J-PARC neutrino experiment Target Specification Graphite or Carbon-Carbon composite cylindrical bar : length 900mm, diameter 25~30mm The bar may be divided into several pieces. The stress generated in the target is proportional to E T where E: Yangs modulus, : linear coefficient of thermal expansion, T : temperature rise. So, we want a material which has high S/E where S is the yield strength. The quantities we concern are (density), E, , S(yield and compression strength) and resistivity against radiation. A.K.Ichikawa 15 th May 2003 Especially, Target by Y. Hayato with KEK Target&Monitor group lead by Noumi Horns Conceptual design by A. K. Ichikawa supported by Y. Yamanoi, Y. Suzuki and Target&Monitor group R&D of Target and Horns are in progress by Neutrino construction group and Target&Monitor group in KEK. Target for K2K Target for J-Parc Al 30mm x 660mm (Embedded in the horn) Heat was generated by the horn-current 12kJ in 1.1 s 2.6MJ in 5 s Aluminum cannot withstand. Only low-Z material such as graphite or beryllium. Graphite w/ water cooling J/gK degree Z R Temperature rise due to the radiation w/ 1 pulse cal. w/ MARS Density ~1.8g/cm 3 Melting point ~3600 o C Good thermal conductivity Mechanically strong Target Size Pion absorption Temperature rise Energy concentration Inner radius of the horn Beam size ~1cm Currently, 25mm ~30mm is being considered. Time dependence of temperature max ~200 o C at center ~40 o C ( Thermal convection coefficient on the surface should be larger than to satisfy