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Update of the injection test

06/2007 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

• Magnets system • collection reservoir

– Pyrex Cell design– Cs coating– monitoring 3He-4He mixture

• Design of Pulsed NMR system

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Superconducting Magnets

• Tri-coils and solenoid coils– 20G,spin rotation of 45 deg.– 1.2KG, holding field for NMR

• Tri-coil – A bath of liquid He

• Cooling can built by MIT

– June, by Cryomagnetics

• Solenoid coil (Cu:NbTi)– Conductive cooled by Al6061 mandrel– June, by AMI

Tri-coil--Caltech

Solenoid coil

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Power supply for superconducting solenoid

• A Kepco Power supply with quench protection– Cost reduced by a factor of 10

– Power supply from Superconducting magnet company is an overkill, too expensive

– Pure inductive load,• ~1400V spike voltage at

quenching

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New design of collection reservoir

• Glass to metal adaptor• Glass joint with kapton O-

ring is hard to seal

• A separated bottom cell– Closer to final test.– Solenoid coil for pNMR is

applicable• Instead of side coil

– Smaller sample size• Longer T2: ~5.5ms

pre-filled 4He

Bottem cell for pNMR

NMR solenoid Probe coil

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Cell inner Surface treatment at room

temperature• Cs coating reduces wall

depolarization effect– Cs Azide Rod moves

down into top/bottom cell– heating Cs Azide (CsN3)

rod• Cs moves straightly in

vacuum• No shadow area

Cs Aziderod

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3He-4He mixture

• temperature and pressure measurements provide valuable information – 3He vapor concentration X :

– 3He liquid concentration Xliq , W/k=1.54 Kelvin

– Applicable at equilibrium state P.J. Nacher, J low Temp. Phys V97, p417,1994

• ~10 temperature sensors will be installed• Ruthenium Oxide RTDs from Lakeshore

41satP

XP

(1 2 )3

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e1

X WliqKT

satliqX

X satliq

X P

X P

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Polarization measurmnet

• Plused NMR– Resonance frequency at 3.89MHz– Very low density of 3He: 1014atoms/cc

• Very good signal to noise ratio– Must Push what is possible for pNMR– Most helpful to have squids detector

• Will squids work without magnetic shielding?

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Schematic of pNMR probe

• Signal in the probe coil– >160V during RF transmitter– ~1uV NMR signal of FID

Inside dewar

RF amp

Apollo console from NCSU

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pNMR : tank circuit• Tank circuit:

– Probe Coil at resonance• Inductance: 32uH with 40 turns

– Tunable capacitor• non magnetic• low temperature• High voltage

– piston trimmer

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Resonance tuning inside dewar

• Piston trimmer close to probe coil

• Very small signal: 1nV/loop • the circulating current does not need to go

through the coax

• Piston trimmer capacitor ordered

– 5~120pF

30 40 50 60 70 80

50

100

150

200

Number of turns

C (pF)

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Probe of pNMR close to our design

Rev. of Sci. Instr. 68, 2132 (1997).

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COAX connects the tank circuit

• High-Q Coax cable:– inner: Ag plated BeCu– outer: CuNi – insulated with Teflon

• good electric conductivity• Poor thermal conductivity

Courtesy by Dr. William Halperin, NWU

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Inhomogeneous B1 field for single solenoid probe

coil

A separate Helmholtz coil for RF power transmitting is under design

Spins rotate by 90 deg.RF pulse duration time: ~100uSB1 field: 7.6G2cm

2cm

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pNMR: RF amplifier

• From Tomco – Linear amplifier

type: AB– Blanking time

~1us• 1dBm=0.22V

– RF noise:~ 0.2uV

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pNMR: lumped circuit and RF Amplifier

• lumped circuit Works as a duplexer – Block pre-amp during

RF transmitting– Conducting for FID

• RF Amplifier From Tomco – Blanking time ~1us

• 1dBm=0.22V

– RF noise:~ 0.2uV

Zi Zo = Z2 = 1/ω2c2

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Other studies on cryogenic pNMR

• Low noise high impedance Pre-amp

• Q-spoils circuit to shorten the recovery time

• Ground loop • Ultrasonic noise

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Schedule

• Test and install the magnet system • in June , July and August

• Start pyrex cell fabrication • June and July

• Optimize pNMR system– To see glycerol signal with Apollo console at low field– Improve the signal/noise ratio at room temperature– Cool the sample and tank circuit– improve signal at low temperature

• June , July and August

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Thanks!

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Design of Feed through and trimmer handle

BNC-SMA

Hermetically sealed

SMA bulkhead

SMA-coax adaptor

Courtesy by Dr. William Halperin, NWU