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The use of ion sources in induction linacs for heavy ion fusion is fundamentally different from their use in the rf linac‐storage rings approach. Induction linacs require very high current, short pulse extraction usually with large apertures which are dictated by the injector design. One is faced with the problem of extracting beams in a pulsed fashion while maintaining high beam quality during the pulse (low emittance). Four types of sources have been studied for this application. The vacuum arc and the rf cusp field source are the plasma‐types and the porous plug and hot alumino–silicate surface source are the thermal types. The hot alumino–silicate potassium source has proved to be the best candidate for the next generation of scaled experiments. The porous plug for potassium is somewhat more difficult to use. The vacuum arc suffers from noise and lifetime problems and the rf cusp field source is difficult to use with very short pulses. Operational experience with all of these types of sources is prese...

Heavy ion fusion experiments require very high current beams with excellent beam quality during a short pulse. Scaled experiments planned at LBL require very short pulses (/spl mu/sec) compared to what one expects in an HIF driver (20-30 /spl mu/s). A 1 MV acceleration column composed of aperture lenses has been constructed at LBL in order to study the propagation effects on such ion pulses. The column is initially empty of space charge but with the full acceleration potential applied. A short current pulse is then injected into the column with a planar diode "current valve". Effects on the pulse propagation due to rise time, pulse duration, and beam size have been studied. Experiments on transported beam current and emittance have been conducted using a carbon arc plasma source (2" and 5" diameter) and a 1" diameter potassium alumino-silicate ion source. Computer simulations using a 2.5D time dependent code are compared with the experimental data. >

An injector for the second axis of the Dual-Axis Radiographic Hydrotest Facility (DARHT) is been built at LBNL. The proposed injector consists of a single gap diode extracting 4 kAmps, 3 MV electrons from a thermionic dispenser cathode and powered through a high voltage ceramic insulator column by a Marx generator. The key issues in the design are the control of beam quality to meet the DARHT 2nd axis final focus requirements and to minimize high-voltage breakdown risks. We present the conceptual design of the injector as well as preliminary results on a scaled experiment and breakdown tests in vacuum using the Berkeley RTA facility.

The use of ion sources in induction linacs for heavy ion fusion is fundamentally different from their use in the rf linac‐storage rings approach. Induction linacs require very high current, short pulse extraction usually with large apertures which are dictated by the injector design. One is faced with the problem of extracting beams in a pulsed fashion while maintaining high beam quality during the pulse (low emittance). Four types of sources have been studied for this application. The vacuum arc and the rf cusp field source are the plasma‐types and the porous plug and hot alumino–silicate surface source are the thermal types. The hot alumino–silicate potassium source has proved to be the best candidate for the next generation of scaled experiments. The porous plug for potassium is somewhat more difficult to use. The vacuum arc suffers from noise and lifetime problems and the rf cusp field source is difficult to use with very short pulses. Operational experience with all of these types of sources is prese...