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

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

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

.

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

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

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

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.

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

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.

Beam DirectionFor both SK and possible HK.

Decay pipe

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

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

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

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

Target -for 4MW-

Not yet considered well.

Radiation cooling, Liquid target………

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

Decay Volume –Cooling-

Iron

Concrete

~600 o

FEM analysis for

4MW beam

53°

Collimator after Horns

Side View

Service pit

iron

concrete

Important for DV

z(m)

W/m3

For 0.75MW beam

Strategy to change peak energy

Dipole magnet

gap 1m×1m×1m

One method is changing the beam axis.

The other…. OAB+Bending Magnet

OAB vs OAB+Bending

No need to access target and horns.

Easy to change the peak energy

By T.Oyabu

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.

Supplement

2cm Y

X

Waist mode

Total Length=37.5m

120mm 200m200m

120mm

4m

3cm@target

Applicable to 6 mm.mr<<24 mm.mr

Vertical bending magnets

Arc section

Size (radius) dependence of neutrino yield

=1cm

=2cm

=3cm

=1cm

=2cm

=3cm

Al target

Maximum energy deposit of aluminum target (3cm)

/spill700J/cm~ 3

→ 290°/pulse

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.