Gun-only magnet used for a multi-stage depressed collector klystron

A vacuum electron device including a source of electrons, said electrons being configured into a narrow beam, and a multi-stage depressed collector for collecting said electrons, the improvement comprising:

• a magnet arrangement surrounding and focusing said narrow beam, the magnetic flux of said magnet arrangement being parallel to and collinear with the centerline of said electron beam, said magnet arrangement having a first open pole piece adjacent to the area of said source of electrons to initially focus said electron beam, and a second open pole piece along said centerline to focus and drive said electron beam, said magnet having no open magnet pole piece in the vicinity of said multi-stage depressed collector so that any magnetic flux from the magnet is directed back into said magnet arrangement, and
• a magnetic material surrounding the multi-stage depressed collector such that substantially no magnetic field reversal is present at the multi-stage depressed collector.

A gun only magnet utilized in a multi-stage depressed collector high-energy vacuum electron device comprising:

• a first pole piece region generating magnetic flux adjacent a cathode of said vacuum electron device to drive and initially focus electrons emitted from said cathode,
• a second pole piece region providing magnetic flux along the path of electrons to focus said electrons into a narrow beam, said magnet having no pole magnet piece in the region of said vacuum electron device where the electrons are collected and returned to said cathode, and
• a magnetic material surrounding the region of collected electron such that substantially no magnetic field reversal is present at the region of collected electron.