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

扫频式核磁共振谱仪测量铁磁材料的核磁共振谱时，需要对测量系统在各个频率进行调谐和匹配，这是一个非常耗时的过程，实现扫频式核磁共振谱仪的自动化比较困难。这与用于顺磁性材料的扫场型NMR光谱仪的情况不同，扫场型NMR光谱仪仅通过以固定频率扫描所施加的磁场就可以容易地自动化。本课题的目的是利用宽带放大器和市场上的其他元件组装一台计算机控制的铁磁材料核磁共振谱仪。(1)利用非调谐式取样电路和宽带元件，对自制调谐式核磁共振谱仪进行了改造，使其工作在10 ~ 1000 MHz的宽频率范围内。组装了继电器电路，自动控制第一脉冲的180 Ω相位和第二脉冲的90 Ω相位。 ...更多信息 双平衡混频器的参考信号。(2)编制了控制信号发生器和数字示波器的计算机程序。(3)通过对系统的调整，使系统在整个频率范围内对核磁共振信号的探测灵敏度尽可能一致，并成功地用于Gd化合物和过渡金属化合物的核磁共振测量。在10- 1000 MHz的宽频率范围内，即使在夜间和白天，也能自动连续测量。例如，灵敏度在高于500 MHz的频率范围内稍低，并且由于电路中各种元件的连接点处的阻抗失配，在某些特定频率处发生放大器的饱和。在不久的将来，将使用在500 MHz以上频率范围内具有高增益的宽放大器和高质量的Aweep发生器来改善这些。少

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