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Plan of the injection test

02/2007 nEDM

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

Duke University

And others in nEDM collaboration

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Outline

• Introduction • Experiment procedure

– Spin injection/collection• Tri-coil and Transport Solenoid Coil

– polarization measurement• Tri-coil and correction coil• Pulsed NMR setup

• Issues • Schedule

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Introduction• The goal of the injection test

– 3He injected from ABS, collected– NMR to establish polarization

update

Tri-coil

Solenoid coil

Correction coil?

Cs ring

Oct. 2006 Jan. 2007

Passive film burner

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Step 1.Injection/collection

• Collection volume pre-filled with superfluid 4He– 4He Temp. at

0.3~0.5K– 4He Volume=79cc,

R=2.5cm, H=3.9cm • 3He flux

– intensity:1014 atoms/s, Velocity~100m/s

• After ~100s, ~1016 3He atoms are collected and diffuse within 4He liquid

4He

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Spin rotation

• During injection, spins experience curved magnetic field .– At ABS exit, 3He spin parallel to B field– Solenoid coil

• Axial field along ABS axis – 43deg tilted

– Tri-coil system• field along -z axis• Only vertical direction

– Due to space limit

• During injection, spin rotates 47 deg.

Tri-coil

Solenoid coil

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Transport field design

• To keep polarization during spin rotation– Superconducting transport solenoid coil

• 20G Axial field along ABS axis – 43deg tilted

• R=5.08cm, L=40cm• I =1588.9A/m

– Superconducting tri-coil system• 20G field along -z axis• R=17cm H=12.92cm

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Spin rotation: Polarization loss is negligible (1)

• spin would follow the field direction– AFP condition:

.

40

0

~ 625 ~ 6 10zB

Hz f HzB

3He trajectory

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Spin rotation: Polarization loss is negligible (2)

• Monte-carlo simulation:– Sampling the velocity profile of 3He at ABS

exit– B field information along the trajectory

• maximum field rotation rate: 3343±295 rad/s• minimum field: 5.86±0.04G

– TOSCA modeling ---- Tim, ASU

– Average tip angle~3.35±0.30 deg• Maximum tip angle~4.46deg

– Polarization ~98.8%

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Longitudinal Spin relaxation during

injection• Wall relaxation dominates likely• Dipolar interaction is negligible• Field gradient contribution:

– T1>1000s, Field gradient: – Transport solenoid must be 34cm away

• From solenoid exit edge to the center of tri-coil

21.6 /xB mG cm

22

2

0

1

1x yB B

DT B

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Step 2. Polarization

Measurement• Pulsed NMR with a single transceiver coil

– Probe construction is simple:

• No worry about temperature variations affect orthogonal

alignment of RF and pickup coils

– Probe is not susceptible to mechanical vibration

– small transmitter power due to smaller volume

– better signal/noise ratio expected

• high Q factor

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Schmatic diagram of

pNMR• Holding field: 1.2KG

• Reson. freq. ~4MHz

• NMR system

– Tecmag Apollo

console

– Cover 10k~250MHz» From NCSU

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To be customized

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Study needed for pNMR• Pre-amplifier ?

• Duplexer ?

• probe

– Birdcage coil?

• Signal/noise

• Open setup

– Saddle coil?

– Side mounted coil?

Side mounted coil

Birdcage coil

Collaboration with Prof. Q.H. Liu’s group

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Field homogeneity for pNMR

• The block/dead time of pNMR is ~20μs • Transverse spin relaxation time T2>200 μs

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

• T2 related to longitudinal field gradient:

• Longitudinal field gradient at 1.2kG setting

• Field homogeneity ~ 27.5 ppm/cm

33 /zB mG cm

24 2

2

0

81

2 175zR B

T D B

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Tri-coil design

• Starting with improved Helmholtz coils– 2nd order cancellation: I2/I1=0.53146– 4th order cancelation: H/R=0.76005

» By B. Filippone

• TOSCA Optimization » By Tim, ASU

• Numerical and analytical calculation– T2~2.59ms

• Average over the liquid He volume, by T.Mestler

– T2~0.430ms• Considering current distribution within wire, by W. Zheng

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Gradient coil

• Additional gradient coil can further increase T2 to 8.42 ms.– Ig = 500 A, R=19cm, H=10cm

• Potential Problem: Great reduction in T2 when any of these parameters are varied slightly. – A 2mm variation will reduce T2 with

gradient coil by a factor of 4 !

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Specifications of magnetic coils

• Tri-coil– R=17.00±0.01cm, H=12.92±0.01cm– I1 = 21072A, I2= 11199A

• I2/I1=0.53146

– B0=1.2kG– Field gradient inside reservoir:

• A pair of Helmholtz correction coil– R=19±0.01cm– H=10±0.01cm– I = 0~500 A

40 /zB mG cm

Correction coils

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Cs-ring to stop superfluid film

45’

5’

4He transfer tube

4He level sensor (Might be too short, got a long one)

Gas filling station

Vacuum

LN2 layer

Vacuum

Temp. SensorsCs ring

Capillary tubing

1’ dia. pyrex

10’

Determined by the length of the level sensor

HeatingWires

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Detachable glass tube with kapton sealing

• Glassware to be sealed by clamp– Kapton sealing

works good with stainless steel, however, stiff

– Low temp. is challenging

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Other items

• Cs port for coating the collection volume

• Glass shutter• Temperature/

pressure monitors

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Schedule

• Everything should be ready in 6 months– 6 months for the company to deliver

superconducting tri-coils » B. Filippone

– Transport coil: 3 months– 6 months for pNMR setup– Glassware: 1 months– Cs ring test: 2 months

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Thanks!