A simple theory of magnetic insulation from basic physical considerations

Mendel, C. W.; Seidel, D. B.; Rosenthal, S.E.

doi:10.1017/s0263034600000379

Cited by 109 publications

(60 citation statements)

References 8 publications

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“…[4], the sheath current obtained in these simulations is larger than 1D models predict. One estimate of the equilibrium sheath current in a constant impedance MITL is [16,30,31] …”

Section: A Cathode Electron Emissionmentioning

confidence: 99%

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Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Rose

Madrid

Welch

et al. 2015

Phys. Rev. ST Accel. Beams

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Numerical simulations of a vacuum post-hole convolute driven by magnetically insulated vacuum transmission lines (MITLs) are used to study current losses due to charged particle emission from the MITL-convolute-system electrodes. This work builds on the results of a previous study [E. A. Madrid et al. Phys. Rev. ST Accel. Beams 16, 120401 (2013)] and adds realistic power pulses, Ohmic heating of anode surfaces, and a model for the formation and evolution of cathode plasmas. The simulations suggest that modestly larger anode-cathode gaps in the MITLs upstream of the convolute result in significantly less current loss. In addition, longer pulse durations lead to somewhat greater current loss due to cathodeplasma expansion. These results can be applied to the design of future MITL-convolute systems for high-current pulsed-power systems.

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“…[4], the sheath current obtained in these simulations is larger than 1D models predict. One estimate of the equilibrium sheath current in a constant impedance MITL is [16,30,31] …”

Section: A Cathode Electron Emissionmentioning

confidence: 99%

“…[4]. That work showed that in the limit of cathode electron emission, the load current scales roughly as Z 2 Load [16,22,30,31].…”

Section: Parameter Studies a Operating Parameter Variationsmentioning

confidence: 99%

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Rose

Madrid

Welch

et al. 2015

Phys. Rev. ST Accel. Beams

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“…A low MITL impedance is advantageous for a z-pinch IFE system as it minimizes the inductance between the driver and the load; thus, the voltage generated by dI/dt (required to drive the z-pinch) is minimized [15]. The effective impedance of the MITL is described best by the flow impedance Z f , which is a function of both the geometry and the voltage [16][17][18][19][20][21][22][23][24] and is less than the vacuum impedance of the line Z 0 because of the distributed electron current. Additionally, high current resistively heats the electrode surfaces; when the anode surface is heated above T = 400° C [25][26][27][28][29][30], ions are emitted.…”

Section: Recyclable Transmission Line (Rtl) (C L Olson Snl)mentioning

confidence: 99%

Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield.

Sharpe¹,

Kingsep

Smith³

et al. 2007

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Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot zpinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO 2 production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber.Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and 4 will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-ofPrinciple) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is demonstrated at the SNL Z-IFE LTD laboratory with rep-rates up to 10.3 seconds between shots (this is essentially at the goal of 10 seconds for Z-IFE). (7) A single LTD switch at Tomsk was fired repetitively every 12 seconds for 36,000 shots with no failures. Present results from all of these power flow studies validate the whole LTD/RTL concept for single-shot ICF high yield, and for repetitive-shot IFE.

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“…The difference between I a and I c is the free electron current flowing along the MITL. Based on the theory of Mendel [9], the MITL voltage can be calculated as a function of the anode and cathode currents:…”

Section: B Electrical Diagnosticsmentioning

confidence: 99%

Demonstration of the self-magnetic-pinch diode as an X-ray source for flash core-punch radiography.

Cordova¹,

Rovang²,

Portillo³

et al. 2007

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Minimization of the radiographic spot size and maximization of the radiation dose is a continuing long-range goal for development of electron beam driven X-ray radiography sources. In collaboration with members of the Atomic Weapons Establishment(AWE), Aldermaston UK , the Advanced Radiographic Technologies Dept. 1645 is conducting research on the development of X-ray sources for flash core-punch radiography. The Hydrodynamics Dept. at AWE has defined a near term radiographic source requirement for scaled core-punch experiments to be 250 rads@m with a 2.75 mm source spot-size. As part of this collaborative effort, Dept. 1645 is investigating the potential of the SelfMagnetic-Pinched (SMP) diode as a source for core-punch radiography. Recent experiments conducted on the RITS-6 accelerator [1,2] demonstrated the potential of the SMP diode by meeting and exceeding the near term radiographic requirements established by AWE. During the demonstration experiments, RITS-6 was configured with a low-impedance (40 Ω) Magnetically Insulated Transmission Line (MITL), which provided a 75-ns, 180-kA, 7.5-MeV forward going electrical pulse to the diode. The use of a low-impedance MITL enabled greater power coupling to the SMP diode and thus allowed for increased radiation output. In addition to reconfiguring the driver (accelerator), geometric changes to the diode were also performed which allowed for an increase in dose production without sacrificing the time integrated spot characteristics. The combination of changes to both the pulsed power driver and the diode significantly increased the source x-ray intensity.

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A simple theory of magnetic insulation from basic physical considerations

Cited by 109 publications

References 8 publications

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

Recyclable transmission line (RTL) and linear transformer driver (LTD) development for Z-pinch inertial fusion energy (Z-IFE) and high yield.

Demonstration of the self-magnetic-pinch diode as an X-ray source for flash core-punch radiography.

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