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Review of Scientific Instruments

Issue 2 • Date Feb 2011

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Displaying Results 1 - 25 of 90
  • Atom chips on direct bonded copper substrates

    Page(s): 023101 - 023101-7
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    We present the use of direct bonded copper (DBC) for the straightforward fabrication of high power atom chips. Atom chips using DBC have several benefits: excellent copper/substrate adhesion, high purity, thick (>100 μm) copper layers, high substrate thermal conductivity, high aspect ratio wires, the potential for rapid (<8 h) fabrication, and three-dimensional atom chip structures. Two mask options for DBC atom chip fabrication are presented, as well as two methods for etching wire patterns into the copper layer. A test chip, able to support 100 A of current for 2 s without failing, is used to determine the thermal impedance of the DBC. An assembly using two DBC atom chips is used to magnetically trap laser cooled 87Rb atoms. The wire aspect ratio that optimizes the magnetic field gradient as a function of power dissipation is determined to be 0.84:1 (height:width). View full abstract»

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  • Monte Carlo simulations of microchannel plate detectors. II. Pulsed voltage results

    Page(s): 023102 - 023102-8
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    This paper is the second part of a continuing study of straight-channel microchannel plate (MCP)-based x-ray detectors. Such detectors are a useful diagnostic tool for two-dimensional, time-resolved imaging and time-resolved x-ray spectroscopy. To interpret the data from such detectors, it is critical to develop a better understanding of the behavior of MCPs biased with subnanosecond voltage pulses. The subject of this paper is a Monte Carlo computer code that simulates the electron cascade in a MCP channel under an arbitrary pulsed voltage, particularly those pulses with widths comparable to the transit time of the electron cascade in the MCP under DC voltage bias. We use this code to study the gain as a function of time (also called the gate profile or optical gate) for various voltage pulse shapes, including pulses measured along the MCP. In addition, experimental data of MCP behavior in pulsed mode are obtained with a short-pulse UV laser. Comparisons between the simulations and experimental data show excellent agreement for both the gate profile and the peak relative sensitivity along the MCP strips. We report that the dependence of relative gain on peak voltage is larger in pulsed mode when the width of the high-voltage waveform is smaller than the transit time of cascading electrons in the MCP. View full abstract»

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  • Analysis of photonic Doppler velocimetry data based on the continuous wavelet transform

    Page(s): 023103 - 023103-4
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    The short time Fourier transform (STFT) cannot resolve rapid velocity changes in most photonic Doppler velocimetry (PDV) data. A practical analysis method based on the continuous wavelet transform (CWT) was presented to overcome this difficulty. The adaptability of the wavelet family predicates that the continuous wavelet transform uses an adaptive time window to estimate the instantaneous frequency of signals. The local frequencies of signal are accurately determined by finding the ridge in the spectrogram of the CWT and then are converted to target velocity according to the Doppler effects. A performance comparison between the CWT and STFT is demonstrated by a plate-impact experiment data. The results illustrate that the new method is automatic and adequate for analysis of PDV data. View full abstract»

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  • Improved low concentration gas detection system based on intracavity fiber laser

    Page(s): 023104 - 023104-4
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    The improvement of a low concentration gas detection system based on the intracavity fiber laser is proposed in this paper. The sensitivity of the system is deduced based on Lambert–Beer law. The optimized system was established with the gas cell made elaborately. In order to apply the wavelength sweeping technique, the fiber Bragg grating reflector was substituted by the wavelength independent Faraday rotation reflector. The sensitivity of the system for acetylene detection is reduced to less than 100 ppm by using the average of three absorption spectra. The acetylene detection coefficients of variation with different concentrations are measured. The gas measurement system is validated to detect low concentration gas effectively. View full abstract»

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  • Fizeau interferometer system for fast high resolution studies of spectral line shapes

    Page(s): 023105 - 023105-10
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    A monochromator/Fizeau interferometer/intensified CCD camera system is described that was developed for the measurement of the shape of spectral lines that are rapidly time varying. The most important operating parameter that determines the performance of the instrument is the size of the entrance aperture as this determines both the light throughput and the effective interferometer wavelength resolution. This paper discusses, both theoretically and experimentally, the effect of the finite source area on the instrumental resolution to assist in optimizing the choice of this parameter. A second effect that often produces a practical limit to the quality of the spectra is drift of the interferometer plates. Measurements of the shapes of spectral lines of ions and atoms ejected from the cathode spot of continuous and pulsed cathodic arcs are presented to demonstrate the utility of this instrument. View full abstract»

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  • Construction and evaluation of a disposable pH sensor based on a large core plastic optical fiber

    Page(s): 023106 - 023106-7
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    The fabrication and characterization of a disposable optical fiber sensor for the detection of pH in the range 5–8 are described. The sensing element is a drop of sol–gel hybrid material containing phenol red and deposited onto the tip of a large core plastic optical fiber. This fiber is also exploited for the optical interrogation. This probe can be used as a disposable part of a measuring system. The dynamic range and temporal response of the sensor are here investigated. View full abstract»

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  • A novel facility for ageing materials with narrow-band ultraviolet radiation exposure

    Page(s): 023107 - 023107-6
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    A facility for exploring wavelength dependencies in ultraviolet (UV) radiation induced degradation in materials has been designed and constructed. The device is essentially a spectrograph separating light from a lamp to spectrally resolved UV radiation. It is based on a 1 kW xenon lamp and a flat-field concave holographic grating 10 cm in diameter. Radiation at the wavelength range 250–500 nm is dispersed onto the sample plane of 1.5 cm in height and 21 cm in width. The optical performance of the device has been characterized by radiometric measurements. Using the facility, test samples prepared of regular newspaper have been irradiated from 1 to 8 h. Color changes on the different locations of the aged samples have been quantified by color measurements. Yellowness indices computed from the color measurements demonstrate the capability of the facility in revealing wavelength dependencies of the material property changes in reasonable time frames. View full abstract»

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  • Single-shot beam-position monitor for x-ray free electron laser

    Page(s): 023108 - 023108-6
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    We have developed an x-ray beam-position monitor for detecting the radiation properties of an x-ray free electron laser (FEL). It is composed of four PIN photodiodes that detect backscattered x-rays from a semitransparent diamond film placed in the beam path. The signal intensities from the photodiodes are used to compute the beam intensity and position. A proof-of-principle experiment at a synchrotron light source revealed that the error in the beam position is reduced to below 7 μm by using a nanocrystal diamond film prepared by plasma-enhanced chemical vapor deposition. Owing to high dose tolerance and transparency of the diamond film, the monitor is suitable for routine diagnostics of extremely intense x-ray pulses from the FEL. View full abstract»

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  • A two-dimensional polarization interferometry based parallel scan angular surface plasmon resonance biosensor

    Page(s): 023109 - 023109-8
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    We describe a two-dimensional polarization interferometry based parallel scan angular surface plasmon resonance (SPR) biosensing technique. The method of line-shaped light illumination and parallel scan offers a high throughput. The simultaneous record of SPR angular spectrum enables the system to be unaffected by the time-dependent variation of the light source. The polarization interferometry technique lowers the minimum of the SPR dip and thereby reduces the noise related to the light intensity. Refractive index resolutions of 1.4 × 10-6 refractive index unit (RIU) under normal condition and 4.6 × 10-7 RIU under a more time-consuming condition are achieved in our angle interrogation based sensor. Meanwhile, a manually prepared DNA microarray has been detected, showing the potential applications of this technique in microarray analysis. View full abstract»

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  • Ghosting phenomena in single photon counting imagers with Vernier anode

    Page(s): 023110 - 023110-7
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    We provide the ghosting theory of two-dimensional Vernier anode based imagers. The single photon counting detection system based on Vernier anode is constructed. The ghosting, which occurs during the decoding of two-dimensional Vernier anode, and its possible solutions are described in detail. On the basis of the discussion of the decoding algorithm, the ghosting theoretical model is established. Phase conditions on which imaging ghosting can be avoided and the probability distribution function are proposed; the root causes of ghosting of two-dimensional Vernier anode are also discussed. View full abstract»

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  • High-energy x-ray backlighter spectrum measurements using calibrated image plates

    Page(s): 023111 - 023111-10
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    The x-ray spectrum between 18 and 88 keV generated by a petawatt laser driven x-ray backlighter target was measured using a 12-channel differential filter pair spectrometer. The spectrometer consists of a series of filter pairs on a Ta mask coupled with an x-ray sensitive image plate. A calibration of Fuji™ MS and SR image plates was conducted using a tungsten anode x-ray source and the resulting calibration applied to the design of the Ross pair spectrometer. Additionally, the fade rate and resolution of the image plate system were measured for quantitative radiographic applications. The conversion efficiency of laser energy into silver Kα x rays from a petawatt laser target was measured using the differential filter pair spectrometer and compared to measurements using a single photon counting charge coupled device. View full abstract»

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  • Emission spectroscopy of laser ablation plasma with time gating by acousto-optic modulator

    Page(s): 023112 - 023112-7
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    The capability of acousto-optic modulator (AOM) to perform time-gated measurements for laser ablation plasma spectroscopy has been examined. Especially, we focused on the capability of the “AOM gating” to exclude the continuum and extremely broadened spectra usually observed immediately after the laser ablation. Final goal of the use of the AOM is to achieve considerable downsizing of the system for in situ and on-site analyses. In the present paper, it is shown that narrow and clear spectral lines can be obtained with the AOM gating even if the target is submerged in water. Also, application of this technique to the targets in air is demonstrated. It has been revealed that the AOM gating is fast enough to exclude the continuum and broadened lines, while effectively acquiring sufficiently narrow atomic lines lasting slightly longer than the continuum. View full abstract»

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  • A reversible time-of-flight detector for use in pseudocontinuous resonance enhanced multiphoton (pc-REMPI) detection

    Page(s): 023113 - 023113-5
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    A time-of-flight coincidence detector is demonstrated. This detector is optimized for use in a pseudocontinuous resonance enhanced multiphoton ionization scheme that requires photoelectrons and photoions to be detected in coincidence. The detector utilizes two simultaneously operating charged particle detectors, one for the detection of electrons and the other for the detection of ions. In order to allow for field reversal, the detectors are physically identical, differing only by the value of applied voltages. Particular attention is given to the implementation of a charge-to-voltage transducer that allows for subnanosecond detection of both electrons and ions. View full abstract»

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  • Masking a CCD camera allows multichord charge exchange spectroscopy measurements at high speed on the DIII-D tokamak

    Page(s): 023114 - 023114-4
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    Charge exchange spectroscopy is one of the standard plasma diagnostic techniques used in tokamak research to determine ion temperature, rotation speed, particle density, and radial electric field. Configuring a charge coupled device (CCD) camera to serve as a detector in such a system requires a trade-off between the competing desires to detect light from as many independent spatial views as possible while still obtaining the best possible time resolution. High time resolution is essential, for example, for studying transient phenomena such as edge localized modes. By installing a mask in front of a camera with a 1024 × 1024 pixel CCD chip, we are able to acquire spectra from eight separate views while still achieving a minimum time resolution of 0.2 ms. The mask separates the light from the eight spectra, preventing spatial and temporal cross talk. A key part of the design was devising a compact translation stage which attaches to the front of the camera and allows adjustment of the position of the mask openings relative to the CCD surface. The stage is thin enough to fit into the restricted space between the CCD camera and the spectrometer endplate. View full abstract»

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  • Three-beam interference lithography methodology

    Page(s): 023115 - 023115-8
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    Three-beam interference lithography represents a technology capable of producing two-dimensional periodic structures for applications such as micro- and nanoelectronics, photonic crystal devices, metamaterial devices, biomedical structures, and subwavelength optical elements. In the present work, a systematic methodology for implementing optimized three-beam interference lithography is presented. To demonstrate this methodology, specific design and alignment parameters, along with the range of experimentally feasible lattice constants, are quantified for both hexagonal and square periodic lattice patterns. Using this information, example photonic crystal rodlike structures and holelike structures are fabricated by appropriately controlling the recording wavevector configuration along with the individual beam amplitudes and polarizations, and by changing between positive- or negative-type photoresists. View full abstract»

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  • Terrace retro-reflector array for poloidal polarimeter on ITER

    Page(s): 023116 - 023116-5
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    A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter. View full abstract»

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  • Far-field plasmonic resonance enhanced nanoparticle image velocimetry within a microchannel

    Page(s): 023117 - 023117-6
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    In this paper, a novel far-field plasmonic resonance enhanced nanoparticle-seeded particle image velocimetry has been demonstrated to measure the velocity profile in a microchannel. Chemically synthesized silver nanoparticles have been used to seed the flow in the microchannel. By using discrete dipole approximation, plasmonic resonance enhanced light scattering has been calculated for spherical silver nanoparticles with diameters ranging from 15 to 200 nm. Optimum scattering wavelength is specified for the nanoparticles in two media: water and air. The diffraction-limited plasmonic resonance enhanced images of silver nanoparticles at different diameters have been recorded and analyzed. By using standard particle image velocimetry techniques, the velocity profile within the microchannel has been determined from the images. View full abstract»

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  • Low power high-performance radio frequency oscillator for driving ion traps

    Page(s): 023118 - 023118-5
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    We report a simple, efficient, high voltage radio frequency (RF) generator powered by a single voltage source (1.5–7 V) to resonantly drive ion traps or other capacitive loads. Our circuit is able to deliver RF voltages > 500 Vp-p at frequencies ranging from 0.1 to 10 MHz. This RF oscillator uses low-cost, commercially available components, and can be easily assembled onto a circuit board of a few cm2. Because of its simplicity and good efficiency, this circuit is useful in applications requiring small size and low power consumption such as portable ion trap systems where the duration of operation under battery power is of concern. View full abstract»

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  • Transmission line based short pulse generation circuits in a 0.13 μm complementary metal–oxide–semiconductor technology

    Page(s): 023301 - 023301-5
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    A few traditional pulse forming circuits are implemented and compared in a commercial 0.13 μm digital CMOS technology. Standard on-chip transmission lines are used as pulse forming lines (PFLs), while CMOS transistors are used as switches. The shortest output pulses of these circuits are analyzed and compared through Cadence Spectre simulations. All the CMOS circuits are fabricated in the commercial technology. Pulses of ∼170 ps durations and 120–400 mV amplitudes are obtained when the power supply is tuned from 1.2 to 2 V. The results show that these traditional PFL based circuits can be implemented in standard CMOS technology for high power short pulse generations. Furthermore, the PFL circuits significantly extend the short pulse generation capabilities of CMOS technologies. View full abstract»

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  • NATALIE: A 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques

    Page(s): 023302 - 023302-6
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    We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the β+ activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons. View full abstract»

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  • First plasma of megawatt high current ion source for neutral beam injector of the experimental advanced superconducting tokamak on the test bed

    Page(s): 023303 - 023303-4
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    High current ion source is the key part of the neutral beam injector. In order to develop the project of 4 MW neutral beam injection for the experimental advanced superconducting tokamak (EAST) on schedule, the megawatt high current ion source is prestudied in the Institute of Plasma Physics in China. In this paper, the megawatt high current ion source test bed and the first plasma are presented. The high current discharge of 900 A at 2 s and long pulse discharge of 5 s at 680 A are achieved. The arc discharge characteristic of high current ion source is analyzed primarily. View full abstract»

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  • Li+ ion emission from a hot-plate alumina-silicate source stimulated by flash heating with an infrared laser

    Page(s): 023304 - 023304-9
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    The Neutralized Drift Compression Experiment-II accelerator under construction at Lawrence Berkeley National Laboratory has been designed to employ a lithium-doped alumino-silicate (Al-Si) hot-plate surface-ionization ion source. In order to achieve the design 1 mA/cm2 current density, the emitter must be constantly kept at a high temperature, leading to the accelerated loss of Li material as ions or neutrals. As a result, the estimated lifetime of the source is 50 h. This lifetime can be extended if the source is kept at low temperature during standby, and pulse heated to the high temperature during the ion extraction phase only. A pulsed heating technique based on an infrared laser (CO2 gas discharge, λ = 10.6 μm) is described in this paper. The feasibility of ion current emission stimulated by flash heating with an infrared (IR) laser was demonstrated. High repeatability of the laser-stimulated ion current was observed, creating an opportunity for modulation and gating of the ion current with a laser pulse. It was found that with the available low power (≈115 W/cm2) IR laser, current densities as high as 0.8 mA/cm2 could be achieved with a 2.8 mm diameter source. Various approaches for scaling to a larger (10 cm diameter) source and the application of short pulse, high power lasers are discussed. The results and conclusions of this paper may apply to various species of hot-plate ion sources. View full abstract»

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  • Practical selection of emission lines of He I to determine the photon absorption rate

    Page(s): 023501 - 023501-5
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    A combination of helium line intensities and a collisional radiative model has been used to measure electron density and temperature. However, radiation trapping of resonance lines may disturb the measurements due to disturbances in the population distribution of helium atoms. In this study, we show that the principal contribution of radiation trapping in helium plasma can be evaluated by additionally measuring one or two specific line intensities from the singlet state. The inclusion of the effects of radiation trapping sufficiently compensates for anomalous increases in the electron density and temperature, and consequently yields proper values. An experiment was performed in the divertor simulator NAGDIS-II, and the method's validity was confirmed by comparing the spectroscopically obtained results and the values from the electrostatic probe method. View full abstract»

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  • Development of effective power supply using electric double layer capacitor for static magnetic field coils in fusion plasma experiments

    Page(s): 023502 - 023502-5
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    A cost-effective power supply for static magnetic field coils used in fusion plasma experiments has been developed by application of an electric double layer capacitor (EDLC). A prototype EDLC power supply system was constructed in the form of a series LCR circuit. Coil current of 100 A with flat-top longer than 1 s was successfully supplied to an equilibrium field coil of a fusion plasma experimental apparatus by a single EDLC module with capacitance of 30 F. The present EDLC power supply has revealed sufficient performance for plasma confinement experiments whose discharge duration times are an order of several seconds. View full abstract»

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  • Improved hydrogen ionization rate in enhanced glow discharge plasma immersion ion implantation by enlarging the interaction path using an insulating tube

    Page(s): 023503 - 023503-6
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    A small pointed hollow anode and large tabular cathode are used in enhanced glow discharge plasma immersion ion implantation (EGD-PIII). Electrons are repelled from the substrate by the electric field formed by the negative voltage pulses and concentrate in the vicinity of the anode to enhance the self-glow discharge process. To extend the application of EGD-PIII to plasma gases with low ionization rates, an insulating tube is used to increase the interaction path for electrons and neutrals in order to enhance the discharge near the anode. Results obtained from numerical simulation based on the particle-in-cell code, finite element method, and experiments show that this configuration enhances the ionization rate and subsequent ion implant fluence. The process is especially suitable for gases that have low ionization rates such as hydrogen and helium. View full abstract»

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Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Albert T. Macrander
Argonne National Laboratory