<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mn>10</mml:mn><mml:mn>7</mml:mn></mml:msup></mml:math>-A load-current<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math>-dot monitor: Simulations, design, and performance

Rose, D. V.; Welch, D. R.; Miller, Carol; Clark, Robert E.; Madrid, E. A.; Mostrom, C. B.; Wagoner, T. C.; Moore, J.; Stygar, W. A.; Bailey, James E.; Nash, T. J.; Rochau, G. A.; Sinars, Daniel Brian

doi:10.1103/physrevstab.13.040401

Cited by 19 publications

(9 citation statements)

References 26 publications

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“…The vacuum sections of the Z [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and ZR [19][20][21][22][23][24][25] accelerators have been successful, providing efficient, high-current delivery from the generator to a variety of loads. On ZR, the upstream transmission lines are 3 m in diameter, the DPHC begins at a radius of approximately 11 cm, and the final radial transmission line begins at a radius of $5 cm.…”

Section: Introductionmentioning

confidence: 99%

“…The outer MITL current is measured by B-dot monitors that are located in all four MITLs at radii of $65 cm; the inner MITL current (also referred to as load current) is measured downstream of the DPHC at a $6 cm radius [24,34]. The measured current loss between these two locations when driving a z-pinch load appears to range from 1 to 4 MA, depending on the impedance history of the load.…”

Section: Introductionmentioning

confidence: 99%

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Steady-state modeling of current loss in a post-hole convolute driven by high power magnetically insulated transmission lines

Madrid

Rose

Welch

et al. 2013

Phys. Rev. ST Accel. Beams

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Quasiequilibrium power flow in two radial magnetically insulated transmission lines (MITLs) coupled to a vacuum post-hole convolute is studied at 50 TW-200 TW using three-dimensional particle-in-cell simulations The voltages assumed for this study result in electron emission from all cathode surfaces. Electrons emitted from the MITL cathodes upstream of the convolute cause a portion of the MITL current to be carried by an electron sheath. Under the simplifying assumptions made by the simulations, it is found that the transition from the two MITLs to the convolute results in the loss of most of the sheath current to anode structures. The loss is quantified as a function of radius and correlated with Poynting vector stream lines which would be followed by individual electrons. For a fixed MITLconvolute geometry, the current loss, defined to be the difference between the total (i.e. anode) current in the system upstream of the convolute and the current delivered to the load, increases with both operating voltage and load impedance. It is also found that in the absence of ion emission, the convolute is efficient when the load impedance is much less than the impedance of the two parallel MITLs. The effects of space-charge-limited (SCL) ion emission from anode surfaces are considered for several specific cases. Ion emission from anode surfaces in the convolute is found to increase the current loss by a factor of 2-3. When SCL ion emission is allowed from anode surfaces in the MITLs upstream of the convolute, substantially higher current losses are obtained. Note that the results reported here are valid given the spatial resolution used for the simulations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Steady-state modeling of current loss in a post-hole convolute driven by high power magnetically insulated transmission lines

Madrid

Rose

Welch

et al. 2013

Phys. Rev. ST Accel. Beams

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“…Current ( _ B) measurements are also made near the experimental load, at a radial position of about 6 cm from the Z axis of symmetry, and again at multiple azimuthal angles ( Fig. 2) [23,25]. For the experiments presented in this paper, approximately sixteen _ D and sixteen _ B probes were used on each of the four levels of the vacuuminsulator stack, and six _ B probes were used at the load.…”

Section: Introductionmentioning

confidence: 99%

Displacement current phenomena in the magnetically insulated transmission lines of the refurbishedZaccelerator

McBride

Jennings

Vesey

et al. 2010

Phys. Rev. ST Accel. Beams

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Experimental data is presented that illustrates important displacement current phenomena in the magnetically insulated transmission lines (MITLs) of the refurbished Z accelerator [D. V. Rose et al., Phys. Rev. ST Accel. Beams 13, 010402 (2010)]. Specifically, we show how displacement current in the MITLs causes significant differences between the accelerator current measured at the vacuuminsulator stack (at a radial position of about 1.6 m from the Z axis of symmetry) and the accelerator current measured at the load (at a radial position of about 6 cm from the Z axis of symmetry). The importance of accounting for these differences was first emphasized by Jennings et al. [C. A. Jennings et al., IEEE Trans. Plasma Sci. 38, 529 (2010)], who calculated them using a full transmission-lineequivalent model of the four-level MITL system. However, in the data presented by Jennings et al., many of the interesting displacement current phenomena were obscured by parasitic current losses that occurred between the vacuum-insulator stack and the load (e.g., electron flow across the anode-cathode gap). By contrast, the data presented herein contain very little parasitic current loss, and thus for these low-loss experiments we are able to demonstrate that the differences between the current measured at the stack and the current measured at the load are due primarily to the displacement current that results from the shunt capacitance of the MITLs (about 8.41 nF total). Demonstrating this is important because displacement current is an energy storage mechanism, where energy is stored in the MITL electric fields and can later be used by the system. Thus, even for higher-loss experiments, the differences between the current measured at the stack and the current measured at the load are often largely due to energy storage and subsequent release, as opposed to being due solely to some combination of measurement error and current loss in the MITLs and/or double post-hole convolute. Displacement current also explains why the current measured downstream of the MITLs (i.e., the load current) often exceeds the current measured upstream of the MITLs (i.e., the stack current) at various times in the power pulse (this particular phenomenon was initially thought to be due to timing and/or calibration errors). To facilitate a better understanding of these phenomena, we also introduce and analyze a simple LC circuit model of the MITLs. This model is easily implemented as a simple drive circuit in simulation codes, which has now been done for the LASNEX code [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Controlled Fusion 2, 51 (1975)] at Sandia, as well as for simpler MATLABÒ-based codes at Sandia. An example of this LC model used as a drive circuit will also be presented.

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“…In linear induction accelerator (LIA), azimuthal B-dot probes (commonly referred as B-dots) are used to measure the current and position of a pulsed beam by detecting azimuthal magnetic field generated by the beam, in purpose to correct beam trace with correcting magnets. [1][2][3] They are also applied in current measurements in pulsed-power accelerators 4 and in diagnosing exploding plasmas. 5 Axial B-dots probes can be used to direct measure the tilt angle of a pulsed beam by detecting the dipole term of axial magnetic field generated by the beam traveling with nonzero beam tilt.…”

Section: Introductionmentioning

confidence: 99%

Hybrid monitor for both beam position and tilt of pulsed high-current beams

Pang

et al. 2014

Review of Scientific Instruments

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A Hybrid beam monitor, integrated with both azimuthal and axial B-dot probes, was designed for simultaneous measurement of both beam position and beam angle for pulsed high-current beams at the same location in beam pipe. The output signals of axial B-dot probes were found to be mixed with signals caused by transverse position deviation. In order to eliminate the unwanted signals, an elimination method was developed and its feasibility tested on a 50-Ω coaxial line test stand. By this method, a waveform, shape-like to that of input current and proportional to the tilt angle, was simulated and processed by following integration step to achieve the tilt angle. The tests showed that the measurement error of displacement and tilt angle less than 0.3 mm and 1.5 mrad, respectively. The latter error could be reduced with improved probes by reducing the inductance of the axial B-dot probe, but the improvement reached a limit due to some unknown systemic mechanism.

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107-A load-currentB-dot monitor: Simulations, design, and performance

Cited by 19 publications

References 26 publications

Steady-state modeling of current loss in a post-hole convolute driven by high power magnetically insulated transmission lines

Steady-state modeling of current loss in a post-hole convolute driven by high power magnetically insulated transmission lines

Displacement current phenomena in the magnetically insulated transmission lines of the refurbishedZaccelerator

Hybrid monitor for both beam position and tilt of pulsed high-current beams

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