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Feb 2000

Volume 71, Issue 2, pp. 335-1239

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Molecular ion implanter equipped with liquid-metal alloy ion source

Y. Gotoh, H. Tsuji, and J. Ishikawa

Rev. Sci. Instrum. 71, 780 (2000); http://dx.doi.org/10.1063/1.1150292 (3 pages)

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Molecular ion implanter was developed with a liquid-metal alloy ion source. Use of a liquid-metal alloy ion source enables us to generate various kinds of molecular ions. To apply liquid-metal ion source to a general ion implanter, it is necessary to converge the divergent beam. We adopted the lens system we have already developed, and examined its performance by computer simulation and experiments. An example of molecular ion implantation was demonstrated with gold-antimony ion source. 24 keV AuSb2+ was implanted into silicon, and presence of gold and antimony atoms was confirmed by Rutherford backscattering spectrometry and particle induced x-ray emission measurements. © 2000 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
85.40.Ry Impurity doping, diffusion and ion implantation technology

High current and high intensity pulsed ion-beam sources for combined treatment of materials

A. I. Ryabchikov, A. V. Petrov, I. B. Stepanov, I. A. Shulepov, and V. G. Tolmachjeva

Rev. Sci. Instrum. 71, 783 (2000); http://dx.doi.org/10.1063/1.1150293 (3 pages) | Cited 1 time

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The complex installation for combined materials treatment with accelerated ion beams of different peak power and metallic plasma flows is described. The installation comprises the high-current repetitively pulsed vacuum arc ion source, high-intensity pulsed ion beam source, and direct-current vacuum arc plasma source combined with the plasma filter for plasma cleaning from the microparticle fraction. It has been found that the preliminary treatment of stainless steel samples with the high-power ion beam of nanosecond pulse duration results in the reduction of ion sputtering coefficient at the implantation of tungsten ions. It has been shown that the increase of maximum implanted tungsten concentration is influenced by changing the surface morphology and element structure of the samples affected by the high-power ion beam. © 2000 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors

The L3A facility at the Vinča Institute: Surface modification of materials, by heavy ion beams from an electron cyclotron resonance ion source

A. Dobrosavljević, M. Milosavljević, N. Bibić, and A. Efremov

Rev. Sci. Instrum. 71, 786 (2000); http://dx.doi.org/10.1063/1.1150294 (3 pages) | Cited 6 times

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This article describes the L3A experimental facility for surface modification of materials at the Vinča Institute of Nuclear Sciences, in Belgrade. This facility was completed and put into operation in May 1998. It is connected to the mVINIS ion source, an electron cyclotron resonance ion source capable of producing a wide range of multiply charged ions from gaseous and solid substances. The heavy ion beams obtained from mVINIS are separated by charge to mass ratio (q/m) and transported to the target chamber for sample irradiation and modification. The target chamber is equipped with a multipurpose target holder, an electron-beam evaporation source for thin layer deposition, a residual gas analyzer, and other auxiliary equipment. There is also an additional low energy argon ion source for target preparation/sputtering and for ion beam assisted deposition. In this article we describe the layout and performances of the L3A facility, the experience gained during 1 yr of operation, and the requirements imposed by the current and future experimental programs. Currently, there are 24 experimental programs competing for the ion beam time at the L3A facility. © 2000 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
41.75.Ak Positive-ion beams

Specific modification of polysulfone with cluster bombardment with assistance of Ar ion irradiation

Guochun Xu, Y. Hibino, K. Awazu, M. Tanihara, and Y. Imanishi

Rev. Sci. Instrum. 71, 789 (2000); http://dx.doi.org/10.1063/1.1150295 (4 pages)

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Objective: To develop a rapid method for the modification of polysulfone with ammonium sulfamate with the assistance of Ar ion irradiation with a multi-source cluster deposition apparatus. These surfaces mimicking the structure of heparin, a bioactive molecule, have a high anti-thrombosis property. Experimental Design: Polysulfone film, setting on a turning holder, was irradiated by Ar ions during bombardment with ammonium sulfamate clusters. The Ar ion source serves for the activation of a polymer surface and a cluster ion source supplies ammonium sulfamate molecules to react with the activated surface. After thorough washing with de-ionized sterile water, the modified surfaces were evaluated in terms of the contact angle of water, elemental composition, and binding state on electron spectroscopy for chemical analysis and platelet adhesion with platelet rich plasma. Results: The modification of polysulfone decreased the contact angle of water on surfaces from 82.6 ° down to 34.5 °. Ammonium, amine, sulfate, and thiophene combinations were formed on the modified surfaces. The adhesion numbers of the platelet were decreased to one tenth compared to the original surface. The same process was also applied to other polymers such as polyethylene, polypropylene, and polystyrene and similar outcomes were also observed. Conclusion: The primary studies showed successful modification of polysulfone with ammonium sulfamate with the assistance of Ar ion irradiation. Since the same concept can also be applied to other materials with various substrates, combined with the features of no solvent and no topographic changes, this method might be developed into a promising way for modification of polymeric materials. © 2000 American Institute of Physics.
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81.65.-b Surface treatments
61.82.Pv Polymers, organic compounds
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
87.85.J- Biomaterials
61.80.Jh Ion radiation effects
68.35.Dv Composition, segregation; defects and impurities
68.03.Cd Surface tension and related phenomena
82.50.-m Photochemistry

Theoretical analysis of the embedded layer formed by high-energy Au implantation into Si(II)

S. T. Nakagawa, S. Nakano, H. Ogiso, M. Iwaki, M. Hashimoto, and W. Eckstein

Rev. Sci. Instrum. 71, 793 (2000); http://dx.doi.org/10.1063/1.1150296 (4 pages) | Cited 3 times

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We performed a high-energy and high-fluence ion implantation, expecting to fabricate micromachines. (100) Si was bombarded by 3.1 MeV Au2+ ion with a fluence of 1017/cm2 at 95 K. Then an embedded layer was extracted after chemical etching (30% KOH, at 333 K). The stoichiometric change was evaluated by both experiments and simulation using TRIDYN. The experiments showed, although qualitatively, that Au clustering occurred even at a temperature lower than had ever been reported. From a critical ion fluence, which is necessary to extract a material after etching, we estimate a local concentration to be 1.0–1.2 at. %, which caused a physicochemical change by Au doping. A probable model for the clustering is proposed. It is a nonthermal atomic transfer mechanism following the electronic excitation. Here the electronic stopping power just beneath the surface is 140 eV/Å, which is large enough to ionize valence electrons of Si. Also, a wide amorphized region supports an unstable electrostatic field, which should be produced by many odd-number member rings made of host(Si) atoms. Both ionization of Si and the unstable electrostatic field may most likely trigger the Au clustering. © 2000 American Institute of Physics.
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61.72.uf Ge and Si

A negative ion beam application to artificial formation of neuron network in culture

Hiroshi Tsuji, Hiroko Sato, Takahiro Baba, Yasuhito Gotoh, and Junzo Ishikawa

Rev. Sci. Instrum. 71, 797 (2000); http://dx.doi.org/10.1063/1.1150297 (3 pages) | Cited 1 time

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A negative ion beam modification of the biocompatibility of polystyrene surface was investigated for the artificial formation of neuron network in culture with respect to negative ion species. Negative ions of silver, copper or carbon were implanted in nontreated polystyrene (NTPS) dishes at conditions of 20 keV and 3×1015 ions/cm2 through a mask with many slits of 60 μm in width. For the surface wettability, the contact angle of ion-implanted NTPS was about 75° for silver-negative ions, which was lower than 86° of the original NTPS. For carbon implantation, on the contrary, the contact angles did not change from the original value. In culture experiment using neuron cells of PC-12h (rat adrenal pheochromocytoma), the cells cultured with serum medium in two days showed the cell attachment and growth in number only at the ion-implanted region on NTPS for all ion species. In another two days in culture with nonserum medium including a nerve growth factor, the outgrowth of neural protrusions was also observed only at the ion-implanted region for all ion species. There was a difference in number of attached cells for ion species. The silver-negative ion-implanted NTPS had a large effect for cell attachment compared with other two ion species. This reason is considered to be due to the lowest contract angles among them. © 2000 American Institute of Physics.
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87.85.Wc Neural engineering
87.85.Lf Tissue engineering
81.65.Cf Surface cleaning, etching, patterning
87.18.Sn Neural networks and synaptic communication
61.80.Jh Ion radiation effects
61.82.Pv Polymers, organic compounds

Microwave plasma source for high current ion beam neutralization

D. Korzec, A. Müller, and J. Engemann

Rev. Sci. Instrum. 71, 800 (2000); http://dx.doi.org/10.1063/1.1150298 (4 pages) | Cited 6 times

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A new microwave based plasma source for high current ion beam neutralization is presented. It consists of a tapered WR340 waveguide with a directly coupled 2.45 GHz magnetron and a quartz tube of 40 mm diameter inside the waveguide confined by two graphite electrodes. The upper electrode houses the gas feed, whereas the lower electrode serves as the plasma outlet. Both electrodes can be biased independently. Tuning is done via a magnetically controlled stab inserted into the waveguide. The plasma was characterized by use of the Langmuir probe. The electron concentration of 5×1011 cm−3 at 250 W was measured. Typical electron temperature is below 2.5 eV even for pressure as low as 2×10−3 Pa. The extractable electron current is dependent on microwave power and gas flow. A limitation is caused by the ion saturation current to the negatively biased electrodes. The voltage on the electrodes allows an easy control of electron current. Maximum electron current achieved so far is 400 mA for an argon flow of 5 sccm and microwave power of 300 W. © 2000 American Institute of Physics.
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29.25.Bx Electron sources
41.75.Ak Positive-ion beams
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
07.77.Ka Charged-particle beam sources and detectors

Negative-ion implanter for powders and its application to nanometer-sized metal particle formation in the surface of glass beads

Hiroshi Tsuji, Shunsuke Kido, Hitoshi Sasaki, Yasuhito Gotoh, and Junzo Ishikawa

Rev. Sci. Instrum. 71, 804 (2000); http://dx.doi.org/10.1063/1.1150299 (3 pages) | Cited 9 times

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We have developed a negative-ion implanter for uniform implantation into each powder surface without particle scattering. It consists of a plasma sputter-type negative-ion source, a mass separator, an acceleration tube, a lens, X–Y deflectors, a 90° deflector, and a Faraday cup with an agitator. The electrostatic 90° deflector bends a horizontal beam to a vertical direction and leads it into the Faraday cup. The agitator is an electromagnetic vibrator at a frequency of 120 Hz, which mixes particles for whole surface treatment and uniform implantation. In this implanter, we obtained no scattering implantation for spherical oxide beads with diameters ranging from 5 to 1000 μm in an agitated state, and also obtained a good uniformity of implanted atoms among beads. For an application of the negative ion implantation into powders, copper ions were implanted into soda-lime glass beads and plates at conditions of 50 and 30 keV, respectively, with 1×1017 ions/cm2. In linear optical properties, both implanted samples show a clear absorption at a photon energy of 2.2 eV due to resonance absorption of copper surface plasmon. In addition, the implanted glass plate shows the large third-order nonlinear susceptibility, χ(3) = 1.3×10−7 esu. These results suggest the existence of copper nanometer-sized particles in glass. © 2000 American Institute of Physics.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.72.up Other materials
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.65.-b Surface treatments

High current injectors for heavy ion driven inertial fusion

J. W. Kwan

Rev. Sci. Instrum. 71, 807 (2000); http://dx.doi.org/10.1063/1.1150300 (3 pages) | Cited 1 time

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Conceptual heavy ion driven inertial fusion (HIF) drivers typically have an array of up to 100 parallel beams each supplying a beam current of ≈0.25 A. According to space-charge limitations in beam extraction and in the low energy beam transport section, there are two options in building injectors for HIF drivers. The traditional way is to use low current density, large aperture, contact ionization sources. The major disadvantage of this approach is the very large size of the injector and matching section. The other option is to use high current density, multiple beamlet ion sources. From various scaling rules, it is found that the multiple beamlet approach is the more attractive one because it can be smaller, and more efficient, although the requirements on the ion source are more demanding. © 2000 American Institute of Physics.
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28.52.Cx Fueling, heating and ignition
29.25.Lg Ion sources: polarized
29.27.Ac Beam injection and extraction

Initial growth temperature of crystalline SiC by simultaneous irradiation of energetic 28Si− and 12C+

Nobuteru Tsubouchi, Akiyoshi Chayahara, Atsushi Kinomura, and Yuji Horino

Rev. Sci. Instrum. 71, 993 (2000); http://dx.doi.org/10.1063/1.1150369 (3 pages) | Cited 2 times

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Initial growth temperature of SiC polycrystalline films by simultaneous irradiation of energetic, isotopical mass-separated 28Si− and 12C+ ions was investigated. The kinetic energies of both ions were 200 eV and deposition temperatures were room temperature, 400 °C, and 600 °C. The SiC films deposited at ∼600 °C showed the infrared absorption peak at 802 cm−1 and weak ring patterns on reflection high-energy electron diffraction measurements, characteristics for crystalline SiC. With x-ray photoelectron spectroscopy, transmission electron microscopy, and transmission electron diffraction, the films were nearly stoichiometric and the initial growth of nanocrystalline 3C–SiC at ∼600 °C under ion irradiation was observed. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.46.-w Structure of nanoscale materials

Preparation of giant magnetostrictive thin film by magnetron and ion beam sputtering processes

K. Nakazato, M. Hashimoto, H. Uchida, and Y. Matsumura

Rev. Sci. Instrum. 71, 996 (2000); http://dx.doi.org/10.1063/1.1150370 (3 pages) | Cited 5 times

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Thin films of giant magnetostrictive materials were formed by dc magnetron sputtering and ion beam sputtering processes. A systematic investigation was made to examine the effect of these deposition processes on the magnetic properties and magnetostriction of TbFe2 and (Tb, Dy)Fe2 thin films. The magnetostriction of the films formed by dc sputtering was in the range from 200 to 400 ppm at a magnetic field H = 15 kOe, whereas the films formed by the ion beam sputtering exhibited a slightly higher magnetostriction. For both processes, the increase in Ar partial pressure in the deposition processes strongly changed magnetic anisotropy from perpendicular to in plane, and increased magnetostriction and magnetostrictive response at low magnetic fields. However, the mixture of Xe gas into Ar gas in the dc sputtering lowered magnetization and gave almost no effect on magnetic anisotropy. © 2000 American Institute of Physics.
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81.15.Cd Deposition by sputtering
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

MgO thin film formation by ion enhanced deposition processes

M. Hashimoto, Y. Onozaki, H. Uchida, and Y. Matsumura

Rev. Sci. Instrum. 71, 999 (2000); http://dx.doi.org/10.1063/1.1150371 (3 pages)

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MgO thin films were prepared by ion plating systems and by an ion beam sputtering system with a plasma filament type ion source. Triode-type and rf ion plating processes were employed. MgO films were prepared with various oxygen partial pressures ranging from 10−3 to 10−2 Pa. In the triode-type ion plating process, the MgO(200) was the preferred growth orientation of film. In the rf ion plating process, MgO(111) and (220) reflection peaks appeared in the x-ray diffraction patterns of films. The films were transparent, and those values of transmittance of ultraviolet region were increased as increasing oxygen partial pressure. In the ion beam sputtering process, the film showed amorphous structure and low transmittance. © 2000 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics

Application of compact microwave ion source to low temperature growth of transition metal nitride thin films for vacuum microelectronics devices

Y. Gotoh, H. Tsuji, and J. Ishikawa

Rev. Sci. Instrum. 71, 1002 (2000); http://dx.doi.org/10.1063/1.1150372 (4 pages) | Cited 5 times

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A compact microwave ion source was applied to the low temperature growth of transition metal nitride thin films for the cathode of vacuum microelectronics devices. An ion beam assisted deposition system consisted of a compact microwave ion source and an electron beam evaporator was developed. Depositions of zirconium nitride and niobium nitride thin films were performed and the film properties were investigated. As a result, it was found that polycrystalline films of zirconium nitride and niobium nitride were prepared at the substrate temperature as low as 500 °C, which was almost 200 °C lower than the results shown in the literature. The reason for this reduction of substrate temperature might be attributed to low gas pressure during deposition, due to the use of a single aperture ion source. The control of film composition by controlling the ion-atom arrival rate ratio achieved the control of work function. It was concluded that the ion beam assisted deposition with microwave ion source provides a possible process of cathode deposition. © 2000 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
85.45.Db Field emitters and arrays, cold electron emitters
29.25.Ni Ion sources: positive and negative
73.30.+y Surface double layers, Schottky barriers, and work functions

Experimental study of three-dimensional microfabrication by focused ion beam technology

Fu Yongqi, Ngoi Kok, Ann Bryan, N. P. Hung, and Ong Nan Shing

Rev. Sci. Instrum. 71, 1006 (2000); http://dx.doi.org/10.1063/1.1150373 (3 pages) | Cited 7 times

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Combined with experimental milling, three-dimensional (3D) microfabrication by focused ion beam (FIB) technology has been studied. Rules among limiting aperture size, dwell time, retrace time, tail of Gaussian distribution, etc., have been analyzed in terms of experimental results. Some phenomena are explained from the theoretical point of view. In addition, influence of redeposition for the sidewall root of microstructure in the process of milling is analyzed, and the avoidance methods are used in the meantime. It was proved by experiment that beam current (representing ion beam energy) and beam spot size play an important role in the etching process. Nonlinear variation of these parameters led to the broadening of edge periphery and redeposition at the root of the sidewall. On the other hand, milling order is vital for the 3D microfabrication result by FIB sputtering due to the redeposition effect and profile broadening effect. © 2000 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.20.Wk Machining, milling
06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)

Calibration of etching uniformity for large aperture multilevel diffractive optical element by ion beam etching

Yongqi Fu, Ngoi Kok Ann Bryan, and Ong Nan Shing

Rev. Sci. Instrum. 71, 1009 (2000); http://dx.doi.org/10.1063/1.1150374 (3 pages) | Cited 1 time

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Ion beam milling is a suitable technique for manufacturing optical elements. It has the advantages of accurately controlling and maintaining a constant optical index. However, it is very difficult to ensure etching uniformity on large areas due to the instability of the machine during sputtering. In this article, the etching speed is analyzed, and selection criteria of corresponding technological parameters are proposed. An available calibration method is put forth to improve etching depth uniformity. Etching is divided into several steps and the sample is rotated to change its position on the target after each step. It is proved by experiment that this is very practical for actual fabrication with a 5%–15% improvement of depth uniformity from previous results. © 2000 American Institute of Physics.
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42.86.+b Optical workshop techniques
81.65.Cf Surface cleaning, etching, patterning

Sputtering and thermal effect during ion microbeam patterning of polymeric films

A. M. Ektessabi and T. Sano

Rev. Sci. Instrum. 71, 1012 (2000); http://dx.doi.org/10.1063/1.1150375 (4 pages) | Cited 4 times

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The purpose of this article is to investigate the machinability of polymers and the main parameters involved during ion microbeam processing of polymers. Investigations were made for the case of ion microbeam patterning of polyethyleneterephthalate and nylon-6 using a focused ion beam system with a needle type ion source. The extracted beam diameter was 0.2 μm, the current density on the target was 1.0 A/cm2, and the beam energy was 30 keV. The removal rate, which shows the number of atoms removed when an ion impinges on the surface, was obtained experimentally. By comparing the removal rate and the theoretical sputtering yield, it became clear that effects other than sputtering have a great influence on the machinability of polymers. Two-dimensional unsteady heat conduction equations were computed using the finite difference method in order to estimate the temperature increment within and around the beam irradiated area. The results show that localized heating and a change of chemical bonding state during ion microbeam processing strongly influence the patterning of polymers. © 2000 American Institute of Physics.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.20.Wk Machining, milling
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Electron cyclotron resonance light source assembly—A vacuum-ultraviolet radiation source based on an electron cyclotron resonance plasma

P. Grübling, J. Hollandt, and G. Ulm

Rev. Sci. Instrum. 71, 1200 (2000); http://dx.doi.org/10.1063/1.1150427 (3 pages) | Cited 3 times

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A vacuum-ultraviolet radiation source based on an electron cyclotron resonance plasma was developed. Electron cyclotron resonance light source assembly (ELISA) is a 10 GHz monomode source of compact design featuring a tunable cavity and permanent magnets which can be axially positioned. The radiation emission of the source can be detected simultaneously in the vacuum-ultraviolet spectral range via a toroidal grating monochromator and in the x-ray spectral range via a Si(Li) detector. Spectroscopic investigations of a krypton and a neon plasma in the 9–27 nm spectral range show that ELISA produces complex line spectra of highly ionized atoms by applying only 12 W microwave power. © 2000 American Institute of Physics.
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42.72.Bj Visible and ultraviolet sources
52.50.Gj Plasma heating by particle beams

Studies on enhancement of x-ray flux in the compact electron cyclotron resonance plasma x-ray source

R. Baskaran and T. S. Selvakumaran

Rev. Sci. Instrum. 71, 1203 (2000); http://dx.doi.org/10.1063/1.1150428 (3 pages) | Cited 9 times

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The electron cyclotron resonance (ECR) plasma x-ray source has a potential application for medical imaging. The plasma and x-ray characterization studies on the ECR x-ray source based on cylindrical cavity operated in TE111 mode were reported earlier by us. In order to enhance the x-ray flux and the effective energy of the x-ray spectrum, the use of rectangular cavity in ECR x-ray source is studied. In this article, the theoretical analysis of electron acceleration in TE101 rectangular cavity used as a cyclotron resonance accelerator is presented. The electron orbital values of rectangular cavity are compared with that of cylindrical cavity (TE111 mode). It is found that there is an increase in final energy of electron (170 keV), reduction in electron transit time, and increase in distance between the successive orbits in the rectangular cavity than the cylindrical cavity. An ECR x-ray source based on rectangular cavity has been designed and constructed and the experimental system is described. © 2000 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.50.Gj Plasma heating by particle beams
84.40.Az Waveguides, transmission lines, striplines

Production of multiply charged ion target for photoionization studies using synchrotron radiation

Masaki Oura, Hitoshi Yamaoka, Kiyoshi Kawatsura, Tatsuji Hayaishi, Junichi Kimata, Takao M. Kojima, Masahiro Kimura, Tsuguhisa Sekioka, and Mititaka Terasawa

Rev. Sci. Instrum. 71, 1206 (2000); http://dx.doi.org/10.1063/1.1150429 (4 pages) | Cited 6 times

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Multiply charged ions for some gaseous and metallic elements have been produced as the target for photoionization studies using synchrotron radiation. The target densities have been measured to be typically of the order of 106 ions/cm3. Characteristics of the beam transport system is described and the feasibility of photoionization experiments along the isonuclear and the isoelectronic sequences is also discussed. © 2000 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
41.85.Ja Particle beam transport
41.60.Ap Synchrotron radiation
32.80.Fb Photoionization of atoms and ions

Beam optics in inertial electrostatic confinement fusion

Masami Ohnishi, Chikara Hoshino, Kiyoshi Yoshikawa, Kai Masuda, and Yasushi Yamamoto

Rev. Sci. Instrum. 71, 1210 (2000); http://dx.doi.org/10.1063/1.1150430 (3 pages) | Cited 1 time

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We study the transport of ions and electrons near the cathode of the inertial electrostatic confinement fusion that is expected to be a portable neutron source. We carry out a PIC particle simulation in order to obtain the self-consistent electrostatic potential and the transparency of the cathode for the accelerated ions. The transparency is shown to be much less than a geometrical transparency and possesses a strong dependence on the energy of ions. The increase of the applied voltage results in larger neutron production due to increased fusion cross section and also increased ion current by the improved transparency. © 2000 American Institute of Physics.
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52.58.Ei Light-ion inertial confinement
29.25.Dz Neutron sources
52.65.Rr Particle-in-cell method
41.85.Ja Particle beam transport

Measurements on H− sources for spallation neutron source application

R. Thomae, R. Gough, R. Keller, M. Leitner, K. Leung, D. Meyer, and M. Williams

Rev. Sci. Instrum. 71, 1213 (2000); http://dx.doi.org/10.1063/1.1150431 (3 pages) | Cited 1 time

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Lawrence Berkeley National Laboratory is engaged in the development of H− ion sources for the upgrade of the Los Alamos Neutron Science Center (LANSCE) facility and the spallation neutron source (SNS) to be built in the U.S. For the upgrade of the LANSCE facility, the H− ion generator has to deliver an output current of 40 mA. The repetition rate must be 120 Hz at a pulse length of 1 ms (12% duty factor). Furthermore, the normalized emittance must be less than 0.1π mm mrad. During the last years, the Ion Beam Technology Group of the LBNL improved the so-called surface conversion source for the generation of higher H− currents. In the first part of this article, we discuss the operation conditions of the source at the required 40 mA output current. The ion source for the 1 MW spallation neutron source is required to provide 35 mA of H− beam current at 6% duty factor (1 ms pulses at 60 Hz) with a normalized rms emittance of less than 0.2π mm mrad. The H− beam will be accelerated to 65 keV and matched into a 2.5 MeV RFQ. The ion source is expected to ultimately produce 70 mA of H− at 6% duty factor when the SNS is upgraded to 2 MW of power. For this application, a radio-frequency driven, magnetically filtered multicusp source is being developed at LBNL. Experimental results (including emittance measurements) on the performance of the prototype ion source operated at the demanded beam parameters will be presented in this article. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
29.25.Dz Neutron sources

Development of a high-current laser ion source for induction accelerators

M. Yoshida, J. Hasegawa, S. Fukata, Y. Oguri, M. Ogawa, M. Nakajima, K. Horioka, and M. Shiho

Rev. Sci. Instrum. 71, 1216 (2000); http://dx.doi.org/10.1063/1.1150437 (3 pages) | Cited 3 times

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We have developed a high-current laser ion source that can provide low-charge-state ions for induction accelerators. A frequency-doubled Nd:YAG laser (λ = 532 nm) irradiated a copper target with relatively low intensities of 108–109 W/cm2. The laser-produced plasma supplied a large number of Cu+ and Cu2+ ions over 1014 ions/cm2 at a distance of 10 cm from the target. We have successfully extracted high-current copper beams over 0.1 A/cm2 using an inductive acceleration module. The beam emittance measured by a pepper-pot method was about 40 πmm mrad. © 2000 American Institute of Physics.
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29.20.-c Accelerators
29.25.Ni Ion sources: positive and negative
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
29.27.Ac Beam injection and extraction
41.75.Jv Laser-driven acceleration
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