Study of PEDRI (Proton Electron Double Resonance Imaging)

为了研制0.2 Testar Pedri(质子电子双共振成像仪)，研制了微波辐射器，其频率分别为8 MHz(核磁共振)和5.6 GHz(EPR)。EPR微波辐射器必须能够承受5W CW，并产生大约10 mm×20 mm的均匀磁场。在本研究中，用于获得上述微波磁场的基本施加器由TE&lt；10&gt；矩形波导组成。我们测量了(1)无凸缘波导、(2)带凸缘波导、(3)栅极端面TE101腔谐振器和(4)导电板的磁场分布。用于测量磁场的拾取线圈的内径为1 mm。钢丝的直径为0.3毫米。以下三个问题变得显而易见。(1)切割波导孔口处的磁场强度约为最大值的1/10，磁场主要集中在波导壁较长一侧的中心，磁场分布不均匀。定义为场强最小值/最大值的磁场分布均匀度在孔口处为0.09，在孔口处为0.45。(2)带凸缘的波导在孔口处的磁场分布的均匀性为0.14，比孔口处的磁场分布更均匀，即孔口外侧的磁场分布为0.70。(3)栅端接TE101腔腔的场分布均匀度的最佳值为0.37。(4)端接开路的导电板的场强分布的均匀性最好。

In order to develop a 0.2 Testar PEDRI (Proton Electron Double Resonance Imaging), microwave applicators have been studied.The frequencies are 8 MHz for NMR and 5.6 GHz for EPR.A NMR RF applicator is a solenoid or a birdcage coil. An EPR microwave applicator must be able to withstand 5 W CW and to generate homogeneous magnetic fields of about 10 mm X 20 mm. In this study, a basic applicator consists of a TE_<10> rectangular waveguide to obtain microwave magnetic fields mentioned above. We measured distribution of magnetic fields of (1) a waveguide without a flange, (2) a waveguide with a flange, (3) a TE101 cavity resonator terminated by grids and (4) a conducting plate. The inner diameter of the pick up coil used for the measurement of the magnetic field is 1 mm. The diameter of the wire is 0.3 mm.Following three matters have become obvious. (1) The magnetic field strength at the aperture of a cut waveguide is about 1/10 of the maximum value, the magnetic field mainly concentrates at the center of the longer side of the waveguide-wall and the distribution of the field is not homogeneous. The magnetic field distribution homogeneity which is defined as the minimum value /the maximum value of the field strength is 0.09 at the aperture and is 0.45 at the outer side of the aperture. (2) The magnetic field distribution homogeneity of the waveguide with the flange is 0.14 at the aperture and is better homogeneous than the magnetic field distribution at the aperture, that is, 0.70 at the outer side of the aperture. (3) The best value of the field distribution homogeneity for the TE101 cavity resonator terminated by grids is 0.37. (4) The homogeneity of the field strength distribution for a conducting plate which is terminated by the open-circuit and connected to the cut waveguide has the best homogeneity.