Muon Beam for COMET/PRISMM. Yoshida (Osaka Univ.)
NP08 @ MitoMar. 6, 2008
M. Yoshida, NP08, Mito 2Mar. 6, 2008
CONTENTS
Layout of COMET/PRISMProton Beam for COMETSuperconducting Solenoid System
Pion CapturePion Production TargetMuon Transport
Muon Yields expected in COMET
M. Yoshida, NP08, Mito 3Mar. 6, 2008
PRISM/COMET projectPRISM stands for Phase Rotated Intense Slow Muon sourceProposal of COMET was submitted to J-PARC PAC in Jan. 2008 aiming for 10-16 sensitivityCollect 68MeV/c μ-
pion production, captureand transport system
proton beam
Phase rotator
PRIME detector
M. Yoshida, NP08, Mito 4Mar. 6, 2008
Proton BeamPulsed beam from slow extraction.8GeV x 7microA
Total beam power is 56 kW~1/8 of the JPARC full beam power of 450 kW (30 GeVx15 microA)
8x1020 protons in total2x107 sec running for a single event sensitivity < 10-16.
Need proton extinction by 10-9
AC dipole in Main RingProton monitor after extractionR&D in US-Japan program
M. Yoshida, NP08, Mito 5Mar. 6, 2008
Extinction Monitor R&D
Gas Cherenkov detectorMonitor off-time protons in between bunchesC2H6 (1atm) has been investigated to have enough low scintillation tail in Signal Time Window. R&D underway
High pressure situation, necessary to produce Cherenkov for 8GeV protonsGating PMT…
T. Yano3x10-4 photons/MeV track
α
PMT
PINPD
M. Yoshida, NP08, Mito 6Mar. 6, 2008
Concepts of pion capture/transport system for COMET
Capture low-energy pions with 5T solenoid fieldLow-Z material
Graphiteto avoid absorption LE pions in the targetlarge diameter can be chosen for beam steering/ support structure
High-Z material targetTungstenLarge production cross section; 2 times or more yieldsSmall diameter to avoid absorptionNeed precise proton beam steeringNeed careful study on cooling
Collect backward pions from the targetTilt target by 10 deg. to implement proton beam pipeEnergy deposit on superconducting coil of capture solenoid << 100WAl-stabilized SC coil to reduce cold mass
Transport pions+muons in long 2T solenoid channelBent solenoid channel
Target should be off-site from experimental areaReduce background by wiping out higher energy particles
M. Yoshida, NP08, Mito 7Mar. 6, 2008
Pion Capture Solenoid
Radiation Shieldneed thick shield to reduce radiation on SC conductor30cm-thick Tungsten around the targetkeep 20cm space along beam axis
beam steeringHE particles escape forward
DimensionsCoil should have enough length for large boreLength: 1.4mCoil Diameter: 1m1-ton coil mass
Achieve 5T on Targetby stacking only 2 layers of SC conductor80 A/mm2 with 60 mm thicknessLoad line ratio = 0.63
Stored energy = 12 MJ10
00
1400
200
300
80A/mm80A/mm22
M. Yoshida, NP08, Mito 8Mar. 6, 2008Z position along solenoid axis (cm)
Magne
tic field
(Tesla)
0
2
4
6
-100 0 100 200 300
Pion Capture Solenoid
450
1000
1400
200To transportsolenoid
300
1200600300
1590A/mm1590A/mm3800A/mm3800A/mm4821 A/mm (80A/mm4821 A/mm (80A/mm22))
12201340
6001000
1100A/mm1100A/mm1590 A/mm1590 A/mm
800
M. Yoshida, NP08, Mito 9Mar. 6, 2008
Heat load on capture solenoid
Superconducting coilDensity: 4g/cm3
6cm thick (50cm<R<56cm)
Energy deposit on coil2x10-5 W/g for 8GeV x 7microA10 W in total
Radiation dose on coil0.3 MGy for 4x1020
protons
0.6 MGy/8x1020protons
2kW
10W
M. Yoshida, NP08, Mito 10Mar. 6, 2008
Heat Load with Tungsten Target
No significant difference on Coil
4kW on Target
15W on Coil10W on Coil
2kW on Target
M. Yoshida, NP08, Mito 11Mar. 6, 2008
0246810121416
00.20.40.60.8
11.21.41.61.8
2
0 10 20 30 40 50 60
Temperature Rise in TargetGraphite target
Length: 60cmDiameter: 4cmMaximum : 15 [J/g]
DT = 23 K, if no heat transfer
Gas He coolingTungsten target
Length: 16cmDiameter: 0.8cmMaximum : 280 [J/g]
DT= 2200 K , if no heat transfer
Need careful calculation and design cooling mechanism
Z [cm]
R [c
m]
Deposit energy distribution [J/g/pulse]
0
50
100
150
200
250
300
00.05
0.10.15
0.20.25
0.30.35
0.4
0 2 4 6 8 10 12 14 16
Graphite
Tungsten
M. Yoshida, NP08, Mito 12Mar. 6, 2008
Yields at Capture Solenoid Exityields at 3m downstream of the target
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 5 10 15 20 25 30 35
Target Radius (mm)
pion
s+m
uons
/ pr
imar
y pr
oton
Tungsten (beam:2mm)Tungsten (beam:4mm)
Tungsten (beam:10mm)
Graphite (beam:2mm)
Graphite (beam:10mm)
Graphite (beam:4mm)
Length Graphite : 60 cm Tungsten : 16 cm
M. Yoshida, NP08, Mito 13Mar. 6, 2008
Superconducting Solenoid System
Long enough for pions to decay to muons
20 meters => Psurvive=2x10-3
high transport efficiency
inner bore = 35cmPμ ∼ 40 MeV/c
Negative charge selectionLow momentum selection
Pμ<75 MeV/c
M. Yoshida, NP08, Mito 14Mar. 6, 2008
Magnetic field profile
M. Yoshida, NP08, Mito 15Mar. 6, 2008
Muons at the end of decay solenoid
Graphite target case
# stopping muons / proton = 0.00075.6x1017 muons for 8x1020 protons
Tungsten target case
# stopping muons / proton = 0.00181.4x1018 muons for 8x1020 protons
Momentum Angle
ProfileTime of flight
pions
2x10-4μ/proton
M. Yoshida, NP08, Mito 16Mar. 6, 2008
SummaryPreliminary design study of pion capture solenoid and transport bent solenoid for PRISM Phase-I is presented.Capture solenoid can be constructed with Al-stabilized superconducting coil
5 TeslaLarge bore with thick radiation shield insideHeat deposit on coils can be reduced to 10 W-15W, at 8 GeV proton injection, with 56kW beam power
Long decay/transport solenoid is designed2 Tesla, >15metersBent to reject high energy muons --> slant coil windingkeep high transport efficiency for low energy muons
Temperature rise of target is estimatedGraphite target can be cooled by He gas flowNeed R&D on Tungsten target
We will continue to make studies for realistic target cooling mechanism and maintenance scheme.
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