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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...

An update on the development of the 500-mA/beam sixteen-beam injector being built at Lawrence Berkeley Laboratory is presented. An inductively graded Marx bank provides the acceleration potential on the electrostatic column. A carbon arc source provides the pulsed current for the injector. Recent results on extracted beam parameters, column performance, generator performance and system design changes are reported. The carbon ion beam is diagnosed with Faraday cups and with a double-slit emittance measurement system. Controls for the final machine are also discussed. >

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. >

Heavy ion fusion requires high current density, low‐emittance ion sources that are reliable and long lived. We report experimental and simulation results on the performance of carbon arc ion sources intended for use in a scaled induction linac experiment. These sources use a planar electrostatic plasma switch to prevent plasma from entering the extraction gap before the extraction voltage pulse is applied. This provides good beam optics for short pulse extraction. Measurements of current density and emittance are presented. Both double‐slit and channel plate‐pepper pot techniques are used for emittance measurement. Data presented are from a compact three‐arc source with plasma coupling of the cathodes. Data on lifetime and multiple arc triggering are also presented. The plasma switch performance has been modeled with a 2D explicit electrostatic particle‐in‐cell code. Results showing plasma shutoff phenomena and behavior during extraction are presented. A 2D steady‐state ion flow model is also used to pred...

We report on three experiments performed in connection with the 2MV electrostatic quadrupole (ESQ) injector under construction at Lawrence Berkeley Laboratory. Scaled experiments have been conducted to study possible beam emittance growth due to beam aberrations in an ESQ injector. The experiment uses the SBTE (Single Beam Transport Experiment) accelerator system, quarter-scale ESQ set-up and a potassium ion diode source. Measured emittance growth changes significantly with variations in current and diode energy, in good agreement with theoretical predictions. In addition, beam transport experiments were performed in a 1MV axisymmetric electrostatic aperture column using a zeolite 1″ diameter potassium ion source. Experimental measurements in good agreement with 2-1/2D simulations showed that low-emittance beams can be produced in axisymmetric structures. Finally, ESQ breakdown voltage tests without beam were performed at up to two times the quadrupole working voltage.

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...