11. Optical Refractivity of Plasmas

Jahoda, F. C.; Sawyer, G.A.

doi:10.1016/s0076-695x(08)60858-3

Cited by 29 publications

(19 citation statements)

References 49 publications

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“…A linearly-polarized light wave propagating through water in the presence of a longitudinal magnetic field will under go a rotation in the plane of its polarization 27 by an angle α:…”

Section: Measurement Of the Current In A Water Switch Using The Faradmentioning

confidence: 99%

Laser triggering of water switches in terrawatt-class pulse power accelerators.

Woodworth¹,

Johnson

Wilkins

et al. 2005

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Focused Beams from high-power lasers have been used to command trigger gas switches in pulse power accelerators for more than two decades. This LaboratoryDirected Research and Development project was aimed at determining whether high power lasers could also command trigger water switches on high-power accelerators. In initial work, we determined that focused light from three harmonics of a small pulsed Nd:YAG laser at 1064 nm, 532 nm, and 355 nm could be used to form breakdown arcs in water, with the lowest breakdown thresholds of 110 J/cm 2 or 14 GW/cm 2 at 532 nm in the green. In laboratory-scale laser triggering experiments with a 170-kV pulse-charged water switch with a 3-mm anode-cathode gap, we demonstrated that ~90 mJ of green laser energy could trigger the gap with a 1-σ jitter of less than 2ns, a factor of 10 improvement over the jitter of the switch in its self breaking mode. In the laboratoryscale experiments we developed optical techniques utilizing polarization rotation of a probe laser beam to measure current in switch channels and electric field enhancements near streamer heads. In the final year of the project, we constructed a pulse-power facility to allow us to test laser triggering of water switches from 0.6-MV to 2.0 MV. Triggering experiments on this facility using an axicon lens for focusing the laser and a switch with a 740 kV self-break voltage produced consistent laser triggering with a + 16-ns 1-σ jitter, a significant improvement over the + 24-ns jitter in the self-breaking mode.

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“…A linearly-polarized light wave propagating through water in the presence of a longitudinal magnetic field will under go a rotation in the plane of its polarization 27 by an angle α:…”

Section: Measurement Of the Current In A Water Switch Using The Faradmentioning

confidence: 99%

Laser triggering of water switches in terrawatt-class pulse power accelerators.

Woodworth¹,

Johnson

Wilkins

et al. 2005

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“…The output from an amplified Korad K-IQ pulsed ruby laser (180 mJ output with a pulse width of 40 ns) was split into a 'scene' beam passing through the discharge region and a reference beam which were then recombined at a holographic plate (Agfa IOE75). The method is described in more detail by Jahoda and Sawyer (1971). Background fringes were incorporated for ease of interpretation and accuracy.…”

Section: (E) Holographic Interferometrymentioning

confidence: 99%

The Effects of Preionization Level on a ?Stabilized? Z-pinch

Silawatshananai¹,

Anderson²,

Brennan³

et al. 1980

Aust. J. Phys.

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“…There are two important advantages that the interferometric set-up used here has over other more commonly used interferometers (7). The first advantage is the minimal cost of the laser, detection system, and optics resulting from the use of a He-Ne CW laser light source (A=6328A).…”

Section: Experimental Approachmentioning

confidence: 99%

Studies of end loss from a theta pinch using a Twyman--Green interferometer. Scientific report 77-4

Freeman¹

1977

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The transient rate of flow of plasma from the ends of a short, high density, low temperature linear theta pinch was studied experimentally and analytically. Diagnostic devices were used to study the discharge and plasma properties; these included a Rogowski coil, a magnetic field probe and a Twyman-Green double pass interferometer which was illuminated by a 7 mW He-Ne laser. The interferometer was used to monitor the passage of fringes with respect to time at two radial positions simultaneously by the use of a photodetector consisting of two fast silicon photodiodes with supporting circuitry. One complete fringe represented a change in number density of 2.942xl0 16 cm" 3 .Compatible interpretation of the above-mentioned diagnostics allowed evaluation of the loss rate of plasma. The major uncertainty in obtaining 1/e particle end loss times from the Twyman-Green interferometric data was associated with lack of data on the density profile. Two different techniques were developed to provide estimates of the profile. These led to loss times estimates of 1.82 usee and 2.85 usee for a 50 millitorr fill pressure of H_, and 2.39 usee and 2.81 psec for a 65 millitorr fill pressure. These loss times were compared with: results obtained from magnetic field probe data on plasma column oscillation which indicated the loss rate; loss times analytically determined by scaling experimental results from a larger theta pinch; and loss time predicted by a zero dimensional computer code. It was determined that, for the 65 millitorr fill pressure, agreement between loss time predicted by these four techniques was good; however, both experimental uncertainties and loss time uncertainties were greater for the 50 millitorr fill pressure.IV

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11. Optical Refractivity of Plasmas

Cited by 29 publications

References 49 publications

Laser triggering of water switches in terrawatt-class pulse power accelerators.

Laser triggering of water switches in terrawatt-class pulse power accelerators.

The Effects of Preionization Level on a ?Stabilized? Z-pinch

Studies of end loss from a theta pinch using a Twyman--Green interferometer. Scientific report 77-4

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