Spatial deconvolution technique to obtain velocity profiles from chord integrated spectra

Golingo, R.P.; Shumlak, U.

doi:10.1063/1.1556956

Cited by 26 publications

(12 citation statements)

References 11 publications

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“…29 Doppler shifted and unshifted spectra are collected by viewing the plasma 35°and 90°to the z axis. 30. A shell model is then used to deconvolve the line-integrated data to give the ion velocity profile.…”

Section: Diagnosticsmentioning

confidence: 99%

Formation of a sheared flow Z pinch

2005

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The ZaP Flow Z-Pinch project is experimentally studying the effect of sheared flows on Z-pinch stability. It has been shown theoretically that when dV z / dr exceeds 0.1kV A the kink ͑m =1͒ mode is stabilized. ͓U. Shumlak and C. W. Hartman, Phys. Rev. Lett. 75, 3285 ͑1995͒.͔ Z pinches with an embedded axial flow are formed in ZaP with a coaxial accelerator coupled with a 1 m assembly region. Long-lived, quiescent Z pinches are generated throughout the first half cycle of the current. During the initial plasma acceleration phase, the axial motion of the current sheet is consistent with snowplow models. Magnetic probes in the assembly region measure the azimuthal modes of the magnetic field. The amplitude of the m = 1 mode is proportional to the radial displacement of the Z-pinch plasma current. The magnetic mode levels show a quiescent period which is over 2000 times the growth time of a static Z pinch. The axial velocity is measured along 20 chords through the plasma and deconvolved to provide a radial profile. Using data from multiple pulses, the time evolution of the velocity profile is measured during formation, throughout the quiescent period, and into the transition to instability. The evolution shows that a sheared plasma flow develops as the Z pinch forms. Throughout the quiescent period, the flow shear is greater than the theoretically required threshold for stability. As the flow shear decreases, the magnetic mode fluctuations increase. The coaxial accelerator provides plasma throughout the quiescent period and may explain the evolution of the velocity profile and the sustainment of the flow Z pinch.

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Section: Diagnosticsmentioning

confidence: 99%

Formation of a sheared flow Z pinch

2005

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“…These profile shapes allow a shell model to be used to calculate the velocity profile. 30 Deconvolved velocity profiles from the four pulses are shown in Figs. 12-15.…”

Section: Velocity Evolutionmentioning

confidence: 99%

“…A shell model is then used to deconvolve the line-integrated data to give the ion velocity profile. 30 A complete discussion of the error determination is found in Ref. 30.…”

Section: Diagnosticsmentioning

confidence: 99%

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The ZaP Flow Z-Pinch Project

Shumlak¹,

Nelson²

2005

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“…A four-chord, heterodyne-quadrature, visible HeNe interferometer can be located at several axial points along the length of the machine (several locations in the accelerator and several along the pinch) giving chordintegrated, time-dependent densities. A 1-meter, 20-chord spectrometer with an intensified CCD (ICCD) can be used to measure orthogonal emission to determine ion temperature profiles or oblique emission to determine velocity profiles 3 . An Imacon 790 camera is used to take high frame rate (500 kHz to 5MHz) images of the pinch through one of three locations in the assembly region of the machine.…”

Section: The Zap-experimentsmentioning

confidence: 99%

Quasi-steady accelerator operation on the ZAP flow Z-pinch

Hughes¹,

Shumlak²,

Golingo³

et al. 2014

AIP Conference Proceedings

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Abstract. The ZaP Flow Z-Pinch Experiment utilizes sheared flows to stabilize an otherwise unstable equilibrium. The sheared flows are maintained by streaming high velocity plasma parallel to the pinch. Previous operations of the machine show depletion of the accelerator's neutral gas supply late in the pulse leading to pinch instability. The current distribution in the accelerator exhibits characteristic modes during this operation, which is corroborated by interferometric signals. The decrease in density precipitates a loss of plasma quiescence in the pinch, which occurs on a timescale related to the flow velocity from the plasma source. To abate the depletion, the geometry of the accelerator is altered to increase the neutral gas supply. The design creates a standing deflagration front in the accelerator that persists for the pulse duration. The new operating mode is characterized by the same diagnostics as the previous mode. The lessons learned in the accelerator operations have been applied to the design of a new experiment, ZaP-HD.

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Spatial deconvolution technique to obtain velocity profiles from chord integrated spectra

Cited by 26 publications

References 11 publications

Formation of a sheared flow Z pinch

Formation of a sheared flow Z pinch

The ZaP Flow Z-Pinch Project

Quasi-steady accelerator operation on the ZAP flow Z-pinch

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