Example of 2 D and 4 D global transfer matrix (LHC TI 8) with error Ø Simulation of same measurements in CTF 3 with RMS errors needs be done. Ø Optics Ø Element (BPM etc. ) configuration Y. Chao Ø Measurement errors 2008 CTF 3 Collaboration Meeting

Transport Optics Ø Ø Ø Orbit launched in TL 1 Initial trajectory coordinates measured at CR start Diagonally reflected scan pattern to combat pulseto-pulse jitter, and increase signal amplitude. X’ Diff. Orbit Amplitudes Conventional vs Diagonal reflection X’ X Corrector Scan Pattern X Initial Trajectory Coordinates Determined Orbit Monitored in Entire CR Y. Chao 2008 CTF 3 Collaboration Meeting

Transport Optics Customized optics - Combiner Ring Ø Ø Reduced betatron phase advance Reduced optical sensitivity more robust measurement Symmetric closed optics suitable for multi-turn measurements (C. Biscari) Y. Chao 2008 CTF 3 Collaboration Meeting

Transport Optics Customized optics - Combiner Ring debugging Ø Ø Optics established with different quad families switched off in turn to isolate individual effects One-turn optics (no respect for symmetry, isochronicity, etc. )with pronounced betatron & dispersion responses Ø Simulation in CTF 3 with realistic configuration & errors needs be done to Y. Chao evaluate effectiveness and impact, and to identify signatures of distinct errors. 2008 CTF 3 Collaboration Meeting

Transport Optics Customized optics – TL 1 Ø Optics shaped to allow easy orthogonal coverage of phase space by correctors X’ Ø 3 correctors - closer to CR - larger kicks X Ø 2 correctors - farther from CR - smaller kicks Ø 3 correctors - closer to CR - smaller kicks Y. Chao 2008 CTF 3 Collaboration Meeting START & END Position = 2. 5 mm Angle = 0. 3 mrad @ CR. BPI 0130

Transport Optics Difference Orbit across Linac to Delay Loop Ø Ø Verify/Correct transport Verify momentum profile (damping of macro particle emittance) Global transfer matrix used for Twiss matching Same degree of detail to be worked out Y. Chao 2008 CTF 3 Collaboration Meeting

Characterizing Beam Phase Space Customized optics optimizing signal orthogonality More robust measurement Software accounting for both optics Ø Rigorous error analysis Ø More than Twiss parameters Ø Transport optics characterization is an integral part Especially for matching. Ø Y. Chao 2008 CTF 3 Collaboration Meeting

Beam Phase Space Examples of OTR Based Beam Profile Measurement (LHC TI 8) Ø Orthogonality of the measurement system has been verified. Y. Chao 2008 CTF 3 Collaboration Meeting

Task Ahead Production grade applications for diagnosing / tuning Ø Production grade applications for real time monitoring Ø Configuration improvements Ø ØEnhanced + Additional signals ØDecoupled knobs Ø Need to work with software experts Y. Chao 2008 CTF 3 Collaboration Meeting

Summary Proposed systematic procedures for ensuring model adherence of beam transport and phase space characteristics. Ø Techniques have to be iteratively debugged on -line. Ø Pre-emptive simulation can save time & efforts. Ø Y. Chao 2008 CTF 3 Collaboration Meeting