Target R&D for JHF neutrino KEK Yoshinari Hayato
Introduction Target for K2K No Problem JHF neutrino Al 3cmf x 660mm Embedded in the horn Cooled by water No Problem JHF neutrino Maximum energy deposit of aluminum target (3cmf)
Target for JHF neutrino Solid target Easy to handle Heat (melting point) Thermal shock Carbon Target Melting point Thermal conductivity Thermal expansion
Determination of the size (radius) of the target Yield of pions (=neutrinos) Smaller is better ( pion absorption ) Energy concentration (heat & thermal shock) Larger radius is easier to handle Other limitations Inner radius of the horn (<~5cm) Size of the beam Larger than
Size (radius) dependence of neutrino yield Effect of the absorption of pions is fairly small current design of the beam current design of the beam f=1cm f=1cm f=2cm f=2cm f=3cm f=3cm r=1cm kjkj
Energy deposit in the target Target and beam size dependence Carbon (density ) 3cm
Heat generation in the target Parameters used in the simulation (incl. material properties of Carbon) Density Specific heat Thermal conductivity Thermal convection coefficient at the surface beam direction
Temperature in the target After 5msec (just after the spill) After 3.42sec (just before the next spill) (Z=300mm) (Z=300mm)
Time dependence of temperature Maximum temperature At the center r=0mm,z=300mm Far below the melting temperature r=1.5mm,z=300mm On the surface 4 8 12 32 (Sec.) This should be lower than for water cooling. (Thermal convection coefficient on the surface should be larger than to satisfy this condition.)
Thermal stress Small enough 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.
Summary Maximum temperature Target for JHF neutrino project Material Carbon Size radius 15mm length 1000mm (In total) Maximum temperature core (@r=0mm) on the surface Cooling method Water Dynamic thermal stress Split target