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  • American Institute of Physics (AIP)  (154,279)
  • Sage Publications
  • 101
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: By using a reference-beam diffraction data-collection technique, it is possible to directly measure a large number of relative phases of Bragg reflections on an area detector in a typical protein crystallography experiment. The technique, being developed at Cornell, incorporates the principle of three-beam diffraction into the most common method of data collection, i.e., the oscillating-crystal method, and allows recordings of many phase-sensitive three-beam interference profiles simultaneously. Recent advances include a dedicated five-circle κ diffractometer and new data acquisition and analysis algorithms. Experimental results on a protein crystal are presented and the strategies of using the measured phases for solving crystal structures are discussed. © 2002 American Institute of Physics.
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  • 102
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Diffraction enhanced x-ray imaging (DEI) has simultaneous contrast sources from absorption, x-ray refraction gradients, and scatter-rejection (extinction). The combination of these contrast mechanisms generally allows many more features in objects to be observed compared to conventional radiography. In some instances or in specially prepared systems it is possible to eliminate one of the contrast mechanisms so as to create features that arise from a single contrast mechanism. With the DEI technique it is most interesting to either eliminate the absorption contrast of an object or conversely eliminate the refraction gradient contrast. We have explored both extremes of this contrast scale in order to better understand the DEI contrast mechanisms and to exploit the absence of a contrast mechanism for technical purposes. © 2002 American Institute of Physics.
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  • 103
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Small-angle scattering is widely used for measuring materials microstructure in the 1–100 nm size range. Ultrasmall-angle x-ray scattering (USAXS), typically achieved through crystal collimation, extends this size range to include features over 1 μm in size. This article reports on USAXS on the UNICAT beam line 33-ID at the Advanced Photon Source. The instrument makes use of a six-reflection crystal pair as a collimator and another six-reflection crystal pair as an analyzer. First principle absolute calibration and a broad scattering vector range make this a very effective instrument, limited only by the fact that the measurement of anisotropic microstructures is excluded due to slit smearing from the crystal collimation. This limitation has recently been removed by adding a horizontally reflecting crystal before and another after the sample. This creates a USAXS instrument with collimation in two orthogonal directions. We call this configuration effective pinhole USAXS. Now, anisotropic materials are probed using 9–17 keV photons in the same physically-relevant (from 50 nm to over 1 μm) microstructural size range as that available for materials which scatter isotropically. © 2002 American Institute of Physics.
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  • 104
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new setup for measuring partial photoion yields was developed and built at the Synchrotron Radiation Center. The vacuum chamber, which accommodates an ion time-of-flight spectrometer, a metal vapor oven, and a liquid nitrogen cooled trap, consists mainly of a standard conflat 6 in. six-way cross and a 6 in. tee. A differential pumping stage separates the vacuum chamber from the beam line. First experiments with this apparatus were performed using neon, lithium, and beryllium. © 2002 American Institute of Physics.
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  • 105
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have designed and fabricated, for the first time, a simple, compact, and low-cost electrostatic plasma lens based on the use of permanent magnets rather than an electrically driven solenoid to establish the magnetic field. Characteristics of the focused ion beam passed through the lens have been measured. Some of the beam characteristics depend strongly on the applied magnetic field strength and the precise form of the external potential distribution applied along the lens electrodes. The experimental results obtained at the Institute of Physics (Kiev) and at the Lawrence Berkeley National Laboratory (Berkeley) show that this plasma optical device can be used beneficially for focusing and manipulating moderate energy, large area, heavy metal ion beams. © 2002 American Institute of Physics.
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  • 106
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Spallation Neutron Source requires an ion source capable of delivering a high-current (∼50 mA) H− beam with a 6% duty cycle continuously for the three weeks between the scheduled maintenance periods. The cesium-enhanced, multicusp volume ion source under development on the integrated test facility at LBNL delivers H− ion currents up to 50 mA, increasing approximately linearly with the rf power. Initial experience using porcelain-coated copper antennas, however, indicates lifetimes will fall below the desired three-week period, mostly limited by antenna failures. In an effort to improve our understanding of the antenna limitations, we are in the process of developing an antenna test dome, which will allow us to visually observe and study the rf-initiated discharge at low-power levels. We hope to be able to test antennas for invisible defects by observing and measuring the onset of the discharge. In addition, we are planning to test different antennas. Results will be presented at the meeting. © 2002 American Institute of Physics.
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  • 107
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The H− ion source for the Spallation Neutron Source (SNS) is a cesiated, radio-frequency driven multicusp volume source which operates at a duty cycle of 6%. In pulsed rf driven plasma sources, ignition of the plasma affects the stability of source operation and the antenna lifetime. We report on ignition schemes, based on secondary electron generation by UV light, a hot filament, a low power rf plasma (cw, 13.56 MHz), as well as source operation solely with the high power 2 MHz rf. We find that the dual frequency, single antenna scheme is most attractive for the operating conditions of the SNS H− source. © 2002 American Institute of Physics.
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  • 108
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The high current injector (HSI) was set into operation in 1999. The maximum ratio of mass to charge state of this new injector has been increased from 25 to 65 with a lower injection velocity of 2.2 keV/u (11.7 keV/u before). The space charge limit of the RFQ (0.25*A/ζ[mA]) was reached for argon and lighter ions but not for U4+ or rare isotopes. For that reason further modifications of the high current ion injector, e.g., geometry of the acceleration gap, solenoid for focusing, were necessary. Here we present beam emittance measurements after the acceleration system for different ion species with beam energies up to 150 keV and beam currents up to 100 mA. For the measurements a multicusp ion source with a multiaperture accel–decel extraction system has been used to produce high ion beam currents in low charge states. The commissioning has been made using an Ar+ beam. This ion beam is easy to produce in nearly one charge state with emission current densities up to 150 mA/cm2. The emittance measurements will be presented in view of the two main dependencies: the focussing strength of the acceleration gap and the space charge forces in the acceleration gap. © 2002 American Institute of Physics.
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  • 109
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The development of a high current bismuth ion source is motivated by heavy ion driven fusion (HIF) and is part of the conceptual design of a HIF-relevant Bi+ test injector with four beamlets, which could serve as a HIF driver front end element. Envisaged is the development of a 300 mA Bi+ injector that can deliver four parallel beams from a 500 kV platform with 75 mA per beam. The first prototype source is driven by an arc discharge and provides singly charged Bi ions with a fraction more than 92% of the total extracted current. At its perveance limit this source delivers current of 70 mA, with the corresponding voltage being 27.5 kV. The emittance of a 21 mA/18.2 keV beam was measured and it amounted to 0.27 π mm mrad (80%, normalized, 4 root mean square) provided by a seven hole extraction system. Based on these investigations a new ion source will be designed and tested that will deliver current of 75 mA at ion energies up to 65 keV. In order to fulfill the requirements of HIF the emittance has to be in the vicinity of 0.4 π mm mrad (normalized). In this article we give a brief description of the design of an advanced ion source. Based on experimental experience using the previous prototype source one major modification made is the construction of an external oven. The use of more than one filament to increase the source lifetime is also planned. © 2002 American Institute of Physics.
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  • 110
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Heavy ion beam inertial fusion driver concepts depend on the availability and performance of high-brightness high-current ion sources. Surface ionization sources have relatively low current density but high brightness because of the low temperature of the emitted ions. We have measured the beam profiles at the exit of the injector diode, and compared the measured profiles with EGUN and WARP-3D predictions. Spherical aberrations are significant in this large aspect ratio diode. We discuss the measured and calculated beam size and beam profiles, the effect of aberrations, quality of vacuum, and secondary electron distributions on the beam profile. © 2002 American Institute of Physics.
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  • 111
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Negative H− ion beams produced by a tandem-type H− ion source have good beam optics with a typical beam divergence angle of less than 5 mrad. However, the physical reason has not yet been made clear. To clarify the mechanism, we investigate a velocity distribution of negative ions at the extraction holes by a three-dimensional (3D) Monte Carlo transport code. In this code, surface-produced H− ion trajectories are calculated by numerically solving the 3D equation of motion for H− ions. The energy of the H− ions is relaxed through Coulomb collision with the background plasma (H+ ions), which has a low temperature of ∼1 eV in the tandem-type H− ion source. Therefore, energy relaxation by Coulomb collision plays an important role in good beam optics. © 2002 American Institute of Physics.
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  • 112
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The influence of a dipole magnetic field in the extractor on the beamlet deflection has been investigated using a JAERI 400 keV H− ion source. The beam deflection angle decreased from 10.2 to 7.0 mrad when the integrated value of the magnetic field was changed from 2530 to 910 G cm. The measured deflection angle was larger than the estimated value from the ion trajectory considering the magnetic field. To understand the dominant factor that enhances the beam deflection angle, three-dimensional trajectory simulation was performed. It was confirmed that the axis of the beamlet deflected by the magnetic field in the extractor is displaced from the center of the aperture at the grounded grid (GRG). This displacement enhances the beam deflection angle due to the effect of the electrostatic lens at the GRG. This phenomenon is similar to the beam deflection by aperture displacement of the GRG. © 2002 American Institute of Physics.
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  • 113
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A radio-frequency-driven hydrogen-ion source of the diagnostic neutral beam has been developed for the Hanbit magnetic mirror device at the Korea Basic Science Institute [S. M. Hwang et al., Trans. Fusion Technol. 35, 99 (1999)]. The three-electrode system with 37 apertures extracts the hydrogen-ion beam with 29.8 keV beam energy and 1.2 A beam current at a 9.6 cm diam. The ion source has the capability of varying the beam pulse width from 10 to 100 ms and also is capable of beam modulation at 50 Hz with a 10 ms flattop pulse width. The beam power and the ratio of the mixed ion species were measured by infrared thermography and Doppler shift spectroscopy, respectively. Most recent experimental results will be presented in this article. © 2002 American Institute of Physics.
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  • 114
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1083-1083 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Following the withdrawal of the U.S. from the International Thermonuclear Experimental Reactor project, the U.S. Fusion Energy Science program has put increased emphasis on plasma science addressing the fundamental scientific issues facing the realization of fusion energy, with decreased emphasis on long-term fusion technology development, except for that which is needed to support near-term experiments. At the same time, the U.S. fusion program has broadened research from the nearly exclusive development of the Tokamak previously, to include now a variety of smaller-scale alternative fusion approaches, including more work on inertial fusion energy (primarily heavy-ion induction accelerators), Spheromaks, Spherical Tori, Stellerators, reversed field pinches, and field-reversed configurations. The largest U.S. Tokamak, the TFTR at PPPL, has been shut down after achieving over 10 MW of DT fusion power, and is now being decommissioned. The powerful TFTR neutral beams, including the ones that injected 120 keV tritium beams, have been decontaminated and stored for possible future use. One of the TFTR beamlines is being used to power the 1 MA National Spherical Torus Experiment (NSTX) located in what was the nearby TFTR hot-cell room. For heavy-ion fusion, the advent of 100 s, 100 TW table-top lasers has increased interest in using field ionization to achieve controlled levels of high-charge-state heavy ions. © 2002 American Institute of Physics.
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  • 115
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The target performance for the KAMABOKO ion source on the MANTIS test bed in Cadarache is to accelerate a beam of D− with a current density of 200 A/m2 and 〈1 extracted electron per accelerated D− ion, at an injected power ranging between 1 and 2 kW per liter of source volume, at a source pressure of 0.3 Pa. For ITER, a continuous neutral beam must be assured for pulse lengths of 500 s, but beams of up to 3600 s are also envisaged. During the last campaign, continuous beam pulses of duration up to 1000 s were demonstrated both in hydrogen and in deuterium. In this article, the source performance, the effect of the plasma grid temperature for long pulse operation, and the limits of the present experimental setup are described. Additionally, the effect of changing the strength of the magnetic filter in the ion source on the extracted ion and electron currents and the beam transmission is reported. © 2002 American Institute of Physics.
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  • 116
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 259-262 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Laser-based cavity ringdown techniques have demonstrated ultrahigh sensitivities for trace gas detection in the optical and infrared wavelength regions. We have investigated the applicability of the cavity ringdown technique in the millimeter wave region, which is rich in the rotational spectra of molecules. The millimeter-wave system uses a tunable Fabry–Perot cavity that is excited by a continuous-wave, phase-locked source at the W band; a fast PIN diode switch that turns off the excitation after the cavity is tuned to resonance; and a diode detector that records the resonance decay. Proof of concept has been established by measuring the ringdown times with absorbing materials in the cavity and comparing them with theoretical prediction. © 2002 American Institute of Physics.
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  • 117
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method for evaluating aberration in the crossover image in a cell projection lithography system has been developed. In an electron-beam lithography system of projection-type such as a cell projection lithography system, the aberration in the crossover image causes the electron beam to pass off-axis in the electron optics. Optical simulation has quantitatively shown that the aberration in the crossover image causes an electron-beam blur and a positioning error on a writing sample. The evaluating method consists of four square apertures and a mark-detection function in a cell projection system. By measuring each position of the images of the four square apertures on the writing sample at difference focuses, the aberration can be calculated. The field curvature and the astigmatism in a cell projection system were evaluated by using this method. The field curvature agrees with the simulation. In addition, the measurement of the effect of beam alignment is also demonstrated. It is thus concluded that the method can effectively evaluate the aberration in the crossover image. This method is also useful for other projection-type lithographies of charged particles—like ion and electron beams. © 2002 American Institute of Physics.
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  • 118
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A variational method is employed to retrieve the phase from broadband reflectometry signals. The method yields the so-called in-phase and quadrature components of a signal (the signal quadratures in short), by stipulating that these should have the smallest possible amount of functional variation, whereby the signal carrier frequency is also recovered as a by-product. The variational approach is based on the reasonable assumption that, for given data, the quadratures are expected to be as slow as possible, as they contain the slow modulations of amplitude and phase, while rapid variations are accounted for by the carrier frequency. The advantages and shortcomings of the variational method are discussed, and a pertinent comparison with the analytic signal—recently proposed as a means to extract the phase from broadband reflectometry signals—is also carried out. The application of the variational method to the reflectometry problem is shown to yield results that are similar to those obtained via the analytic signal. The difference is not significant, especially if detailed measurements are not required, but only averaged ones. © 2002 American Institute of Physics.
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  • 119
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A frame-cooled plasma grid for the International Thermonuclear Experimental Reactor (ITER) was designed in view of temperature and stress distributions using three-dimensional numerical simulations. As a material of the plasma grid, copper–chrome–zirconium was examined, since it has high mechanical strength as well as high thermal conductivity. The numerical simulations indicated that the plasma grid would be kept at about 300 °C, which is optimum temperature for negative-ion production. They also indicated that thermal stress in the plasma grid would be less than yield stress. To demonstrate it, a frame-cooled plasma grid, which corresponds to a subsegment of the ITER plasma grid, was fabricated; an experiment was performed with a prototype of an ITER ion source named Kamaboko source. Experimental results showed that its surface temperature is continuously kept at about 300 °C; it was demonstrated that the frame-cooled plasma grid is applicable to long pulse operations, meeting the temperature requirement for the cesium effect. © 2002 American Institute of Physics.
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  • 120
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    Review of Scientific Instruments 73 (2002), S. 323-329 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents a homodyne pulse-sampling electrostatic force microscopy technique using a pulse position modulation method for the noncontact measurement of internal voltage waveforms in integrated circuits. The measurement system operates by monitoring the mechanical deflection of a micromachined probe as it responds to electric forces induced by the circuit voltage waveform. Although the mechanical response of typical probes used in such systems is limited to few kHz, measurement of high frequency repetitive waveforms is enabled by applying a high speed sampling pulse signal to the probe with the pulse position modulated at a rate below the probe mechanical resonance. This results in down conversion of the circuit induced electric force harmonics to within the probe mechanical response, thus allowing the measurement of high frequency signals. The proposed technique is modeled using Fourier analysis of the measurement system response, and is demonstrated by the measurement of a 0.8 Mbit/s digital pattern on a CMOS test pad. The performance of the measurement system is analyzed based on obtained measurements and simulated system response. An analysis of the method capabilities shows a measurement sensitivity of 13 mVrms/(square root of)Hz. © 2002 American Institute of Physics.
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  • 121
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 350-353 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have devised a method of obtaining an absolute intensity calibration for photoemission measurements. The calibration function a(Ek), where Ek is the measured electron kinetic energy, can be derived solely from the experimental data without any uncertain assumptions. The method is based on the relation between the integrated photoemission intensity and the sample current. This method is especially effective for low energy photoelectrons and is applicable even when the sample is biased with respect to the analyzer. © 2002 American Institute of Physics.
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  • 122
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 362-368 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The characterization and application of a multi-element Ge solid state detector in time-domain laser pump, x-ray probe (LPXP) x-ray absorption fine structure (XAFS) using a third-generation synchrotron source (Advanced Photon Source or APS) are described. In particular, the following problems are discussed: (1) proper handling of high numbers of x-ray photons within a single pulse or pulse cluster, (2) optimizing the incident number of photons, (3) synchronization of the laser pulse, the x-ray pulse and the detector readout, and (4) shaping time and timing requirements of the detector. Based on the study, we estimate the detector efficiency for LPXP-XAFS experiments and identify the problems and possible solutions. © 2002 American Institute of Physics.
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  • 123
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A GaN-based blue diode laser is employed for laser absorption spectroscopy in an aluminum hollow cathode glow discharge plasma. A Littrow grating stabilized external resonator is used for tuning the wavelength of laser emission. Scanning the wavelength of the laser probes the absorption profile of aluminum transitions yielding ground state aluminum densities. Hyperfine structure has to be taken into account in order to obtain correct temperatures. The diode laser is used to investigate both the temperature and the density of aluminum atoms sputtered from a cathode surface by ion bombardment from the cathode fall region. The blue diode laser allows quick and easy access to aluminum ground state atoms at low costs. © 2002 American Institute of Physics.
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  • 124
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 398-403 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A device is described which allows the measurement of the gas permeability of a single foam film upon variation of its thickness and specific interaction film free energy. A variable external pressure is applied on the film, which results in corresponding variations of the film thickness and the specific interaction film free energy. The apparatus allows the gas permeability of foam films to be investigated at different desired values of these quantities. The method can be used to gain information about the structure of the foam film. Small changes in the adsorption density in the stabilizing surfactant monolayers of the film result in dramatic changes of the permeability. Therefore measurements of the permeability coefficient may be used as a tool to detect variations in composition and structure of the film monolayers. This apparatus will also be extremely useful for the study of the permeation of pure gases and vapors and of gas separation by foam films for purposes of chemical technology or medicine. © 2002 American Institute of Physics.
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  • 125
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    Review of Scientific Instruments 73 (2002), S. 422-428 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new experimental setup for time resolved x-ray diffraction is described. Designed for the LURE H10 beamline and its 4 (+2) circles goniometer, it allows simultaneous recordings of x-ray patterns with a rate of 30 patterns per second, a maximum 2θ range of 120°, infrared thermography at the same rate, and thermocouples readings at a frequency of up to 3×104 Hz. Preliminary results obtained using this setup are presented, showing how it is possible to analyze a solid–solid or solid-liquid reaction. As an example, an in situ study of phase transformation and temperature evolution during the self-sustaining synthesis of an FeAl intermetallic compound starting from a mechanically activated mixture is investigated. The versatility of the setup was proved and could even be enhanced by the design of new sample holders, thus expanding its area of use at low cost. © 2002 American Institute of Physics.
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  • 126
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, we describe the design rationale and performance features of an integrated multichannel continuous wave (cw) near-infrared (NIR) optical tomographic imager capable of collecting fast tomographic measurements over a large dynamic range. Fast data collection (∼70 Hz/channel/wavelength) is achieved using time multiplexed source illumination (up to 25 illumination sites) combined with frequency encoded wavelength discrimination (up to four-wavelength capability) and parallel detection (32 detectors). The described system features a computerized user interface that allows for automated system operation and is compatible with various previously described measuring heads. The results presented show that the system exhibits a linear response over the full dynamic measuring range (180 dB), and has excellent noise (∼10 pW noise equivalent power) and stability performance (〈1% over 30 min). Recovered images of laboratory vessels show that dynamic behavior can be accurately defined and spatially localized. © 2002 American Institute of Physics.
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  • 127
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A balloon-borne mass spectrometer system has been flown successfully to determine the chemical composition of polar stratospheric aerosols over northern Scandinavia. The experiment combines an aerodynamic lens which collimates the aerosols into a narrow beam, a small sphere in which they evaporate, and a mass spectrometer for gas analysis. High-speed differential pumping by two liquid helium pumps effectively lowers the presence of ambient gases without affecting the particles of the beam. Field measurements and aerosol studies inside a large cryo-chamber have shown that the concept of particle focusing, evaporation and subsequent mass spectrometric gas analysis is a reliable technique to determine the molecular composition of aerosols especially in polar stratospheric clouds. © 2002 American Institute of Physics.
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  • 128
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    Review of Scientific Instruments 73 (2002), S. 480-481 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In pressure cells, optical windows are usually fastened to clamping disks by a metallic cover and screws. We show that it is possible instead to glue the window on the disk through a polymer composite made of a polyimide foil between melted fluorinated coatings. © 2002 American Institute of Physics.
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  • 129
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    Review of Scientific Instruments 73 (2002), S. 486-487 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The development of a low-noise variable-temperature preamplifier for self-sensing piezoelectric tuning fork force sensors is presented. The preamplifier utilizes a pair of commercially available GaAs field effect transistors to achieve high impedance and low noise over a wide range of temperatures. Using a standard 32 kHz quartz tuning fork, the base noise level achieved is 20 dB below the thermal noise resonance at room temperature and at 4.2 K. The circuit diagram, biasing points, and noise specifications are presented, and the application for variable temperature scanning probe microscopy is discussed. © 2002 American Institute of Physics.
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  • 130
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    Review of Scientific Instruments 73 (2002), S. 493-494 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have produced a rf discharge in 40Ar and used saturated absorption spectroscopy to offset lock a Ti:Sapphire laser to the absorption peak of the 43P2→43D3 cooling transition at 811 nm. We describe the procedure for fabrication of the cell and production of the discharge. © 2002 American Institute of Physics.
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  • 131
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the needs of future heavy ion accelerators, electron cyclotron resonance ion sources (ECRISs) should be able to deliver higher intensities and higher charge states. The 1e mA level intensity has already been reached by room temperature ECRIS for medium charge states of light elements (O6+, Ar8+). However, such level of intensity for heavy elements (like Pb27+ for CERN/LHC and GSI) requires more powerful ECRIS with higher electron densities (up to 1013 cm−3). On the other hand, an optimized magnetic configuration system has to be used in order to obtain the suitable compromise between the electron confinement and the high flux ion losses. Before the design of the future "high intensity ECRIS," experiments have been performed with the superconducting SERSE source both at 18 and 28 GHz. After an overview of major results recently obtained, some scaling laws will be presented. Our results show that much larger intensities and charges can be reached with ECRIS. Then, we will show how the next ECRIS generation will look like, based on the scaling laws derived in the above-mentioned experiments. © 2002 American Institute of Physics.
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  • 132
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The large number of different experiments performed at the 88 Inch Cyclotron requires great variety and flexibility in the production of ion beams. This flexibility is provided by the two high performance electron cyclotron resonance (ECR) ion sources, the LBL ECR and the AECR-U, which can produce beams of ions as light as hydrogen and as heavy as uranium. With these two sources, up to six different metals can be preloaded using two types of ovens. The ovens are mounted radially on the ion sources and inject the metal vapor though the open sextupole structure into the plasma chamber. For the superconducting ECR ion source VENUS, which is under construction at Lawrence Berkely National Laboratory, the use of radial ovens is no longer possible, because the magnetic structure is closed radially. Therefore, we are developing two new axial oven types for low and high temperature applications. Metal ion beam production in ECR ion sources using the oven technique is discussed. The design of the axial oven is presented. Finally, the efficiency of the axial oven is compared with the radial oven for the production of Ca. © 2002 American Institute of Physics.
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  • 133
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to study the possibilities to produce high currents of pulsed heavy ion beams dedicated to synchrotron injection, two new approaches of ECR devices are now underway. The basic principle consists in maintaining a functioning point of the source with the highest density as possible and a minimum confinement time for the production of a given charge state. It means that for a constant neτi product we try to maximize ne and minimize τi. For this purpose two experiments are in progress at ISN/Grenoblea and IAP/Nizhny Novgorod.b The first one consists of using a minimum |B| magnetic structure with a 1.8 mirror ratio characteristic value with a 28 GHz frequency injection. In this case we explore different functioning points up to 10 kW of UHF power. The second one consists of a simple mirror magnetic system (simple mirror ion source, SMIS) working at 37.5 GHz with a mirror ratio up to 3 (2.5 T) where we study discharges with a peak power up to 100 kW. We will show that, in spite of a very short rising time of the current, we can maintain the production of multicharged ions and that we can observe very high current densities. In the future, the challenge will be the design of an extraction geometry matching theses current levels. © 2002 American Institute of Physics.
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  • 134
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Multicharged Si and Fe ions are produced from solid materials in a 2.45 GHz electron cyclotron resonance (ECR) ion source. The ECR plasma is confined in a magnetic mirror field superimposed on an octupole magnetic field. Ar gas is normally chosen for working gas at pressures of 10−4 to 10−3 Pa. Si and Fe ions are produced by sputtering and evaporating solid materials, which are safe and easy to handle. The Fe (or Si) target is mounted at the tip of an insulated holder and inserted into the plasma. The negative dc bias voltages are applied to the target and multicharged Fe (or Si) ions are produced. Fe filament is evaporated in the ECR plasma by direct ohmic heating, and multicharged Fe ions are produced. Multicharged ions up to Fe6+ are produced by using both methods of sputtering and evaporating and Si4+ by using the sputtering method. The maximum ratio of the Fe and Si ion currents to total Ar ion current are about 15% and 13% obtained by the sputtering method, respectively. The maximum current densities of Fe+ and Fe4+ are 1.1×10−1 and 4.1×10−4 mA/cm2 obtained by the sputtering method, respectively. © 2002 American Institute of Physics.
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  • 135
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two techniques for the discrete injection of material into an Electron Cyclotron Resonance ion source (ECRIS) have been developed for the purpose of measuring the ionization and confinement times of ion species. Previously only solid materials in conjunction with a pulsed laser were used in these studies due to the discrete material introduction produced by this configuration. The first method replaces the pulsed laser with a fast high voltage pulse applied to a sputter sample. The high voltage pulse has a rise time of 100 ns, fall time of 80.0 μs, and variable pulse duration. The second method utilizes a fast-pulsed gas valve capable of producing a gas pulse 160 μs in width. These pulse widths are well below the ionization times of the lower charge states and thus allows for time measurements to be made of all charge states. Both of these techniques can be employed to study the effects of rf power, coil configuration, biased disk, and gas mixing on ionization and confinement times. Rise times for neon, argon, and gold will be presented. © 2002 American Institute of Physics.
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  • 136
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In recent years, progress concerning the production of high intensity of metallic ion beams (58Ni, 48Ca, 76Ge) at GANIL have been performed. The metallic ion from volatile compound method has been successfully used to produce a high intensity nickel beam with the ECR4 ion source: 20 e μA of 58Ni11+ at 24 kV extraction voltage. This beam has been maintained for 8 days and accelerated up to 74.5 MeV/u by our cyclotrons with a mean intensity of 0.13 pμA on target. This high intensity, required for experiment, led to the discovery of the doubly magic 48Ni isotope. The oven method has been first tested with natural metallic calcium on the ECR4 ion source, then used to produce a high power beam (740 W on target, i.e., 0.13 pμA accelerated up to 60 meV/u) of 48Ca still keeping a low consumption (0.09 mg/h). A germanium beam is now under development, using the oven method with germanium oxide. The ionization efficiencies have been measured and compared. © 2002 American Institute of Physics.
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  • 137
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact electron cyclotron resonance ion source has been developed for heavy-ion medical facilities. The beam intensity and stability were considerably improved by recent modifications on three points (length of sextupole, cooling system for the extraction electrode, and position of the Einzel lens). Initial results of C4+ beam tests show that an intensity of 180 eμA can be routinely obtained with simple tuning. The best record was 220 eμA for C4+, which meets the medical requirements. Throughout these tests, CH4 gas was used with 0.1 cc/min and the extraction voltage was fixed at 25 kV. Results on beam emittance and long-term stability are also briefly discussed. © 2002 American Institute of Physics.
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  • 138
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new electron cyclotron resonance (ECR) ion source (LECR3—Lanzhou Electron Cyclotron Resonance Ion Source No. 3) has been constructed this year. The main purpose of this source is to provide highly charged ion beams for atomic physics and surface physics research. The design of this ion source is based on the IMP 14.5 GHz ECR ion source (LECR2—Lanzhou Electron Cyclotron Resonance Ion Source No. 2) with double rf heating by inserting waveguide directly and aluminum chamber. Furthermore, the volume of the plasma chamber is larger than that of LECR2 so as to increase the rf power and improve beam intensity for highly charged ions. But the hexapole field on the chamber wall is kept the same value in order to compare with the performance of LECR2. After only four days conditioning the first test results were obtained. The final result of this ion source is expected to be better than LECR2's. © 2002 American Institute of Physics.
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  • 139
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact 2.45 GHz electron cyclotron resonance (ECR) ion source has been developed as an etching device for diffusion experiments in the solid-state matter. This source is a little bit different from those of a usual industrial ECR device, i.e., it is to extract high intensity beams from a relatively small single hole with low emittance under the extraction voltage of several kV and high vacuum. Summary of the design, manufacture, and the initial beam extraction tests are described. © 2002 American Institute of Physics.
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  • 140
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have constructed a liquid He free SC-ECRIS and successfully extracted intense beams of various heavy ions. To improve its performance, we installed a negatively biased electrode in the plasma chamber and observed its effect on the beam intensity systematically. We measured the beam intensity and the current of biased electrode as a function of both the applied bias voltage and the electrode position. Using the negatively biased electrode, the beam intensity of highly charged Xe ions was strongly enhanced. Furthermore, both the beam intensity and the current of biased electrode oscillated strongly. The frequency became higher when increasing the magnitude of bias voltage. This result shows that the biased electrode causes a certain instability in the electron cyclotron resonance plasma, so that the beam intensity is enhanced. In this contribution, we present the results of our experiment and the discussions about possible mechanisms of such instability. © 2002 American Institute of Physics.
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  • 141
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Extraction and transport of multicharged ions have been experimentally investigated on a 2.45 GHz electron cyclotron resonance (ECR) source. The extractor consists of an electrode facing the ECR plasma (plasma electrode) and three cylindrical electrodes (E1–E3). The extractor is moved at several positions on the geometrical axis. The gap length between the plasma and E1 electrodes can be moved in vacuum while keeping gaps of the other electrodes constant. Characteristics of the total extraction current are investigated by a Faraday cup set just downstream at the extractor while simultaneously monitoring the currents flowing to electrodes and the drain in various experimental conditions. Several kinds of potential forms of the electrodes are investigated and the gap lengths are surveyed and optimized experimentally. The mass/charge spectrum of the extracted multicharged ion current is investigated by the Faraday cup set downstream at the sector magnet. The features of the extraction condition for the charge states are also investigated. After optimization in these procedures, the multicharged ion currents have been enhanced by 1 order of magnitude more than those in the previous experiments. © 2002 American Institute of Physics.
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  • 142
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The plasma topography of the vacuum-ultraviolet (VUV) radiation source ELISA (electron cyclotron resonance light source assembly) was investigated. ELISA is operated at a VUV spectrometer which allows two-dimensional images of the axially observable plasma shape to be taken with a spatial resolution of 150 μm in the spectral range from 40 to 400 nm. The VUV radiance profile of the electron cyclotron resonance plasma was investigated for different working conditions of the source, with the source operated with nitrogen and krypton. Under specific operating conditions, the observed plasma radiance profile shows a structure similar to calculations performed by the group of Andrä. It was shown for the first time that the plasma topography can be interpreted by an electron density distribution as simulated there for a monomode electron cyclotron resonance ion source. © 2002 American Institute of Physics.
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  • 143
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Microwave power absorption and intense collimated beam production is studied in the pulsed high-power microwave ion source at RIKEN by varying the radius of the plasma chamber (circular waveguide) in integer multiples of a quarter wavelength of the wave (nλ/4), where n is an integer (n=2–5) and λ is the vacuum wavelength of microwaves. Optimum wave coupling and power absorption due to a change in the microwave power density and the electric field distribution are investigated from measurements of the total achievable current density and the optical intensity, emitted by the pulsed argon plasma in the visible region at a wavelength of 404.3 nm. Results indicate a nonlinear absorption of microwave power. Depending upon the pressure, a decrease in the chamber radius leads to an enhancement of the electron temperature. Favorable beam conditions, i.e., highest density and temperature are obtained for the chamber with radius (similar, equals)λ. © 2002 American Institute of Physics.
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  • 144
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact electron cyclotron resonance (ECR) ion source (compact ECRIS) for the mass spectrometer was tested. A feature of the compact ECRIS is its size, i.e., inner diameter: 22.5 mm (1 in. tube), length: 56 mm. ECR plasmas in this ion source using argon gas were discharged by high-frequency microwaves, 7–10 GHz. It was confirmed that the plasma was generated in the pressure range 30–410 mPa at the low input power of 5 W. © 2002 American Institute of Physics.
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  • 145
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A one-dimensional (1D) fluid computer model for multiple ion species in an electron cyclotron resonance ion source (ECRIS) plasma has been developed. The ions species are assumed to be highly collisionally coupled and are treated using 1D fluid equations. The non-Maxwellian anisotropic electron distribution function is modeled by a 1D bounce-averaged Fokker–Planck code. ECR heating is included in the model as a quasilinear rf-diffusion term including relativistic detuning, rf pitch-angle scattering, and multiple resonance frequencies/locations. In a typical ECRIS, the electrons are very noncollisional and confined magnetically. The ions follow this electron confinement via the electrostatic potential. The 1D axial electrostatic potential profile predicted by the model shows an ion confining core electrostatic well as expected in ECRIS plasmas. Modeling results for the Argonne National Laboratory ECR-I ECRIS configuration are presented along with a discussion of the difficulties in benchmarking the model with Faraday cup measurements. © 2002 American Institute of Physics.
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  • 146
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The ECLISSE (ECR coupled to Laser Ion Source for charge State Enhancement) project started in 1999 with the aim to obtain an intense beam of highly charged ions (pulsed mode) by means of the coupling between a laser ion source (LIS) and an electron cyclotron resonance (ECR) ion source. The major points to be investigated appeared to be the coupling efficiency between the ion beam produced by the LIS and the ECR plasma, as well as the possibility to enhance the available charge state by an ECRIS with respect to the standard methods which are used to produce ion beams from solid samples (e.g., evaporation, sputtering). The calculations have confirmed that this concept may be effective, provided that the ion energy from the LIS is lower than a few hundred eV. The main features of the calculations will be shown, along with the results obtained in the off-line test facility at laser power densities below 1011 W/cm2. © 2002 American Institute of Physics.
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  • 147
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Charge breeding inside electron cyclotron resonance (ECR) ion sources is a promising way to produce radioactive ion beams with a high charge state, based on deceleration and capture of the primary ion beam by the ECR plasma, trapping, multi-ionization, diffusion, and extraction. A detailed analysis of these processes could help to improve the efficiency (reducing ion loss to walls) and the charge breeding time. An estimate of the deceleration length is given. Collisions, external magnetic field, and ambipolar potential are the fundamental parameters for the ion motion inside the trap, which is simulated by a program, including statistical averaging over many (400–3200) particle histories. Characteristics of trapped and extracted ions are shown with simulations taking in account the design of the PHOENIX ion source. Since particle losses are found to increase rapidly with the radius of injection, the injection system should form an image at the beam stopping plane. Analysis of additional source parameters is discussed. © 2002 American Institute of Physics.
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  • 148
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 545-547 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to realize new investigations on physics, biology, and other fields, a metallic ion beam is quite effective and essential. To produce the metallic ion beam in an electron cyclotron resonance (ECR) ion source, how to supply the metallic gas into the ECR plasma is most important. At present, the NIRS-HEC, which is an 18 GHz ECR ion source installed for the Heavy Ion Medical Accelerator in Chiba at the National Institute of Radiological Sciences (NIRS), enables us to produce a stable Fe9+ beam of 180 eμA by the metal ions from volatile compounds technique. In addition, the development of a new gas supply method, using the electron-bombardment technique, is in progress. In this method, the tip of a metal target rod (2–6 mm diameter) at a high positive potential is melted by bombarding the thermoelectrons emitted from a surrounding hot filament and the evaporated gas is supplied into the ECR plasma. © 2002 American Institute of Physics.
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  • 149
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    Review of Scientific Instruments 73 (2002), S. 555-557 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The ion cooling exerted by lighter ions inside an ECR plasma is often credited as an explanation of the well-known gas mixing effect, since the ion temperature is about a constant Tp for all the ion species in the plasma. Here the energy balance equations are written in detail for any ion species, including the improved evaporation cooling in the collisional confinement regime. A formula for Tp and decoupled equations for small corrections around Tp are given, accounting for the colder gas input. The charge state distribution are written in closed form. Gas flow between plasma center and periphery is described. Some equilibria for most common gas mixing cases are compared, showing in particular the efficacy of neon. © 2002 American Institute of Physics.
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  • 150
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The CERN heavy ion community, and some other high energy physics experiments, are starting to demand other ions, both heavy and light, in addition to the traditional lead ions. Studies of the behavior of the afterglow for different operation modes of the ECR4 at CERN have been continued to try to understand the differences between pulsed afterglow and continuous operation, and their effect on ion yield and beam reproducibility. The progress in adapting the source and ion beam characteristics to meet the new demands will be presented, as will new information on voltage holding problems in the extraction. © 2002 American Institute of Physics.
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  • 151
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 576-579 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new 10 GHz electron cyclotron resonance ion source (ECRIS) has been constructed and commissioned for the ATLAS accelerator. This new source replaces the original ATLAS ECRIS that has been in operations since 1987. The goal of this upgrade project was to significantly improve the source performance while maintaining maximum operational flexibility for solid material feeds. The new source design includes a large magnetic-field gradient, aluminum plasma chamber, and bias disk following modern ECRIS design concepts. Eight solenoid coils from the original source along with a new iron yoke form the magnetic mirror. Hall Probe measurements showed the axial B field to be within 1% of the POISSON design model calculated at 400 A per coil. The injection and extraction mirror ratios are approximately 4.4 and 2.9, respectively, with a minimum field of 3.0 kG. A new aluminum plasma chamber houses the NdFeB hexapole magnets, which are encased in austenitic stainless steel to allow for direct water cooling. An open hexapole configuration provides six radial access ports, 1.7 cm×4.1 cm, to the plasma chamber for solid material feeds and vacuum pumping at an estimated rate of 20 l/s per radial port. Measurements of the hexapole field near the plasma chamber wall, 4 cm in radius, were within 13% of the designed B field of 9.3 and 5.7 kG along the poles and pole gaps, respectively. The first plasma in the new source was obtained on October 10, 2000. Already it has exceeded the best 16O6+ beam current obtained from the original ECR-I by a factor of roughly 2.3, achieving 140 e μA with a biased disk. The source is back in regular operation and ATLAS experiment runs have been performed with He, O, Ar, Kr, Ni, and Zr. © 2002 American Institute of Physics.
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  • 152
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: When a large current is accelerated, many radio frequency quadrupole (RFQ) LINAC are needed, because the acceleration limit of a RFQ LINAC is 20 mA–30 mA. Therefore the same number of ion source are needed. But the limit is not the current limit of ion source. If the RFQ LINAC has many RFQ channels, it can accelerate large currents. We designed an accelerator with four RFQ channels to prove this principle. An ion source which extracts four equal beams from one chamber is needed for this RFQ LINAC. A four-hole ECR ion source was designed and manufactured after calculating the magnetic fields by OPERA, and simulating beam trajectory using the program FUGUN. In this ion source, since four extraction holes are located off axis by about 50 mm, the beam is deflected. We calculated this deviation. © 2002 American Institute of Physics.
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  • 153
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To investigate the effect of the plasma electrode position on the beam intensity, we measured the beam intensity of Ar ions, with various charge states as a function of the electrode position. In this experiment, we observed that the beam intensity of highly charged Ar ions is strongly dependent on the electrode position and that there is the suitable position to maximize the beam intensity. The optimum position varies with the charge state of ions. The beam intensity of 1.3 mA for Ar8+ was obtained at the optimum plasma electrode position. © 2002 American Institute of Physics.
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  • 154
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The effect of the surface of Al2O3 on the beam intensity of highly charged Ar ions is described. To investigate this effect clearly, we directly plated the surface with 20 μm Al2O3 of the Al cylinder (Al2O3 plating method). This cylinder was inserted into the plasma chamber and it covered its inner wall of. We then measured the beam intensity of highly charged Ar ions carefully. By comparing the beam intensity using the Al2O3 plating method and the Al cylinder, it is confirmed that the Al2O3 surface is very effective in increasing the beam intensity of highly charged heavy ions. The best result of 290 eμA of Ar11+ was obtained by using this method. © 2002 American Institute of Physics.
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  • 155
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron cyclotron resonance (ECR) plasmas have already been studied in many ways, mainly by x-ray and UV measurements. Langmuir-probes, however, have proven useful for other kind of plasmas, and have rarely been used to explore the ECR plasma. A diagnostics setup has been built at the 14.5 GHz ATOMKI-ECRIS. Results of the cold plasma region measurements are shown. A modified version of the original methods for characteristics analysis is reported. This includes the complex nature of the plasma ion component. Calculated electron densities yielded by the two compared theoretical models up to a factor of 3 were observed. This obviously shows the necessary consideration of this effect. Studies of two-faced external effects, e.g., biased-disk on/off, beam extraction on/off, have also started; first results are reported. © 2002 American Institute of Physics.
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  • 156
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Dedicated experiments have been carried out at the Frankfurt 14 GHz electron cyclotron resonance ion source (ECRIS) by using a special double biased-electrode assembly, which consists of a conventional disk electrode and a separately biased ring electrode installed in front of it. In this assembly, the ring can be used to modulate the fluxes to the disk and allows a detailed study of the role of secondary electron fluxes in ECRIS operation. It was found that these fluxes contribute more than 50% to the total disk currents. However, blocking them did not result in a drop in the extracted ion currents. Instead, it was observed that, under certain operational conditions, the injection of secondary electrons results in a decrease in the extracted currents by up to 20%. Parallel to the double disk measurements, Langmuir probe measurements have been performed close to the position of Bmax. From the probe characteristics, plasma potentials were determined to be about +30 V at the conditions of the experiment. Applying a negative voltage to the double disk electrodes leads to a decrease of the plasma potential by approximately 5 V. Changes in the plasma shape were observed when the biased electrode voltage was changed. We conclude that the main effect of the biased electrode is a decrease of the plasma potential by reflecting a sufficient amount of electrons back to plasma, which otherwise would have been lost. © 2002 American Institute of Physics.
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  • 157
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An updated and more accurate database for single- and double-ionization cross sections for almost all argon ions has been developed for the modeling of the charge state distribution (CSD) within an electron cyclotron resonance ion source. When the highly non-Maxwellian anisotropic electron-distribution function, is modeled by a Fokker–Planck code, one has to use the ionization cross sections instead of the Maxwellian rate coefficients. Most of the fitting coefficients used within the well-established semi-empirical formulas for direct ionization and double ionization have been recalculated using more accurate crossed-beam experimental data available. The shift of the CSD to higher-charge states due to the contribution of excitation autoionization and double ionization is presented by comparing the GEM code modeling using the Lotz formula and the cross sections with updated fitting coefficients. © 2002 American Institute of Physics.
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  • 158
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Increasing the brightness of the ion beam is a typical demand for any accelerator. In order to fill the heavy ion synchrotron (SIS) up to the space charge limit, higher pulse currents are necessary. The UNILAC is operated with a pulse length up to 6 ms and a repetition rate up to 50 s−1. For the injection into the SIS a pulse length of 300 μs at 0.3 s−1 is required. The transverse acceptance of the RFQ is 138 π mm mrad. According to Child's law, the ion current density which can be extracted from a plasma source is for the space charge limited flow proportional to Φ1.5/d2. With Φ and d denoting the extraction voltage and the width of the extraction gap. One approach to generate higher ion currents is to increase the extraction voltage in the regularly used extraction system. However, the required beam velocity is fixed by the RFQ structure with 2.2 keV/u. The mass-to-charge ratio which is to be accelerated can be between 1 and 65, resulting in a total voltage drop from 2.2 up to 143 kV (extraction and postacceleration voltage). The other approach is to decrease the gap width in the extraction system, but there is an optimum in the aspect ratio. To generate an ion beam with a higher current at low energy, a triode extraction system operated in accel–decel (Uacc,Udec) mode is a possible solution. By applying a negative potential at the second electrode a higher extraction field strength can be achieved. The effects of extraction field, arc current, and ion energy on the extracted ion beam current and its emittance were investigated. © 2002 American Institute of Physics.
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  • 159
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    Review of Scientific Instruments 73 (2002), S. 732-734 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Vacuum arc ion sources are known for delivering high currents of metal ion beams. By Langmuir probe and Faraday cup measurements it is shown that fluctuations of the ion-beam current are due to the fluctuations of plasma density which in turn are due to the explosive nature of plasma production at cathode spots. Humphries and co-workers and later Oks and co-workers have shown that beam fluctuations can be reduced by inserting biased meshes in the plasma. Here, the idea of ion extraction at kV level with post-acceleration is investigated. The high voltage allows us to use coarse, ridged meshes or grids. The combination of an extractor operating in the overdense plasma regime with post-acceleration lead to very reproducible, practically "noiseless" ion beams, however, at the expense of low ion current density. The noise reduction is due to ion optics effects; more ions supplied by plasma lead to greater ion-beam losses after the first extraction system. Although the current setup is not suitable for a heavy ion fusion injector due to the low beam current and the risk of extractor voltage breakdown, further development of the concept may lead to reproducible beam pulses of sufficiently high current and brightness. © 2002 American Institute of Physics.
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  • 160
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Different types of high temperature ion sources such as surface, laser, and electron beam ionization ion sources have been developed and tested in off-line and on-line experiments. All types of developed ion sources have an essential common feature: an existence of the ion confinement inside the ion source cavity. © 2002 American Institute of Physics.
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  • 161
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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 Lawrence Berkeley National Laboratory 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, which are the same for different ion charge states of a material, into account. The results of simulations of the processes involved are in good agreement with the experimental results. © 2002 American Institute of Physics.
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  • 162
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Numerous approaches to the production of intense beams of highly charged heavy ions are compared and contrasted. The competing processes of ionization and electron capture are described and evaluated to explore ways to further improve upon the encouraging recent results from electron-beam (E-MEVVA) and low-impedance Z-discharge (LIZ-MeV) variations on the venerable metal vapor vacuum arc (MEVVA) ion source. © 2002 American Institute of Physics.
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  • 163
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The low inductance Z-discharge metal vapor (LIZ-MeV) ion source, which uses a magnetized Z-pinch, is a pseudo-spark device capable of producing intense currents (several kA) of highly charged gold or other ions. Typical operations produce an extracted charge-state distribution with a range in gold ion charge state from 4 to 19. Time-of-flight (TOF) spectra (excluding contributions from impurities) indicate that charge states at least as high as Au+12 were generated. Various TOF spectra are presented here to support this conclusion. Although the results are preliminary, LIZ-MeV shows great potential. Existing heavy-ion sources can produce either high beam currents, but low charge states (e.g., the metal-vapor vacuum arc) or high charge states, but low beam currents (e.g., the electron beam ion source). For ion beam injection our goal has been to develop an ion source that produces both high charge states and high beam currents. The existing LIZ-MeV has sufficiently large electron impact energies and electron current densities, but performance is limited by charge exchange with ambient gas and short confinement times. Plans are underway to add another Z-pinch stage to both lengthen confinement times and to minimize charge-state reducing processes. Such an enhanced LIZ-MeV should eventually produce even larger currents of more highly ionized heavy metal ions for accelerator applications. © 2002 American Institute of Physics.
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  • 164
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 751-753 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The hollow anode ion-electron source is based on the hollow anode discharge, a kind of plasma utilizing a cold cathode and a tiny bore or slot in the anode that simultaneously serves as exit aperture of the ion (or electron) source. These sources are particularly suitable, for example, for deposition of films on large flat surfaces. The length of the slot-shaped hollow anode aperture can be sufficient so that, together with sweeping of either source or substrate, large area substrates can be processed, thereby simulating the function of large area plasma sources. © 2002 American Institute of Physics.
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  • 165
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper is devoted to research and development of an ion source which is able to work by the cw-operation for a long time at the gas-discharge chamber temperature of ∼1500 °C and higher. The problem of discharge chamber heat is solved with the help of special graphite heaters. The method of heat is combined: heat radiation and electronic heating. As a result it was possible to create a palladium ion source with the current density up to 60 mA/sm2 which operates in a steady-state condition of more than 100 h. © 2002 American Institute of Physics.
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  • 166
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel helicon ion source has been developed as a high current density ion source. High plasma generation efficiency of helicon wave lends various high-density, high-temperature plasmas available for ion sources. High-density plasmas of 1012 cm−3 are generated to implement a high current density ion source with 1 kW, 13.56 MHz rf power source. An axial magnetic field of up to 900 G has been applied with a set of permanent magnets to make the helicon wave propagate. Various gaseous ion beams have been extracted with this source. Beam characteristics such as ion energy spread and ionic charge states will be discussed with the plasma parameters. © 2002 American Institute of Physics.
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  • 167
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Optical emission spectra from plasma produced by a copper vacuum arc with argon and nitrogen have been investigated for the case when the plasma was guided by a straight solenoid. The spectra have been compared with those obtained from inductively coupled rf multicusp discharge in the 10−4–10−2 Torr argon and nitrogen pressure range and at an input power of up to 500 W. It has been found that the spectral line intensity distributions of neutral and ion species for arc and rf discharge were different. Also, the intensity evolutions of the lines have shown a different behavior between the arc current and rf power. Electron excitation temperature (Tex) for rf argon plasma at low pressure has been found to be approximately 2.5 eV which was about ten times higher than for Cu-argon arc discharge. Possible mechanisms of ionization-excitation of guest atoms/molecules in the case of metal vacuum arc discharge are discussed. © 2002 American Institute of Physics.
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  • 168
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The temporal change of the H− beam current extracted from a volume-production-type negative ion source by injecting a Nd-YAG laser beam into the ion source plasma was measured. The measured change was about 0.3% of the dc H− beam current. The validity of the method was confirmed using Ar plasma which showed no photodetachment signal. The contribution of the local H− density upon the extracted beam was investigated by changing the distance between the center of the laser beam and the plasma grid. The result showed that the contribution took the maximum at about 8 mm distance from the laser beam center to the plasma grid surface. © 2002 American Institute of Physics.
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  • 169
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An apparatus capable of measuring the angle-resolved energy distribution function of ions produced by backscattering at metal surfaces is designed and tested. To exclude noise due to other impurity ions and electrons from the signal of target ions, a water-cooled magnetic deflection-type momentum analyzer is installed on a rotating table in a vacuum chamber. In addition to the beam forming and beam diagnostics components, work function monitoring equipment and an ion source for surface cleaning are installed. Preliminary tests of the apparatus was conducted to measure He+ emission from neutral He beam injection onto a Mo surface. With an improvement of the signal-to-noise ratio, the apparatus can be used to measure the angle-resolved energy distribution function of He− produced at a metal surface by He beam injection. © 2002 American Institute of Physics.
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  • 170
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The cusp leak was found to have a profile of multiple peaks, when measured near the filaments. This is attributable to multiple discharge paths of primary electrons. The supercusp magnetic configuration is one of several configurations in which strong magnetic-field lines flow into the backplate from the extraction grid. The negative-ion current was measured with a Faraday cup with a magnetic filter changing current from 0 to 100 A. The plasma characteristics were measured in the driver and the extraction regions. © 2002 American Institute of Physics.
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