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JHF2K neutrino beam line
A. K. Ichikawa
KEK
2002/7/2 NuFact02@CERN
• Overview
• Primary Proton beamline
• Target
• Decay Volume
• Strategy to change peak energy
•Summary
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Overview of experimentOverview of experiment
Conventional beam of ~1GeV
Kamioka
JAERI(Tokai-mura)
→ → xx disappearance
→ → ee appearance NC measurement
0.75MW 50 GeV PS
Super-K: 50 ktonWater Cherenkov
~Mt “Hyper Kamiokande”
4MW 50GeV PS
CPVproton decay
1st Phase2nd Phase
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Off Axis Beam(ref.: BNL-E889 Proposal)
Target HornsDecay Pipe
Far Det.
Quasi Monochromatic Beam x2~3 intense than NBB
Exp’ed # of evts(1yr,22.5kt)~4500 tot ~3000 CC e contamination ~0.2% at peak
Expected spectrum(OAB2o)~102 x (K2K)
OA3°OA2°OA1°
Osc. Prob.=sin2(1.27m2L/E)
m2=3x10-3eV2
L=295km
Tuned at oscillation maximum
(OAB 2degree)
osc.
max
.
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Overview of FacilityPrimary Proton beamline
Target Station
Decay
Volume
280m Near Detector
SK Beam Axis
50GeV PS
pit
JHF NuMI
(FNAL)
K2K
E(GeV) 50 120 12
Int.(1012ppp) 330 40 6
Rate(Hz) 0.275 0.53 0.45
Power(MW) 0.75 0.41 0.0052
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Overview -Primary proton beamline-
Preparation section
Arc R=106m
Final Focusing Section
Single turn fast extraction
8 bunches/~5s
3.3x1014proton/pulse
3.94 (3.64) sec cycle
1 yr≡ 1021proton on target(POT)
=6 mm.mr
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Beam loss
No way to know absolute beam loss Assumed by HAND Assure hands on maintenance (1W/m) Shielding design based on the assumption Same order as KEK-PS beam line ~102 relative suppression!!Challenging
Fast ext.(kicker, septum)1.125kW (0.15%)
Matching section(ctrl’ed loss by collimator)
0.75kW (0.1%)
50GeV ring0.5W/m
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Acceptance : 60 mm.mrad (cf Acc. design = 6 mm.mr)
Waist mode & normal mode.
monitor
V
H
24 Collimator/shield
Matching Point10cm
10cm
Preparation sectionMake the matching with the Arc.
Consists of normal conducting magnets.
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2cm
X
Y
Normal Mode
Matching Point
beam ellipse is tilted
to achieve small size.
2cm
Primary Beamline –Arc-B
B
Q
Q
Bends by
3m long 4 T superconducting magnet.
+ 1m long Q-superconducting magnet.
Bore : ~180mm
To prevent the quenching,
the beam size and halo should be small.
FODO lattice x 10,
about 80o bending
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Beam halo study using Geant
60 mm.mr beam 1,000 events
100 mm.mr beam 500 protons
Preparation section
Arc
Magnet geometry and field are set via data file.
applicable to different beamlines.
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Beam DirectionFor both SK and possible HK.
Decay pipe
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Target Station
Side View
Off Axis Beam
Plan to change the axis by moving horns or w/ dipole after horns.
OAB 2o, 2.5o, 3o
Service pit
ironconcrete
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Target
Graphite (or Be) is a unique solution. ← Heat problem
(except for liquid target)
density ~1.8 g/cm3
Interaction length 79g/cm2 (44cm)
Melting point >3000 o
Thermal conductivity ~ 115W/m ・ K
Thermal expansion 4.2×10-6/ o C
Yang Modulus ~ 1E10 Pa
Sound velocity 7,400 m/s → 3.7 cm/5s
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Energy deposit in the target
Graphite( =1.81g/cm3)
/spillJ/cm3/spillJ/cm3
3J/cmMaximum 460 3J/cmMaximum 300
2cm target, beam=0.4cm 3cm target, beam=0.6cm
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Temperature in the target (FEM analysis)
C230 C43
1000mmL 30mm,
300mm~z0,rC230~ @
surfaceC70~ @
beam directionr=0mm,z=300mm
r=1.5mm,z=300mmC70
C230
4 8 3212 (Sec.)
Time Evolution
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Target -for 4MW-
Not yet considered well.
Radiation cooling, Liquid target………
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Decay Volume
Side View
Concrete shield
w/ additional 60cm thick concrete,
it can accept ~4MW beam.
Top view
6.6m
To SK/HK OAB 2 o
OAB3 o
-pit
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Decay Volume –Cooling-
Iron
Concrete
~600 o
FEM analysis for
4MW beam
53°
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Collimator after Horns
Side View
Service pit
iron
concrete
Important for DV
z(m)
W/m3
For 0.75MW beam
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Strategy to change peak energy
Dipole magnet
gap 1m×1m×1m
One method is changing the beam axis.
The other…. OAB+Bending Magnet
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OAB vs OAB+Bending
No need to access target and horns.
Easy to change the peak energy
By T.Oyabu
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Summary
JHF will produce 0.75 MW 50 GeV proton beam.
Quasi Monochromatic Beam with off-axis method.
Peak Energy can be tuned
by changing axis or w/ bending magnet.
Facility is being designed to accept 0.75 MW beam
while keeping extendibility for 4 MW beam.
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Supplement
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2cm Y
X
Waist mode
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Total Length=37.5m
120mm 200m200m
120mm
4m
3cm@target
Applicable to 6 mm.mr<<24 mm.mr
Vertical bending magnets
Arc section
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Size (radius) dependence of neutrino yield
=1cm
=2cm
=3cm
=1cm
=2cm
=3cm
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Al target
Maximum energy deposit of aluminum target (3cm)
/spill700J/cm~ 3
→ 290°/pulse
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Thermal stress
)Tα(Tν-
EP 021
0,TT
α
ν
E
P Pressure
Young modulus
Poisson ratio
Linear expansion rate
Temperature
MPa12~P
2.0C /102.4 6
GPa8.10
CC 25,235
Small enoughSimulation results (by ANSYS)
are almost consistent (or smaller).
Dynamic thermal stress can be reduced
by splitting the target in a few cm pieces.