No abstract available

[en] By using parameters of ion sources when operating in a pulsed mode and without cooling (pulse length < 0.1 s), requirements have been determined for a long pulse (several seconds) or steady state operating mode and two sources have been designed and fabricated. First of the two is a penning source, designed for a steady state operation with a cathode power density of 1 kW/cm². For the range of cathode power densities between 0.2 kW/cm² and 1 Kw/cm², nucleated boiling has to be used for heat removal; below 0.2 kW/cm² water flow cooling suffices. Although this source should deliver 0.3 to 0.5 A of H^- ions in a steady state operation and at full power, the other source, which has a magnetron geometry, is more promising. The latter incorporates two new features compared to first designs, geometrical focusing of fast, primary negative hydrogen ions from the cathode into the extraction slit, and a wider discharge gap in the back of the source. These two changes have resulted in an improvement of the power and gas efficiencies by a factor of 3 to 4 and in a reduction of the cathode power density by an order of magnitude. The source has water cooling for all the electrodes, because maximum power densities will not be higher than 0.2 kW/cm². Very recently a modification of this magnetron source is being considered; it consists of plasma injection into the source from a hollow cathode discharge

[en] This paper is a report on H^- ion source development at BNL over the past ten years, with most emphasis on the selected approach for the design of a steady state operating source. Sources of this kind will be used in neutral beam lines of future fusion devices, for plasma heating and toroidal current drive. In addition to the steady state operation, H^- ion sources for this application have to show very high gas and power efficiencies. 16 references, 8 figures

[en] Charge state of an H^- ion can be changed easily by either single (neutralization) or double (ionization) electron stripping, in a very wide energy range. Development of H^- ion sources has been stimulated by several areas of application: production of high power beams of hydrogen atoms with energies of several hundred keV for plasma heating and current drive in fusion devices, production of high brightness beams of hydrogen atoms in the energy range around 100 MeV, and for use in some accelerators where H^- ions facilitate and improve the injection or ejection processes. This paper will put most emphasis on the accelerator application. Two types of sources will be considered, those where H^- ions are produced in processes on a low work function surface and those where they are produced in collisions occurring in the plasma. After a short outline of theoretical work and experimental studies of relevant processes and phenomena, a review of existing sources designs will be given, describing their performance

[en] This paper is a progress report on the studies of the BNL volume H^- ion source. We have measured the H^- yield, I_H^-, and the ratio I_e/I_H^- as function of the size of the extraction aperture, strength of the conical filter field, size and position of the filament, and of the phase of the filament heating current. The H^- current density in the extraction aperture was lower for the largest aperture, while there was a broad maximum when the conical field varied. Position of the filament and the phase of the filament heating current are very important parameters. 5 refs., 10 figs., 1 tab

[en] Light ion beams have been used for cancer therapy for about twenty years; several dedicated facilities are presently either planned or under construction. In addition, several synchrotrons designed for other purposes are now considered for medical applications as well. A medical synchrotron needs a preaccelerator to produce and inject a range of different light ions, preferably fully stripped, into the ring. The size, cost and complexity of the preaccelerator depend on the performance of its first element, the ion source, and these features will be optimized if the source itself produces fully stripped ions. An EBIS (Electron Beam Ion Source) is capable of producing fully stripped light ions up to argon with intensities sufficient for medical applications. As it has been pointed out in the past, this source option may require just one stage of preacceleration, an RFQ linac, thus making it very simple and compact. The AGS Department has a separate project already under way to develop a very high intensity EBIS for our nuclear physics program. It is, however, our plan first to construct and test an intermediate size device and then to proceed to the design of the final, full scale device. Parameters of that intermediate model are close to those that would be needed for a medical synchrotron. This paper describes the BNL program and considers parameters of EBIS devices for possible use in synchrotron facilities serving as sources of high energy light ions for cancer therapy

[en] Negative ion sources offer an attractive alternative in the design of high energy neutral beam injectors. The requirements call for a single source unit capable of yielding H^- or D^- beam currents of up to 10 A, operating with pulses of 1 s duration or longer, with gas and power efficiencies comparable to or better than achievable with double electron capture systems. H^- beam currents of up to 1 A have already been achieved in pulses of 10 ms; gas and power efficiencies were, however, lower than required. In order to increase the H^- yield, extend the pulse length and improve gas and power efficiencies fundamental processes in the source plasma and on cesium covered electrode surfaces have to be analyzed; these processes will be briefly reviewed and scaling rules established. Based on these considerations as well as on results obtained with 1 A source models a larger model was designed and constructed, having a 7.5 cm long cathode with forced cooling. Results of initial tests will be presented and possible scaling up to 10 A units discussed

[en] During the past few years or so, the development of steady state sources of negative hydrogen or deuterium ions has made a substantial progress. There are several approaches under investigation, some operating with long pulses and some in a true steady state, and delivering H^- or D^- beam currents of several hundred mA up to 1 A. The improvement in the gas efficiency from a few percent for pulsed sources to the range of 5% to 15% and possibly even higher for the new sources, is another advance that was not anticipated only 4 to 5 years ago. A higher gas efficiency has come as the result of using independent plasma generation and geometrical focusing of surface produced negative ions. The power efficiency has not been changed so much, but, in a high energy system, savings of a few kW/A are less important than the reduction of the gas load. It can be expected that within five or so years a small (<1 MW) long pulse or steady state neutral beam system based on negative ions could be put into operation

[en] There are two main areas of negative hydrogen ion applications: injection into high energy accelerators and production of beams of energetic hydrogen atoms for fusion devices. In both cases, the ease with which the charge state of negative ions can be changed by either single or double electron stripping is the reason that made their application attractive. In tandem accelerators, the final energy of H⁺ ions is twice as high as it would correspond to the terminal voltage, in circular accelerators (synchrotrons, storage rings) injection of H⁺ ions by full stripping of H^- ions in a foil inside the ring is not limited by the Liouville's theorem and results in a higher phase space density than achieved by direct H⁺ injection. Finally, beams of hydrogen atoms at energies above 100 keV, which will be required for plasma heating and current drive in future fusion devices, can efficiently be produced only by acceleration of negative ions and their subsequent neutralization

[en] Parameters of the conceptual design of the BNL neutral beam system were determined as follows: beam energy, 200 keV; negative ion current, 10A; neutral beam power, 1 MW; pulse length, multisecond to steady state. The completed system study, supported by successful ion source operation at the required level, will serve to evaluate and compare different approaches in the design of a negative ion based system and, eventually, lead to the design and construction of an operational system