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Simulation comparison / tools / issues

Simulation comparison / tools / issues. Henry Nebrensky Brunel University. There are two kinds of fool. One says, 'This is old, and therefore good.' And one says, 'This is new, and therefore better.' —Dean Inge. MICE Beamline Simulation. We are using two sets of code:

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Simulation comparison / tools / issues

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  1. Simulation comparison / tools / issues Henry Nebrensky Brunel University There are two kinds of fool. One says, 'This is old, and therefore good.' And one says, 'This is new, and therefore better.' —Dean Inge MICE Beamline Design and Commissioning Review16th Nov 2007

  2. MICE Beamline Simulation We are using two sets of code: • PSI Graphic TURTLE and TRANSPORT (1st, 2nd and 3rd order matrix ray tracing and beam propagation) • Fast (min/Mpion), extensive history including use in other pion-muon decay channels • Tom Roberts’ G4beamline (Geant4 based) • New, has comprehensive scattering and trajectory physics, but slow (hours/Mpion) MICE Beamline Design and Commissioning Review16th Nov 2007

  3. Simulation differences For a beamline expected to result in a 6π emittance beam, • Turtle beam was found to be 7.1π mm rad [1] • G4beamline (G4BL) gave 11.7π mm rad [2, 3] Also significant differences in beam profile… 1. http://www-kuno.phys.sci.osaka-u.ac.jp/~yoshida/MICE-CM14/talks/cm14_28_drumm_design.ppt 2. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2006-05-31/CM14-7.1pi-200-TJR.ppt 3. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2006-08-02/CM14_200MeV_c_summary.pdf MICE Beamline Design and Commissioning Review16th Nov 2007

  4. cm MICE Beam Widths 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-03-27/AllMuonsTTlvG4BL.xls m Changing Turtle options and interpretation of its output gives a wide range of beam sizes (none matching G4BL) MICE Beamline Design and Commissioning Review16th Nov 2007

  5. Common 30 mrad beam after B2 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-06-07/TTlvG4BL_1stStage_JustNoDecData.xls Identical input beams, scattering elements removed MICE Beamline Design and Commissioning Review16th Nov 2007

  6. Common 10 mrad beam after B2 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-06-07/TTlvG4BL_1stStage_JustNoDecData.xls Stopping down the beam removes differences MICE Beamline Design and Commissioning Review16th Nov 2007

  7. Common 30 mrad beam after B2 (rev. pol.) 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-07-24/TTlvG4BL_1stStage_JustNoDecData_postCM18_2.xls N.B.Graph upside-down as quad polarities reversed (not the point… ) MICE Beamline Design and Commissioning Review16th Nov 2007

  8. Turtle only in 1st order (rev. pol.) 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-07-24/TTlvG4BL_1stStage_JustNoDecData_postCM18_2.xls Dropping higher-order term removes differences MICE Beamline Design and Commissioning Review16th Nov 2007

  9. MICE Beamline Simulation Is TURTLE correct? Is G4beamline correct? Are both codes modelling the same lattice? ( Does the model match what’s being built? ) MICE Beamline Design and Commissioning Review16th Nov 2007

  10. Is G4beamline correct? (1) A number of bugs found, including significant issues with fringe fields in both dipoles and quads[1]. 1. Tom Roberts: “G4beamline Fringe Field Study” 27th Sept. 2007 Comparison of generic dipole fringe fields with field map [1] MICE Beamline Design and Commissioning Review16th Nov 2007

  11. Is G4beamline correct? (2) Also correctly imports field maps. Use version 1.14pre or later. 1. Tom Roberts: “G4beamline Fringe Field Study” 27th Sept. 2007 Comparison of generic quad fringe field with Q35 field map[1] MICE Beamline Design and Commissioning Review16th Nov 2007

  12. Are input decks equivalent? Worked through by hand, believe they are now for Decay Solenoid and Transport Channel. Issues found in: • Dipole fringe fields • Quad apertures and fringe fields • Scattering • Reference particle trajectory Aligned cuts taken, and emittance calculations (converged on ecalc9 ) Add reference G4BL decks to repository MICE Beamline Design and Commissioning Review16th Nov 2007

  13. Is TURTLE correct? Have reverse-engineered several features! :( Turtle incorporates fringe fields by parameterising them as dimensionless integrals. • Dipole integrals (“K1”, “K2”) inconsistently documented – have decided on appropriate values [1] • Quad integrals – use example values when needed. Real quads will have mirror plates so can treat as no fringe fields.(Code to calculate is on PSI site, haven’t tried it yet) 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-01-16/K1K2Status2.ppt MICE Beamline Design and Commissioning Review16th Nov 2007

  14. Is TURTLE correct - single muon tracks Have sent single particles through a single MICE quad (Q4) with correct aperture, field strength, muon momentum etc. But: no fringe fields, and no air. Have compared Turtle running in 1st and 3rd order with 1st order equations implemented in Excel. Tested a series of cases, and looked at difference in x’ after the quad. The muon trajectories are confined to either the focussing or defocussing plane. For each case, the geometry is illustrated by just the 3rd order Turtle results in the focussing plane, followed by a graph showing the difference in x’ using the Excel 1st order model as the reference . 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-11-08/TTLvG4BL_Single_v2.pdf MICE Beamline Design and Commissioning Review16th Nov 2007

  15. MICE Beamline Design and Commissioning Review16th Nov 2007

  16. MICE Beamline Design and Commissioning Review16th Nov 2007

  17. Converging group, x’ 0 to 432 mrad MICE Beamline Design and Commissioning Review16th Nov 2007

  18. Outermost muon not scraped in 3rd order Turtle MICE Beamline Design and Commissioning Review16th Nov 2007

  19. Single muon tracks The two 1st order models give near-identical results; confirms 1st order Turtle is arithmetically correct. With 3rd order, can get ~ 2% difference in x’ per quad; compounds down beamline. Gets worse for large-amplitude particles. Is the contribution from the extra term in 3rd order Turtle correct? Will check. 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-11-08/TTLvG4BL_Single_v2.pdf MICE Beamline Design and Commissioning Review16th Nov 2007

  20. (Is the model right?) Lattice checked as part of the inter-code comparison. Kevin Tilley has added a set of “patches” to the TURTLE to overcome its limited handling of scattering, esp. from the air along the beamline. 1. http://www.isis.rl.ac.uk/accelerator/MICE/Task%20Notes%20and%20Specifications/beamline%20-%20optics/2007-01-16/K1K2Status2.ppt MICE Beamline Design and Commissioning Review16th Nov 2007

  21. Current beam size comparison Agreement in horizontal but still difference in the vertical plane MICE Beamline Design and Commissioning Review16th Nov 2007

  22. Conclusions The latest comparison for “6π” beamline: • TURTLE gives 8.4π mm rad beam • G4BL gives 8.8π mm rad beam (as seen in Kevin’s talk) (Turtle: FOR035_1s_Ptotcut_noffs.DAT) G4BL: NoFF, 10%Cut) MICE Beamline Design and Commissioning Review16th Nov 2007

  23. Further Work We have identified a need to check 3rd order Turtle; implement 3rd Order in Excel to compare (not trivial - see right) G4BL comparison? Move ref. deck repository into CVS. D.L. Smith: “Focusing Properties of Electric and Magnetic Quadrupole Lenses” NIM79 pp.144-164 (1970) MICE Beamline Design and Commissioning Review16th Nov 2007

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