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Enrique Valderrama

  • PhD in Physics
  • Assistant Professor
  • Oral Roberts University
  • 10PublicationsNumber of items in Enrique's My Publications folder on Mendeley.
  • 18Followers

About

Doctoral Research Experience: {Broad Area of Research: Experimental Plasma Physics and Thin Films deposition} After completing my undergraduate studies in physics in 2004, I began my doctoral research work at PUC Chile. My focus has been experimental research in plasma physics, working with pulsed plasma discharges (plasma focus, capillar) and continuous plasma production using radiofrequency power. My activities included building, testing and improving diagnostic techniques to characterize and study high and low density plasmas, as well as applying plasma science to material processing technology. I fabricated faraday cups and, using time of flight technique, I studied the anisotropic spatial distribution of ions after the disruption of a z-pinch in a plasma focus discharge. Using methane, we characterized the state of charge, energy and ux density of carbon and hydrogen ions following the high electromagnetic eld created by the pinch. Complementary with this, we investigated how the irradiation of high energy carbon ions on different solid targets produces a variety of nanostructured composites, depending on the angle of emission of the beam. This work produced several publications in peer-reviewed journals. In my thesis research, I set up a capacitively coupled radiofrequency plasma. I characterized the discharge using a self-compensated Langmuir probe of my own design and construction. Using plasma enhanced chemical vapor deposition (PECVD), I produced diamond-like carbon coatings on a silicon substrate mounted on the cathode, thereby obtaining thin films of 5 nm thickness, with a density of 2.6 gr/cm3. Using a third electrode, silicon and titanium substrates were biased with negative pulses for the collection of carbon spheres, created in an acetylene/hydrogen radiofrequency Dusty Plasma. This experiment produced carbon coatings with micro/nano-structures at room temperature. Using Raman spectroscopy, we observed an increase in carbon-hydrogen bondings on the samples, as the flux of hydrogen was incremented in the discharge, allowing the functionalization of the coating in a single step. My doctoral thesis Plasmas de Radiofrecuencias: un diagnóstico y dos técnicas para producir DLC, con y sin contenido micro/nano-estructurado 2, was written under the guidance of Prof. Mario Favre. On September 7-11 2009, I attended the 10th International Workshop on Plasma-Based Ion Implantation and Deposition (PBII&D) held in Sao José dos Campos, SP, Brazil. I presented a paper titled Sub-Micron Size Carbon Structures Synthesized Using Plasma Enhanced CVD, Without External Heating and No Catalyzer Action., published in Surface and Coating Technology in 2011 a special issue devoted to the PBII&D workshop. Professional Experience: {February 2010 to February 2012 Alameda Applied Sciences Corporation(AASC); Research Scientist reporting directly to CEO, M. Krishnan Research on coatings for superconductor radio-frequency accelerators} In February of 2010, I joined Alameda Applied Sciences Corporation (AASC), to work in the deposition of superconducting thin-films produced by energetic condensation using a plasma discharge. At AASC I studied the growth of metallic crystal films of Nb;Nb3Sn; andMo3Re, produced by a High Vacuum Cathodic Arc in a coaxial geometry in the presence of a low DC magnetic Field(CEDTM). Collaboration with Thomas Jefferson National Accelerator Facility (Jefferson Lab) and Norfolk State University (NSU) permits the study of the epitaxial growth of single crystal niobium films using a state-of-the-art metrology suite(resistivity at cryogenic temperature, SEM, XRD, EBSD, TEM, SIMS). Dense films with non measurable defects were grown on several crystal and amorphous substrates where superconducting properties of the films were correlated with the crystal structure. World record results of RRR(587) on MgO(100) substrates have been achieved, reaching values comparable to those in bulk niobium. Also we study the vortex penetration and SRF transport of Nb films on different cryogenic scenarios, through a new collaboration with Los Alamos National Laboratories(LANL) and The High Energy Accelerator Research Organization on Japan (KEK). Again the results of Nb thin films have been unprecedented, obtaining performance of the best Nb bulk(Bpen~180mT). This open new possibilities for the advance of SRF cavities where the use of copper cavities with a thin film of Niobium will allow higher field operation at lower frequency(from 1.3GHz to 650 MHz) at permissible costs. Several publications have resulted from this work, in the Journal of Applied of Physics, Superconductor Science and Technology, Advances in Cryogenic Engineering and several conferences. My involvement in a wide variety of experiments has provided me with a spectrum of laboratory skills in high-power and high vacuum diagnostics and instrumentation, as well as surface science material characterization. My hands-on activities have provided extensive experience in PVD, PECVD and PBII&D deposition techniques.

Recent publications

  • Very high residual resistivity ratios of heteroepitaxial superconducting niobium films on MgO substrates

    • Krishnan M
    • Valderrama E
    • Bures B
    • et al.
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    N/ACitations
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  • High energy ion beam irradiation on titanium substrate in a pulsed plasma device operating with methane

    • Bhuyan H
    • Favre M
    • Valderrama E
    • et al.
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    N/ACitations
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Professional experience

Assistant Professor

Oral Roberts University

August 2013 - Present

Adjunct Professor

Oral Roberts University

August 2012 - Present

Scientist

AASC

February 2010 - February 2012(2 years)

Education

PhD in Plasma Physics

Catholic University of Chile

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