Automatic Coupling Control of a Loop–Gap Resonator by a Variable Capacitor Attached Coupling Coil for EPR Measurements at 650 MHz
Automatic Coupling Control of a Loop–Gap Resonator by a Variable Capacitor Attached Coupling Coil for EPR Measurements at 650 MHz
复制标题
通过附加耦合线圈的可变电容器对环路间隙谐振器进行自动耦合控制，用于 650 MHz 下的 EPR 测量
DOI：
10.1006/jmre.2000.2268
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发表时间：
2001
影响因子：
2.2
通讯作者：
H. Kamada
中科院分区：
文献类型：
--
作者：
H. Yokoyama;Toshiyuki Sato;T. Ogata;H. Ohya;H. Kamada
摘要 制造了一种耦合线圈，可以通过电气方式改变与环隙谐振器 (LGR) 的磁耦合，用于 650 MHz 下的 EPR 研究。它由单匝线圈和包含变容二极管的耦合控制电路组成。通过机械改变LGR与单匝线圈之间的距离来实现磁耦合的粗调。通过改变与单匝线圈并联的变容二极管的电容来实现精细控制。通过改变来自可变偏置电压源的反向电压来控制该电容。因为它可以远离谐振器，所以可以远程控制 LGR 的耦合。自动耦合控制(ACC)是通过当LGR以其谐振频率精确照射时从LGR反射到耦合控制电路的无线电波中的直流分量的负反馈来实现的。为了实现这一点，使用了自动频率控制（AFC）。在对包含含有硝基氧自由基的生理盐水溶液的体模进行 EPR 测量时，证实由共振性质的扰动引起的耦合和共振频率的漂移可以由 ACC 和 AFC 系统充分补偿。在体内EPR研究中，发现小鼠胸部的耦合偏差大于大鼠头部的耦合偏差，但ACC系统可以补偿活体动物的呼吸运动。
Abstract A coupling coil was fabricated that can electrically change the magnetic coupling with a loop–gap resonator (LGR) for EPR studies at 650 MHz. It is composed of a single-turn coil and a coupling control circuit that includes a varactor diode. The coarse control of the magnetic coupling is made by mechanically changing the distance between the LGR and single-turn coil. The fine control is obtained by changing the capacitance of the varactor diode that is connected in parallel with the single-turn coil. This capacitance is controlled by changing reverse voltage from a variable bias voltage source. Because this can be located far from the resonator, remote control of coupling of the LGR is possible. Automatic coupling control (ACC) was accomplished by negative feedback of the DC component in the radiowaves reflected from the LGR to the coupling control circuit when the LGR was irradiated precisely at its resonant frequency. To accomplish this, automatic frequency control (AFC) is used. In EPR measurements of a phantom that included a physiological saline solution containing a nitroxide radical, it was confirmed that the drifts in the coupling and resonant frequency caused by the perturbation of the resonant nature could be sufficiently compensated by the ACC and AFC systems. In the in vivo EPR studies, it was found that the deviation of coupling at the chest of a mouse is greater than that at the head of a rat, but the ACC system could compensate for the respiratory motions of a living animal.