3 He Polarization Tests at UIUC Danielle Chandler David Howell UIUC

Overview Confirmation of successful 3 He polarization using 1083-nm optical signal Use of optical signal to calibrate perturbing field (B 1 ) NMR setup and initial tests

Tests using optical signal cell light detector cell

Confirmation of 3 He Polarization Baseline drops on the 1083-nm light signal when B 0 is turned on 1083-nm light produced in cell decreases when 3 He is polarized because polarized atoms do not interact with the circularly-polarized laser light

Response of optical signal to continuous oscillatory B 1 field Scanned through the B 1 resonance frequency and recorded the optical signal At resonance, the perturbing field rotates the 3 He spins away from the B 0 axis, which makes the optical pumping more efficient… therefore there is a peak in the optical signal at resonance.

Results of B 1 frequency scans Non-zero width as B 0 → 0 reflects nonuniformity in B 0 /B 1 fields B 1 dependence suggests B 0 /B 1 nonuniformity

Response of optical signal as a function of time Amplitude of oscillation damps out as cell becomes depolarized Signal decays as laser light repolarizes the 3 He cell end of pulse Optical signal peaks when the pulse time gives a π pulse, since this should orient the spins antiparallel to the B 0 axis, making optical pumping maximally efficient

Using optical signal to calibrate π/2 burst pulse First maximum corresponds to π pulse T B 1 program voltage = 2.5 V pp For a given B 1 : Can use this optical method to calibrate B 1 :

NMR Measurement Setup Adiabatic fast passage method Free induction decay method

NMR Measurements With current setup, we observe the sensitivity to detect NMR signal at a level of 0.2 μ V Need to improve the design of the NMR for a better signal/noise ratio Calculate that NMR signal should be of the same order of magnitude Response of NMR coil to B 1 pulse burst

Conclusion Optical signal tests were successful and provide a method of calibrating B 1 Preparing to make improvements on NMR sensitivity (for example) increase number of turns on pickup coils optimize position and geometry of coils optimize Q-factor introduce second pair of pickup coils