Thesis
A dual-beam free induction decay magnetometer
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T17014
- Person Identifier (Local)
- 201978577
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- 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.
- Advisor / supervisor
- Griffin, Paul
- Riis, Erling
- Resource Type
- DOI
Relations
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PDF of thesis T17014 | 2024-07-16 | Public | Download |