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Comments on velocity space relaxation in high charge-state plasma neutralizers

Description: Scaling of velocity space relaxation rates, which affect the final temperature of a natural beam, with ion charge state in plasma neutralizers is examined. Overall, this scaling indicates a substantial enhancement in emittance growth of the neutral beam with increase in the charge state of ions in plasma neutralizers. 9 refs.
Date: January 1, 1989
Creator: Hershcovitch, A.
Partner: UNT Libraries Government Documents Department

Design aspects for a pulsed-mode, high intensity, heavy negative ion source

Description: A high-intensity, plasma-sputter, negative ion source, which utilizes multi-cusp, magnetic-field, plasma-confinement techniques, has been designed at the Oak Ridge National Laboratory (ORNL). The source is an axial-geometry version of the radial-geometry source which has demonstrated pulsed-mode peak intensity levels of several mA for a wide spectrum of heavy negative ion species. The mechanical design features include provisions for fast interchange of sputter samples, ease of maintenance, direct cooling of the discharge chamber, and the use of easily replaced coaxial LaB{sub 6} cathodes. 13 refs., 3 figs., 1 tab.
Date: January 1, 1990
Creator: Alton, G.D.
Partner: UNT Libraries Government Documents Department

Rf breakdown studies in copper electron linac structures

Description: This paper presents a summary of rf breakdown-limited electric fields observed in experimental linac structures at SLAC and a discussion of how these experiments can be interpreted against the background of existing, yet incomplete, theories. The motivation of these studies, begun in 1984, is to determine the maximum accelerating field gradients that might be used safely in future e/sup /+-// colliders, to contribute to the basic understanding of the rf breakdown mechanism, and to discover if a special surface treatment might make it possible to supersede the field limits presently reachable in room temperature copper structures. 6 refs., 4 figs., 1 tab.
Date: March 1, 1989
Creator: Wang, J.W. & Loew, G.A.
Partner: UNT Libraries Government Documents Department

Charge state distribution studies of the metal vapor vacuum arc ion source

Description: We have studied the charge state distribution of the ion beam produced by the MEVVA (metal vapor vacuum arc) high current metal ion source. Beams produced from a wide range of cathode materials have been examined and the charge state distributions have been measured as a function of many operational parameters. In this paper we review the charge state data we have accumulated, with particular emphasis on the time history of the distribution throughout the arc current pulse duration. We find that in general the spectra remain quite constant throughout most of the beam pulse, so long as the arc current is constant. There is an interesting early-time transient behavior when the arc is first initiated and the arc current is still rising, during which time the ion charge states produced are observed to be significantly higher than during the steady current region that follows. 12 refs., 5 figs.
Date: June 1, 1989
Creator: Galvin, J.E.; Brown, I.G. & MacGill, R.A.
Partner: UNT Libraries Government Documents Department

Broad-beam multi-ampere metal ion source

Description: An embodiment of the MEVVA (metal vapor vacuum arc) high current metal ion source has been developed in which the beam is formed from a 10-cm diameter set of extractor grids and which produces a peak beam current of up to several Amperes. The source, MEVVA V, operates in a pulsed mode with a pulse width at present 0.25 ms and a repetition rate of up to several tens of pulses per second (power supply limited). The multicathode feature that was developed for the prior source version, MEVVA IV, has been incorporated here also; one can switch between any of 18 separate cathodes and thus metallic beam species. Maximum beam extraction voltage is over 90 kV, and since the ion charge state typically from Q = 1 to 5, depending on the metal employed, the ion energy in the extracted beam can thus be up to several hundred keV. This source is a new addition to the MEVVA family of metal ion sources, and we are at present investigating the operational regimes and the limits to the source performance. In this paper we describe the source and present some preliminary results. 10 refs., 4 figs.
Date: June 1, 1989
Creator: Brown, I.G.; Galvin, J.E.; MacGill, R.A.; Paoloni, F.J. (Lawrence Berkeley Lab., CA (USA) & Engineering), Wollongong Univ. (Australia). Dept. of Electrical
Partner: UNT Libraries Government Documents Department

Some novel design features of the LBL metal vapor vacuum arc ion sources

Description: The family of MEVVA (metal vapor vacuum arc) high current metal ion sources developed at LBL over the past several years has grown to include a number of different source versions with a wide range of some of the design and operational parameters. The MicroMEVVA source is a particularly compact version, about 2 cm diameter and 10 cm long, while the MEVVA IV weighs some 30 kG. MEVVAs IV and V incorporate multiple cathode assemblies (16 and 18 separate cathodes, respectively), and the operating cathode can be switched rapidly and without down-time. The new MEVVA V embodiment is quite compact considering its broad beam (10 cm), high voltage (100 kV) and multiple cathode features. The large-area extractor grids used in the MEVVA V were fabricated using a particularly simple technique, and they are clamped into position and so can be changed simply and quickly. The electrical system used to drive the arc is particularly simple and incorporates several attractive features. In this paper we review and describe a number of the mechanical and electrical design features that have been developed for these sources. 9 refs., 5 figs.
Date: June 1, 1989
Creator: MacGill, R.A.; Brown, I.G. & Galvin, J.E.
Partner: UNT Libraries Government Documents Department

High performance single stage operation of the LBL ECR and the design of an advanced ECR ion source

Description: A new mode of operation using only the second stage of the LBL ECR has been developed. This single stage mode produces charge states and currents equal to or better than the traditional two stage operation of the LBL ECR for a variety of gases such as nitrogen, oxygen, and argon. The critical parameter for this mode appears to be conditioning the plasma chamber walls with a coating of SiO/sub 2/. Various models to explain this effect will be discussed along with implications for ECR ion source design. A new Advanced ECR ion source which will operate at 14 GHz is being designed for the 88-Inch Cyclotron. Construction is scheduled to begin in the fall of 1988 and test operation should begin in the fall of 1989. The design includes hollow core copper wire solenoids, iron yoke, a Nd-Fe-B sextupole, radial pumping, and access to the plasma chamber. 8 refs., 4 figs., 1 tab.
Date: September 1, 1988
Creator: Lyneis, C.M.
Partner: UNT Libraries Government Documents Department

Grid-controlled metal ion sources for heavy ion fusion accelerators

Description: A variety of metal ions can be generated using vacuum arcs, but due to the nature of these arcs, the flux generated fluctuates in time. We have successfully employed electrostatically biased grids to control the plasma and to provide a well-behaved, space charge limited ion source. The grid prevents the plasma from entering the extraction gap before the main voltage pulse is applied. The extracted ion current is space charge limited, resulting in a constant output current even though the ion flux from the vacuum arc source varies considerably. There are several advantages over other conventional sources, for instance, thermionic sources are faced with heating problems especially for large area configurations, while gas-injection sources cause prefill problems because they take too long to reach equilibrium. We have performed extraction experiments with aluminium and indium arc sources. We have extracted 300 mA of pure Al/sup +/ at 30 kV for 10 ..mu..s. The normalized beam emittance has been measured to be 8 /times/ 10/sup /minus/7/ ..pi..-m-rad. 3 refs., 5 figs.
Date: January 1, 1986
Creator: Len, L.K.; Humphries, S. Jr. & Burkart, C.
Partner: UNT Libraries Government Documents Department

Progress in the art of producing polarized ions

Description: A short review of the progress that has been made during the last two years in the design and construction of polarized-ion sources is given and current research efforts on new types of ion sources are summarized. The emphasis is on the production of polarized negative ions, but positive ions are mentioned because in the conventional atomic-beam source, negative ions are obtained by charge exchange of a positive polarized beam. While originally beams of polarized negative ions were developed for tandem accelerators, negative ions have important advantages also for synchrotrons and cyclotrons, because the stripping of H/sup -/ to H/sup +/ in a thin foil can be used either for multiturn injection or for east in extraction. (WHK)
Date: January 1, 1980
Creator: Haeberli, W.
Partner: UNT Libraries Government Documents Department

Radio frequency photocathode guns

Description: This report examines the causes and the effects of beam emittance growth on the performance of radio frequency photocathode guns. (LSP)
Date: April 1, 1992
Creator: Palmer, R.B. (Brookhaven National Lab., Upton, NY (United States) Stanford Linear Accelerator Center, Menlo Park, CA (United States))
Partner: UNT Libraries Government Documents Department

Survey of methods for rapid spin reversal

Description: The need for rapid spin reversal technique in polarization experiments is discussed. The ground-state atomic-beam source equipped with two rf transitions for hydrogen can be reversed rapidly, and is now in use on several accelerators. It is the optimum choice provided the accelerator can accept H/sup +/ ions. At present all rapid reversal experiments using H/sup -/ ions are done with Lamb-shift sources; however, this is not a unique choice. Three methods for the reversal of the spin of the atomic beam within the Lamb-shift source are discussed in order of development. Coherent intensity and perhaps focus modulation seem to be the biggest problems in both types of sources. Methods for reducing these modulations in the Lamb-shift source are discussed. The same Lamb-shift apparatus is easily modified to provide information on the atomic physics of quenching of the 2S/sub 1/2/ states versus spin orientation, and this is also discussed. 2 figures.
Date: January 1, 1980
Creator: McKibben, J.L.
Partner: UNT Libraries Government Documents Department

New high temperature plasma ion source for the TRISTAN ISOL facility

Description: A vigorous program of ion source development at TRISTAN has led to several types of ion sources that are especially suited to extended operation at a reactor-based ISOL facility. The latest of these is a high temperature plasma ion source in which a 5 gm /sup 235/U target is located in the cathode and can be heated to 2500/sup 0/C. The ion source has a lifetime of >1000 hours and produces a wide array of elements, including Pd. Off-line investigations indicate that the source functions primarily in an electron impact mode of ionization and exhibits typical ionzation efficiencies of >30% for Xe.
Date: August 1, 1986
Creator: Piotrowski, A.; Gill, R.L. & McDonald, D.C.
Partner: UNT Libraries Government Documents Department

Analytical methods of electrode design for a relativistic electron gun

Description: The standard paraxial ray equation method for the design of electrodes for an electrostatically focused gun is extended to include relativistic effects and the effects of the beam's azimuthal magnetic field. Solutions for parallel and converging beams are obtained and the predicted currents are compared against those measured on the High Brightness Test Stand. 4 refs., 2 figs.
Date: May 9, 1985
Creator: Caporaso, G.J.; Cole, A.G. & Boyd, J.K.
Partner: UNT Libraries Government Documents Department

Use of molybdenum ion source electrodes at RTNS-II

Description: Reports are reported for an ongoing effort to optimize D+ beam production by the MATS-III ion source used at RTNS-II. The three seven-aperture electrodes, originally consisting of water-cooled copper, have now been tested using uncooled molybdenum and with water cooling on the second (decel) electrode only. Details of the change, the results of the testing, and the benefits in operation, performance and cost are given.
Date: September 29, 1986
Creator: Massoletti, D.J.; Harter, G.A. & Heikkinen, D.W.
Partner: UNT Libraries Government Documents Department

Development of high current and high brightness negative hydrogen ion sources

Description: Negative hydrogen ions have found important applications in particle accelerators and in fusion research. These ions can be generated from two different types of ion sources---the surface conversion source and the volume production source. Recent experiments demonstrate that H/sup /minus// current exceeding 1 A can be obtained from both types of ion sources. Because of the lower H/sup /minus// ion temperature and the fact that they can be operated without cesium, volume H/sup /minus// sources are highly desired. However, further technology must be developed on the control of electrons and the reduction of gas flow before this type of sources become practical units of a multiampere neutral beam injection system.
Date: April 1, 1988
Creator: Leung, K.N.
Partner: UNT Libraries Government Documents Department

Oxide cathode lifetime improvements at RTNS-II

Description: Results are reported for an ongoing effort to optimize D/sup +/ beam production by the MATS-III ion source used at the RTNS-II. The oxide cathode assembly originally designed for lower power operation has been modified and redesigned for higher electron current yield, longer life and serviceability. A factor of 2.5 has been gained in cathode lifetime due to these changes. The details of the changes and results and benefits in operation and performance are given. In addition, the technique used for manufacture of the filament is described.
Date: September 29, 1986
Creator: Massoletti, D.J.
Partner: UNT Libraries Government Documents Department

Beam dynamics of a liquid metal ion source

Description: RMS emittance growth of liquid metal ion sources is studied. Processes included are nonlinear expansion through extractor and accelerator fringe fields, nonlinear beam space charge, plasma effects near needle, and waves (either ion-acoustic or space charge limited as considered by V.I. Dudnikov). This investigation consists of 2-D analysis of appropriate Vlasov-Poisson equations in both steady-state and time-dependent formulations. Various geometries will be considered such as some used by G. Alton of ORNL. 2 refs., 7 figs.
Date: January 1, 1989
Creator: Whealton, J.H.; Meszaros, P.S.; Rothe, K.E.; Raridon, R.J. & Ryan, P.M.
Partner: UNT Libraries Government Documents Department

Single-crate stand-alone CAMAC control system for a negative ion source test facility

Description: A single-crate CAMAC system was configured to control a negative ion source development facility at ORNL and control software was written for the crate microcomputer. The software uses inputs from a touch panel and a shaft encoder to control the various operating parameters of the test facility and uses the touch panel to display the operating status. Communication to and from the equipment at ion source potential is accomplished over optical fibers from an ORNL-built CAMAC module. A receiver at ion source potential stores the transmitted data and some of these stored values are then used to control discrete parameters of the ion source (i.e., power supply on or off). Other stored values are sent to a multiplexed digital-to-analog converter to provide analog control signals. A transmitter at ion source potential transmits discrete status information and several channels of analog data from an analog-to-digital converter back to the ground-potential receiver where it is stored to be read and displayed by the software.
Date: January 1, 1979
Creator: Juras, R.C. & Ziegler, N.F.
Partner: UNT Libraries Government Documents Department

ECR sources for the production of highly charged ions

Description: Electron Cyclotron Resonance Ion Sources (ECRIS) using RF between 5 and 16 GHz have been developed into stable, reliable sources of highly charged ions produced from a wide range of elements. These devices are currently used as ion sources for cyclotrons, synchrotrons, and heavy-ion linacs for nuclear and relativistic heavy-ion physics. They also serve the atomic physics community as a source of low energy multiply-charged ions. In order to improve their performance both with respect to maximum charge state and beam intensity, ECRIS builders are now designing and constructing sources which will operate at frequencies up to 30 GHz. In this paper we review the present status of operating ECRIS, review recent experimental measurements on plasma parameters, and look at the technology and potential of sources operating at frequencies up to 30 GHz. 14 refs., 4 figs., 1 tab.
Date: September 1, 1989
Creator: Lyneis, C.M.; Antaya, T.A (Lawrence Berkeley Lab., CA (USA) & Michigan State Univ., East Lansing, MI (USA))
Partner: UNT Libraries Government Documents Department

LBL EBIS Program

Description: It has been decided to increase the energy range of the LBL 88-Inch Cyclotron by constructing an advanced ion source for installation on the existing axial injection system. The type of advanced ion source chosen is the Electron Beam Ion Source. The energy range will be increased to 40 MeV/nucleon for the lighter heavy ions and with development to over 20 MeV/nucleon at mass 100. Besides the 88-inch Cyclotron, present accelerators at LBL include the SuperHILAC, with beam energy up to 8.5 MeV/A, and the Bevalac, which will provide beams from 40 MeV/A to 2 GeV/A at all masses upon completion of the current Uranium Beams line item. Initial ion source design and design of the test bench are described.
Date: May 1, 1981
Creator: Brown, I. & Feinberg, B.
Partner: UNT Libraries Government Documents Department

The SuperHILAC heavy ion intensity upgrade

Description: A high current MEtal Vapor Vacuum Arc (MEVVA) ion source is to be installed in the third injector (Abel) at the SuperHILAC, representing the first accelerator use of this novel ion source. The MEVVA source has produced over 1 A of uranium in all charge states, with more than 100 electrical mA (emA) of U/sup 5 +/. Transport of the space-charge dominated beam through the charge-state analysis dipole will be enhanced by a 100 kV extractor voltage and neutralization by secondary electrons. In addition to the MEVVA source, other improvements already in place include a lower pressure in the Low Energy Beam Transport line (15.8 keV/AMU) to reduce charge exchange for the heavy elements, and the addition of a second 23 MHz buncher upstream of the Wideroe linac and two 70 MHz bunchers between the 23 MHz Wideroe and the 70 MHz Alvarez linacs. The project is expected to result in a fivefold increase in beam delivered to Bevatron experiments, increasing the extracted uranium beam to 5 x 10/sup 7/ ions/pulse.
Date: March 1, 1987
Creator: Feinberg, B. & Brown, I.G.
Partner: UNT Libraries Government Documents Department

Directly heated LaB/sub 6/ cathodes for ion source operation

Description: Some physical properties of lanthanum hexaboride ''filaments,'' when operated as cathodes in a gas discharge, are presented. These directly heated hairpin shaped filaments have been tested in different types of ion sources and are shown to be capable of long pulse or cw discharge operations. The characteristics of a shaped lanthanum hexaboride filament for the purpose of further extension of lifetime is described. The design and operation of a magnetic-field-free, directly-heated, coaxial LaB/sub 6/ cathode is also discussed.
Date: March 1, 1986
Creator: Leung, K.N.
Partner: UNT Libraries Government Documents Department

Method of generating intense nuclear polarized beams by selective photodetachment of negative ions

Description: A novel method for production of nuclear polarized negative hydrogen ions by selective neutralization with a laser of negative hydrogen ions in a magnetic field is described. This selectivity is possible since a final state of the neutralized atom, and hence the neutralization energy, depends on its nuclear polarization. The main advantages of this scheme are the availability of multi-ampere negative ion sources and the possibility of neutralizing negative ions with very high efficiency. An assessment of the required laser power indicates that this method is in principle feasible with today's technology.
Date: January 1, 1986
Creator: Hershcovitch, A.
Partner: UNT Libraries Government Documents Department