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Characterization: CNM Proposal

Investigate changes in surface composition and structure under electron exposure to determine ageing factors in materials. Equipment includes non-destructive probe, SEM, and AES. Procedure involves exposure to varying electron fluences and sample heating for thermal desorption analysis. Gas exposure will examine effects on composition. Detailed discussion on equipment procurement and planned measurements.

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Characterization: CNM Proposal

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  1. Characterization: CNM Proposal Slade J. Jokela, Igor V. Veryovkin, Alexander V. Zinovev

  2. Purpose • Our goal is to determine what is responsible for the ageing of secondary electron emissive materials. • Will examine changes in surface composition and structure under electron exposure • This experiment will not perfectly emulate normal MCP ageing as it must be carried out in a limited time. High electron flux must be used to complete experiment in the allotted time.

  3. Equipment • Four-point non-destructive probe (can be used as STM) • SEM for positioning of probe can be used for surface examination • Gemini column for high resolution (energy and spatial) mapping of surface chemical composition using Ager Electron Spectroscopy (AES).

  4. Procedure • Examine sample under SEM, STM, and AES • Determine Secondary Emissive Yield (LEED System) • Expose small sample area to some fluence of electrons from (LEED System) • Start with large fluence to see if there is a detectable change, then perform smaller fluence exposures to determine dynamics • Repeat…

  5. Variations • Sample heating up to 500 °C for examination of thermal desorption/diffusion . • Especially carbon • Gas exposure for examining effects on composition and morphology. • Primarily interested in atmospheric gasses

  6. What needs to be done • Equipment needs to be checked out by CNM • Voltage Sources • Plan on starting measurements in July or August. • Still need to check calendar at CNM

  7. Vacuum Transfer System • This is for the characterization instrument (XPS, UPS, LEED) in building 200-D110. • Discussion between Hau Wang, myself, and Igor have resulted in shared costs for this hardware • Some items remain to be purchased • Vacuum Chamber ($1840) • Machining (Estimates must be made)

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