MICE Beamline Design and Commissioning Review 16 th Nov 2007 Slide 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
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: - PowerPoint PPT Presentation
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MICE Beamline Design and Commissioning Review16th Nov 2007 Slide 1
Simulation comparison / tools / issues
Henry NebrenskyBrunel 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 Slide 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 Slide 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]
MICE Beamline Design and Commissioning Review16th Nov 2007 Slide 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 Slide 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. 2007Comparison of generic dipole fringe fields
with field map [1]
MICE Beamline Design and Commissioning Review16th Nov 2007 Slide 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 Slide 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 trajectoryAligned cuts taken, and emittance calculations
(converged on ecalc9 )Add reference G4BL decks to repository
MICE Beamline Design and Commissioning Review16th Nov 2007 Slide 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)
MICE Beamline Design and Commissioning Review16th Nov 2007 Slide 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 .