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Update on Pulsed Secondary Electron Measurements

Update on Pulsed Secondary Electron Measurements. Slade J. Jokela, I. Veryovkin, A. Zinovev. Pulsed Electron Beam. By pulsing the electron beam we will be able to obtain accurate emission characteristics of the secondary electron emission layer Insulating materials charge over time

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Update on Pulsed Secondary Electron Measurements

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  1. Update on Pulsed Secondary Electron Measurements Slade J. Jokela, I. Veryovkin, A. Zinovev

  2. Pulsed Electron Beam • By pulsing the electron beam we will be able to obtain accurate emission characteristics of the secondary electron emission layer • Insulating materials charge over time • If charging still occurs, rapid alternating of sample potential can eliminate the charge • When sample is biased negative, SEY is measured • When sample is biased positive, no secondary electrons escape surface, allowing incident beam to eliminate the positive charge accumulated during SEY measurement

  3. Filament Emission Grid Current State of Pulsed Operations • New(er) LEED system is installed • Electron beam current can now be controlled using a Keithley SourceMeter to bias emission grid. • Elimination of emission occurs when grid is biased -30V relative to the filament.

  4. Results From New LEED • New LEED system lacks periodic noise that plagued old system; less noisy in general • Produce similar SEY profiles • The OLD scan was started with zero electron flux. The NEW scan was started after an unknown electron flux had hit the sample, hence its increased SEY.

  5. Necessary Work • Programming Keithleys to work in a pulsed mode • Meters can provide a ~150 s pulse. • May have to implement better shielding in BNC cables to reduce noise • Noise has already been reduced simply by using a new LEED system (old power supply was noisy)

  6. Pulsed Experiment Plans • Compare pulsed MgO thickness series with unpulsed measurements already gathered • Expect to see increased yield for pulsed measurements, especially for thicker samples • Perform both pulsed and continuous measurements on Al2O3. • Diamond thickfilms (relatively thick, that is)

  7. CO2 Snow Cleaning • Tests have been performed on old MCP • Old MCP tested by Matt W., contained damage from arcing. • No new macroscopic damage to surface from snow cleaning • Arranged to test on new, uncoated MCP and compare microscopic features. Once coated, performance will also be compared with an MCP that has not undergone CO2 snow cleaning.

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