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.