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1
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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%
9
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
10
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
11
Schmatic diagram of
pNMR• Holding field: 1.2KG
• Reson. freq. ~4MHz
• NMR system
– Tecmag Apollo
console
– Cover 10k~250MHz» From NCSU
4
To be customized
12
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
13
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
14
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
15
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 !
16
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
17
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
18
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
19
Other items
• Cs port for coating the collection volume
• Glass shutter• Temperature/
pressure monitors
20
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