W. K. Dagenhart

Oak Ridge National Laboratory, Oak Ridge, FL, United States

Are you W. K. Dagenhart?

Claim your profile

Publications (52)35.6 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The emittances of hydrogen and deuterium negative ion beams produced by volume ion sources have been measured in a transverse plane normal to the beam trajectory. The extraction voltage was varied from 10 to 40 kV, and the transverse magnetic field in the Penning discharges was varied from 0.1 to 0.2 T. Measurements were made on beams with current densities up to 60 mA/cm<sup>2</sup> at Oak Ridge National Laboratory with an emittance scanner originally developed at Los Alamos National Laboratory. The beam profile at the scanner can be used to improve the accuracy of the emittance measurements. Other factors affecting emittance measurements are discussed. This analysis may be applicable to other ion sources.
    Review of Scientific Instruments 03/1990; · 1.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The emittances of hydrogen and deuterium negative ion beams produced by volume ion sources have been measured in a transverse plane normal to the beam trajectory. The extraction voltage was varied from 10 to 40 kV, and the transverse magnetic field in the Penning discharges was varied from 0.1 to 0.2 T. Measurements were made on beams with current densities up to 60 mA/cm2 at Oak Ridge National Laboratory with an emittance scanner originally developed at Los Alamos National Laboratory. The beam profile at the scanner can be used to improve the accuracy of the emittance measurements. Other factors affecting emittance measurements are discussed. This analysis may be applicable to other ion sources.
    Review of Scientific Instruments 01/1990; 61. · 1.60 Impact Factor
  • Proc SPIE 07/1989;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The next-generation fusion devices based on the tokamak confinement concept are expected to emphasize steady-state operation. Such future reactors may include designs like the International Thermonuclear Experimental Reactor (ITER) and that of the recent International Tokamak Reactor (INTOR) program. Effective means of non-inductive plasma current drive would therefore be necessary. This paper describes a neutral beam concept for a current drive system (which will heat the plasma as well) that is based on negative ions and has a beam energy > 1 MeV. Such systems, at much lower power levels, are also being considered for alpha diagnostics. Preliminary physics calculations show that the plasma core current necessary for stability enhancement can best be achieved in these future reactor-like machines with tangentially injected beams having energies ranging from 1 to 4 MeV. Further study and experiments will better define the optimum energy. Studies of how to accomplish beams of this energy led to the system described in this paper.
    02/1989
  • [Show abstract] [Hide abstract]
    ABSTRACT: An electrostatic emittance scanner has been used to measure the emittance of intense H/sup -/ and D/sup -/ beams formed by ion sources developed at the Oak Ridge National Laboratory (ORNL). The ion sources have been operated reliably in both the Surface Ionization with Transverse Extraction (SITEX) and Volume Ionization with Transverse Extraction (VITEX) modes. The emittance measurements were made in a magnetic field of about 1 kg. The effective dimensions of the beamlet sample at the accelerator exit in the SITEX mode were 0.21 cm by 0.16 cm. (Here 0.16 cm is the central part of a 12.7-cm beam ribbon that is parallel to the applied source magnetic field.) The normalized rms emittances for such SITEX beamlets (approx.1.14 mA) were 0.01 ..pi.. . cm. mrad measured transverse to the field and 0.003 ..pi.. . cm . mrad measured parallel to the field for 10-keV D/sup -/ beams (36 mA/cm/sup 2/). The dimensions of H/sup -/ beams at the accelerator exit in the VITEX mode were 0.1 cm by 2.0 cm. The normalized rms emittances were about 0.013 ..pi.. . cm . mrad measured transverse to the field and 0.017 ..pi.. . cm . mrad measured parallel to the field for 15-keV, 12-mA (or 60-mA/cm/sup 2/) beams. The highest current density achieved is above 150 mA/cm/sup 2/. Ion temperatures obtained from the parallel emittance measurements were 9.4 eV for SITEX beams and 0.6 eV for VITEX beams. In this report, the method used to analyze the measured emittance data is described, and the potential errors in measurement are discussed. 9 refs., 16 figs., 1 tab.
    10/1987;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Beam parameters have been measured for both the Surface Ionization with Transverse Extraction (SITEX) and Volume Ionization with Transverse Extraction (VITEX) H−/D− ion sources. Both sources use a reflex discharge to generate the main plasma. Beam energies up to 18 keV were used for pulse lengths up to several seconds. For SITEX, Faraday cup magnetically analyzed D− beam currents of 110 mA at extraction densities of 48 mA/cm2 and at a source ion temperature of 4 eV have been measured. For the VITEX results, Faraday cup magnetically analyzed beam currents of up to 80 mA at extraction densities of 27 mA/cm2 and at a source ion temperature of 0.5 eV have been measured. Virtually all extracted electrons were recovered at an energy of 10–30% of the accel beam energy, and there were none in the analyzed beam.
    AIP Conference Proceedings. 07/1987; 158(1):366-377.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Surface ionization with Transverse Extraction (SITEX) and Volume Ionization with Transverse Extraction (VITEX) ion sources are being developed to produce intense beams of light negative ions for neutral particle beam applications. The salient feature of these ion sources is their ability to form intense negative‐ion beams. With the objective of improving the performance of these sources, an experimental study of their plasma properties has been conducted. The effects of various electrodes in the plasma generator were investigated. Low electron and ion temperatures (below 1 eV) and positive plasma potential up to +6V have been measured. The measured distributions of plasma density and potential reveal the existence of multichamber characteristics in the source plasma. The significant discharge characteristics and the plasma properties associated with the performance of SITEX and VITEX ion sources are discussed.
    AIP Conference Proceedings. 07/1987; 158(1):194-205.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A dc negative hydrogen and/or deuterium ion source is needed to prouce high-power, high-energy neutral beams for alpha diagnostics and current drive applicatiosn in fusion devices. The favorable beam particle energy for such applications extends to 1.5 MeV/amu. Continuous-wave (cw) radio-frequency quadrupole (RFQ) accelerators have been proposed to accelerate negative ions effeciently to this energy range. In this paper, the desired beam properties for ion beams injected into cw RFQ accelerators are summariezed. A number of candidate ion sources being developed at Culham, JAERI, LBL, and ORNL may prove useful for these applications. The properties of the Volume Ionization with Transverse Extraction (VITEX) ion sources being developed at ORNL are presented. Scaling such a dc ion source to produce ampere beams is discussed. 53 refs., 4 figs., 2 tabs.
    01/1987;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Beam parameters have been measured for both the Surface Ionization with Transverse Extraction (SITEX) and Volume Ionization with Transverse Extraction (VITEX) H⁻/D⁻ ion sources. Both sources use a reflex discharge to generate the main plasma. Beam energies up to 18 keV were used for pulse lengths up to several seconds. For SITEX, Faraday cup magnetically analyzed D⁻ beam currents of 110 mA at extraction densities of 48 mA/cm² and at a source ion temperature of 4 eV have been measured. For the VITEX results, Faraday cup magnetically analyzed beam currents of up to 80 mA at extraction densities of 27 mA/cm² and at a source ion temperature of 0.5 eV have been measured. Virtually all extracted electrons were recovered at an energy of 10 to 30% of the accel beam energy, and there were none in the analyzed beam.
    12/1985;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A quasi‐steady‐state (pulse duration of 30 s) ion source of the duoPIGatron type has been developed for fusion applications. It was designed to deliver an 80‐keV hydrogen ion beam of low beamlet divergence (Θ rms = 0.26°) at a current density of 0.19 A cm<sup>-</sup><sup>2</sup>. Hydrogen ion beams of 40 to 48 A were extracted at beam energies of 77 to 80 keV for 30‐s‐long pulses. The reliability and stability of the ion source operation were demonstrated by extracting about 600 beam pulses at full power and full pulse length. The ion source was also operated with deuterium as the working gas, and the optimum current at 80 keV was found to be about 33 A, in agreement with the expected inverse square‐root scaling of current density with atomic mass.
    Review of Scientific Instruments 03/1985; · 1.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The surface ionization with transverse extraction (SITEX) negative ion source utilizes a 100-V/20-A reflex arc discharge in a 1300 gauss magnetic field to generate Cs+ ions and H+ or D+ ions, depending on the beam required. A shaped molybdenum plate is placed directly behind the arc column. Cesium coverage on this plate is used to minimize the surface work function, which requires two thirds of a monolayer coverage. Cesium coverage is adjusted both by cesium flow control into the arc discharge chamber and by temperature control of the converter using gaseous helium cooling channels in the converter plate. Normal converter operational temperatures are 300 C to 500 C H(-)/D(-) beams are generated at the biased converter surface by Cs(+) sputtering of absorbed hydrogen or deuterium and by the reflection conversion mechanism of H(+)/D(+) ions which strike the converter surface at 150 eV. The negative ions are accelerated through the 150-V plasma sheath at the converter surface and are focused by the converter geometry and magnetic field so as to pass through the exit aperture with minimum angular divergence. The ion optics of the SITEX accelerator is calculated by ORNL 3-D optics code and results in a divergence perpendicular to the slot of theta/sub perpendicular rms/ = 0.35(0). This beam divergence should be adequate for injection into a radio frequency quadrupole (RFQ) for further acceleration.
    01/1985;
  • W. K. Dagenhart, T. C. Tucker
    [Show abstract] [Hide abstract]
    ABSTRACT: An ion beam raster scanning method utilizing a wide gap dipole magnet has been developed at the Oak Ridge National Laboratory that can reduce the time‐averaged amplitude of the ion beam power density on the ion beam dump by factors of 3 to 6. Time‐varying in‐phase and out‐of‐phase modulation current components are used in the dipole magnet coils in order to generate a time‐varying magnetic field shape and magnitude whose magnetostatic central surface position oscillates between the two magnet iron poles. This time‐varying three‐dimensional (3‐D) magnetic field shape deflects the ion beam onto an ion dump and can be programmed to produce a raster scan pattern that depends on the coil current modulation pattern. The 3‐D magnetic field produced by an iron yoke system has been computed for different coil current ratios using a finite‐element integral method. Ion orbit equations do not need to include the small space‐charge forces present in the beam used for these purposes. The time‐averaged amplitude of beam dump power densities should be lowered by a factor of 6 by sharing the beam impact pattern over a larger area with a short raster scan period compared to the ion dump thermal time constant.
    Journal of Applied Physics 08/1984; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An emittance measurement employing two techniques are being made on SITEX. To this end, a 2‐D calculation was performed to design the accelerator in order to reduce electric field aberrations. The calculated normalized emittance is 6×10−4 πcm mrad for an angular divergence θRMS≊0.280. Status of the experimental findings are presented and a comparison made to the calculated value which will yield the ion sputter energy.
    AIP Conference Proceedings. 02/1984; 111(1):450-457.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Solving the Poisson-Vlasov equations ∇2ϕ=∫fdv−e−ϕ (1) (v×B+∇ϕ) ⋅ ∇v f=v ⋅ ∇f=0 (2) where the magnetic field, B, is assumed constant, we optimize the optical system of a SITEX negative ion source in ∞ slot geometry. Algorithms designed to solve the above equations were modified to include the curved emitter boundary data appropriate to a negative ion source. Other configurations relevant to negative ion sources are examined.
    01/1984;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A neutral beamline generator with unneutralized ion energy recovery is provided which enhances the energy recovery of the full energy ion component of the beam exiting the neutralizer cell of the beamline. The unneutralized full energy ions exiting the neutralizer are deflected from the beam path and the electrons in the cell are blocked by a magnetic field applied transverse to the beamline in the cell exit region. The ions, which are generated at essentially ground potential and accelerated through the neutralizer cell by a negative acceleration voltage, are collected at ground potential. A neutralizer cell exit end region is provided which allows the magnetic and electric fields acting on the exiting ions to be closely coupled. As a result, the fractional energy ions exiting the cell with the full energy ions are reflected back into the gas cell. Thus, the fractional energy ions do not detract from the energy recovery efficiency of full energy ions exiting the cell which can reach the ground potential interior surfaces of the beamline housing.
    01/1984;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A quasi-steady-state ion source has been developed for neutral beam injection applications. It is of the duoPIGatron type designed for delivering 50 A of hydrogen ions at 80 keV for 30-s-long pulses. Ion beams of 40 A at 75 keV were extracted for pulse lengths up to 30 s, maintaining excellent optical quality in the beam for the entire pulse duration. The design features and operational characteristics of the ion source are elaborated.
    12/1982
  • [Show abstract] [Hide abstract]
    ABSTRACT: Conceptual and preliminary engineering design for the National RF Test Facility at Oak Ridge National Laboratory (ORNL) has been completed. The facility will comprise a single mirror configuration embodying two superconducting development coils from the ELMO Bumpy Torus Proof-of-Principle (EBT-P) program on either side of a cavity designed for full-scale antenna testing. The coils are capable of generating a 1.2-T field at the axial midpoint between the coils separated by 1.0 m. The vacuum vessel will be a stainless steel, water-cooled structure having an 85-cm-radius central cavity. The facility will have the use of a number of continuous wave (cw), radio-frequency (rf) sources at levels including 600 kW at 80 MHz and 100 kW at 28 GHz. Several plasma sources will provide a wide range of plasma environments, including densities as high as approx. 5 x 10/sup 13/ cm/sup -3/ and temperatures on the order of approx. 10 eV. Furthermore, a wide range of diagnostics will be available to the experimenter for accurate appraisal of rf testing.
    12/1982
  • [Show abstract] [Hide abstract]
    ABSTRACT: The properties of an intense 50‐kV neutral‐beam system are discussed. The salient features of this system are a transmission efficiency of 76% of the extracted ion beam through a 30×34 cm aperture that is 4.5 m from the ion source, a transmitted neutral power of 1.8 MW H<sup>0</sup> (2.0 MW D<sup>0</sup>) at extraction parameters of 50 kV/100 A/0.1 s (53 kV/85 A/0.1 s), a proton fraction of ∼80%, an ion‐source arc efficiency of ∼1.3 A/kW, an ion‐source gas efficiency of ∼35%, and a reliability of ≳90%.
    Review of Scientific Instruments 05/1982; · 1.60 Impact Factor
  • W.K. Dagenhart, W.L. Stirling, J. Kim
    [Show abstract] [Hide abstract]
    ABSTRACT: Parametric studies were made on a hot cathode reflex discharge H/sup -/ Surface Ionization source with Transverse Extraction (SITEX) in both the pure hydrogen and the mixed hydrogen-cesium mode. Extraction current density, beam current, gas efficiency, extracted electron-to-H/sup -/ current ratio, heavy negative ion impurities, optics, and long pulse operation were investigated as a function of time, arc voltage, arc current, converter voltage, H/sub 2/ gas flow, cesium feed rate, and plasma generator geometries. Initial results of the research were an extracted H/sup -/ beam current density of 56 mA/cm/sup 2/ at 23 mA for 5 s pulses and, gas efficiency of 3%, theta/sub perpendicular/ (1/e) approx. 2 +- 1/sup 0/, theta/sub parallel/ (1/e) approx. 1 +- 1/sup 0/, at a beam energy of 25 keV. Negative heavy ion beam impurities were reduced to < 1% at low current densities. H/sup -/ ions are produced prinicpally by positive ion surface conversion using elemental cesium fractional monolayer coverage on a molybdenum converter substrate, which is biased negatively with respect to the anode.
    04/1982;
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper describes the development of a long-pulse positive ion source that has been designed to provide high brightness deuterium beams (divergence approx. = 0.25/sup 0/ rms, current density approx. = 0.15 A cm/sup -2/) of 40 to 45 A, at a beam energy of 80 keV, for pulse lengths up to 30 s. The design and construction of the ion source components are described with particular emphasis placed on the long-pulse cathode assembly and ion accelerator.
    12/1981