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 – 3 He injected from ABS, collected – NMR to establish polarization update Tri-coil Solenoid coil Correction coil? Cs ring Oct. 2006Jan Passive film burner

4 Step 1.Injection/collection Collection volume pre- filled with superfluid 4He – 4 He Temp. at 0.3~0.5K – 4 He Volume=79cc, R=2.5cm, H=3.9cm 3 He flux – intensity:10 14 atoms/s, Velocity~100m/s After ~100s, ~ He atoms are collected and diffuse within 4 He liquid 4He

5 Spin rotation During injection, spins experience curved magnetic field. – At ABS exit, 3 He 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: 3He trajectory

8 Spin rotation: Polarization loss is negligible (2) Monte-carlo simulation: – Sampling the velocity profile of 3 He 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

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

14 Tri-coil design Starting with improved Helmholtz coils – 2nd order cancellation: I 2 /I 1 = – 4 th order cancelation: H/R= » 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 T 2 to 8.42 ms. – I g = 500 A, R=19cm, H=10cm Potential Problem: Great reduction in T 2 when any of these parameters are varied slightly. – A 2mm variation will reduce T 2 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 – I 1 = 21072A, I 2 = 11199A I 2 /I 1 = – 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 Correction coils

17 Cs-ring to stop superfluid film 45 ’ 5’5’ 4He transfer tube 4He level sensor (Might be too short, got a long one) Gas filling station Vacuum LN2 layer Vacuum Temp. Sensors Cs ring Capillary tubing 1 ’ dia. pyrex 10 ’ Determin ed by the length of the level sensor Heating Wires

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

21 Thanks!