Patent ID: 8427057

Claim:
A microwave frequency structure for microwave tube comprising: a cylindrical vacuum jacket and a device for containing an electron beam in the axis of revolution ZZ′ of the cylindrical jacket, the containing device comprising a magnetic structure having p rows R 1 , R 2 , . . . , Rp of permanent magnets, distributed at an angular pitch equal to 360°/p around the axis ZZ′, p being an integer equal to or greater than 2, each row having n containing permanent magnets e 1 , e 2 , . . . ei, . . . en, i being an integer between 1 and n, n being greater than or equal to three, the rows being equidistant from the axis ZZ′, the n containing permanent magnets e 1 , e 2 , . . . ei, . . . en, being of the same parallelepipedal shapes and having magnetic polarization parallel to one of its edges in a plane transversal to the axis ZZ′, their direction of magnetization in the row changing alternately from one containing magnet ei to another next containing magnet ei+1, or preceding containing magnet ei−1, to create an alternating periodic magnetic field along the containment axis ZZ′, wherein the magnetic structure of the containing device is unchanging for a rotation of 360°/p of said p rows about the axis ZZ′.