1. Target R&D for the J-PARC neutrino experiment (II) Yoshinari Hayato (KEK/IPNS) for the J-PARC target R&D group

2. Temperature rise estimation (simulation input parameters) Target size 30mm  x 900mm L Energy deposit58kJ/spill Maximum energy deposit 185.9J/g Distribution of the energy deposit r z Heat transfer rate @ surface 6.5kW/m 2 /K Temperature @ surface (environment) 25 o C

3. Temperature rise estimation (simulation input parameters) Temperature ( o C) MaterialIG-43 (Toyo Tanso) density1850kg/m 3 Temperature dependent material parameters Thermal conductivity Specific Heat 020040060080010001200020040060080010001200 500 1000 1500 2000 (J/kg/K) (W/m/K) 20 60 100

4. Temperature rise estimation (simulation input parameters ) 1234101112 03.42 Time (sec) 6.8410.2630.7834.2037.62 Heat Load 5s5s 58ns 598ns 8spills/bunchaveraged Time structure : for the detailed study, two patterns were simulated.

5. Temperature rise estimation results : (I) distribution in the target just after the 11 th spill r z Maximum Temperature : 45 o C just before the 11 th spill relative temp. from 25 o C r z Maximum Temperature : 236 o C

6. 50 100 150 200 250 ( o C) Maximum temperature at the center Maximum temperature on the surface 50 100 150 200 250 ( o C) 37.6200037.6200237.62004(sec.) 0510152530203540(sec.) Temperature rise gradually decreased because of the temp. dependence of Cp. Temperature is saturated in a few spills. 236 o C @maximum 85 o C @maximum (Initial temp. : 25 o C) Temperature rise estimation results : (II) time dependence

7. Thermal stress & displacements estimation ( simulation input parameters ) time step : 1  s (from 0 to 205  s) Two types of the stress analysis (LS-DYNA) For the radial displacements (fast components) For the longitudinal displacements (slower components) time step : 10  s (from 0 to 2050  s) 3.762063 10790 20.0 4.065344 10920 100.0 4.48612 11080 200.0 4.926584 11410 400.0 3.6814 10760 0.0 （ MPa ） （oC）（oC） Linear Expansion Coeff. (x10 -6 ) Young’s modulus Temperature Cycle 11Cycle 12 Cycle 11 and 12 of the previous analysis 50 100 150 200 ( o C) 01325467981110 Time (sec) Material properties

8. Thermal stress & displacements estimation results : (I) equivalent stress Just after the 11th spill Maximum equivalent stress (x10 MPa) 6.8MPa

9. Thermal stress & displacements results : (II) displacements (radial direction) 5.000055.05.000105.000155.00020 1.0 2.0 3.0 4.0 5.0 6.0 x10 -3 (mm) Vibration cycle Maximum displacement ~ 6x10 -3 mm ~ 6  s Displacement in the radial direction (sec.)

10. Thermal stress & displacements results : (III) displacement (longitudinal direction) 5.00055.05.00105.00155.0020 -2.00 x10 -1 (mm) (sec.) Vibration cycle Maximum displacement ~ 2.5x10 -1 mm ~ 250  s Displacement in the longitudinal direction

11. Summary & future prospects (I) Maximum temperature @ center Maximum temperature @ surface FEM simulation results ~ 236 o C ~ 85 o C (analytical : @ center ~ 250 o C ) Maximum stress (analytical ~ 7.5MPa) Consistent with the analytical calculation. ~ 6.8MPa Vibration cycle Maximum displacement radial ~ 6x10 -3 mm longitudinal ~ 2.5x10 -1 mm radial ~ 6  s longitudinal ~ 250  s

12. Summary & future prospects (II) 1 piece or split the target into smaller pieces? Off centered tolerance has to be estimated. (Non-uniform heating may cause the problem.) Can we put the graphite target in the water? Is it necessary to put the target in the container (to avoid graphite to touch the cooling water)? If we split the target into smaller pieces, we have to put the target in the container. Remaining questions / problems water flow (To avoid the water to get in the middle of the beam.) container(?) Schematic view of the possible target (cooling) system Graphite target

13. Summary & future prospects (II) Irradiation effects Target may shrink by ~1(a few?)% If we put the target in the container, they will be separated. Large target (L=900mm) may not be possible. How to hold the target (in the container)? Plan to measure the irradiation effects on the material properties Very rough schedule FY 2003simulation studies & basic cooling tests. design the prototype (target holder, cooling system). FY 2004make the prototype and test. design the target support & handling system. measure the irradiation effects. FY 2005mockup tests (including supports & handling system). material determination.

14. 変形倍率 200 倍にて表示 赤ライン = 変形前 変形値単位 =mm A 部拡大図 B 部拡大図 グラファイトターゲット熱応力衝撃解析 : 変形図 （⑦ 軸変形最大 =5.000125sec ） 拡大図