Vacuum Technology Book, Volume II

Sector field mass spectrometers for detecting helium are today integrated in leak testers with an automatically controlled vacuum system. As a result the operator does not have to worry about the functional capability of the spectrometer. We would draw your attention at this point to the importance of the cleanliness of the interior surfaces for maintaining a high detection sensitivity.

  • Deposits can result in local space charges when bombarded with scattered ions. These charges deflect the path of the helium ions and reduce the number of ions reaching the detector.
  • Deposits on the micro channel plate reduce the yield of secondary electrons and so lower the amplification factor.

While it is possible to simply clean the interior walls of the spectrometer, contaminated micro channel plates must be replaced. It is extremely important for objects and equipment to be clean so as to maintain the high detection sensitivity of the instruments.

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