Dressed Spin Studies with Polarized 3He

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Dressed Spin Studies with Polarized 3He
Andrea Esler Jen-Chieh Peng (UIUC)
Steve Lamoreaux Chen-Yu Liu (LANL)
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Dressed Spin

• Strong RF fields change the effective magnetic
  moments of neutrons and 3He
• First 3He spin dressing measurements performed in
  April 2005
• Change of 3He Larmor frequency with a dressing
  field has been observed.

In the B0ltltB1 limit, the g factor modification
has a simple formula
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Dressed Neutron Spin already observed
Muskat, PRL 58(20), 1987
Numerical simulations reproduced these results
Fits the J0(gB1/w) prediction
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Critical dressing equalizes precession rates

• Reduce the effect of B0 instability on the two
  species
• A check of gng3 scintillation no longer
  modulated

Crossing points equalize neutron and 3He g
factors
Effective dressed g factors
neutron
3He
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Polarized 3He Source
Spin flip region
3He detector
Injection nozzle
Quadrupole analyzer
1 K cold head
Quadrupole separator
4 m
Experiment
Solenoid field 8 Gauss
3He detector RGA
Spin polarizer
Spin analyzer
B1 rf
90 cm
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Ramsey experiment technique (SOF)
Images courtesy Sussex Neutron EDM group
Free precession
Incoming 3He
p/2 pulse
Second p/2 pulse
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Z component of nuclear spin
Analyzer Counter
-1
accepts P1 state
When the RF pulses are applied on resonance (at
the Larmor frequency) the 3He spin direction is
completely reversed (minimal transmission)
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3He experiment setup
Ramsey coils and dressing coils are inside the
solenoid
source
solenoid
to analyzer and RGA detector
polarizer
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3He beam polarization P gt 95
Unpolarized transmission
Full beam transmission
RGA pressure reading
p pulse field setting
Spin-flip magnetic field B1 x distance
Dec. 2004 P99.6 was measured with better
shielding
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From Dec. 2004 meeting

• Polarization (as fn. of B1) averages over 3He
  velocities
• P(B1) measures Fourier cosine transform of
  velocity spectrum
• Invert the FT to measure N(v)

Velocity spectrum deduced from April measurements
needs to be calibrated, but we expect agreement
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3He beam background pressure
open and closed shutter
6 nTorr
the same, log scale
0.01 nTorr
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Dressing magnet coil
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Dressing coil field map
Average field 1.6 Gauss / Ampere
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3He dressed spin results I
Dressing field frequency 43.5 kHz
Increasing dressing field
Minimal transmission rate observed at the 3He
Larmor precession frequency
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3He Larmor Freq. Dressed at 43.5 kHz
Max B field 5.8 G
Inconsistent with simple formula B0B1
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43.5 kHz data vs. simulation
Rough agreement with Bloch-equation simulations
I am working to refine the code
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3He dressed spin results II
Dressing field frequency 8.1 kHz
Increasing dressing field
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3He Larmor Freq. Dressed at 8.1 kHz
Max B field 1.6 G
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Outlook

• Continue analysis
• Understand observed Larmor freq. behavior
• Upcoming measurements (this week) will emulate
  EDM experimental conditions
• More intense dressing fields over smaller volume
  (new coils already built)
• Smaller B0 (limited by earths field 5 G)
• Larger dressing field frequency 50-100 kHz