Mu2e Experiment and Issues

Rick Coleman, Fermilab RESMM’12, February 2012

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Mu2e talks Today

Now: Mu2e Experiment and Issues Overview, Status of Project, Production & Transport

Solenoids

16:30 Superconducting Magnets of Mu2e- Michael Lamm

17:00 Mu2e Production Solenoid- Vadim Kashikhin

Tuesday 16:00 Radiation Studies for Mu2e Magnets- Vitaly

Pronskikh

Special Thanks to: R. Bernstein, J. Miller, D. Glenzinski, for some material used

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Introduction

• Mu2e experiment is a search for Charged Lepton Flavor Violation (CLFV) via the coherent conversion of m-Ne-N

• In wide array of New Physics models CLFV processes occur at rates we can observe with next generation experiments

• The proposed experiment uses current proton source at Fermilab with some modifications

• Target sensitivity has great discovery potential

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Beam Intensity and Pulsed Proton Beam

• Deliver high flux m- beam to stopping target • proton flux ~6 x 1012 /sec at 8 GeV (8 kW)• ~2 x 1010 Hz m- , 1018 total, 4 conversion e- at Rme~10-16

• 103 more muons than SINDRUM II previous best limt

• Pulsed Proton beam – Wait 670 ns to reduce prompt background, extinction = 10-10 using Debuncher Ring and oscillating (AC) dipole sweeper in external proton beamline m(Al)=864 ns

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Pulsed Beam and Radiative Pion Capture Background

Wait ~ 700 nsreduced 1011

time (ns)

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Protons from 8 GeV Booster to Mu2e

New beamline shared by Mu2e and g-2

2/13/12

Steve Werkema

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Muon Campus for Mu2e and g-2 with Cryo Plant

Compressed He from existing TeV

compressors

Three TeV refrigeratorsinstalled in MC-1

Cold He lines to experiments

g-2 building (MC-1) has evolved to support needs of g-2 and Mu2e• Low bay is Muon Campus Cryo Building• Medium Bay will house beamline power supplies and equipment.

New transfer line forcompressed He builtfrom recycled parts

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Mu2eg-2

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Schedule

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MECO at BNL

m/p ~ 10-4 vs

conventional ~10-8

1996-2005

1989

MELC at Moscow

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COMET at J-PARC: proposal Nov 2007 & Mu2e at FNAL: proposal Oct 2008

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Mu2e Apparatus

• Mu2e experiment consists of 3 solenoid systems

ProductionSolenoid

TransportSolenoid

DetectorSolenoid

ProductionTarget Collimators

StoppingTarget Tracker Calorimeter

(not shown: Cosmic Ray Veto, Proton Dump, Muon Dump, Proton/Neutron absorbers, Extinction Monitor, Stopping Monitor)

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Mu2e Apparatus

• Mu2e experiment consists of 3 solenoid systems

ProductionSolenoid

TransportSolenoid

DetectorSolenoid

ProductionTarget Collimators

StoppingTarget Tracker Calorimeter

(not shown: Cosmic Ray Veto, Proton Dump, Muon Dump, Proton/Neutron absorbers, Extinction Monitor, Stopping Monitor)

protons

2.5T~5T

2.0T

1.0T

e-

m-, p-

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Goals:—Transport low energy

m- to the detector solenoid —Minimize transport of positive

particles and high energy particles—Minimize transport of neutral particles- curved section—Absorb antiprotons in a thin window—Minimize particles with long transit time

Transport SolenoidInner radius=24 cmLength=13.11 mTS1: L=1 mTS2: R=2.9 mTS3: L=2 mTS4: R=2.9 mTS5: L=1 m

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Charge, Momentum Selection and Rejection of Long-lived Particles

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Muon Flux- before and after Transport Solenoid

Negative Muons

Positive Muons

p(MeV)

p(MeV)2/13/12

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Muons Reaching the Stopping Target in the Detector Solenoid

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Production Solenoid

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L= radius

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Heat and Radiation Shield Dimensions from Simulation

0.6 m 1.4 m

4 m

See Vitaly Pronskikh’s talktomorrow

25 kW

8 kW

W Cu

W

Cu

Bronze

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Some Early Comparisons to MECO (2009)

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Muon Yield vs Bmax Production SolenoidGraded Field Bmin =2.5 T

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6

Bmax (T)

Relative Muon Yield

MECO

Mu2e

Study of Muon Yield vs Maximum Field in Production Solenoid

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Target z position Study (2009)

muon yield vs target position in Production Solenoid

0

0.2

0.4

0.6

0.8

1

1.2

-2 -1 0 1 2 3 4

z (m)

Relative muon yield

Mu2e- g4beamline

MECO GEANT3

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0 m

1 m

COMET

MECO

400

1400

5200

Joint Meeting in Berkeley Jan 2009with COMET group- direct comparisonsdifficult due to differing physics models

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Sergei Striganov improved fit for Mu2e2009, similar fits by Bob Bernstein

File of pions weighted by HARP data used

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Stopped Muon Yield vs Initial Pion Kinetic Energy

1

10

100

1000

0 40 80 120 160 200 240 280 320 360 400 440 480 520 560 600

Kinetic Energy (MeV)

Stopped Muons per 1E6 incident protons

Stopped Muon Yield vs Initial Pion Angle

0

50

100

150

200

250

300

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

cos angle

Stopped Muons per 1E6 incident protons

Pion Production- what energies and angles are important?

~60% from 20-60 MeV kinetic energy or p = 77- 143 MeV

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Increase Field in Short PS from 4T to 5T max field

0

1

2

3

4

5

6

-2000-1000010002000300040005000

z(mm)

Bz(T)

Use HARPStandard PS-5Tmax

Short PS- 4T max Short PS- 5T max

Mu- hitting stoppingtarget

1955 1603 1917

Mu- stopping 1280 970 1109

Relative stopped yield =1.00 0.76 0.87

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MECO

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Optimize target z position for Stopped muon yield for L= 4m Mu2e PS

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With this target location muon yield is down ~ 7%with L=4 m vs L=5.2 m (MECO)

Some cost savings reducing L, but most important feature isDPA requirements can be satisfied in region where proton beam exits PS- see Vitaly’s talk tomorrow

0.2 0.7 1.2 1.7 2.2 2.7 3.2 3.7 4.20.4

0.5

0.6

0.7

0.8

0.9

1

z(m)

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Production Solenoid- Some Engineering Aspects – Heat Shield

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25 kW versionRequires Tungsten $$$Heat Transfer issues

8.3 kW current version

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Exploded view showing radiation labyrinths and all parts

Bolt-on rails

13.6 tons 12.4

tons13.2 tons 6.6 tons

L. BartoszekBARTOSZEK

ENGINEERING

The Mu2e All-Bronze Heat and Radiation Shield Design

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46 tons total

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Status of Heat Shield Engineering

We have to build drawings on all-bronze 8.3 kW

3 cost estimates, very consistent, significant savings in 8.3 kW version over 25 kW version which uses tungsten

Thermal analysis in progress, not expected to be a problem

Need to explore other materials (Copper, Copper/Nickel)

Continue simulations to optimize design

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Backup Slides

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Electron Flash and Middle-Collimator

All particles

negative muons electrons

e/m ~20 -> 1 & stopped m reduced 20%

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e- / - flux entering the Detector Solenoid

e-

-

Momentum (MeV/c)

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Time distribution entering Detector Solenoid

-

e-

Time (ns)2/13/12

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Time vs p - negative muons reaching stopping target

MECO PS

Mu2e PS

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pp=54 MeV scatters to ~0 pitch anglein pbar windowpbar window

TS with gradient

TS without gradient

t= ~900 ns

t= ~200 ns

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Study of the Production Solenoid Gradient vs Muon Yield

normal time distribution

positive gradient leads to long times

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