Study of PEDRI (Proton Electron Double Resonance Imaging)

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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.