Abstract
Pulsed magnetic field generation is a critical aspect of all nuclear magnetic resonance (NMR) experiments. In this paper, a novel design for a low field, low frequency (less than 5 MHz), pulsed magnetic field generation circuit suited for unilateral NMR applications is presented. A pulsed sinusoidal current is generated at an inductive load connected to an FET-based switch. The inductive load resonates at a frequency of approximately 2 MHz, which is also the precession frequency of $^{1}H$ protons in an external magnetic flux density of 500 G. The designed circuit can be tuned to operate at resonant frequencies of other chemical species as well. In this paper, the design parameters and operation of the prototype pulsed field generator will be discussed.
Highlights
P ULSED magnetic fields find wide use in communication systems [1], optical switching [2], Q-switched pulsed lasers [3], [4], biological applications [5], [6], and medical applications, such as transcranial magnetic stimulation [7].Nuclear magnetic resonance (NMR) is one such technique where the presence of particular nuclear species is detected by applying pulsed magnetic fields in the presence of static fields
Most of the magnetic moments tend to align in the lower energy orientation, while some will align in the higher energy orientation
The circuit can generate variable oscillating magnetic fields that is required for pulsed nuclear magnetic resonance (NMR) applications
Summary
Nuclear magnetic resonance (NMR) is one such technique where the presence of particular nuclear species is detected by applying pulsed magnetic fields in the presence of static fields. The technique is popular in biological applications, and in particular, it is widely used for imaging human tissue [8]. In NMR, the detection process relies on the relaxation of nuclear magnetic moments in an externally applied magnetic field [9]. A uniform static magnetic field is applied to pre-align the magnetic moments in a particular orientation. The moments are constantly precessing along the external magnetic field direction. This is known as Larmor precession and can be induced by application of an external radio frequency (RF) pulse
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