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144 Appendix Awhere S 0 is a constant proportional to M 0 , and T 2 is the transverse or spin-spin relaxationtime. As the magnetization is tipped to the transversal plane by the 90 ◦ the longitudinalmagnetization M z is zero but restores to the equilibrium magnitude M 0 in the course oftime due to energy transfer between the spins and the thermal reservoir (lattice). Themagnetization restores with an exponential function given by(M z (t) = M 0[1 − exp − t )], (A.10)T 1where T 1 is the longitudinal or spin-lattice relaxation time. In case of hydrogen therelaxation processes are driven by dipole-dipole interactions among the protons [51].Fig. A.4: The two NMR set-ups used for the experiments. (left) 4.7 Tesla super-conductingmagnet (Oxford, Oxon, UK) with a 3D-imaging, pulsed-gradient insert (Doty,Columbia, SC, USA). (right) 0.95 Tesla iron-cored electromagnet with a home-builtinsert equipped with a 1D static gradient. The insert is designed to measure bothhydrogen and deuterium.A.2 NMR set-upTwo NMR scanners were employed for the experiments (see Figure A.4). The first system,consisting of a 4.7 Tesla super-conducting magnet and a 3D-imaging insert with pulsedgradients, was used for the first set of bulk experiments and the IFT analysis (see Chapters2 and 3). The second system, consisting of a 0.95 Tesla iron-cored electromagnet andhome-built insert, was used for the second set of bulk experiments (see Chapter 4) andfor the core injection experiments (see Chapter 6).The 4.7 Tesla scanner has a vertical insert with an inner diameter of 40 mm and isequipped with a set of three pulsed magnetic gradients for imaging purposes. The rfcircuit contains a Litz volume coil [153] and three adjustable capacitors for tuning andimpedance matching. A duplexer is used to separate the transmitted rf power from thereceived rf signal. A schematic of the set-up is shown in Figure A.5. The circuit isdesigned for hydrogen and is tuned at 200 MHz.