Discriminators are used by the electronic circuitry that detects and amplifies the detector signal to discriminate between X-ray peak signals and noise in the FET output. If the discriminators are set too high, then low energy peaks will be rejected with the noise. If the discriminators are set too low, the circuitry may not prevent pulse-pile up. As a result, X-ray signals that arrive in close succession may be counted as a single event - the main cause of sum peaks in the ED spectrum.

By calibrating the discriminators, the system will automatically set the discriminator levels to the optimum for efficient low energy X-ray detection, whilst avoiding pulse pile-up and sum peaks in the spectrum.

For further information on detector circuitry please refer to Scanning Electron Microscope and X-ray Microanalysis, editor: Joseph Goldstein, Publisher: Kluwer Academic/Plenum, Chapter 7. ISBN 0-306-47292-9

1.

Launch INCAMonitor and select the X-ray calibration step.

2.

Switch on the microscope electron beam and place any metal sample under the beam. From the calibration mode drop down, select the discriminators only option.

3.

Follow the on-screen instructions to ensure the beam current and dead-time for calibration are correct. The discriminator calibration will then progress automatically.

4.

On completion, save the discriminator calibration using an appropriate file name.