NMR Lock Controller RF Pulses for Faster Equilibrium Recovery
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Solution Overview
Problem
Existing NMR measurement systems face challenges in quickly achieving equilibrium state during NMR lock control, particularly after disturbances such as gradient pulses, leading to suboptimal measurement accuracy and prolonged settling times.
Innovation Solution
Applying targeted RF pulses to align the x-component of spin magnetization with its equilibrium value, either before or after disturbances, using angles determined by time constants T1 and T2 of the reference substance and NMR lock excitation strength, to rapidly establish the lock equilibrium state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If excitation power is increased to accelerate the growth of the x-component of spin magnetization at the beginning of NMR lock control, then the attainment of equilibrium state is accelerated, but the system overshoots the target equilibrium value and requires additional delay time to reach it
Solution Approach 1:
The invention applies a preliminary RF pulse before starting the NMR lock control to pre-align the spin magnetization vector such that its x-component already corresponds to the equilibrium value. This preliminary action prevents the overshooting problem that occurs when excitation power is increased, allowing the system to reach equilibrium faster without the need for corrective delay time.
2Productivity
If gradient pulses are applied for NMR measurement, then the NMR measurement can be performed, but the spin magnetization is cancelled in an uncontrolled manner and requires long settling time
Solution Approach 1:
The invention applies a preliminary RF pulse after gradient pulses to realign the spin magnetization vector and restore the x-component to its equilibrium value. This preliminary action after disturbance quickly recovers the lock equilibrium state without requiring long natural settling times, enabling faster repetition of NMR measurements with gradients.
3Adaptability or versatility
If the radio frequency channel is used for decoupling during NMR measurement, then the decoupling can be performed, but the spin magnetization is disturbed and measurement accuracy is reduced
Solution Approach 1:
The invention applies a preliminary RF pulse after decoupling operations to restore the spin magnetization to its lock equilibrium state. This ensures that subsequent lock control measurements are performed from a known, stable equilibrium state, maintaining measurement accuracy while preserving the versatility of using the radio frequency channel for decoupling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach accelerates the attainment of the lock equilibrium state, improving measurement accuracy and reducing the impact of disturbances on NMR measurements.
Implementation Method 1
a measuring RF coil for exciting nuclear spins of a measuring substance
Implementation Method 2
a main field magnet for generating a static main magnetic field in a z-direction
Implementation Method 3
an NMR lock controller for detecting field disturbances and for generating a correction field by means of a compensation coil
Data Source
Figure 1~2b
Figure 3~4
Figure 5
AI summary
The invention relates to a method for operating an NMR measurement system with a main field magnet for generating a static main magnetic field B0 in a z direction, a measurement HF coil for exciting core spins of a measurement substance, an NMR lock controller for detecting field interferences and for generating a correction field by means of a compensation coil, wherein lock controlling is carried out during which spins of a reference substance are excited, characterised in that by applying an HF pulse (1, 1') a spin magnetisation M of the reference substance is brought from a non equilibrium state into a state in which the x component Mx of the spin magnetisation has an equilibrium value Mxeq, wherein the x component Mx of the spin magnetisation is oriented in an x direction which is perpendicular to the z direction. Improved measuring accuracy is achieved as a result.