1

The 3He Injection Test for the nEDM Experiment

10/2008

Xiaofeng Zhu

D. Dutta, H. Gao, M. Busch, Q. Ye, T. Mestler, X. Qian, W. Zheng

Duke University

nEDM collaboration

2

Outline

• Introduction • Experimental setup• Experimental procedure

– 3He injection/collection– Polarization measurement

• Summary

3

Neutron EDM

• A permanent EDM dn

• The current upper limit : dn<2.9x10-26e•cm

Phys. Rev. Lett. 97, 131801 (2006) • Improve sensitivity by 2 orders of

magnitude – A mixture of ultra-cold neutrons in superfluid

4He, and polarized 3He Physics Report 237, 1 (1994)

+-s = 1/2d•E

• T and CP violation• Physics beyond SM• Baryon Asymmetry of Universe

4

Why Polarized 3He?

• Extract n precession frequency using spin dependant nuclear reaction

• Co-magnetometer

3He + n t + p (parallel) ~ 2x104 b (opposite) ~ 4x106 b

dn dipole moment d3He =0

+-EB EB

s = 1/2

n 3He

5

R&D Efforts on 3He at TUNL

• 3He T1 measurement in d-TPB coated acrylic cell filled with superfluid 4He

H. Gao, R. Golub, P. Huffman, Q. Ye, and others at TUNL

• Preparation for injection test– Collect polarized 3He in a pyrex cell filled

with superfluid 4He – Demonstrate polarization

loss is acceptable

6

Setup for 3He Injection Test

Atomic Beam Source: ~100% polarized 3He 1014 atoms/s

CryostatWith 4K 50K shield

Dilution Refrigerator

Liquid He tank at 4K

Tri-coil magnet

Solenoid magnet

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Injection/Collection• Collection volume pre-filled

with superfluid 4He– 4He Temp. at 0.3~0.5K– 4He Volume~27cc

• 3He flux from ABS– Intensity:1014 atoms/s,– Velocity~100m/s

• After ~100s, ~1016 3He atoms are expected in superfluid 4He

8

Dilutionrefrigerator

tricoil

Helium bath vesselHelium gasFilling pipe

To ABS at room temp.

50K4k

Film burner

Helium @0.35k

Pyrex cell

Heat exchanger

1.3k

0.7k

0.24k

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Cool the pyrex cell to 0.35K

• Thermal Link : OFHC copper foil– DR cooling power: 13.8mW with mixing

chamber at 0.24K

Measurement cell @.35K

Copper foil to cool the cell

DR MX at 0.24K

To ABS

DR 1K pot

Cs ring

Filling pipe for L-He

10

superfluid film suppression

• Active method– Film burner

• Passive method (optional)– Cs ring

• Non wetting of He on Cs surface

• Safety issues

April 21, 2023nEDM collaboration meeting

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Spin Rotation

• During injection, 3He travel through a curved magnetic field .– At ABS exit, 3He spins parallel to B field– Solenoid coil (20G)

• Axial field along ABS axis

– Tri-coil system (20G)• Vertically down direction

– Due to space limitation

• During injection, spins rotate by 45 deg.

Tri-coil

Solenoid co

il

4545o

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Spin Rotation: Polarization Loss

Negligible • Spin follows the field

direction– AFP condition:

• Monte-carlo simulation:– Average spin rotation ~ 3.35±0.30 deg– Polarization ~98.8%

• Low vapor density to suppress collisions

40

0

~ 625 ~ 6 10z Hz f HzB

B

3He trajectory

AFPNon AFP

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Polarization Measurement

with 1014 3He/cc• Measurement at high field ~1kG to

increase signal size

• Pulsed NMR with a single transceiver

coil

– Less sensitive to thermal displacement

– Smaller RF power

– Better signal/noise ratio expected than that

of AFP

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Field Homogeneity for pNMR

• T*2 related to longitudinal field gradient:

• The block time of pNMR is ~20μs • Transverse spin relaxation time T*

2>200 μs – Averaged within 4He liquid ( R<2.5cm,|z|<2cm)

• At 1.2kG, Field homogeneity needs to be < 27.5 ppm/cm (30mG/cm)

24 2

*2

81

175zR B

T D

Phy. Rev. A , 37 2877

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Tri-coil Design and Test• Starting with improved Helmholtz coils

– 2nd and 4th order cancellation:• I2/I1=0.53146; H/R=0.76005

– By B. Filippone, Caltech

• TOSCA Optimization – By S. Balascuta, ASU

• Numerical and analytical calculation– T*

2~2.59ms • Average over the liquid He volume, by T.Mestler,

Yale

– T*2~0.430ms

• Consider wire geometry, by W. Zheng, Duke

• Tri-coil built , axial field uniformity is ~16ppm (<27.5ppm)

I2

I1

I1

R

H

Rev. Sci. Instr. V73, 2175

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pNMR for Injection Test

• pNMR setup at Duke– An existing magnet

modified for this test:• 1kG • Uniformity ~ 80mG/cm

– Tank circuit tuned ~ 3.89MHz

– Proton FID signal is observed at room temperature

• Comparable to 3He density during injection test

~1X1014 polarizedprotons/cc

magnetTank circuit magnet

Tecmag Apollo console

Tank circuit

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Trying to improve S/N on 1H

• Spin tipping angle at room temp.– RF duration time

• Spin echo signal– For calibration

purpose• Cryogenic pre-

amplifer , RF shielding, etc

FID signal

2

T2 measurement on water sample

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Cryogenic pNMR system

• Faraday cage– Two tunable

capacitor – Resonant coil– Copper

enclosure@1.3K• Semi-rigid coax

– Center: Ag coated BeCu

– Dielectric: teflon– Sheath: BeCu

• From D. G. Crabb, UVA

Faraday cage

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Summary

• Magnets are ready, to be assembled with cryostat

• pNMR system under optimization

• Injection test will be carried out at LANL

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Acknowledgement

• Los Alamos National Laboratory• U.S. Department of Energy under

contract # DE-FG02-03ER41231

• Collaborating institutions– ASU, BU, Caltech, Duke, LANL, MIT,

MSU, NCSU

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Backup slides

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Cryogenics• Heat load to DR mix:~ 5mW

– 13.8mW cooling power @0.24K

– By T. Ito

– ~2.5mW from film burner– By G. Seidel

– 0.5mW pNMR and support– 1.1mW gas introduction

tube• Cs ring to slow down

superfluid flow rate– Torch to chase Cs vapor– Dry ice to condense Cs

effectively – CsN3 test will continue

• Sealing test undergoing– Pyrex to copper adapter

• 15 thermal cycles– After fail and try, kapton

gasket seals well with copper flange

Kapton gasket

Epoxy2850GT

Cs ringMade by dry ice

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Safety II: boil off of LHe within Tricoil can

• Siphon pipe to fill LHe into tricoil can

• Pipe for safety venting– Heat rate: 2 kW/m2

– Pressure drop: 5.5 psi• Gas

density@50K,1atm– By J. Long

• Venting velocity: 97m/s

• 1.375” ID, 45” length• Reynold number:

5.7x105

• resistant coefficient: 0.49

– Rupture disc@4K• Avoiding Taconis

resonance

Siphon pipe

Vacuumvent pipe

24April 21, 2023 nEDM collaboration meeting 24

Injection test cell cooling power

K24.01T K35.05 T

2T

DR Mixing Chamber

Injection test collection volume 4He4T3T

2_1R 3_2R 4_3R 5_4R

)target(35.0Tito), From(est.24.0

est.2a gPollack Fi,15.0

Boundary4He-Pyrex

W/mK001.0,cm90,mm0.1,WallPyrex

est.x.x tablePobell,002.02

daryPyrex BounGlueCopper

W/mK100,cm5.2,m9.0,busCopper

:

,mW6.0Q

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5_4

24_3

3_2

22_1

5_44_33_22_1

KKA

R

ALA

LR

AR

ALA

LR

where

RRRRRR

T

TT

totaltotal

~36 ~22 ~111 ~15

25April 21, 2023 nEDM collaboration meeting 25

Injection test vs nEDM injection

Parameter Injection Test nEDM Injection

Mechanical Scale 0.5 – 1.0 1.0

4-He Collection volume

25 cc 50 – 400 cc

Injection volume outlet NMR measurement volume Outlet valve to IV1

Injection port from ABS

Requires film burner with ID 1.05” aperture

Requires film burner with ID 1.55” aperture

Material requirements Cs coated Pyrex cell, no magnetic materials in magnetic field area

identical

Heat load ~0.5mW, conduction cooled from DR mixing chamber via 0.83 m long OFHC Copper foils

Similar heat load, ~1.2 m away from DR mixing chamber

Measurement technique

pNMR SQUIDS