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Applications


Applications

LANL Large Orbit Gyrotron

[June 1996] - Gridgen was used to generate this grid for a 3D electromagnetic particle-in-cell simulation of the Los Alamos Large Orbit Gyrotron high power microwave source. The 3D ISIS code was used for the simulation wich was performed at Los Alamos National Laboratory by R.J. Kares, M.E. Jones and V.A. Thomas.

Gyrotron Grid

The first figure below shows a side view of the geometry rotated slightly to reveal the vacuum gap between the cathode and anode. The cathode, which is the structure on the left in this first view, consists of a long metal stalk with a metal disk on the right hand end. The disk has a cone shaped indentation which serves to focus the electron beam which is emitted off the face of the cathode. On the right in this view is a circular plate which is the anode. This plate has an annular slot in it which can be seen in the view. This slot with its central disk support by three metal posts, allows the annular electron beam from the cone surface of the cathode to enter the hollow microwave resonator region which is visible on the far right. This resonator consists of a hollow metal cylinder with three annular vanes on its interior surface.

Gyrotron

The next two images rotate the geometry slightly to reveal the vanes of the resonator structure. The idea is that when a voltage pulse is applied to the cathode-anode gap, a hollow annular electron beam is emitted off the cathode cone surface, and propagates across the gap while at the same time spinning up in an external magnetic field. The hollow spinning electron beam then passes through the annular slot in the anode and into the vaned resonator region where the rotating electron charge generates microwave fields in the vaned structure. The last block of the mesh represents a region where the resultant microwaves propagate out into vacuum. The views represented here are of the interior of the problem geometry. The outer cylindrical boundary of the meshed region is a metal wall and is naturally not shown.

Gyrotron

Gyrotron

The simulation of this device was performed with the Los Alamos 3D electromagnetic PIC code ISIS. This code utilizes a block structured curvilinear hexahedral mesh and can run extremely large problems on the Cray T3D massively parallel supercomputer.