Update: Geant4 Simulations of the MICE Beamline – Absolute Normalization

1. Update:Geant4 Simulations of the MICE Beamline –Absolute Normalization Tom Roberts Illinois Institute of Technology 9/24/03 (With thanks to Paul Drumm for great assistance)

2. Updates from 9/24/03 video discussion • Target intersecting beam: 10 mm2 => 2 mm2 • Layout of beamline added • G4beamline input file added (gives geometrical details)

3. Goals • Compute the absolute normalization of the beamline • Mu/sec at Diffuser1 • Good Mu/sec through the MICE detector • Singles rates in the beamline • Generate lots of muons at Diffuser1 to use in optimization studies of the MICE detector

4. MICE Beamline Layout Diffuser1 Here B2 = 30° Decay Solenoid, 3 T Old line (ignore) Q3 B1 = 60° Q2 Q1 Angle = 25° MICE Target ISIS Beam

5. G4beamline Input File (1 of 3) # define basic parameters; startEvent comes from the commandline param pionP=300.0 muP=200.0 histoFile=$startEvent histoUpdate=100000# sigma<0 means flat distribution, that half-width beam rectangular beamWidth=4.22 beamHeight=2 meanMomentum=$pionP particle=pi+\ sigmaXp=-0.0143 sigmaYp=-0.0369 sigmaP=-55 nEvents=100000000 # define the decay solenoid; put into a group so it can be rotated (all other elements # can be rotated on their own) coil default material=Cu dR=5.0 dZ=5.0coil Decay innerRadius=200.0 outerRadius=250.0 length=5000.0solenoid DecayS coilName=Decay current=47.94 color=1,0,0group DecaySolenoid place DecayS rename=''endgroup # define shielding. Tubs = tube solid tubs SolenoidBody innerRadius=250 outerRadius=1000 length=5000 kill=1tubs TargetShield innerRadius=101.6 outerRadius=1000 length=1 kill=1

6. G4beamline Input File (2 of 3) # define the magnets param Q1g=-1.0879963 Q2g=1.2981088 Q3g=-0.61072278 idealquad Q1 fieldLength=853.44 fieldRadius=101.6 gradient=$Q1g \ ironRadius=381 ironLength=1104.9 ironColor=0,.6,0 kill=1idealquad Q2 fieldLength=853.44 fieldRadius=101.6 gradient=$Q2g \ ironRadius=381 ironLength=1104.9 ironColor=0,0,.6 kill=1idealquad Q3 fieldLength=853.44 fieldRadius=101.6 gradient=$Q3g \ ironRadius=381 ironLength=1104.9 ironColor=0,.6,0 kill=1mappedmagnet B1 mapname=RALBend1 Bfield=-0.9646 \ fieldWidth=660.4 fieldHeight=152 fieldLength=2000 fieldColor='' \ ironLength=1397 ironHeight=1320 ironWidth=1981 ironColor=1,1,0 kill=1mappedmagnet B2 mapname=RALBend1 Bfield=-0.3512 \ fieldWidth=660.4 fieldHeight=152 fieldLength=2000 fieldColor='' \ ironLength=1397 ironHeight=1320 ironWidth=1981 ironColor=1,1,0 kill=1 # define detectors (tracks which intersect them are put into an NTuple) detector Diffuser1 radius=250 length=1.0 color=0,1,1asciifile Diffuser1a radius=250 length=1.0 file=$startEvent

7. G4beamline Input File (2 of 3) # Place the defined elements into the beamline. # The z coordinate is the centerline of the beamline; x=beam left, y=up. # Each corner bends the beamline appropriately (Y30 => rotate around y by 30 degrees) place TargetShield z=2441place Q1 z=3000place Q2 z=4400place Q3 z=5800place B1 z=7855.8 rotation=Y30.0 x=250corner B1c z=8000 rotation=Y60.0place DecaySolenoid z=12200place SolenoidBody z=12200place B2 z=16135 rotation=Y15.8 x=175corner B2c z=16185 rotation=Y31.7place Diffuser1 z=18800place Diffuser1a z=18801

8. The Bottom Line Protons/sec in accelerator: 3.7×1016 Protons/sec intersecting target: 1.7×1012 Pions/sec into beamline accept.: 3.0×106 Pi+ + Mu+ /sec at Diffuser1: 37k Mu+/sec at Diffuser1: 25k Good Mu+/sec through the detector: 54 All of these “per sec” occur during the 1 ms per second when our target is in the beam and our RF is active.

9. Comparison to the MICE proposal • Mu+/sec at Diffuser1: • MICE Proposal: 3,000 • This computation: 25,000 • Major differences: • 700 MeV/c protons → 800 MeV/c • Target geometry: • Height = 2 mm → 10 mm • Diffuser1 geometry: • r=20 cm → 25 cm • Diffuser1-B2 = 3 m → 2 m • These differences account for a factor of ~6

10. The Details (1 of 2)

11. The Details (2 of 2)

12. Additional Slides(From my 7/30/03 talk) The following plots are all at Diffuser1.

13. MICE Beam Layout and Tune • Layout from “LAYOUT-MICE 14May03” • Bend 1 is 60°, Bend 2 is 30° • Target to Diffuser1 is 18.8 m • Quad (Type IV) and Bending Magnet (Type I) parameters are from RAL drawings and tables. • Fringe fields for Bending Magnets were computed via Laplace’s equation; quads are ideal (no fringe fields). • Bend 1 is tuned for 300 MeV/c pions • Bend 2 is tuned for 200 MeV/c muons • Quads are tuned for maximum mu/pi ratio at Diffuser1 (using minuit) – the triplet is configured DFD (~20% better than FDF) • Target re-oriented so a long edge is along the beam.

14. Input Beam • Pi+ beam • 200 MeV/c < P < 400 MeV/c (uniform) • dxdz and dydz generated to cover Q1 aperture (uniform) • Target is 10 mm high, 10*cos(25°) mm wide (uniform) • All materials kill tracks instantly, without secondaries

15. Momentum at Diffuser1

16. P at Q1 for mu+ at Diffuser1

17. Mu+ Correlation Matrix (normalized) P < 250 MeV/c

18. Mu+ X vs Y

19. Pi+ X vs Y

20. Mu+ X vs P

21. Pi+ X vs P

22. Mu+ X’ vs P Note where X’=0 is.

23. Pi+ X’ vs P Note where X’=0 is.

24. Mu+ X vs X’ Note where X’=0 is.

25. Pi+ X vs X’ Note where X’=0 is.