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  • 1
    Electronic Resource
    Electronic Resource
    Conceptual design of a helicon ion source for high-current dc accelerators : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1344-1348 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Characteristics of helicon plasmas are examined as a candidate for accelerator ion sources. Helicon plasmas have much higher density with very high power efficiency in a relatively lower magnetic field than electron cyclotron resonance plasmas do. High electron density and high electron temperature are beneficial to extract high ion current density. Low magnetic field favors for low-emittance accelerators. Taking advantage of placing antenna outside of the plasma chamber, source contamination can be kept low enough to maintain a stable operation for longer periods. Based on these characteristics, new designs of high current ion sources using helicon waves are proposed for accelerator applications for the first time. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148804
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  • 2
    Electronic Resource
    Electronic Resource
    Line emission tomography for CDX-U using filtered diodes : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1059-1062 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Electron density and temperature in the CDX-U low aspect ratio tokamak are too low to allow observation of fast magnetohydrodynamic activity using soft x-ray continuum emission. However, spectroscopic measurements show that extreme ultraviolet (XUV) line emission of intrinsic impurities is bright enough to observe such activity. In addition, a fast monitoring system for local temperature changes in the plasma core is required for planned auxiliary heating experiments. We present a spectrally resolved tomographic system for fast imaging of O VI 2s–np, 2p–nd (n≥3), C V 1s2–1s2p and C VI 1s–2p XUV transitions. Using this emission, we can study both core and edge MHD activity, while the C VI to C V intensity ratio can indicate local changes in electron temperature. To achieve maximal throughput together with the needed spectral resolution, we use arrays of surface barrier diodes filtered with bandpass elemental filters. Using M edge filters (Zr, Pd, and Ag), we achieve both good discrimination between the above charge states and large transmission at the wavelengths of interest. Preliminary results obtained from CDX-U are presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147787
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  • 3
    Electronic Resource
    Electronic Resource
    Multipass/multipulse Thomson scattering on CDX-U (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 689-689 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multipass/multipulse Thomson scattering system has been implemented on CDX-U in collaboration with the Ioffe Institute, St. Petersburg. The system consists of a low energy (1.5– 2.5 J), passively Q-switched ruby laser, and a multipass optical cavity enclosing the plasma. Multiple reflections of the beam within the cavity increase by about an order of magnitude the number of scattered photons, allowing temperature density to be measured with good accuracy even at very low plasma density. By feeding the returned beam back into the laser, the system can deliver several pulses over a 1 ms period. However, the experiments on CDX-U show that a mechanical shock wave reaching the multipass system affects the feedback and laser output per pulse drops significantly. Therefore we operate the system by fine tuning the laser cavity, so that output is practically independent of feedback from multipass cavity. Also, by optimizing the transmission of the passive Q-switch and the pumping power, we obtain that laser output is concentrated in single large pulse of 2–2.5 J energy. We achieve circulating energy in the plasma in excess of 12 J per pulse, while minimizing at the same time stray light. As shown by results from CDX-U, this enables in some cases better than 10% accuracy, despite relatively low plasma density conditions. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147674
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  • 4
    Electronic Resource
    Electronic Resource
    Development of a high-current microwave ion source for Korean Multipurposed Accelerator (abstract) : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1015-1015 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-current, proton linear accelerator, named as Korean multipurposed accelerator (KOMAC), is being proposed mainly for accelerator-driven transmutation technology (ADTT) by Korea Atomic Energy Research Institute (KAERI). High-current, low emittance continuous power (cw) linear accelerators favor electron cyclotron resonance (ECR) microwave ion sources as an injector (Ref. 〈citeref RID="R1" STYLE="ONLINE"〉1). Recently, these microwave sources are developed and constructed by several institutes especially for high-current cw linear accelerators. A high-density microwave ion source has been designed and constructed as a prototype ion source for the proposed KOMAC linear accelerator. The design of microwave power injection system is similar to that of the 75 keV proton injector at Los Alamos National Laboratory (Ref. 〈citeref RID="R2" STYLE="ONLINE"〉2). A 2.45 GHz, 1.5 kW magnetron source is introduced into the stainless steel plasma chamber with 10 cm diam and 20 cm length through a tapered, double-ridged waveguide and a quartz window. The microwave power supply is separated from the plasma chamber by a high-voltage waveguide break. Axial magnetic fields up to 1 kG can be provided by two sets of water-cooled solenoid coils. A single-hole extraction system is designed for extraction current up to 50 mA at 50 kV extraction voltage. The design and initial operations of the ion source in ECR regimes will be presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148744
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  • 5
    Electronic Resource
    Electronic Resource
    Conceptual design of a helicon ion source for high-current dc accelerators : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1016-1016 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Characteristics of helicon plasmas are examined as a candidate for accelerator ion sources. Helicon plasmas have much higher density with very high power efficiency in a relatively lower magnetic field than electron cyclotron resonance plasmas do. High electron density and high electron temperature are beneficial to extract high ion current density. Low magnetic field favors for low-emittance accelerators. Taking advantage of placing antenna outside of the plasma chamber, source contamination can be kept low enough to maintain a stable operation for longer periods. Based on these characteristics, new designs of high current ion sources using helicon waves are proposed for accelerator applications for the first time. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148745
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  • 6
    Electronic Resource
    Electronic Resource
    Multilayer mirror based line emission tomography for spherical Tokamaks : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1055-1058 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Due to their highly shaped plasma and possible poloidal asymmetry in impurity concentration, spherical Tokamaks will require tomographic reconstruction of local emissivities to assess impurity content and transport. To collect in an effective manner the data required for such reconstruction, we develop arrays of high throughput "mini-monochromators" using extreme ultraviolet multilayer mirrors as dispersive elements and filtered surface barrier diodes as detectors. We discuss monochromator optimization and show that by working at near normal incidence throughput and spectral resolution are simultaneously maximized. A system proposed for tomographic reconstruction of C V and C VI resonance emission at 33.7 and 40.5 Å respectively, achieves 0.9 Å spectral resolution, 2 cm spatial resolution, and 0.2 ms temporal resolution, together with good sensitivity and background rejection. Preliminary results obtained from CDX-U low aspect ratio tokamak are also presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147786
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  • 7
    Electronic Resource
    Electronic Resource
    Observations with a Mach probe on edge plasma of the CDX-U : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 986-989 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Using a rotatable three-electrode Mach probe at the outer edge region of the plasma, preliminary observations indicate the existence of a toroidal rotation in the ion flow direction (of the toroidal current) with no comparable poloidal rotation. This rotation cannot be in the direction of the magnetic field, because of the large pitch of the local magnetic field. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147732
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  • 8
    Electronic Resource
    Electronic Resource
    Microwave polarimetry system in the CDX-U tokamak : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 379-381 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An existing microwave interferometer system is modified to add the capability of polarimetry in the CDX-U tokamak. Though this interferometer system can scan vertically and radially, only the vertical view channel is modified to accomodate Faraday rotation measurements, with its radial scanning capability preserved. For our relatively long microwave wavelength, the signal amplitude variation due to refraction is more important than effects due to vibration. An amplitude independent design of Faraday rotation diagnostics has been developed. By using a linearly polarized beam as input and putting a rotating polarizer in the beam after the plasma, birefringency effects are minimized. A digital phase detection technique has been developed for better resolution of the Faraday rotation angle. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146418
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  • 9
    Electronic Resource
    Electronic Resource
    Feasibility experiments for electron ripple injection on current drive experiment-upgrade (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 966-972 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In search of a method to generate a radial electric field in tokamak plasmas, an experimental study has been performed to investigate the possibility of inducing radial electrical current. An external coil array has been used to create a local magnetic ripple well and the electron cyclotron resonance heating (ECH) has been used to trap some electrons that will then be subject to rapid vertical drifts into the plasma. Using a simplified experimental arrangement with only a toroidal magnetic field, an ECH-driven radial electrical current has been observed. The ECH-driven elecron temperature anisotropy, which is necessary for ripple trapping and electron drifts, has been determined by several different methods. The perpendicular temperature can be shown to be as large as 11 times the parallel temperature, which should yield a significant amount of ripple trapping and radial current. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872665
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  • 10
    Electronic Resource
    Electronic Resource
    Novel high temperature multilayer electrode-barrier structure for high-density ferroelectric memories (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 719-721 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This has been accomplished in the past using four/five separate electrode- and diffusion-barrier layers. In this letter, we report a novel Pt–Rh–Ox/Pt–Rh/Pt–Rh–Ox electrode-barrier structure which acts as an electrode as well as a diffusion barrier for integration of the ferroelectric capacitors directly onto silicon deposited using an in situ reactive rf sputtering process. The electrodes have a smooth and fine grained microstructure and are excellent diffusion barriers between the PbZr0.53Ti0.47O3 (PZT) and Si substrate and exhibit good thermal stability up to very high processing temperatures of 700 °C. The ferroelectric (PZT) test capacitors using these electrode barriers grown directly on Si, show well saturated hysteresis loops with Pr and Ec of 16 μC/cm2 and 30–40 kV/cm, respectively. The capacitors exhibit no significant fatigue loss (〈5%) up to 1011 cycles and have low leakage currents (2×10−8 A/cm2 at 100 kV/cm). These electrode barriers can be used to directly integrate the thin film capacitors on the source/drain of the transistors of the memory cell structure for accomplishing large scale integration.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119840
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