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 BPM’s immediately following correctors Advantages  Don’t care about corrector detail (calibration, hysteresis, location, alignment, ……)  Don’t 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 BPM’s.  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.