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  • 1
    Electronic Resource
    Electronic Resource
    Transport of high-current electron beams in a racetrack betatron (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 411-421 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper reports theoretical and experimental work on the transport of space-charge-dominated relativistic electron beams in a racetrack betatron with cusp focusing. High-efficiency propagation of 550-keV, 280-A beams through a complex optical system consisting of two 180° arcs with 36 focusing cells and a straight section was observed. More than 90% of the injected beam was captured and transported through the 7-m system. The experiments resolved several recent problems of beam injection and trapping in the machine and showed that electron beam transport at the space-charge limit is possible in a curved cusp array despite strong axial variations of focusing forces. We encountered no problems with the transitions between curved and straight focusing sections. The experiments demonstrated good beam containment in a cusp array with mixed focusing cell geometries as long as the axially averaged focusing force was the same for all cells. The ability to use long cells is a critical feasibility issue for other planned injection experiments into a closed racetrack geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346837
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  • 2
    Electronic Resource
    Electronic Resource
    Image current guiding of a relativistic electron beam in a foil focusing system (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2195-2197 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intense relativistic electron beams can be focused by arrays of transverse conducting foils or meshes. The meshes cancel beam-generated radial electric fields, allowing a self-pinched equilibrium. The experiments reported confirm that foil focusing systems can also steer high-current beams. We applied a dipole perturbation field to deflect a 3.8 kA, 280 keV beam in a foil array. We found that image current forces centered the beam in the transport pipe. The measured deflection was more than an order of magnitude smaller than the predicted value for single electron orbits. The results show that foil focusing may have application to recirculating accelerators for high-current electron beams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101142
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Space-charge correction of solenoidal lenses (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1569-1576 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A trapped distribution of low-energy electrons was used to alleviate spherical aberration in a solenoidal magnetic lens. The space-charge-correction method has potential application to the focusing of heavy, negatively charged particles such as H− ions. In the geometry investigated, the field contributions from trapped electrons cancel net electric fields along magnetic flux surfaces. The lens magnetic fields therefore define equipotential surfaces. Experimental results were obtained using a 10-keV electron beam as a nondestructive probe in a solenoid lens with 65-G peak field. Annular distributions of trapped electrons were achieved that were stable against the diochotron instability. Deflections of the probe beam were consistent with theoretical predictions. The peak focused current density of the 10-keV beam was improved twentyfold with the addition of trapped electrons in the lens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337293
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Grid-controlled extraction of pulsed ion beams (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 1790-1798 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results are presented on a method for extracting well-focused ion beams from plasma sources with time-varying properties. An electrostatic grid was used to stop the flow of plasma electrons so that only ions entered the extraction gap. In this case, ion flow in the gap was controlled by space-charge effects as it would be with a thermionic ion source. Constant extracted current was observed even with large variations of source flux. An insulator spark source and a metal-vapor vacuum arc were used to generate pulsed ion beams. With a hydrocarbon spark, current densities of 44 mA/cm2 were achieved at 20-kV extractor voltage for an 8-μs pulse. With an aluminum-vapor arc, a current density of 15 mA/cm2 (0.3 A total) was measured for a 50-μs pulse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336401
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Correction of charged particle beam optics by a programmed electrostatic wire array (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 471-478 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical and experimental results are reported on a method for the correction of aberrations in optical elements for high-power ion beams. The approach involves the use of arrays of wires immersed in large diameter beams. Individually controlled voltages are applied to the wires, resulting in local transverse deflections of beam particles. With regard to wire survivability and voltage requirements, the method appears feasible for application to high-intensity negative ion beams. A formalism is described for the calculation of optimum wire voltages to achieve a specified beam angular correction in a Cartesian geometry. The results of the calculations were tested in modeling experiments using an 8-keV electron beam. The experimental array consisted of 46 wires and boundary plates with independent applied voltages up to 3 kV. Voltage profiles for one-dimensional focusing, two-dimensional focusing, and beam steering were studied. The observed particle deflections and beam emittance growth due to the facet lens effect are in agreement with predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341984
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Image charge focusing of relativistic electron beams (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 583-585 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results are reported on the transport of a relativistic electron beam by image charge effects. The transport system consisted of a cylindrical metal tube periodically interrupted by transverse conducting grids with high transparency. Partial cancellation of the beam electric fields increased the space-charge-limited current level, allowing propagation in a magnetically self-pinched mode. A 400-keV, 4-kA beam traveled 30 cm in high vacuum through 10 focusing foils. Capture of the beam was almost 100% efficient; beam emittance was not severely degraded during capture and transport. The radius of the self-contained beam was 1.4 cm; the beam position was centered by the image current in the transport tube to within 1 mm. The favorable results imply that image charge focusing could be considered for transport in high-current linear induction accelerators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340094
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Observations of high-current electron beam transport in a curved system with periodic solenoid lenses (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1568-1575 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments were performed on high-vacuum transport of a relativistic electron beam (130 A, 300 keV) through a 180° section of a curved transport system. The system was constructed for high-current betatron experiments. The electron beam was directed by a sector-type bending field and focused by an array of 18 solenoidal lenses. The lenses could be operated with the same field polarity (modulated toroidal field) or with alternating polarity (cusp array). The reversing field of the cusp array canceled beam drift motions. Consequently, the beam was quite stable and could tolerate vertical field errors of ±100%. In contrast, beam motion in the toroidal field was dominated by drifts. After propagation through the 3.2-m-long transport tube, significant beam loss was observed with only an 8% vertical field error. Measured displacements of the beam centroid at the end of the transport system were well described by theory in both field geometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339604
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Operation of a 120-MW ion beam source using an Applied-Bθ ion diode (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 745-753 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operation of an Applied-Bθ ion diode has been studied at voltages up to 1.8 MV and diode currents of 250 kA. Peak ion currents up to 80 kA were observed at diode current efficiencies of up to 33% during the 60 ns power pulse. Ion and electron flow patterns have been carefully measured which indicate electron loss at locations far removed from the anode-cathode gap and ion current density enhancement at the inner anode radius due to motion of the cathode electron sheath. Numerical simulations performed with particle-in-cell codes agree well with the experimentally determined diode parameters including electron dynamics and ion and electron fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339727
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Radial field discharge for high-flux ion extraction (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2929-2934 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experimental results are described on a pulsed plasma source for the generation of intense beams of intermediate mass ions. The source used radial magnetic field and axial electric field to trap a high density of electrons on azimuthal orbits. A self-sustained discharge was maintained with high probability for ionization of injected gas. The large extraction area and narrow discharge gap allowed high current operation and effective extraction of ions. Up to 50 A of argon ions were generated over a 100-μs pulse. The total discharge current was 100 A and the voltage was 1000 V. A current density of 1 A/cm2 argon ions was measured 2 cm from the discharge gap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139019
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple arc ion sources for heavy ion fusion : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 553-555 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Heavy ion fusion requires high current density, low-emittance ion sources that are reliable and long lived. We report experimental and simulation results on the performance of carbon arc ion sources intended for use in a scaled induction linac experiment. These sources use a planar electrostatic plasma switch to prevent plasma from entering the extraction gap before the extraction voltage pulse is applied. This provides good beam optics for short pulse extraction. Measurements of current density and emittance are presented. Both double-slit and channel plate-pepper pot techniques are used for emittance measurement. Data presented are from a compact three-arc source with plasma coupling of the cathodes. Data on lifetime and multiple arc triggering are also presented. The plasma switch performance has been modeled with a 2D explicit electrostatic particle-in-cell code. Results showing plasma shutoff phenomena and behavior during extraction are presented. A 2D steady-state ion flow model is also used to predict the optimum plasma switch geometry for producing minimum emittance generation at the switch surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141249
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    Paper (German National Licenses)
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