Transcript Target R&D for JHF neutrino

Target R&D for JHF neutrino
KEK Yoshinari Hayato
Introduction
Target for K2K
Al 3cmf x 660mm
Embedded in the horn
Cooled by water
JHF neutrino
Maximum energy deposit
of aluminum target (3cmf)
3
~ 700J/cm /spill
No Problem
Target for JHF neutrino
Solid target
Easy to handle
Heat (melting point)
Thermal shock
Carbon Target
Melting point
Thermal conductivity
Thermal expansion

~ 3550 C
~ 115W/m  K
6 
4.2 10 / C
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 ~ 1cm(for 24 mm  mrad)
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=2cm
f=1cm
f=3cm
f=3cm
f=2cm
Energy deposit in the target
Target and beam size dependence
Carbon (density 1.81g/cm3 )
f  2cm, σ beam  0.4cm
f  3cm, σ beam  0.6cm
J/cm3 /spill
Maximum  460J/cm3
J/cm3 /spill
Maximum  300J/cm3
Heat generation in the target
Parameters used in the simulation
(incl. material properties of Carbon)
f  30mm, L  1000mm
Density
~ 70 C @ surface
1.81 g/cm3
Specific heat
0.71 J/cm3 /K
Thermal conductivity
116 W/m
Thermal convection
coefficient at the surface
2
7.887 kW/m /K
beam direction
~ 230 C @ r  0, z ~ 300mm
Temperature in the target
After 5msec
(just after the spill)
After 3.42sec
(just before the next spill)
(Z=300mm)
(Z=300mm)
~ 36 C
~ 70 C
230 C
43 C
Time dependence of temperature
Maximum temperature
At the center

~ 230 C
230 C
r=0mm,z=300mm
70 C
r=1.5mm,z=300mm
Far below the
melting temperature
On the surface

~ 70 C
4 8 12
32
(Sec.)
This should be lower than 100 C for water cooling.
(Thermal convection coefficient on the surface should be
larger than ~ 3000 kW/m 2 /K to satisfy this condition.)
Thermal stress
E
P
 α(T  T0 )
1-2ν
P
Pressure
Young modulus
E
Poisson ratio
ν
Linear expansion rate
α
T ,T0 Temperature
P ~ 12MPa
10.8GPa
0.2
6 
4.2  10 / C
235 C,25 C
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
Target for JHF neutrino project
Material
Size
Carbon
radius
length
15mm
1000mm
(In total)
Maximum temperature
core (@r=0mm)
on the surface
Cooling method
Dynamic thermal stress

~ 230 C
~ 70 C
Water
Split target