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Feb 2002

Volume 73, Issue 2, pp. 241-1098

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Challenges and applications of high brightness beams (plenary)

I. S. K. Gardner

Rev. Sci. Instrum. 73, 892 (2002); http://dx.doi.org/10.1063/1.1430878 (4 pages) | Cited 2 times

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High intensity proton and H− beams are being used and proposed for a wide variety of applications such as spallation neutron sources, drivers for neutrino factories, and accelerator driven systems for waste transmutation and energy production. In cases involving storage rings or synchrotrons the designs are dependent on the production of intense, low emittance, chopped H− beams. Some of these applications are described and the effect of ion source performance on the designs is examined. © 2002 American Institute of Physics.
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41.75.Ak Positive-ion beams

H− ion source test and development capabilities at ISIS

J. W. G. Thomason, R. Sidlow, and M. O. Whitehead

Rev. Sci. Instrum. 73, 896 (2002); http://dx.doi.org/10.1063/1.1430879 (3 pages) | Cited 2 times

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The ISIS ion source is a surface plasma ion source of the Penning type, and routinely produces 35 mA of H− ions during a 200 μs pulse at 50 Hz for uninterrupted periods of up to 50 days. However, because of the constant demands on ISIS from the neutron user community, very little ion source development has ever been possible. It is now necessary to produce sources with enhanced performances for next generation projects such as the European spallation source. Hence a dedicated ion source development rig (ISDR) has been constructed at Rutherford Appleton Laboratory to fully characterize the ISIS ion source and then facilitate appropriate development work. The ISDR has been designed to replicate the beam transport configurations on both the present ISIS preinjector and the proposed ISIS radio frequency quadrupole, while providing additional beam diagnostics equipment. The commissioning of the ISDR will be described, and initial results presented, along with future development plans. © 2002 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors

Negative ion production in multicusp sources (abstract)

Y. I. Belchenko, Y. Oka, O. Kaneko, Y. Takeiri, and K. Tsumori

Rev. Sci. Instrum. 73, 899 (2002); http://dx.doi.org/10.1063/1.1432462 (1 page) | Cited 1 time

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Cesium seed improves multicusp negative ion (NI) Source performance. Experiments display the surface origin of NI production in the multicusp source (MS): a strong NI yield dependence on plasma grid (PG) temperature and work function, a low NI yield sensitivity to Cs density in plasma, etc. On other hand, cesium seed changes the MS plasma potential, electron density, and temperature, decreases the coextracted electron current, and produces a NI density increase in the source volume. Cesium ions can contribute to the slow positive charge in the plasma presheath and extraction region, and improve the NI extraction. The study of NI production was done by the directed deposition of a well-defined amount of cesium, by cesium recovery in the MS. The obtained data evidences the surface origin of H− yield enhancement 3–10 mg cesium deposition was enough for producing a NI yield increase due to hydrogen conversion on the cesiated PG surface. The long-term H− yield enhancement with larger cesium deposition and no change of NI yield with the PG temperature change displays the maintenance of the thick Cs+W coverage, which governs the enhanced surface H− production in the MS. The experimental data and the MS surface–plasma mechanism features will be presented and discussed. © 2002 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
41.85.Ar Particle beam extraction, beam injection
41.75.Cn Negative-ion beams

The plasma–vacuum transition in rf sources for negative hydrogen ions

J. Peters

Rev. Sci. Instrum. 73, 900 (2002); http://dx.doi.org/10.1063/1.1427670 (3 pages) | Cited 2 times

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An intensive study has been made at DESY of the transition region between the plasma and vacuum, the so-called sheath, of rf sources for negative hydrogen ions. The plasma and sheath have been analyzed with Langmuir probes even at extraction at 35 kV, with different geometric arrangements utilizing specially designed collars. Langmuir probes were installed in one of the collars. The use of a long ceramic insulated Langmuir probe made a three-dimensional analysis possible. The density, temperature, and potential of the plasma have been calculated based on these data. These studies have resulted in a better understanding of the transition region of not just rf sources but also of magnetron and Penning sources. Studies with a nine-ring collar made it possible to develop a design with a new method to dump the electrons and deliver an increased negative hydrogen current. © 2002 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
52.40.Kh Plasma sheaths
52.70.Ds Electric and magnetic measurements
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