Orbit Response Matrix Studies PEP-II MAC 14-Dec-2004 P. Tenenbaum

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM ORM Participants M. Donald, K. Sonnad, C. Steier, PT, J. Turner, U. Wienands, A. Wolski, M. Woodley, G. Yocky P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM Brief Introduction “Orbit Response Matrix” (ORM) technique: method for deducing gradient errors in a storage ring A subset of ring correctors is varied The change in the closed orbit is measured Orbit Response Matrix C defined as change in orbit at BPM i per unit excitation of corrector j,  i,j Tune a model lattice until model of C matches measured C P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

Getting and Analyzing Data Data acquisition driven by scripts on control system mainframe both HER and LER scripts exist Vary all selected correctors, read out all BPMs Analysis tool = LOCO (“Linear Optics from Closed Orbits”) Matlab application Uses AT (Matlab “Accelerator Toolkit”) for accelerator model HER: analysis performed on pepoptics (though some preprocessing occurs on my PC) LER: analysis performed on Solaris workstation @ LBL P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

Getting and Analyzing Data (2) LOCO computes d(Cij)/dAk  fit parameters Ak Result is a new design matrix, size = (sizeof C) x (# fit parameters) Design matrix allows LOCO to estimate fit parameter values which minimize difference between measured and model C Iterative after 3-8 iterations χ2 reaches a minimum value P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM Size of the Dataset Size of C = # BPM channels x # Correctors HER: 514 x 287 = 148,379 LER: 424 x 290 = 122,960 Each BPM channel and each corrector has 2 fit parameters (scale factor and coupling) HER Design Matrix = 237 M values, 1.9 GByte! LER: 176 M values, 1.4 GByte! Before adding parameters for quad strengths! P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM Size of the Dataset (2) Computation time not limiting, but: 2 GByte is at or beyond the practical limit for a 32-bit application (Matlab) on a 32-bit OS Strategies for Mitigation: Iterate: fit BPM scale/coupling on 1 iteration, corrector scale/coupling on the next (LER) Reduce: Cut some redundant (arc) correctors and single-view BPMs (HER) Both work, though tests of cutting BPMs and correctors in LER were disappointing P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

MAC Recommendations from April 2004 “Maintain/Increase efforts to develop accurate and usable optics model of the rings.” (Priority 1) “Identify sources of HER beta beat and fix or incorporate in the design optics.” (Priority 2) “Optimize measurement-analysis-correction loop for both speed and effectiveness.” (Priority 2) P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

Progress on HER (since last MAC) Took one new dataset, 10-June-2004 poor data quality Main activities: Optimization of the Fitting Procedure Developing tools for information exchange AT and MAD AT and online characterizations Scale-factor (“fudge”) configurations Streamlining the analysis procedure P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

HER: Fitting Procedure Which parameters to fit? For the present, agreed to fit 1 scale factor per quad power supply Total of 84 (compare to ~1,100 BPM/dipole pars) limits memory usage and speeds execution Trivial to translate to “PS fudge factor” configuration Doesn’t fully answer the question, “What is wrong with my accelerator?”, but rather, “What’s the best way to fix my accelerator?” Fit is performed using measured orbit Online (MCC/pepoptics) tools generate starting model from PS, orbit data P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

HER: Information exchange AT/MAD Allow optics experts to use “fitted” optics as a starting point for MAD modelling Error-catching – “When I run your AT optics in MAD my phase advance is different, something is wrong!” AT/Characterization Comparison to phase/coupling information gives confidence that AT/LOCO “know what they are talking about” P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM HER: AT/MAD Point-to-point betatron phase advance comparison between AT and MAD, 10-June-2004 Fitted Optics P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

HER: AT/Characterization Some examples of comparison: Fitted model tunes, C12bar versus measured from characterization process P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

HER: Scale Factor Configs Done! Software written – scale factors are included when computing optics starting from PS settings Scale factor configs implemented Procedure for generating more ~trivial P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM HER: Streamlining Complete script / “cheat sheet” Human intervention minimized Execution speed test performed 08-Oct-2004, completed analysis in 3 hrs, 10 minutes (actual LOCO computation time was about 1 hour, 20 minutes) P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

Progress on LER (Since last MAC) No additional ORM data taken Main activities: Optimization of the Fitting Procedure AT/MAD interchange transfer of fit parameters to MAD comparison of AT/MAD models with fit parameters transferred P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

LER: Fitting Procedure Similar to HER one fit parameter per power supply, “effective fit” exception: some PS fudges not well determined, set of fit parameters adjusted to avoid “fighting fudges” Actual orbit used for fit (can be different from design) Complication: sextupole feed-downs Quality of fit is significantly better when normal and skew quad terms in sextupoles are used as fit parameters But there’s no sensible way to implement this in the fudge config system Leave out these terms, try to address through BBA and better orbit control P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

LER: AT/MAD comparison P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

LER: AT/Characterization P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM Summary: Where we Are HER: Getting close to a “turnkey” system Expect to take and analyze data in a single shift Fudge factors generated directly LER: Procedures improved Expect an overnight turnaround for analysis P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM Further Improvements HER: migrate tools on PT’s PC to pepoptics Entire operation can be performed on central servers Train additional people to perform analysis LER: migrate tools from LBL Solaris workstation to pepoptics Push to a similar state of “quick and simple” operation P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM Improvements Both rings Consider migrating to 64-bit linux server running Matlab R14SP1 (64-bit version) Allows up to 2 billion double-precision real numbers in a single matrix (recall that we already cannot cope with 200 million) Expand fit parameter set Go to 1 parameter/magnet? Need to think about how to use this information even if we can get it P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM

Response to Recommendations “Maintain/Increase efforts to develop accurate and usable optics model of the rings.” (Priority 1) “Identify sources of HER beta beat and fix or incorporate in the design optics.” (Priority 2) “Optimize measurement-analysis-correction loop for both speed and effectiveness.” (Priority 2) We have increased our efforts. They have not yet reached fruition, but we anticipate that we will perform ORM early in Run 5 and put the results to work immediately. Not yet done. Much progress has been made here, although more remains to be done. P. Tenenbaum -- PEP-II MAC 14-Dec-2004 -- ORM