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Retarding Field Analyzer
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| product name: | Retarding Field Analyzer |
| product category: | Ion beam diagnostics |
| catalog no.: | 21005 |
| datasheet: |  n/a |
The Retarding Field Analyzer (RFA) is a electro static energy analyzer and allows to measure the kinetic energy distribution of charged particles. The analyzer can be mounted on a linear feed trough on a CF 160 flange vertically, but also as an end cup fitting in a CF 100 flange. The RFA realizes kinetic energy distribution measurements up to 15 kV per charge state.
The analyzer features a collimator with changeable apertures of 1 mm, 2 mm or 3 mm diameter for different energy resolution and a length of 50 mm. The analyzing unit consists of three meshes, with the central mesh set on high potential, and a Faraday cup for current measurement. The distance between each mesh is 20 mm.
The functional principle of the RFA is as follows. The ion or electron current is measured by stepwise increasing the retarding potential, and measured current is plot vs. retarding potential (see figure measured curves). The so realized plot Iion – URFA curve is differentiated and fitted with a Gaussian. The center energy of the charge particles Em is defined as the center position of the Gaussian. The energy spread of the charge particles \Delta E is defined as the full width half maximum (FWHM) of the Gaussian.
Example:
Measured Iion – URFA curves for different electron currents was measured at a Dresden EBIS-A with Ar8+. The energy distribution for Ie = 50 mA is shown in the spectrum. (Different electron currents results in a different space charge potential of the electron beam. Therefore the center energy of the ions decreases with increasing electron current.
Recommended equipment:
- computer control unit
- RFA power supply
- electrometer for current and charge measurement
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