Pion Production / Capture

1. Pion Production / Capture M. Yoshida (Osaka Univ.) COMET/Mu2e Joint Workshop Jan. 23, 2009, LBNL

2. Pions at Target Forward • MARS simulation • Count pions at target surface • Compare momentum distribution for Tungsten, Gold, Copper and Graphite • Heavy material has softer distributions Backward

3. Pion Production in MARS/QGSP Backward pions QGSP_BIC MARS • Compare pion yields in tungsten for MARS and QGSP_BIC • # of backward pions in MARS is half of that in QGSP_BIC Forward pions QGSP_BIC MARS

4. Pion capture solenoid • Simple as consisting of 4 coils • Inner bore diameter is 1m - 1.34m • Capture low-energy pions in 5T solenoid field • Collect backward pions • Energy deposit on superconducting coil of capture solenoid should be << 100W • Thin solenoid coil of Al-stabilized SC to reduce cold mass • Thick radiation shield surrounding target • Matching to subsequent transport solenoid • Gradient from 5T to 2T • Inject proton beam at coil gap • Tilt target by 10 deg.

5. 300 600 1200 1400 300 1340 1220 1000 1908 kAT 6720 kAT 954 kAT 1140 kAT Pion Capture Solenoid System To transport solenoid 

6. Radiation on capture coil 0.6 MGy/8x1020protons • SC coil • Density 4g/cm3 • Thickness 60mm (50cm<R<56cm) • Heat load • 30cm-thick tungsten shield inserted • 2x10-5 W/g for 8GeV x 7microA • 10W on coil • Radiation dose • 0.6 MGy for 8x1020 protons 10W 30cm 7kW Graphite: 2kW Tungsten: 3kW

7. Target geometry • Production and transport in MARS simulation down to 3m from target

8. Target position B@target=3.75T B@target=5T • Generate pions by MARS, 500k protons • Tracking to 17m downstream from target in G4Beamline • Straight transport solenoid • 22% more muon yield at Dz=250mm • Need to estimate radiation on coil • Cooling • Radiation damage • Large bore • Target will be shifted by Dz=250mm in the following studies 4.8T 4.99T 3.75T 4.5T 4.9T 5T Target position Dz (mm)

9. Tracking in MARS / G4Beamline • So far, Pions are generated and transported in MARS to 3m downstream, and input them to G4Beamline • Difference in muon momentum distribution • In the following studies, generate particles by MARS, transport by G4Beamline.

10. Yields at z=3m MARS pion 0.0194 muon 0.0234 • Count pions and muons at z=3meter in R<180cm • Muon fraction at 3m downstream from target = 45% (MARS) QGSP_BIC pion 0.0436 muon 0.0473

11. Time spectrum at z=3m MARS pion muon pion muon • MARS production + G4Beamline tracking • Distributions at z=3m from target • Long tale • 0.0027/0.043=6% in 100ns-200ns 6% time (ns)

12. all muons stopping muons Muons at z=17m • MARS production + G4Beamline transport • Transport in straight solenoid 17m down to stopping target • incoming muons • 0.032 muons/proton • Stopping muons • 0.0034 muons/proton • Many muons arrive in measurement time window • need to optimize transport solenoid to select muons momentum (MeV/c) time (ns)

13. Summary • Pion yield in various material • Tungsten/Gold yield • Pion production in MARS and QGSP_BIC is compared • MARS yield half in backward pions • Investigating tracking in MARS and G4Beamline • MARS production + G4Beamline tracking produce 0.043 p-+m- (0.019 m-) / proton at entrance of transport solenoid (z=3m) • Long tale in arrival time distributions at stopping target • need to optimize transport solenoid