This thesis describes an optically pumped magnetometer system incorporating various
microfabricated caesium vapour cells. The experiment operates in a free-inductiondecay
configuration, where two co-propagating laser sources are used for optical pumping
and probing, granting independent control of both. Intense pumping on the D2
transition line is employed to generate a high spin-polarisation, resulting in excellent
performance levels. Magnetic bias field amplitudes of 50 μT emulate the Earth’s field
in a magnetically shielded laboratory setting. Sensitivities at the fT/
√
Hz levels are
demonstrated in both 3 mm and 6 mm thick cells for tuneable Nyquist-limited sensor
bandwidths between 250-500 Hz. A peak sensitivity of 118 ± 11 fT/
√
Hz is obtained
for a 6 mm thick cell.
A novel enhancement to the achievable spin-polarisation created during the optical
pumping stage is established, with promising use in real-world sensing applications.
This technique also enables heating of the vapour cell to be performed during the
conventional dead-time of the sensor. The distribution of the atomic spins is also
manipulated to utilise the sensor as an atomic comagnetometer. The extraction of
the intrinsic longitudinal relaxation rates from multiple cells, as a function of nitrogen
buffer gas pressure content is also undertaken. A minimum relaxation rate of 140 Hz is
determined at a pressure of 115 Torr. The versatility of the sensor is also demonstrated
with successful 1D and 2D magnetic image reconstructions of DC and AC fields.
| Date of Award | 27 Jun 2024 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | University of Strathclyde |
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| Supervisor | Erling Riis (Supervisor) & Paul Griffin (Supervisor) |
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