1. “WISE” Simulation of optical imperfections in LHC P. Hagen AT/MCS Acknowledgements: Colleagues in AT/MAS, AT/MEL, AT/MTM, AB/ABP CERN, October 2006

2. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS2 Motivation ( raison d’être ) “WISE” : What is it? Visual walk through Remarks about implementation Future outlook ( perspectives ) Outline

3. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS3 It is easy to compare measurements against tolerances But it is more difficult to relate imperfections to the final product, that is, the impact on the beams in the LHC accelerator The production of the magnets follow a rigorous QA-plan with several magnetic and geometry measurements; during production and the final “cold” tests in CERN. Some of this data is useful for the LHC commissioning rather than a bi-product of the production process (ending its useful life in an archive) Numeric simulation programs are complementary to analytic estimates. Motivation

4. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS4 WISE : What is it? WISE is a simulation program which tries to assign realistic magnet field and geometry errors to magnets It uses measurements when available It “draws” measurements when needed based upon statistics for the magnet types Uncertainties are “drawn” from tables It is a pre-processor to MAD-X Data driven by numerous tables

5. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS5 Software wise … Implemented as macros in Microsoft Excel using classic Visual Basic code Information from many sources stored in local worksheets: LHC optics layout from Oracle database Magnetic (warm+cold) and geometry measurements from Oracle Slot allocation (MTF+web pages) Calculated tables not known to be available elsewhere (like statistical information about measurement uncertainty) Convenient to store information in Excel sheets (debugging, data verification, execution speed)

6. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS6 Software unwise … Code is growing more than expected (always another feature to add…) OK if you run simulation on the PC desktop, but… cannot be integrated into a web application or easily be called from another application as a library or be turned into an reliable, server process accessible via a network protocol

7. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS7 Installation database Layout + MEB slot allocation Database with warm magnetic measurements Database with cold magnetic measurements WISE generator of magnetic + geometry imperfections Configurable options: (magnets types, optics, error types)… MAD-X LHC machine calculations Nominal LHC sequence and optics definitions. ) Twiss optics calculations ( β-beat, closed orbit …) Simulation block diagram Database with geometry measurements

8. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS8 Short walk through … WISE is run on the PC desktop This is the main menu WISE is run on the PC desktop This is the main menu

9. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS9 Transfer the output from WISE to UNIX using the AFS client software

10. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS10 WISE creates a UNIX batch job for each beam. The main.madx scripts reads magnetic field errors from a TFS table … WISE creates a UNIX batch job for each beam. The main.madx scripts reads magnetic field errors from a TFS table …

11. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS11.. The alignment errors of individual magnets are in another TFS table. The misalignment of cryostats in tunnel are done by a.madx script … The misalignment of cryostats in tunnel are done by a.madx script ….. The alignment errors of individual magnets are in another TFS table. The misalignment of cryostats in tunnel are done by a.madx script … The misalignment of cryostats in tunnel are done by a.madx script …

12. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS12 Per, you forgot to power the MB spool pieces… This is needed to see the b3 feed- down effect when misaligning the cryostats. Per, you forgot to power the MB spool pieces… This is needed to see the b3 feed- down effect when misaligning the cryostats. OK, I will add “it”, based upon the known b3 errors in the MB. OK,

13. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS13 30 iterations of simulation currently takes a few hours. Assigning errors takes 99% of time. The Twiss matrix calculations goes in a few secs

14. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS14 Harvesting the result (Twiss). We compute the beta-beating by comparing the simulation to an unperturbed machine

15. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS15 Remarks about simulation algorithm The slot allocation is drawn when needed (> 90% known from pre-allocatins) Presedence of measurements: Cold measurements (highest) Warm measurement (cold mass) + warm-to-cold correlation Gaussian-draw based upon statistics (real or estimated) Compensation for common error in main field for magnets on same power supply Magnetic history – uncertainty for each magnet Magnet class (MQ, MQX…). Shared uncertainty related to measurement system (drawn once for each run)

16. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS16 Other important remarks Many sources of information makes the code unnecessary complex. Code and data sources must be validated by experts. Thanks to all my colleagues in various AT groups + AB/ABP Semi-automatic update of optics layout (fortunately no big changes last years) Static cycle model: Either “injection” or “collision”. Could have used FiDel for getting errors

17. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS17 Future outlook The implementation of geometry errors is still in the early days. In particular the work of validating the model and measurement data has just started. Missing measurement data for correctors and some warm magnets. Simulation of error correction (closed orbit, tunes, coupling…) First of all, the needs for “missing features” need to be agreed upon

18. Simulation of optical imperfections in LHC October 2006Per Hagen, AT/MCS18 References Chamonix 2006 http://cern.ch/ab- div/Conferences/Chamonix/Chamx2006/PAPERS/SS_4_02.pdf EPAC 2006 http://cern.ch/accelconf/e06/Pre-Press/WEPCH139.pdf Closed orbit correction