1. The JPARC Neutrino Target
Y.Hayato (ICRR, Univ. of Tokyo)
for T.Nakadaira
& J-PARC n beam-line construction group
(I borrowed most of all the transparencies from Nakadaira-san)

2. J-PARC neutrino beam line
Primary Proton
beam line
Proton Energy
50GeV
T=0)
# of Protons / pulse
3.31014
Beam Power
750kW
 Phase II
Extraction
point
Target
Target station
Bunch structure
Decay volume
8 (15) bunches/spill
Spill width ~5ms
beam dump
muon monitor
Cycle: 3~4 sec
Near neutrino
detector
Bunch spacing: ~600(300) ns
Bunch length: 58ns (Full width)

3. Target Station Accommodate Area filled with Helium gas
Baffle: Graphite, 32mmf hole x 1.7m long to protect 1st horn
Target
3 Horns
Area filled with Helium gas
reduce Tritium, NOx production
Highly radio-activated
~1Sv/h,
Need remote-controlled maintenance system
Need cooling (Helium vessel, radiation shield,..)
3rd horn
2nd horn
Trg&
1st horn
Baffle
Target
Baffle
beam
1st Horn
2nd Horn
3rd Horn

4. Target dimension Cooing path
Co-axial 2 layer cooling pipe: Graphite / Ti-6Al-4V, Helium cooling
Outer pipe
47.0
46.4
39.6
35.6
26.0
Ti-6Al-4V
[mm]
Inner pipe
IG-43
target
IG-43
spacer
Sectional area
= 4.610-4 [m2]
Cooing path
f=47mm
f=26mm

5. One design of the target & surrounding cooling pipe
(Not the final design).
陽子ビーム
He inlet
He outlet
Ti-6Al-4V
Beam window
Ti-6Al-4V
陽子ビーム
Target
Need further design study
Graphite IG-43

6. Design of inlet and outlet of He Gas is not fixed.
} To downstream
} To downstream
Design of inlet and outlet
of He Gas is not fixed.

7. Disadvantage Target cooling : Water or Helium? Water Cooling
Helium Gas cooling
Very Efficient  High Heat transfer ratio
Already tested.
Simple circulation system
We can control Ttarget to minimize the irradiation effect. (Ttarget = 400 ~ 800 C)
Reduce radioactive waste water
No target container is needed
large Irradiation effect  Ttarget  300C to avoid the water boiling: surface < 100C
Target container is needed.
DPwater= ~2MPa due to the temperature rise by a beam hit.
Huge radioactive waste water
Very High flow rate ~ 2000 l/min [0.5MPa] ~ l/min [0.1MPa]
Circulation system is complicated.
Special treatment for the high temperature gas (200C) is necessary.
Advantage
Disadvantage

8. Target : Conceptual design
Core: Isotropic-Graphite : IG-43 (Toyo Tanso Co. Ltd)
Energy deposit… Total: ~40kJ/spill (30GeV)  DT  200K. seq = 7.5 [MPa]  Tensile strength = 37.2 [MPa]
Distribution of the energy deposit in the target (w/ 1 spill)
J/gK degree
MARS
proton beam cm
f=47mm
f=26mm

9. Energy deposit (30GeV, s x= s y =4.24mm) Target 39.3 [kJ/spill]
R target
13 [mm]
DR (target ~ horn)
3[mm]
Energy deposit (30GeV, s x= s y =4.24mm)
Target
39.3 [kJ/spill]
3.5 [kJ/spill]
1.1 [kJ/spill]
1.5 [kJ/spill]
99.09%
(0.91%loss)
Inner Pipe
Outer Pipe
Insulator
Targeting Efficiency
For Gaussian beam
Helium flow (T gas < 200C, suction=0.03MPa)
Cross section
459.3 [mm2]
491 [Nm3/h]
246 [m/s]
[MPa]
Flow rate
Avg. target
part+1st hex

10. Irradiation Effect of Graphite
Expected radiation damage of the target
The approximation formula used by NuMI target group : 0.25dpa/year
MARS simulation : 0.15~0.20 dpa/year
Dimension change : shrinkage by ~5mm in length in 5 years at maximum ~75mm in radius
Degradation of thermal conductivity … decreased by 97% @ 200 C 400 C
Magnitude of the damage strongly depends on the irradiation temperature.
It is better to keep the temperature of target around 400 ~ 800 C
400
600
800
1000
Irradiation
Temperature(C) 1 2 3
(dpa)
400oC
800oC
Thermal conductivity (After/Before)
JAERI report (1991)
2dpa
-0.5%
1dpa
Dimension change
Toyo-Tanso Co Ltd. IG-11

11. FEM simulation of He cooling
Assumptions: 0.19MPa He Initial temperature: 25 C He flow rate: [l/min]  194 [m/sec] Heat convection rate: 820 [W/m2/K]
(50GeV,f=15mm)
Target Temperature
Helium Temperature
Max: ~ 500 C
Min: ~ 300 C
Avg. : ~380 C
Max: ~160 C
(DT = 135 C)
Avg. : ~40 C

12. FEM simulation of He cooling
(50GeV,f=15mm)
Assumptions: 0.19MPa (Possible pressure drop at the downstream of target is taken into account.)
He Initial temperature: 25 C He flow rate: [l/min]  194 [m/sec] Heat convection rate: [W/m2/K]

13. fin.