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Applications of the MEVVA high current metal ion source

Description: A new kind of ion source has been developed in which a metal vapor vacuum arc (MEVVA) is used to produce the plasma from which the ion beam is extracted. The novel and exciting feature of this source is the very high metal ion beam current attainable. A total ion beam current of over 1 Ampere has been extracted from the embodiment of the concept that we're presently using, and this is not a limit of the method. The source was developed to upgrade the uranium ion beam intensity of the Bevatron, LBL's heavy ion synchrotron, for basic nuclear physics research. Other important applications include its use within the Heavy Ion Fusion research effort; for ion implantation; and for other basic research uses. In this paper the source is described briefly, its performance outlined, and its poential and limitations for a variety of applications is discussed.
Date: August 1, 1986
Creator: Brown, I.G.
Partner: UNT Libraries Government Documents Department

Comparison of methods of producing very highly stripped uranium beams

Description: A comparison is made between the production of high intensity beams of helium-like uranium ions, U/sup 90 +/, by conventional and exotic ion sources, and by the foil stripping of highly accelerated ions output from the Bevalac. The parameter requirements are specified and compared to the parameters achievable by present day ion source technology. The EBIS (Electron Beam Ion Source) comes closest to satisfying the necessary parameters, and this possibility is considered in some detail. We conclude that existing and near-future ion source technology does not provide a means of production of high intensity U/sup 90 +/ beams. Foil stripping of lower charge state species that have been accelerated through the Bevalac provides a convenient approach.
Date: October 1, 1983
Creator: Brown, I.G.
Partner: UNT Libraries Government Documents Department

On the current intensity limit of a vacuum arc ion source

Description: The maximum ion current that can be produced as a high energy beam from a metal vapor vacuum arc ion source is considered. Results are presented of measurements of the plasma ion current in the MEVVA II ion source. It is shown that this source is an efficient generator of metal ions, an intense flux of which is efficiently transported to the beam extractor. The maximum metal ion current that is available for extraction at the extractor location is 5% of the arc current. The limitation to the intensity of the metal ion beam that can be produced by this kind of ion source is in the extractor design. 27 refs., 6 figs.
Date: March 1, 1987
Creator: Brown, I.G.
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

Intense metal ion beam source for heavy ion fusion

Description: We have developed an ion source which can produce high current beams of metal ions. The source uses a metal vapor vacuum arc discharge as the plasma medium from which the ions are extracted, so we have called this source the MEVVA ion source. The metal plasma is created simply and efficiently and no carrier gas is required. Beams have been produced from metallic elements spanning the periodic table from lithium through uranium, at extraction voltages from 10 to 60 kV and with beam currents as high as 1.1 Amperes (electrical current in all charge states). A brief description of the source is given and its possible application as an ion source for heavy ion fusion is considered. Beams such as C/sup +/ (greater than or equal to99% of the beam in this species and charge state), Cr/sup 2 +/ (80%), and Ta/sup 3+,4+,5+/ (mixed charge states) have been produced. Beam emittance measurements and ways of increasing the source brightness are discussed.
Date: May 1, 1986
Creator: Brown, I.G.
Partner: UNT Libraries Government Documents Department

Metal vapor vacuum arc (MEVVA) high current ion source

Description: An ion source is described in which a metal vapor vacuum arc is used to create the plasma from which the ions are extracted. Beams of a variety of ions have been produced, ranging from lithium up to uranium. At an extraction voltage of 25 kV we've measured an ion beam current of over 1 Ampere, with over 550 ema of the beam in an emittance of 0.07..pi.. cm. mradians (normalized). The ion charge state distribution varies with cathode material and with arc power; for uranium a typical distribution is peaked at U/sup 5 +/, with up to 40% of the beam current in this charge state. 27 refs., 10 figs.
Date: May 1, 1985
Creator: Brown, I.G.
Partner: UNT Libraries Government Documents Department

MEVVA ion source for high current metal ion implantation

Description: The MEVVA (Metal Vapor Vacuum Arc) ion source is a new kind of source which can produce high current beams of metal ions. Beams of a wide range of elements have been produced, spanning the periodic table from lithium up to and including uranium. The source extraction voltage is up to 60 kV, and we are increasing this up to 120 kV. A total ion beam current of over 1 Ampere has been extracted from the present embodiment of the concept, and this is not an inherent limit. The ion charge state distribution varies with cathode material and arc current, and beams like Li/sup +/, Co/sup +,2+,3+/ and U/sup 3+,4+,5+,6+/ for example, are typical; thus the implantation energy can be up to several hundred kilovolts without additional acceleration. The ion source has potential applications for ion implantation and ion beam mixing for achievement of improved corrosion resistance or wear resistance in metals or surface modification of ceramic materials and semiconductors. Here we outline the source and its performance, and describe some very preliminary implantation work using this source.
Date: July 1, 1986
Creator: Brown, I. & Washburn, J.
Partner: UNT Libraries Government Documents Department

Advances in metal ion sources

Description: Beams of metallic ion species can be produced by the ECR (electron cyclotron resonance) ion source and by the MEVVA (metal vapor vacuum arc) ion source. Although the ECR source is fundamentally a gaseous ion source, metal ion beams can be produced by introducing metallic feed material into the plasma discharge using a number of techniques. The ion charge states can be very high, which is a significant advantage to most applications. The MEVVA ion source, on the other hand, is specifically a metal ion source. It has produced metallic ion beams from virtually all the solid metallic elements at a current of typically hundreds of milliamperes; the ions produced are in general multiply ionized, but not as highly stripped as those generated in the ECR source. Although the MEVVA source at present operates in a pulsed mode with a low duty cycle (less than or equal to 1%), work is in progress to increase the duty cycle significantly. In this paper the operation and performance of the LBL ECR and MEVVA ion sources, with respect to metal ion generation, are described.
Date: May 1, 1988
Creator: Brown, I.G.
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

Superhilac upgrade project

Description: This project will increase the uranium output of the Bevalac heavy-ion facility from the currently available 10/sup 7/ to 5 x 10/sup 7/ ions/pulse, allowing accurate Lamb shift measurements to be made in U/sup 90 +/ and U/sup 91 +/ with important applications to the testing of quantum electrodynamics and the development of an x-ray laser. The injected beam intensity will be increased to make better use of the 10emA output space-charge limit of the Wideroe linac. Components will include a new high current MEtal Vapor Vacuum Arc (MEVVA) ion source along with an improved high current, high voltage Cockcroft-Walton power supply to handle the increased beam current. The Low Energy Beam Transport (LEBT) line will be upgraded with additional focusing to manage the increased space-charge forces and with an improved vacuum to reduce charge exchange losses. Finally, the phase matching between the 23MHz Wideroe linac and the 70MHz Alvarez linac will be improved by the addition of the appropriate buncher cavities. Physics design is underway and detailed engineering is scheduled to begin in October 1985, with installation slated for the 1986 summer shutdown.
Date: May 1, 1985
Creator: Feinberg, B. & Brown, I.G.
Partner: UNT Libraries Government Documents Department

SuperHILAC Upgrade Project

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 typically more than 100 electrical mA (emA) of U/sup 5 +/. A substantial fraction of this high current, heavy ion beam must be successfully transported to the entrance of the Wideroe linac to approach the 10 emA space-charge output limit of the Wideroe. Calculations show that up to 50 emA of U/sup 5 +/ can be transported through the present high voltage column. A bouncer will be added to the Cockcroft-Walton supply to handle the increased beam current. The Low Energy Beam Transport line vacuum will be improved to reduce charge exchange, and the phase matching between the 23 MHz Wideroe and the 70 MHz Alvarez linacs will be improved by the addition of two 70 HMz bunchers. The installation of the MEVVA source along with the modifications described above are expected to result in a five-fold increase in beam delivered to Bevatron experiments, increasing the extracted uranium beam to 5 x 10/sup 7/ ions/pulse.
Date: June 1, 1986
Creator: Feinberg, B. & Brown, I.G.
Partner: UNT Libraries Government Documents Department

Feasibility of synthesizing oxide films on ceramic and metal substrates. Final report, August 1994--May 1995

Description: Feasibility of synthesizing highly adherent alumina and chromia films on SiC and FeAl substrates using plasma methods was studied. A magnetically filtered, cathodic-arc-produced, metal plasma (Al or Cr) is deposited on the substrate in presence of low pressure oxygen while the substrate is repetitively pulse biased for control of incident ion energy. In the early stages, the ion energy is held in the keV range to produce atomic mixing at the film-substate interface (ion stitching); in the latter stages, the energy is reduced to about 200 eV (IBAD, or ion beam assisted deposition, range) to control the film structure and morphology. Near-stoichiometric films of alumina and chromia were formed on small SiC and FeAl substrates and characterized by RBS, XRD, adhesion, and temperature cycling. The aluminia films were 0.2 to 1.5 {mu} thick, were amorphous prior to heat treatment, and showed an {alpha}-alumina phase after heat treating at 1000 C for up to 16 h. Film substrate adhesion was typically greater than 70 MPa prior to heating, and the thinner films maintained their adhesion even after repetitive cycling in temperature between ambient and 1000 C. It is concluded that the plasma and ion beam techniques developed provide important tools for forming highly adherent and thermally tolerant ceramic films.
Date: July 1, 1995
Creator: Brown, I.G.
Partner: UNT Libraries Government Documents Department

LBL EBIS test-strand

Description: An EBIS program was initiated at Lawrence Berkeley Laboratory in late 1979. This first stage, construction of an EBIS research and development test-stand is described, along with results of the bare beam experiments.
Date: May 1, 1981
Creator: Feinberg, B. & Brown, I.G.
Partner: UNT Libraries Government Documents Department

High current ion sources

Description: The concept of high current ion source is both relative and evolutionary. Within the domain of one particular kind of ion source technology a current of microamperers might be high', while in another area a current of 10 Amperes could low'. Even within the domain of a single ion source type, what is considered high current performance today is routinely eclipsed by better performance and higher current output within a short period of time. Within their fields of application, there is a large number of kinds of ion sources that can justifiably be called high current. Thus, as a very limited example only, PIGs, Freemen sources, ECR sources, duoplasmatrons, field emission sources, and a great many more all have their high current variants. High current ion beams of gaseous and metallic species can be generated in a number of different ways. Ion sources of the kind developed at various laboratories around the world for the production of intense neutral beams for controlled fusion experiments are used to form large area proton deuteron beams of may tens of Amperes, and this technology can be used for other applications also. There has been significant progress in recent years in the use of microwave ion sources for high current ion beam generation, and this method is likely to find wide application in various different field application. Finally, high current beams of metal ions can be produced using metal vapor vacuum arc ion source technology. After a brief consideration of high current ion source design concepts, these three particular methods are reviewed in this paper.
Date: June 1, 1989
Creator: Brown, I.G.
Partner: UNT Libraries Government Documents Department

Characterization of Kevlar 49 fibers by electron paramagnetic resonance. Final report, 20 May 1981-20 June 1982. [Radicals induced by ultraviolet or fracture]

Description: EPR was used to investigate the free radicals created in Kevlar 49 fibers by stress-induced and photo-induced macromolecular chain scissions. Mn/sup +2/ ions were identified from the EPR spectrum of frozen solutions of concentrated sulfuric acid containing Kevlar 49. Other ions present are Cu/sup +2/, and possibly Fe/sup +3/, Cr/sup +3/, and Ti/sup +3/. EPR lineshape anisotropy indicates that some of the metal ions and first coordinate spheres are oriented. The concentration of stress-induced radicals (2 x 10/sup 10/ per filament) suggest that chain scission occurs in more weak planes than are estimated to exist in the fracture surfaces of the fiber core. These radicals are unstable in air and have some aromatic character. Several different types of radicals were obtained following uv irradiations of the Kevlar 49 fibers in vacuum (photodegradative radicals) and in air (photo-oxidative radicals). The photodegradative radicals are identified with primary radicals involved in the photo-Fries rearrangement reaction, secondary radicals formed as a result of a hydrogen atom abstraction by the primary radical, and/or ketyl radicals produced as a result of uv irradiation of the photo-Fries rearrangement product. The photo-oxidative radicals are identified with the uv irradiation products of a peroxide intermediate. Lineshape anisotropy indicates that both radical types are oriented. 31 figures.
Date: June 20, 1982
Creator: Brown, I.M. & Sandreczki, T.C.
Partner: UNT Libraries Government Documents Department

Plasma containment in a toroidal bicusp (tormac)

Description: The stable confinement of a fully ionized, high-beta plasma in a toroidal bicusp (Tormac) is discussed. The bicusp geometry is described along with ''shaker'' heating by magnetoacoustic waves propagating orthogonal to the internal toroidal magnetic field. (MOW)
Date: August 1, 1975
Creator: Levine, M.A.; Brown, I.G. & Gallagher, C.C.
Partner: UNT Libraries Government Documents Department

Plasma synthesis of alumina films on metal and ceramic substrates

Description: The authors are exploring the feasibility of the plasma synthesis of highly-adherent films of alumina and chromia on SiC and FeAl substrates. A magnetically-filtered cathodic arc plasma deposition technique is used in which a high density metal plasma (Al or Cr) is formed and deposited on the substrate in the presence of a low pressure gaseous oxygen background. The substrate is simultaneously repetitively pulse biased, providing a means of controlling the incident ion energy. In the early stages of the process the ion energy is held in the keV range so as to produce atomic mixing at the film-substrate interface (ion stitching), and in the latter stages of deposition the energy is reduced to {approximately}200 eV (IBAD range) to provide a means of controlling the film structure and morphology. Films that are dense and highly adherent can be formed in this way. The authors have produced near-stoichiometric films of alumina and chromia on small SiC and FeAl substrates and characterized the films in a number of ways, including RBS, X-ray diffraction and adhesion, and we`ve also done some preliminary temperature cycling experiments. The alumina films are of thickness from 0.2 to 1.5.{micro}, amorphous prior to heat treatment, and show an {alpha}-alumina phase after heat treating at 1,000 C for up to 16 hours. The film substrate adhesion is typically greater then {approximately}70 MPa prior to heating, and initial results indicate that the films maintain their adhesion after repetitive cycling in temperature between ambient and 1,000 C. Here they describe the plasma processing method and outline the experimental results obtained to-date.
Date: April 1, 1995
Creator: Brown, I. & Wang, Zhi
Partner: UNT Libraries Government Documents Department

Vacuum arc ion charge state distributions

Description: We have measured vacuum arc ion charge state spectra for a wide range of metallic cathode materials. The charge state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. We have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th and U. The arc was operated in a pulsed mode with pulse length 0.25 msec; arc current was 100 A throughout. This array of elements extends and completes previous work by us. In this paper the measured distributions are cataloged and compared with our earlier results and with those of other workers. We also make some observations about the performance of the various elements as suitable vacuum arc cathode materials.
Date: June 1, 1990
Creator: Brown, I.G. & Godechot, X.
Partner: UNT Libraries Government Documents Department

Tormac confinement, theory, and experiment

Description: Tormac is a stuffed toroidal line cusp: the magnetic field is divided into two distinct regions, i.e., an outside ''sheath'' layer where the plasma is mirror-confined on open field lines and an internal high-..beta.. region of closed nested flux surfaces. The sheath is arranged with the appropriate curvature to ensure absolute MHD stability everywhere. The bulk of the plasma is maintained on closed flux surfaces as in a typical toroidal configuration, but with enhanced MHD stability due to the external field shaping. Experimental results on a toroidal ''bicusp'' (Tormac IV) will be reported. This device has a boro-silicate glass chamber and holds a plasma with an aspect ratio of 4 and a major diameter of 35 cm.
Date: January 1, 1978
Creator: Berk, H.L.; Brown, I.G. & Feinberg, B.
Partner: UNT Libraries Government Documents Department

Multiply stripped ion generation in the metal vapor vacuum arc

Description: We consider the charge state distribution of ions produced in the metal vapor vacuum arc plasma discharge. A high current metal ion source, the MEVVA ion source, in which the ion beam is extracted from a metal vapor vacuum arc plasma, has been used to obtain the spectra of multiple charged ions produced within the cathode spots. A computer calculation of the charge state distribution that evolves within the spots via stepwide ionization of ions by electron impact provides a theoretical basis for comparison of the data. In this paper we report on the measured charge state distributions for a wide variety of metallic species and compare these results with the predictions of this theory. 55 refs.
Date: August 1, 1986
Creator: Brown, I.G.; Feinberg, B. & Galvin, J.E.
Partner: UNT Libraries Government Documents Department

High dose uranium ion implantation into silicon

Description: Implantation of uranium ions into silicon to a maximum dose of 6 x 10/sup 16/ atoms/cm/sup 2/, with a maximum concentration of 6 x 10/sup 21/ atoms/cm/sup 3/, has been carried out. This concentration corresponds to 12 at. % of uranium in the silicon host material. The implanted uranium content was measured by Rutherford backscattering and confirmed by a measurement of the alpha-particle activity of the buried uranium layer. The range and straggling of the uranium, and sputtering of the silicon target by uranium, were measured and are compared with theoretical estimates. The implantation was performed at an ion mean energy of 157 keV using a new kind of high current metal ion source.
Date: May 1, 1987
Creator: Brown, I.G.; Galvin, J.E. & Yu, K.M.
Partner: UNT Libraries Government Documents Department

Multiply stripped ion generation in the metal vapor vacuum arc

Description: We consider the charge state distribution of ions produced in the metal vapor vacuum arc plasma discharge. A new kind of high current metal ion source in which the ion beam is extracted from a metal vapor vacuum arc plasma has been used to obtain the spectra of multiply charged ions produced within the cathode spots. The cathode materials used and the species reportetd on here are: C, Mg, Al, Si, Ti, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Rh, Pd, Ag, In, Sn, Gd, Ho, Ta, W, Pt, Au, Pb, Th, and U; the arc current was 200 A for all measurements. Charge state spectra were measured using a time-of-flight method. The arc voltage was also measured. In this paper we report on the measured charge state distributions and arc voltages and compare the distributions with the predictions of a theory in which ionization occurs in the cathode spots via stepwise ionization by electron impact. 64 refs., 10 figs., 3 tabs.
Date: September 1, 1987
Creator: Brown, I.G.; Feinberg, B. & Galvin, J.E.
Partner: UNT Libraries Government Documents Department

A METHOD FOR PRODUCING A HIGH QUALITY SOLENOIDAL FIELD

Description: A relatively simple and inexpensive device is described which can be used to provide a highly homogeneous solenoidal magnetic field when the solenoid windings are inadequate. Design considerations and experimental measurements are presented. A field straightness of approximately 10{sup -4} radians has been achieved.
Date: January 1, 1981
Creator: Feinberg, B.; Brown, I.G.; Halbach, K. & Kunkel, W.B.
Partner: UNT Libraries Government Documents Department