Proceedings of International Conference on Particle Accelerators
Metal plasma deposition and metal ion implantation techniques have been developed that could prov... more Metal plasma deposition and metal ion implantation techniques have been developed that could provide a good tool for the surface modification of insulating materials for accelerator applications such as ceramics and that could provide a method for tailoring the surface resistivity over a range of many orders of magnitude. The methods make use of the metal plasma that is produced by the cathodic arc discharge; the plasma itself can be deposited onto the surface at an energy of order 100 eV so as to form an adherent thin film, or an energetic metal ion beam can be formed for deep implantation of the metal species below the surface so as to incorporate a controllable amount of metallic composition into the ceramic.
Based on the idea of a space-charge-limited mode of operation, the influence of a pair of electro... more Based on the idea of a space-charge-limited mode of operation, the influence of a pair of electrostatic meshes on the beam parameters of the LBNL MEVVA-5 ion source was investigated. The meshes were placed in the expansion zone of the vacuum arc plasma. Apart from reducing the level of beam current fluctuations, this mode of operation provides significant control over the ion charge state distribution of the extracted beam. These effects can be understood taking not only space charge but also the high-directed ion drift velocities into account that are the same for different ion charge states of a material. The results of simulations of the processes involved are in good agreement with the experimental results.
XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.
We review .sonre recent ezperiiitmtal resu1t.s and oitgoing developntents of vacttttnt-arc-based ... more We review .sonre recent ezperiiitmtal resu1t.s and oitgoing developntents of vacttttnt-arc-based high current nrefal imt source. Tlzese include enhoacement of ion charge states, alternative triggeriitg of vactinin arc, and reduction of ion beant noise, increasedpulse .stability, andgeneration ofKaseous ions.
Implantation of yttrium and other reactive metals has been known to show significant effects on t... more Implantation of yttrium and other reactive metals has been known to show significant effects on the oxidation behavior of Cr203-forming alloys. The oxide growth rate decreases by nearly a factor of ten, and the adhesion of oxide scales to alloys is greatly improved. To better understand the mechanisms by which these elements affect oxidation, it is important to know whether or not they are present in the metal ahead of the oxide layer. In this study, the diffusivity of implanted yttrium in a Ni-25wt%Cr alloy and its distribution in the oxide scale after different oxidation times have been evaluated using secondary ion mass spectroscopy. It was found that only 17 ppm of yttrium was left in the alloy after just 20 minutes of oxidation at 1 000°C. The implanted Y remained concentrated at the oxide/gas interface as the oxide thickened with time. Within the oxide layer, the Y concentration progressively dropped to zero at the scale/alloy interface. These results are discussed in relation to several important mechanisms proposed for the beneficial effects of reactive element additions on scale adhesion.
Optical emission spectroscopy in the range from 200 to 800 nm was applied for investigation of th... more Optical emission spectroscopy in the range from 200 to 800 nm was applied for investigation of the copper plasma produced by a metal vapor vacuum arc plasma source. The experiments were conducted for the cases when the plasma was guided by straight and Ωshaped curved solenoids as well as without solenoids and, also, for different vacuum conditions. It was found that, besides singly and doubly charged ions, a relatively high concentration of excited neutral copper atoms was present in the plasma. The relative fraction of excited atoms was much higher in the region close to the cathode surface than in the plasma column inside the solenoid. The concentration of excited neutral, singly-and doubly-ionized atoms increased proportionally when the arc current was increased to 400 A. Some weak lines were attributed to more highly ionized copper species and impurities in the cathode material.
The stabilization of a hot-electron plasma in a simple mirror geometry is investigated. Controlle... more The stabilization of a hot-electron plasma in a simple mirror geometry is investigated. Controlled quantities of neutral gas generate a cold plasma through hot-electron ionization. Increasing stability is found with increasing gas pressure. The pressure required for stabilization is found to be inversely proportional to the ionization cross section of the type of neutral gas, indicating that the number of cold electrons is the key stabilizing quantity. The stabilization requires the cold electron density to be at least the same order of magnitude as the hot electron density. Line tying to external surfaces does not play a role in the stabilization. A theory in which the electrons, but not the ions, can be treated in the drift approximation is most closely applicable to the experiment. Reasonable agreement between theory and experiment has been obtained.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
... 1997) 188-192 UN B Beam Interactions with Materials & Atoms Self-neutralized ion implanta... more ... 1997) 188-192 UN B Beam Interactions with Materials & Atoms Self-neutralized ion implantation into insulators F. Liu 1, OR Monteiro, KM Yu ... of the somewhat elevated ion charge states produced by this kind of ion source [8]. The targets were small coupons of either Si wafer, or ...
... device processing were investigated. We are indebted to Dr. Fred Stevie and colleagues at ATT... more ... device processing were investigated. We are indebted to Dr. Fred Stevie and colleagues at ATT/Bell Laboratories for collabora-tion in this work; the results are reported in refer-ences [27] and [28]. U and Th were implanted ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Transport of high current beams of metal ions through the injector beam line of the heavy ion lin... more Transport of high current beams of metal ions through the injector beam line of the heavy ion linear accelerator, UNILAC, has been demonstrated using the MEVVA high current metal ion source. Improved operation of the MEVVA source has been achieved in various ways, including shot-to-shot reproducibility of the beam pulse, beam noise, pulse shape, and absence of ``missing'' pulses. The source was first tested on a high current test stand beam line, and then moved over to regularly used UNILAC injector terminal. Flat and reproducible titanium ion beam pulses were efficiently transported through the system from the ion source to the Wideroe preaccelerator entrance. A beam current of 20 mA (pulse current) of titanium (all charge states, q = 1, 2, 3) was accelerated to an energy of 280Q keV through the single-gap accelerating structure, and a current of over 5 mA of Ti2+ was measured at the Wideroe entrance 13 m downstream.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
High current beams of metal ions can be produced by the metal vapor vacuum arc (MEVVA) ion source... more High current beams of metal ions can be produced by the metal vapor vacuum arc (MEVVA) ion source, providing an important tool for injection into particle accelerators and for ion implantation. A characteristic of the beam that is critical it many applications is the beam current fluctuation level. In this paper we report on some experimental observations of the variation of the beam noise level with source operational parameters. We find that the fractional beam noise varies with the arc current, and that the noise is minimum at the perveance match condition. At this optimum operational point, the rms fractional noise level can be as low as 7% of the mean.
The goal of this study was to determine the critical ion-radiation conditions under which heavy i... more The goal of this study was to determine the critical ion-radiation conditions under which heavy ion beams can induce DNA double-strand breaks. Helium, nitrogen and argon-ion beams in the energy range of 20 eV to 2 keV were used to irradiate naked DNA plasmid pGFP to fluences of 1, 2 and 4 × 1015 ions/cm2. The topological forms of DNA were subsequently analyzed using gel electrophoresis. The DNA forms were changed from the original supercoiled to damaged relaxed and linear forms, depending on the ion mass, energy, fluence and inertia. We found ion energy and fluence thresholds above which direct double-strand breaks can occur. The threshold is discussed in terms of the areal ion-energy density and the cross-section.
Cantilevers of atomic force microscope ͑AFM͒ have been uniformly coated with gold and platinum th... more Cantilevers of atomic force microscope ͑AFM͒ have been uniformly coated with gold and platinum thin films. These films are nanostructured with thickness between 18 and 73 nm. Measuring the resonance frequencies of the cantilevers, before and after the Pt and Au coatings, and using the vibrating beam theory we determined the elastic moduli E 2 of the films. We have obtained E 2 ϭ69.1Ϯ2.6 GPa for gold and E 2 ϭ139.7 Ϯ2.7 GPa for platinum, that are about 12% lower than the respective bulk elastic moduli.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures
Vacuum-arc-produced metal plasma can be used as the ion feedstock material in an ion source for d... more Vacuum-arc-produced metal plasma can be used as the ion feedstock material in an ion source for doing conventional metal ion implantation, or as the immersing plasma for doing plasma immersion ion implantation. The basic plasma production method is the same in both cases; it is simple and efficient and can be used with a wide range of metals. Vacuum arc
I ') 0 ('.J !li"O 51 ')'< ..I:-'< (0. P) fi) DISCLAIMER This document was prepared as an account ... more I ') 0 ('.J !li"O 51 ')'< ..I:-'< (0. P) fi) DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. Neither the United States Government nor any agency thereof, nor The Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or The Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or The Regents of the University of California and shall not be used for advertising or product endorsement purposes.
Cathodic arc deposition is a plasma-based technology for the fabrication of films. The process ca... more Cathodic arc deposition is a plasma-based technology for the fabrication of films. The process can be carried out either at high vacuum or in a low pressure gaseous environment, and films can be formed for example of metals, ceramics, diamondlike carbon, some semiconductors and superconductors, and more. The plasma stream can be filtered to remove microdroplet contamination, and the ion energy can be controlled by substrate bias, thereby transforming the straightforward deposition method into hybrids with other surface modification processes such as ion beam-assisted deposition, ion beam mixing, and ion implantation. The method provides a versatile and powerful plasma tool for the synthesis of novel and technically important surfaces.
Ion bombardment of living cellular material is a novel subfield of ion beam surface modification ... more Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty
Proceedings of International Conference on Particle Accelerators
Metal plasma deposition and metal ion implantation techniques have been developed that could prov... more Metal plasma deposition and metal ion implantation techniques have been developed that could provide a good tool for the surface modification of insulating materials for accelerator applications such as ceramics and that could provide a method for tailoring the surface resistivity over a range of many orders of magnitude. The methods make use of the metal plasma that is produced by the cathodic arc discharge; the plasma itself can be deposited onto the surface at an energy of order 100 eV so as to form an adherent thin film, or an energetic metal ion beam can be formed for deep implantation of the metal species below the surface so as to incorporate a controllable amount of metallic composition into the ceramic.
Based on the idea of a space-charge-limited mode of operation, the influence of a pair of electro... more Based on the idea of a space-charge-limited mode of operation, the influence of a pair of electrostatic meshes on the beam parameters of the LBNL MEVVA-5 ion source was investigated. The meshes were placed in the expansion zone of the vacuum arc plasma. Apart from reducing the level of beam current fluctuations, this mode of operation provides significant control over the ion charge state distribution of the extracted beam. These effects can be understood taking not only space charge but also the high-directed ion drift velocities into account that are the same for different ion charge states of a material. The results of simulations of the processes involved are in good agreement with the experimental results.
XXIst International Symposium on Discharges and Electrical Insulation in Vacuum, 2004. Proceedings. ISDEIV.
We review .sonre recent ezperiiitmtal resu1t.s and oitgoing developntents of vacttttnt-arc-based ... more We review .sonre recent ezperiiitmtal resu1t.s and oitgoing developntents of vacttttnt-arc-based high current nrefal imt source. Tlzese include enhoacement of ion charge states, alternative triggeriitg of vactinin arc, and reduction of ion beant noise, increasedpulse .stability, andgeneration ofKaseous ions.
Implantation of yttrium and other reactive metals has been known to show significant effects on t... more Implantation of yttrium and other reactive metals has been known to show significant effects on the oxidation behavior of Cr203-forming alloys. The oxide growth rate decreases by nearly a factor of ten, and the adhesion of oxide scales to alloys is greatly improved. To better understand the mechanisms by which these elements affect oxidation, it is important to know whether or not they are present in the metal ahead of the oxide layer. In this study, the diffusivity of implanted yttrium in a Ni-25wt%Cr alloy and its distribution in the oxide scale after different oxidation times have been evaluated using secondary ion mass spectroscopy. It was found that only 17 ppm of yttrium was left in the alloy after just 20 minutes of oxidation at 1 000°C. The implanted Y remained concentrated at the oxide/gas interface as the oxide thickened with time. Within the oxide layer, the Y concentration progressively dropped to zero at the scale/alloy interface. These results are discussed in relation to several important mechanisms proposed for the beneficial effects of reactive element additions on scale adhesion.
Optical emission spectroscopy in the range from 200 to 800 nm was applied for investigation of th... more Optical emission spectroscopy in the range from 200 to 800 nm was applied for investigation of the copper plasma produced by a metal vapor vacuum arc plasma source. The experiments were conducted for the cases when the plasma was guided by straight and Ωshaped curved solenoids as well as without solenoids and, also, for different vacuum conditions. It was found that, besides singly and doubly charged ions, a relatively high concentration of excited neutral copper atoms was present in the plasma. The relative fraction of excited atoms was much higher in the region close to the cathode surface than in the plasma column inside the solenoid. The concentration of excited neutral, singly-and doubly-ionized atoms increased proportionally when the arc current was increased to 400 A. Some weak lines were attributed to more highly ionized copper species and impurities in the cathode material.
The stabilization of a hot-electron plasma in a simple mirror geometry is investigated. Controlle... more The stabilization of a hot-electron plasma in a simple mirror geometry is investigated. Controlled quantities of neutral gas generate a cold plasma through hot-electron ionization. Increasing stability is found with increasing gas pressure. The pressure required for stabilization is found to be inversely proportional to the ionization cross section of the type of neutral gas, indicating that the number of cold electrons is the key stabilizing quantity. The stabilization requires the cold electron density to be at least the same order of magnitude as the hot electron density. Line tying to external surfaces does not play a role in the stabilization. A theory in which the electrons, but not the ions, can be treated in the drift approximation is most closely applicable to the experiment. Reasonable agreement between theory and experiment has been obtained.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
... 1997) 188-192 UN B Beam Interactions with Materials & Atoms Self-neutralized ion implanta... more ... 1997) 188-192 UN B Beam Interactions with Materials & Atoms Self-neutralized ion implantation into insulators F. Liu 1, OR Monteiro, KM Yu ... of the somewhat elevated ion charge states produced by this kind of ion source [8]. The targets were small coupons of either Si wafer, or ...
... device processing were investigated. We are indebted to Dr. Fred Stevie and colleagues at ATT... more ... device processing were investigated. We are indebted to Dr. Fred Stevie and colleagues at ATT/Bell Laboratories for collabora-tion in this work; the results are reported in refer-ences [27] and [28]. U and Th were implanted ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Transport of high current beams of metal ions through the injector beam line of the heavy ion lin... more Transport of high current beams of metal ions through the injector beam line of the heavy ion linear accelerator, UNILAC, has been demonstrated using the MEVVA high current metal ion source. Improved operation of the MEVVA source has been achieved in various ways, including shot-to-shot reproducibility of the beam pulse, beam noise, pulse shape, and absence of ``missing'' pulses. The source was first tested on a high current test stand beam line, and then moved over to regularly used UNILAC injector terminal. Flat and reproducible titanium ion beam pulses were efficiently transported through the system from the ion source to the Wideroe preaccelerator entrance. A beam current of 20 mA (pulse current) of titanium (all charge states, q = 1, 2, 3) was accelerated to an energy of 280Q keV through the single-gap accelerating structure, and a current of over 5 mA of Ti2+ was measured at the Wideroe entrance 13 m downstream.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
High current beams of metal ions can be produced by the metal vapor vacuum arc (MEVVA) ion source... more High current beams of metal ions can be produced by the metal vapor vacuum arc (MEVVA) ion source, providing an important tool for injection into particle accelerators and for ion implantation. A characteristic of the beam that is critical it many applications is the beam current fluctuation level. In this paper we report on some experimental observations of the variation of the beam noise level with source operational parameters. We find that the fractional beam noise varies with the arc current, and that the noise is minimum at the perveance match condition. At this optimum operational point, the rms fractional noise level can be as low as 7% of the mean.
The goal of this study was to determine the critical ion-radiation conditions under which heavy i... more The goal of this study was to determine the critical ion-radiation conditions under which heavy ion beams can induce DNA double-strand breaks. Helium, nitrogen and argon-ion beams in the energy range of 20 eV to 2 keV were used to irradiate naked DNA plasmid pGFP to fluences of 1, 2 and 4 × 1015 ions/cm2. The topological forms of DNA were subsequently analyzed using gel electrophoresis. The DNA forms were changed from the original supercoiled to damaged relaxed and linear forms, depending on the ion mass, energy, fluence and inertia. We found ion energy and fluence thresholds above which direct double-strand breaks can occur. The threshold is discussed in terms of the areal ion-energy density and the cross-section.
Cantilevers of atomic force microscope ͑AFM͒ have been uniformly coated with gold and platinum th... more Cantilevers of atomic force microscope ͑AFM͒ have been uniformly coated with gold and platinum thin films. These films are nanostructured with thickness between 18 and 73 nm. Measuring the resonance frequencies of the cantilevers, before and after the Pt and Au coatings, and using the vibrating beam theory we determined the elastic moduli E 2 of the films. We have obtained E 2 ϭ69.1Ϯ2.6 GPa for gold and E 2 ϭ139.7 Ϯ2.7 GPa for platinum, that are about 12% lower than the respective bulk elastic moduli.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures
Vacuum-arc-produced metal plasma can be used as the ion feedstock material in an ion source for d... more Vacuum-arc-produced metal plasma can be used as the ion feedstock material in an ion source for doing conventional metal ion implantation, or as the immersing plasma for doing plasma immersion ion implantation. The basic plasma production method is the same in both cases; it is simple and efficient and can be used with a wide range of metals. Vacuum arc
I ') 0 ('.J !li"O 51 ')'< ..I:-'< (0. P) fi) DISCLAIMER This document was prepared as an account ... more I ') 0 ('.J !li"O 51 ')'< ..I:-'< (0. P) fi) DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. Neither the United States Government nor any agency thereof, nor The Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or The Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or The Regents of the University of California and shall not be used for advertising or product endorsement purposes.
Cathodic arc deposition is a plasma-based technology for the fabrication of films. The process ca... more Cathodic arc deposition is a plasma-based technology for the fabrication of films. The process can be carried out either at high vacuum or in a low pressure gaseous environment, and films can be formed for example of metals, ceramics, diamondlike carbon, some semiconductors and superconductors, and more. The plasma stream can be filtered to remove microdroplet contamination, and the ion energy can be controlled by substrate bias, thereby transforming the straightforward deposition method into hybrids with other surface modification processes such as ion beam-assisted deposition, ion beam mixing, and ion implantation. The method provides a versatile and powerful plasma tool for the synthesis of novel and technically important surfaces.
Ion bombardment of living cellular material is a novel subfield of ion beam surface modification ... more Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty
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