Browsing by Author "Valdivia, M. P."

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    Considerations of a high repitition Capillary Discharge operated in nitrogen as a water-window X-ray microscope source
    (IEEE, 2009) Wyndham, Edmund; Favre Domínguez, Mario; Valdivia, M. P.; Valenzuela Ahumada, Julio César
    The capillary discharge is a very bright radiation source. When operated as a ns discharge at a peak current of order 10 kA and at a high repetition rate of order 200 Hz a very bright source at 13.5 nm is obtained. We present a series of observations that will extend the use of the discharge as a source of He-like nitrogen emission at 2.89 nm as a possible source for a water window soft X-ray microscope. A successful source depends on intense axial electron beams generated by the transient hollow cathode mechanism. These e-beams greatly enhance the plasma X-ray emission above that of a quasi Maxwellian distribution. Crucial to the practical realization of such a source is extremely low inductance geometry, effective heat removal and a ceramic wall and electrode heat loading that avoids ablation and impurities in the plasma. Observations of the time resolved optical spectrum from both ends of the plasma together with filtered X-ray diodes and a Faraday cup permit the verification of model parameters and also verify whether the wall loading is not evaporating the surface. Four capillary lengths and internal diameters are explored. Furthermore the electrical circuit based on low cost IGBT's is presented and a drive configuration that minimizes transformer magnetization losses that in other configurations is deposited in the plasma causing wall evaporation and contamination due to damped current oscillations over a period well after the main plasma discharge.
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    Hollow Cathode Electron Beam Formation and Effects on X-Ray Emission in Capillary Discharges
    (2015) Valdivia, M. P.; Wyndham, Edmund; Favre Domínguez, Mario
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    Observations of soft x-ray emission and wall ablation in a fast low-energy pulsed capillary discharge
    (2013) Valdivia, M. P.; Wyndham, Edmund; Ramos Moore, Esteban; Ferrari, P.; Favre Domínguez, Mario
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    Soft X-Ray Emission Analysis Of A Pulsed Capillary Discharge Operated In Nitrogen
    (2014) Valdivia, M. P.; Wyndham, Edmund; Favre Domínguez, Mario; Bhuyan, Heman; Valdivia, M. P.; Wyndham, Edmund; Favre Domínguez, Mario; Bhuyan, Heman
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    Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited)
    (2016) Valdivia, M. P.; Stutman, D.; Stoeckl, C.; Mileham, C.; Begishev, I. A.; Theobald, W.; Bromage, J.; Regan, S. P.; Veloso Espinosa, Felipe Eduardo; Muñoz Cordovez, G.; Vescovi, M.; Valenzuela Villaseca, V.; Klein, S. R.
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    Talbot-Lau x-ray deflectometer: Refraction-based HEDP imaging diagnostic
    (AIP Publishing, 2021) Valdivia, M. P.; Stutman, D.; Stoeckl, C.; Theobald, W.; Collins, G. W.; Bouffetier, V; Vescovi, M.; Mileham, C.; Begishev, I. A.; Klein, S. R.; Melean, R.; Muller, S.; Zou, J.; Veloso, F.; Casner, A.; Beg, F. N.; Regan, S. P.
    C Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High Energy Density Physics (HEDP) experiments. X-ray backlighter targets have been evaluated for Talbot-Lau X-ray Deflectometry (TXD). Cu foils, wires, and sphere targets have been irradiated by 10-150 J, 8-30 ps laser pulses, while two pulsed-power generators (similar to 350 kA, 350 ns and similar to 200 kA, 150 ns) have driven Cu wire, hybrid, and laser-cut x-pinches. A plasma ablation front generated by the Omega EP laser was imaged for the first time through TXD for densities >10(23) cm(-3). Backlighter optimization in combination with x-ray CCD, image plates, and x-ray film has been assessed in terms of spatial resolution and interferometer contrast for accurate plasma characterization through TXD in pulsed-power and high-intensity laser environments. The results obtained thus far demonstrate the potential of TXD as a powerful diagnostic for HEDP. Published under an exclusive license by AIP Publishing.
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    X-ray backlighter requirements for refraction-based electron density diagnostics through Talbot-Lau deflectometry
    (2018) Valdivia, M. P.; Veloso, F.; Stutman, D.; Stoeckl, C.; Mileham, C.; Begishev, I. A.; Theobald, W.; Vescovi, M.; Useche Duque, Wilmer Eleazer; Regan, S. P.; Albertazzi, B.; Rigon, G.; Mabey, P.; Michel, T.; Pikuz, S. A.; Koenig, M.; Casner, A.