Trial Manufacture of Computer-Controlled NMR Spectrometer for NMR of Ferromagnetic Materials in a Wide Frequency Range between 10-1000MHz.

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It is rather difficult to automatize a swept frequency-type spectrometer for measuring the NMR in ferromagnetic materials, because the tuning and matching of the measuring system at each frequency of interest are needed, which consumes time extremely. This is different from the case of a swept field-type NMR spectrometer for paramagnetic materials, which can be easily automatized only by sweeping the applied magnetic field at a fixed frequency. The purpose of this project is to assemble a computer-controlled NMR spectrometer for ferromagnetic materials by using wide band amplifiers and other compornents on the market.The process of assembling a new NMR spectometer was as follows.(1) A self-made NMR spectrometer of the tuned type was rebuilt to work in a wide frequency range between 10 and 1000MHz by using an untuned type of the sample circuit and wide band compornents. Relay circuits were assembled, which control automatically the 180ﾟ phase of the first pulse and the 90ﾟ phase of refe … More rence signal for a double balance mixer.(2) A computer program was made, which controlls a signal generator and a digital oscilloscope.(3) The assembled system was ajusted in such a way that sensitivity for detecting NMR signals is as equal as possible through the whole frequency range.The computer-controlled NMR spectrometer successfully operates for measuring the NMR of ferromagnetic Gd compounds and transsition metal compounds. The measure-ments can be continued automatically over a wide frequency range 10-1000MHz even night and day, if necesary.In our new system there are a few problems to be improved. For example, the sensitivity is a little lower in the frequency range above 500 MHz, and a saturation of the amplifier takes place at some special frequencies owing to mismatch of the impedance at the connecting points of various components in the circuit. These will be improved by using a wide amplifier with high gain in the frequency range above 500 MHz and a aweep generator with high quality in near future. Less