Browsing by Author "Valenzuela Ahumada, Julio César"

Now showing 1 - 12 of 12
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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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    Considerations of a high repitition capillary discharge operated in nitrogen as a water-window X-ray microscope source
    (2009) Wyndham, Edmund; Favre Domínguez, Mario; Valdivia Leiva, María Pía; Valenzuela Ahumada, Julio César
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    Current measurement by Faraday effect on GEPOPU
    (2014) Correa Poblete, Noemí Patricia; Chuaqui, Hernán; Wyndham, Edmund; Valenzuela Ahumada, Julio César; Favre Domínguez, Mario; Bhuyan, Heman; Veloso Espinosa, Felipe Eduardo; Correa, N.; Chuaqui, Hernán; Wyndham, Edmund; Valenzuela Ahumada, Julio César; Favre Domínguez, Mario; Bhuyan, Heman; Veloso Espinosa, Felipe Eduardo
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    Current measurement by Faraday effect on GEPOPU
    (2012) Correa Poblete, Noemí Patricia; Chuaqui, Hernán; Wyndham, Edmund; Veloso Espinosa, Felipe Eduardo; Valenzuela Ahumada, Julio César; Favre Domínguez, Mario; Bhuyan, Heman
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    Experimental observations in compact capillary discharges
    (2008) Favre Domínguez, Mario; Wyndham, Edmund; Leñero Merchant, Ana María; Suzuki, F.; Valenzuela Ahumada, Julio César; Avaria Saavedra, Gonzalo Felipe; Ruiz, M.; Bhuyan, Heman; Chuaqui, Hernán; Choi, P.
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    Fast plasma discharge capillary design as a high power throughput soft x-ray emission source
    (2010) Wyndham, Edmund; Favre Domínguez, Mario; Valdivia Leiva, María Pía; Valenzuela Ahumada, Julio César; Chuaqui, Hernán; Bhuyan, Heman
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    Implementation of moiré-schlieren deflectometry on a small scale fast capillary plasma discharge
    (2012) Valenzuela Ahumada, Julio César; Wyndham, Edmund; Chuaqui, Hernán; Cortes, D.S.; Favre Domínguez, Mario; Bhuyan, Heman
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    MA-class linear transformer driver for Z-pinch research
    (2020) Conti, F.; Valenzuela Ahumada, Julio César; Fadeev, V.; Aybar, N.; Reisman, D. B.; Williams, A.; Collins, G.; Narkis, J.; Ross, M. P.; Beg, F. N.; Spielman, R. B.
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    Measurement of pulsed-power-driven magnetic fields via proton deflectometry
    (2014) Mariscal, Derek; McGuffey, Chris; Valenzuela Ahumada, Julio César; Wei, Mingsheng S.; Chittenden, J. P.; Niasse, Nicolas; Presura, Radu; Haque, Showera; Wallace, Matthew; Arias, A.; Covington, Aaron; Sawada, Hiroshi; Wiewior, Piotr; Beg, Farhat N.
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    Observations of soft X-ray emission and plasma dynamics of a compact capillary discharge operated in xenon
    (2013) Valenzuela Ahumada, Julio César; Wyndham, Edmund; Favre Domínguez, Mario; Chuaqui, Hernán
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    Study of titanium nitride film growth by plasma enhanced pulsed laser deposition at different experimental conditions
    (2021) Escalona Álvarez, Miguel Benito; Bhuyan, Heman; Ibacache, S.; Retamal Ponce, María José; Saikia, P.; Borgohain, C.; Valenzuela Ahumada, Julio César; Veloso Espinosa, Felipe Eduardo; Favre Domínguez, Mario; Wyndham Hodder, Edmund Sydenham
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    Survival of listeria strains and shelf life determination of fresh blueberries (Vaccinium corymbosum) treated with cold atmospheric plasma
    (2024) Concha-Meyer, Anibal A.; González-Esparza, Alexandra; Cullen, Patrick J.; Veloso Espinosa, Felipe Eduardo; Favre Domínguez, Mario; Valenzuela Ahumada, Julio César; Toloza, Lorena; Niemira, Brendan A.
    Fresh blueberries are delicate, hand-picked, packaged, and refrigerated fruits vulnerable to spoilage and contamination. Cold atmospheric plasma (CAP) is a promising antimicrobial technology; therefore, this study evaluated the CAP treatment effect on acid-tolerant Listeria innocua and Listeria monocytogenes and evaluated changes in the quality of the treated fruit. Samples were spot-inoculated with pH 5.5 and 6.0 acid-adapted Listeria species. Samples were treated with gliding arc CAP for 15, 30, 45, and 60 s and evaluated after 0, 1, 4, 7, and 11 days of storage at 4 °C and 90% humidity for the following quality parameters: total aerobic counts, yeast and molds, texture, color, soluble solids, pH, and titratable acidity. CAP treatments of 30 s and over demonstrated significant reductions in pathogens under both the resistant strain and pH conditions. Sixty-second CAP achieved a 0.54 Log CFU g−1 reduction in L. monocytogenes (pH 5.5) and 0.28 Log CFU g−1 for L. monocytogenes (pH 6.0). Yeast and mold counts on day 0 showed statistically significant reductions after 30, 45, and 60 s CAP with an average 2.34 Log CFU g−1 reduction when compared to non-CAP treated samples. Quality parameters did not show major significant differences among CAP treatments during shelf life. CAP is an effective antimicrobial treatment that does not significantly affect fruit quality.