Rotatable target assembly esp. using tritium for particle accelerator - has targets exposed successively to bombardment by movement of previous target

A rotatable target assembly for particle accelerators, esp. a rotatable tritium target assembly, is intended for generating neutron beams, esp. in cancer therapy. Two or more targets of circular shape or circular cross-section and movable one relative to the others are used; each target can be moved so that in one position it itself is bombarded, while in a second position it permits bombardment of the next target in the series. In one preferred arrangement a number of disc-shaped targets are mounted rotatable about a common axis; each target possesses an aperture which, in the appropriate position, can permit the passage of the bombarding beams to the next target. In another embodiment, a number of concentric targets of decreasing size, each of truncated conical shape, operate on a similar principle. A very lage number of targets can be incorporated in one compact appts., thus providing a long target operating life without need to interrupt use of the appts. in order to change targets.