A new PM-focusing system with two regions of uniform magnetic field, suitable for gyrotron is proposed and studied with computer. In the calculation, a radial system made of Sm-Co magnets is used. The maximum magnetic energy-products (BH)max of the magnets are about 20MGOe. In order to adjust the magnitude of the magnetic field, some small coils are inserted into the two regions so that about five percent field change can be obtained.As a computed example a 40-50 kg Sm-Co PM-focusing system for an 8 mm band H02 mode gyromonotron operating at secondary harmonic of the cyclotron frequency is needed to obtain an intense magnetic field of 6500-7000 Gs. This is very atteractive for the development of 8 mm band gyrotrons and near-centimetre band ones. In the last part of the paper some problems such as the extension of the uniform region and increasing the efficiency of magnetic circuit are briefly discussed.
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