JHF2K neutrino beam line A. K. Ichikawa KEK 2002/7/2 Overview Primary Proton beamline Target Decay Volume Strategy to change peak energy Summary

Overview of experiment Conventional  beam of ~1GeV Kamioka JAERI (Tokai-mura)  → x  → x disappearance  → e  → e appearance NC measurement 0.75MW 50 GeV PS Super-K: 50 kton Water Cherenkov ~Mt “Hyper Kamiokande” 4MW 50GeV PS CPV proton decay 1st Phase 2nd Phase

Off Axis Beam (ref.: BNL-E889 Proposal)  Target Horns Decay Pipe Far Det.  Quasi Monochromatic Beam  x2~3 intense than NBB Exp’ed # of evts(1yr,22.5kt) ~4500  tot ~3000  CC e contamination ~0.2% at  peak Expected spectrum (OAB2 o ) ~10 2 x (K2K)  OA3° OA2° OA1° Osc. Prob.= sin 2 (1.27  m 2 L/E )  m 2 =3x10 -3 eV 2 L=295km Tuned at oscillation maximum (OAB 2degree) osc.max.

Overview of Facility Primary Proton beamline Target Station Decay Volume 280m Near Detector SK Beam Axis 50GeV PS  pit JHF NuMI (FNAL) K2K E(GeV) Int.(10 12 ppp) Rate(Hz) Power(MW)

Overview -Primary proton beamline- Preparation section Arc R=106m Final Focusing Section  Single turn fast extraction  8 bunches/~5  s  3.3x10 14 proton/pulse  3.94 (3.64) sec cycle  1 ｙｒ ≡10 21 proton on target(POT)   =6  mm.mr

Beam loss  No way to know absolute beam loss  Assumed by HAND  Assure hands on maintenance (1W/m)  Shielding design based on the assumption  Same order as KEK-PS beam line  ~10 2 relative suppression!!  Challenging Fast ext.(kicker, septum) 1.125kW (0.15%) Matching section (ctrl’ed loss by collimator) 0.75kW (0.1%) 50GeV ring 0.5W/m

Acceptance : 60  mm.mrad (cf Acc. design = 6  mm.mr) Waist mode & normal mode. monitor V H  24  Collimator/shield Matching Point 10cm Preparation section Make the matching with the Arc. Consists of normal conducting magnets.

2cm X Y Normal Mode Matching Point beam ellipse is tilted to achieve small size. 2cm Primary Beamline –Arc- B B Q Q Bends by 3m long 4 T superconducting magnet. + 1m long Q-superconducting magnet. Bore : ~180mm  To prevent the quenching, the beam size and halo should be small. FODO lattice x 10, about 80 o bending

Beam halo study using Geant 60  mm.mr beam 1,000 events 100  mm.mr beam 500 protons Preparation section Arc Magnet geometry and field are set via data file. applicable to different beamlines.

Beam Direction For both SK and possible HK. Decay pipe

Target Station Side View Off Axis Beam Plan to change the axis by moving horns or w/ dipole after horns. OAB 2 o, 2.5 o, 3 o Service pit iron concrete

Target Graphite (or Be) is a unique solution. ← Heat problem (except for liquid target) density~1.8 g/cm 3 Interaction length79g/cm 2 (44cm) Melting point>3000 o Thermal conductivity ~ 115W/m ・ K Thermal expansion4.2×10 -6 / o C Yang Modulus ~ 1E10 Pa Sound velocity 7,400 m/s → 3.7 cm/5  s

Energy deposit in the target Graphite(  =1.81g/cm 3 ) 2cm  target,  beam =0.4cm3cm  target,  beam =0.6cm

Temperature in the target (FEM analysis) beam direction r= 0mm,z=300mm r= 1.5mm,z=300mm (Sec.) Time Evolution

Target -for 4MW- Not yet considered well. Radiation cooling, Liquid target………

Decay Volume Side View Concrete shield w/ additional 60cm thick concrete, it can accept ~4MW beam. Top view 6.6m To SK/HK OAB 2 o OAB3 o  -pit

Decay Volume –Cooling- Iron Concrete ~600 o FEM analysis for 4MW beam 53°

Collimator after Horns Side View Service pit iron concrete Important for DV z(m) W/m 3 For 0.75MW beam

Strategy to change peak energy Dipole magnet gap 1m×1m×1m One method is changing the beam axis. The other…. OAB+Bending Magnet

OAB vs OAB+Bending No need to access target and horns. Easy to change the peak energy By T.Oyabu

Summary JHF will produce 0.75 MW 50 GeV proton beam. Quasi Monochromatic Beam with off-axis method. Peak Energy can be tuned by changing axis or w/ bending magnet. Facility is being designed to accept 0.75 MW beam while keeping extendibility for 4 MW beam.

Supplement

2cm Y X Waist mode

Total Length=37.5m 120mm  200m  120mm  4m 3cm Applicable to 6  mm.mr<  <24  mm.mr Vertical bending magnets Arc section

Size (radius) dependence of neutrino yield  =1cm  =2cm  =3cm  =1cm  =2cm  =3cm

Al target Maximum energy deposit of aluminum target (3cm  ) → 290°/pulse

Thermal stress Pressure Young modulus Poisson ratio Linear expansion rate Temperature Small enough Simulation results (by ANSYS) are almost consistent (or smaller). Dynamic thermal stress can be reduced by splitting the target in a few cm pieces.