Surface Concept MCPD40, Руководство пользователя

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1-Channel MCP Detector MCPD40 Manual | Surface Concept GmbH
6.4 Operation
• A dry-pumped or well-trapped/diffusion-pumped operating environment is desirable. A poor vacuum
environment will most likely shorten MCP life or change MCP operating characteristics.
• A pressure of 1E-6mbar or better is preferred. Higher pressure can result in high background noise or
even to damaging due to ion feedback or to an electrical breakdown.
• Apply voltages as defined in Chapter 4 . If fluctuations appear, damage or contamination should
be suspected and the voltage should be turned off. The assembly should then be inspected before
proceeding.
• Voltage across single MCPs should not exceed the maximum voltage given in the specification sheet of
the detector. Higher potentials may result in irreversible damage.
• MCPs can be degraded by exposure to various types of hydrocarbon materials which raise the work
function of the surface, causing gain degradation.
• Operation at higher temperatures (> 50°C) will cause gain degradation.
• MCPs may degas for quite a while during operation. The pressure increase also depends on the number
of initial particles given to the MCP (e.g. pressure increase from 5E-10mbar up to 5E-9mbar for a new
chevron MCP stack). A degas procedure for MCPs is described in Chapter 6.6 .
6.5 MCP Lifetime and Operation Voltage
The lifetime of the MCPs is determined by the MCPs gain degradation over time, whereas the gain
degradation is a function of the extracted output charge. Therefore the lifetime of the MCPs strongly
depends on the count rate applied to the detector over time.
The typical gain degradation of a MCP is shown in Figure 6 as a function of extracted output charge in
terms of coulombs per square centimeter.
Figure 6: Typical gain degradation of MCPs as function of the extracted output charge.