1. Target R&D for JHF neutrino
KEK Yoshinari Hayato

2. 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)

3. Target for JHF neutrino
Solid target
Easy to handle
Heat (melting point)
Thermal shock
Carbon Target
Melting point
Thermal conductivity
Thermal expansion

4. 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

5. 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

6. Energy deposit in the target
Target and beam size dependence
Carbon
(density )
3cm

7. 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

8. Temperature in the target
After 5msec
(just after the spill)
After 3.42sec
(just before the next spill)
(Z=300mm)
(Z=300mm)

9. 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.)

10. 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.

11. Summary Maximum temperature Target for JHF neutrino project Material
Carbon
Size
radius
15mm
length
1000mm
(In total)
Maximum temperature
core
on the surface
Cooling method
Water
Dynamic thermal stress
Split target