Beam Based Optics Measurements CTF3 Collaboration meeting CERN Yu-Chiu Chao, TJNAF Y. Chao 2008 CTF3 Collaboration Meeting Objectives Suite of systematic tools for validation, monitoring, and troubleshooting Efficient & Reliable Characterization of Transport Optics Efficient & Reliable Characterization of Beam Phase Space Identifying & Resolving Discrepancy with Design Y. Chao 2008 CTF3 Collaboration Meeting Importance of Ensuring Model Agreement with Reality Meeting beam quality/stability requirements to a higher degree Predictable and tractable tuning procedures away from baseline Orbit Linear and higher order transport Multiple pass tuning Y. Chao 2008 CTF3 Collaboration Meeting Characterizing Transport Optics Difference orbit measurement with high precision and rigorous error analysis Complete & even coverage of phase space Observability of the monitoring configuration Customized optics to enhance signal observability, corrector orthogonality, and isolate sources of error Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics Suite of correctors generating difference orbits forming even, complete coverage of phase space Initial orbit coordinates determined by BPMs immediately following correctors Advantages Dont care about corrector detail (calibration, hysteresis, location, alignment, ) Dont care about incoming orbit jitter Can perform rigorous error analysis BPMsCorrectors X X X M Y. Chao 2008 CTF3 Collaboration Meeting Emittance of macro-beam is exactly preserved. Deviation from decoupled symplectic transport can be detected. Transport Optics Emittance should be the same for any subset of BPMs. Deviation from constant 4D emittance signifies further problems. XY Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics Courant Snyder mismatch factor of macro-beam w.r.t. Design Optics Constant CS implies correct transport of Design beam. Deviation indicates optical error. Good phase space coverage is critical. Together with betatron phase (tune) measurement, this forms sufficient and necessary condition for exactly correct local transport as design. XY Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics 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 Number of Orbits Noise to Signal Ratio Orbit Orthogonality Number of BPMs Trajectory Resolution BPMsCorrectors M BPMs Error Covariance between Measured Matrix Elements PQ Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics Example of 2D and 4D global transfer matrix (LHC TI8) with error Simulation of same measurements in CTF3 with RMS errors needs be done. Optics Element (BPM etc.) configuration Measurement errors Y. Chao 2008 CTF3 Collaboration Meeting X X Transport Optics Orbit launched in TL1 Initial trajectory coordinates measured at CR start Diagonally reflected scan pattern to combat pulse- to-pulse jitter, and increase signal amplitude. Diff. Orbit Amplitudes Conventional vs Diagonal reflection Corrector Scan Pattern Orbit Monitored in Entire CR Initial Trajectory Coordinates Determined X X Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics Customized optics - Combiner Ring Reduced betatron phase advance Reduced optical sensitivity more robust measurement Symmetric closed optics suitable for multi-turn measurements (C. Biscari) Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics Customized optics - Combiner Ring debugging 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 Simulation in CTF3 with realistic configuration & errors needs be done to evaluate effectiveness and impact, and to identify signatures of distinct errors. Y. Chao 2008 CTF3 Collaboration Meeting 3 correctors - closer to CR - larger kicks 2 correctors - farther from CR - smaller kicks 3 correctors - closer to CR - smaller kicks Transport Optics Customized optics TL1 Optics shaped to allow easy orthogonal coverage of phase space by correctors START & END X X Position = 2.5 mm Angle = 0.3 CR.BPI0130 Y. Chao 2008 CTF3 Collaboration Meeting Transport Optics Difference Orbit across Linac to Delay Loop 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 CTF3 Collaboration Meeting Characterizing Beam Phase Space Customized optics optimizing signal orthogonality More robust measurement Software accounting for both optics Customized optics optimizing signal orthogonality More robust measurement Software accounting for both optics Rigorous error analysis More than Twiss parameters Transport optics characterization is an integral part Especially for matching. Transport optics characterization is an integral part Especially for matching. Y. Chao 2008 CTF3 Collaboration Meeting Beam Phase Space Examples of OTR Based Beam Profile Measurement (LHC TI8) Orthogonality of the measurement system has been verified. Y. Chao 2008 CTF3 Collaboration Meeting Decoupled Tuning and Matching Efficient modular procedures need be worked out, simulated, tested, implemented. Configuration change? Y. Chao 2008 CTF3 Collaboration Meeting Task Ahead Production grade applications for diagnosing / tuning Production grade applications for real time monitoring Configuration improvements Enhanced + Additional signals Decoupled knobs Need to work with software experts Y. Chao 2008 CTF3 Collaboration Meeting Summary Proposed systematic procedures for ensuring model adherence of beam transport and phase space characteristics. Techniques have to be iteratively debugged on-line. Pre-emptive simulation can save time & efforts.