A device is provided for sealing an inner tube and an outer tube without excessively deforming the tubes. The device includes two ferrules which cooperate to form a vacuum-tight seal between the inner tube and outer tube and having mating surfaces such that overtightening is not possible.

A free electron laser and free electron laser amplifier using beam transport devices for guiding an electron beam to a wiggler of a free electron laser and returning the electron beam to decelerating cavities disposed adjacent to the accelerating cavities of the free electron laser. Rf energy is extracted from the electron beam after it emerges from the wiggler by means of the decelerating cavities which are closely coupled to the accelerating cavities, or by means of a second bore within a single set of cavities. Rf energy extracted from the decelerated electron beam is used to supplement energy provided by an external source, such as a klystron, to thereby enhance overall efficiency of the system.

It is the primary objective or aim of the present invention to provide an electrically conductive composition for the fabrication of susceptors useful for induction melting of uranium and uranium alloys and to also provide such a composition for forming crucibles and other containment vessels utilized to contain uranium at elevated temperatures. This composition does not appear to interact with molten uranium, since there is no significant reaction between the compositional consituents of the susceptor or containment vessel and the confined uranium. This objective is achieved by utilizing a sintered ceramic composition which consists essentially of about 13-67 vol. % of a refractory metal carbide and a nonconductive oxide selected from a group consisting of zirconium oxide, calcium aluminate, yttria, and combinations thereof.

The invention is a process for producing improved electrical-junction devices. The invention is applicable, for example, to a process in which a light-sensitive electrical-junction device is produced by: (1) providing a body of crystalline semiconductor material having a doped surface layer; (2) irradiating the layer with at least one laser pulse to effect melting of the layer; (3) permitting recrystallization of the melted layer; and (4) providing the resulting body with electrical contacts. In accordance with the invention, the fill-factor and open-circuit-voltage parameters of the device are increased by conducting the irradiation with the substrate as a whole at a selected elevated temperature, the temperature being selected to effect a reduction in the rate of the recrystallization but insufficient to effect substantial migration of impurities within the body. In the case of doped silicon substrates, the substrate may be heated to a temperature in the range of from about 200/sup 0/C to 500/sup 0/C.