Abstract
The design and construction of a high-performance, low-cost, and easy to assemble adiabatic extension set for homebuilt and commercial spectrometers is described. Described apparatus set was designed for the fast adiabatic passage generation and is based on direct digital synthesizer DDS. This solution gives generator high signal to noise ratio, phase stability even during frequency change which is only possible in expansive commercial high-end hardware. Critical synchronization and timing issues are considered and solutions are discussed. Different experimental conditions and techniques for the measurements are briefly discussed. The proposed system is very flexible and might be used for the measurement of low-frequency nuclear magnetic resonance.
Highlights
Fast adiabatic passage is a fusion of continuous-wave (CW) and pulse techniques
Described apparatus set was designed for the fast adiabatic passage generation and is based on direct digital synthesizer direct digital synthesis (DDS)
The basic equipment necessary for the adiabatic fast passage (AFP) experiments is a B1 magnetic field sweep generator based on direct digital synthesis (DDS) and RISC microcontroller
Summary
Fast adiabatic passage is a fusion of continuous-wave (CW) and pulse techniques. It has significant advantages. The modification of the commercial Varian HA-100 NMR spectrometer to permit frequency sweep adiabatic fast passage measurements of T1 was described in Ref. The purpose of this work was to describe the versatile experimental setup, apparatus for this purpose and procedure used in our laboratory for the AFP experiments, and to discuss briefly this method for measuring relaxation times and NMR and the possibility to perform a new EPR (radio frequency) T1 imaging. A new technique of the spin–lattice T1 relaxation time measurement based on the fast adiabatic passage and on the longitudinal component of the magnetization [1] is devoid of the aforementioned limitations. The basic equipment necessary for the AFP experiments is a B1 magnetic field sweep generator based on direct digital synthesis (DDS) and RISC microcontroller. This sine wave can be used directly as a frequency source; for NMR purpose an external amplifier with input and output impedance designed at 50X must be added
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