Design of a radiographic integrated test stand (RITS) based on a voltage adder, to drive a diode immersed in a high magnetic field

Smith, I.; Bailey, V.; Fockler, J.; Gustwiller, J.; Johnson, D.L.; Maenchen, J.E.; Droemer, D.

doi:10.1109/27.901250

Cited by 67 publications

(21 citation statements)

References 5 publications

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“…6 Flat cathode diodes have also been utilized to provide a high quality beam. In the TriMeV generator, 15 and more recently on the three-cavity radiographic integrated test stand ͑RITS-3͒ accelerator at Sandia National Laboratories, 16 such a diode provides a focusing beam at the anode foil. This configuration can make use of a completely ballistic transport of the beam without the need for finite net-current generation.…”

Section: Physics Of Plasma Focusing Cellsmentioning

confidence: 99%

Bernstein mode generated anomalous resistivity in a current carrying plasma focusing cell

et al. 2006

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The influence of microinstabilities and turbulence on the resistivity of plasma filled electron beam focusing cells is presented. Using a particle-in-cell simulation code, we have observed the onset of anomalous resistivity for low plasma densities and large embedded magnetic fields. The enhanced resistivity results from wave-particle interactions due to the saturation of the ion Bernstein mode instability in the current-carrying plasma. The growth rate of the mode scales with the relative drift speed between the electrons and ions. Here the scaling of the instability derived from simulation and theory and its impact on the operation of a plasma focusing cell for electron beam driven radiography are discussed. Enhanced resistivity up to 70 times larger than the classical Spitzer value is calculated for relevant plasma parameters.

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Section: Physics Of Plasma Focusing Cellsmentioning

confidence: 99%

Bernstein mode generated anomalous resistivity in a current carrying plasma focusing cell

et al. 2006

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“…To determine the suitability of the self-magnetic-pinch (SMP) diode [1][2][3][4][5][6] as a radiographic source, an experimental campaign was conducted on Sandia's RITS-6 accelerator [7][8][9] to quantify its shot-toshot variation. The accelerator operated at 4.5 MV and the SMP diode was fielded with changes only to the anodecathode (AK) gap and cathode needle radius (r c ).…”

Section: Introductionmentioning

confidence: 99%

Shot reproducibility of the self-magnetic-pinch diode at 4.5 MV

Bennett

Crain

Droemer

et al. 2014

Phys. Rev. ST Accel. Beams

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In experiments conducted at Sandia National Laboratories' RITS-6 accelerator, the self-magnetic-pinch diode exhibits significant shot-to-shot variability. Specifically, for identical hardware operated at the same voltage, some shots exhibit a catastrophic drop in diode impedance. A study is underway to identify sources of shot-to-shot variations which correlate with diode impedance collapse. The scope of this report is limited to data collected at 4.5-MV peak voltage and sources of variability which occur away from the diode, such as sheath electron emission and trajectories, variations in pulsed power, load and transmission line alignment, and different field shapers. We find no changes in the transmission line hardware, alignment, or hardware preparation methods which correlate with impedance collapse. However, in classifying good versus poor shots, we find that there is not a continuous spectrum of diode impedance behavior but that the good and poor shots can be grouped into two distinct impedance profiles. In poor shots, the sheath current in the load region falls from 16%-30% of the total current to less than 10%. This result will form the basis of a follow-up study focusing on the variability resulting from diode physics.

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“…On RITS, as in other high-voltage IVA architectures, the inner conductor of the coaxial line is cantilevered and must support itself and the load. These mechanical stresses place a minimum on the diameter of the inner conductor and, therefore, a maximum on the line impedance of 100 [1,2]. With this constraint, RITS-3 was designed to deliver 150 kA total current at 4 MV.…”

Section: Introductionmentioning

confidence: 99%

“…In high-power systems such as Sandia National Laboratories' Radiographic Integrated Test Stand (RITS [2]), electric field stresses in the transmission line exceed the threshold above which electrons are emitted [3], such that it no longer operates in a vacuum. In negative-polarity coaxial lines, the magnetic field generated by the current prevents electrons from crossing the coaxial gap and the resulting flow proceeds in a sheath layer between the electrodes, more or less tightly bound to the cathode surface, toward the diode.…”

Section: Introductionmentioning

confidence: 99%

Modeling particle emission and power flow in pulsed-power driven, nonuniform transmission lines

Bruner

Genoni

Madrid

et al. 2008

Phys. Rev. ST Accel. Beams

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Pulsed-power driven x-ray radiographic systems are being developed to operate at higher power in an effort to increase source brightness and penetration power. Essential to the design of these systems is a thorough understanding of electron power flow in the transmission line that couples the pulsed-power driver to the load. In this paper, analytic theory and fully relativistic particle-in-cell simulations are used to model power flow in several experimental transmission-line geometries fielded on Sandia National Laboratories' upgraded Radiographic Integrated Test Stand [IEEE Trans. Plasma Sci. 28, 1653 (2000)]. Good agreement with measured electrical currents is demonstrated on a shot-by-shot basis for simulations which include detailed models accounting for space-charge-limited electron emission, surface heating, and stimulated particle emission. Resonant cavity modes related to the transmission-line impedance transitions are also shown to be excited by electron power flow. These modes can drive oscillations in the output power of the system, degrading radiographic resolution.

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Design of a radiographic integrated test stand (RITS) based on a voltage adder, to drive a diode immersed in a high magnetic field

Cited by 67 publications

References 5 publications

Bernstein mode generated anomalous resistivity in a current carrying plasma focusing cell

Bernstein mode generated anomalous resistivity in a current carrying plasma focusing cell

Shot reproducibility of the self-magnetic-pinch diode at 4.5 MV

Modeling particle emission and power flow in pulsed-power driven, nonuniform transmission lines

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