Validation of Enhanced Electron Yield Measurements of Low-Conduct

Utah State University DigitalCommons@USU Presentations Materials Physics Spring 2016 Validation of Enhanced Electron Yield Measurements of LowConductivity, High-Yield Materials Justin Christensen Utah State University Gregory Wilson Utah State University JR Dennison Utah State Univesity Follow this and additional works at: https://digitalcommons.usu.edu/mp_presentations Part of the Condensed Matter Physics Commons Recommended Citation Christensen, Justin; Wilson, Gregory; and Dennison, JR, "Validation of Enhanced Electron Yield Measurements of Low-Conductivity, High-Yield Materials" (2016) Utah State University Student Research Symposium Presentations Paper 131 https://digitalcommons.usu.edu/mp_presentations/131 This Presentation is brought to you for free and open access by the Materials Physics at DigitalCommons@USU It has been accepted for inclusion in Presentations by an authorized administrator of DigitalCommons@USU For more information, please contact digitalcommons@usu.edu Validation of Improvements to Electron Yield Measurement of LowConductivity, High-Yield Materials Justin Christensen JR Dennison What is Yield? - Backscattered Electron - Primary Electron - Secondary Electron (@EQ σ (/ (@ID charge (@SUB emit)) (@ID charge (@SUB inc)))) + Spacecraft Charging Simulating Space Yield of conductors DC Beam Collector Bias Grid Inner Grid (@EQ σ (/ (@ID charge (@SUB emit)) (@ID charge (@SUB inc)))) Emitted Stage Sample A A A A +50 V V Bias Charging - +++++++++ Electron Microscopy How we fix it? Fast Low-Current Measurement Pulsed Electron Beam Charge Neutralization It worked, kind of Problems Problems • Tungsten filament • Grounded inner grid • Flood gun, UVLED ground loops • UVLED ~290 nm, low intensity Improvements Changes • Tantalum disk filament • Biased inner grid • Isolated Flood gun, and UVLED • UVLED ~250nm high intensity Improvements Noise reduced Less charging Collaborative Standard Tests Gold Symbol Facility Refs ● ■ □ ▲ ∆ CSIC SEY Facility (contin.) Onera—DEESSE Facility Onera—DEESSE (Etched) LaSeine—TEY Facility (March 2) LaSeine—TEY Facility (March 6) USU—SEEM Facility (pulsed) USU—SEEM Facility (contin.) Round Robin Average Values Standard: Thomas & Pattinson 1-3 4-5 4-5 6-7 6-7 8-9 8,15 ♦ ◊ ● 11 σmax Measured Values Emax (eV) E1 (eV) E2 (eV) 2.06±0.02 1.81±0.03 1.46±0.03 2.48±0.03 2.3±0.1 1.54±0.08 2.24±0.02 2.0±0.4 2.21±0.02 600±20 360±20 1250±50 200±20 240±30 700±30 650±50 600±460 900±30 NA ~6000 ~6000 NA NA 4000±200 NA 5000±1000 NA 24±1 28±1 NA NA 12±2 55±3 NA 24±9 50±10 HOPG Graphite Symbol Facility Refs ● ■ ▲ CSIC SEY Facility LaSeine—TEY Facility Onera—DEESSE Facility USU—SEEM Facility (clean) Round Robin Average Values Standard 1: Whetten Standard 2: Wintucky 1-3 4-5 6-7 8,9,15 ♦ ● ● 12 13 σmax Measured Values Emax (eV) E1 (eV) E2 (eV) 1.38±0.02 1.48±0.05 1.28±0.05 1.4±0.1 1.39±0.08 1.01±0.01 NA 215±5 270±20 190±10 200±30 220±36 300±20 NA 629±10 610±40 552±20 895±20 670±150 350±20 330±20 68±1 60±2 69±1 40±2 59±13 250±30 NA Future Work •Current analysis program could show how yield changes over the course of a pulse (~1% of total pulse charge) •Gold data should show no charging effects •Zero charge plateau Conclusion • Charge Neutralization • Repeatable measurements • Better analysis methods • Collaborations are underway to improve calibration standards Scan code to access the USU Materials Physics Group papers and presentations at digitalcommons.usu.edu/mp/ Outline Background Improvements Future Work • What is Yield • Measuring Yield • Conductors • Insulators • Measurement • Neutralization • Analysis • Verify Model • Various Insulators Improvements Problems • Tungsten filament • Grounded inner grid • Flood gun, UVLED ground loops • UVLED ~290 nm, low intensity • Emitted charge calculation A Improvements Problems • Tungsten filament • Grounded inner grid • Flood gun, UVLED ground loops • UVLED ~290 nm, low intensity • Emitted charge calculation A .. .Validation of Improvements to Electron Yield Measurement of LowConductivity, High -Yield Materials Justin Christensen JR Dennison What is Yield? - Backscattered Electron - Primary Electron. .. how yield changes over the course of a pulse (~1% of total pulse charge) •Gold data should show no charging effects •Zero charge plateau Conclusion • Charge Neutralization • Repeatable measurements. .. V Bias Charging - +++++++++ Electron Microscopy How we fix it? Fast Low-Current Measurement Pulsed Electron Beam Charge Neutralization It worked, kind of Problems Problems • Tungsten filament