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Table of contents
List of Figures
List of Tables
List of Symbols, Constants, He OP lines, Abbreviations
1 Introduction
2 MEOP basics and OP model
2.1 Short introduction to MEOP
2.2 He level structure at low magnetic field
2.3 Optical transition rates
2.3.1 Monochromatic excitation
2.3.2 Broadband excitation
2.4 Rate equations for OP and ME in pure 3He gas
2.4.1 Generic OP rate equations
2.4.2 Generic ME rate equations
2.5 The improved 2-class OP model
2.5.1 Relaxation processes
2.5.2 Velocity-dependent light excitation
2.5.3 Inhomogeneous light excitation and atomic response: 1-D model
2.6 Comparison of all rates relevant for MEOP in 3He gas
2.7 Numerical computation of MEOP dynamics
2.7.1 Equation solving strategy
2.7.2 Full rate equations
2.7.3 Numerical implementation
2.7.4 Input data and input parameters
2.8 MEOP dynamics
2.8.1 ME-driven spin temperature distribution
2.8.2 Dynamics of polarisation decay (no OP)
2.8.3 OP-driven MEOP dynamics
2.8.4 Angular momentum budget
2.9 Photon efficiencies for low field MEOP
2.10 Final discussions
2.10.1 Comparison with previous OP models
2.10.2 Robustness of our computed OP results
2.10.3 Conclusion
3 Experimental setup
3.1 Magnetic field, cells and rf discharge
3.2 Optical setup
3.3 Measurement and acquisition system
4 Optical measurement of nuclear polarisation
4.1 Longitudinal probe absorption measurements
4.2 Polarisation measurements in the absence of OP light (during polarisation decay)
4.2.1 Determination of M by C8 probe
4.2.2 Determination of M by C9 probe
4.2.3 Influence of residual π-light on longitudinal probe absorption measurements
4.3 Polarisation measurements with OP light (during polarisation build-up)
4.4 Measurements of metastable density nS m
4.4.1 Determination of nS m for single-component and multi-component transitions: Examples of C8 and C9 probe
4.4.2 Influence of collisional broadening and lifetime
5 Methods of data processing and data reduction
5.1 Introduction to data reduction
5.2 Polarisation build-up and decay
5.2.1 Transmitted probe signals
5.2.2 Demodulated probe signals
5.3 Dedicated experiments to account for perturbations of 23S- and 23Ppopulations in presence of the pump laser
5.4 Inferring actual M-values during polarisation build-up in presence of the pump laser
5.5 Analysis of polarisation build-up kinetics
5.6 Pump output signals
5.6.1 Transmitted pump signals
5.6.2 Demodulated pump signals
5.7 Laser-enhanced relaxation
5.7.1 Deriving polarisation loss rates ΓR using the MEOP model
5.7.2 Deriving polarisation loss rates ΓR from a detailed balance of angular momentum
6 Results
6.1 Characterisation of the plasma without OP light
6.1.1 Key plasma parameters for MEOP: nm(M = 0) and ΓD
6.1.2 Transverse distribution of 23S atoms
6.1.3 Variation of metastable density with nuclear polarisation
6.2 Results of dedicated experiments to account for perturbations of 23Sand 23P-populations
6.2.1 Influence of probe detuning on apparent polarisation at M = 0 . 197
6.2.2 Computed Ma at M = 0 with probe laser in resonance as function of pump laser power
6.2.3 Example of apparent polarisation as function of actual polarisation
6.2.4 Reproducibility of apparent polarisation in fixed OP conditions 208
6.2.5 Examples of Ma measured by probe on the C9-transition
6.2.6 Perturbations of 23S and 23P populations in higher magnetic field: B = 30 mT versus 1 mT
6.2.7 Scaling of Ma with incident pump laser power and pressure
6.2.8 Effect of pump beam diameter and probe parameter xs on apparent polarisation
6.2.9 Conclusion
6.3 Optical Pumping results at 1 mT
6.3.1 Results at B = 1 mT and M = 0: Relaxation-free data to test and validate the model for MEOP kinetics
6.3.2 Empirical determination of the intrinsic relaxation rate in the 23P state
6.3.3 Results at Meq (B = 1 mT) and evidence of laser-enhanced relaxation
6.3.4 Results as function of M (B = 1 mT) and further characterisation of laser-induced relaxation
6.4 Effects of magnetic field on OP performances
6.5 Discussion of laser-enhanced relaxation effects
6.5.1 Comparison of ΓL rates of different works
6.5.2 Radiation trapping
6.5.3 OP-induced plasma ’poisoning’ (e.g., by metastable He molecules)292
7 Conclusion and Outlook
A Tables and matrices for low magnetic field (B < 0.162 T): Transition frequencies and intensities for 3He and 4He, Zeeman shifts, hyperfine mixing parameters, vector and matrix operators
B MEOP rate equations and angular momentum budget in the improved OP model
B.1 The improved OP model
B.2 Two-class partition and description of local OP rates
B.3 Local rate equations for 23S and 23P populations
B.4 Rate equation for M, MEOP dynamics, and global angular momentum budget
C Computation of the average pump light intensity inside the cell for the improved OP model
D Computation of photon efficiencies of C8 and C9 lines at null polarisation and in zero magnetic field, for the limits of no and full collisional mixing in the 23P state (Kastler and Dehmelt OP regimes)
E Numerical demodulation of signals
E.1 Requirements and characteristic functionalities
E.2 Rician noise in the context of lock-in detection
F Validation of methodological approach in analysis of polarisation build-up kinetics using synthetic data
G Influence of stimulated emission on scaling of Ma with incident pump laser power and pressure
Bibliography
