Detectors and Analysers

PHOIBOS 150 NAP Analyser

The electron energy analyser is a "PHOIBOS 150 NAP" hemispherical analyser supplied by SPECS, Berlin, Germany (left image). The analyser axis is at an angle of 60.1° with respect to the beam and tilted 30° with respect to the horizontal, i.e. close to the magic angle with respect to the polarization vector (right image). The entire assembly of interface ange and analyser is mounted on a "sledge" which can be moved parallel to the analyser axis. This way the cone-to-beam/sample distance can be changed without having to re-align the endstation, once the beam and the analyser axis have been adjusted such that they intersect in one point. The typical working distance between cone and sample is 0.2 - 0.3 mm. Compensation of residual magnetic fields is achieved via three pairs of Helmholtz coils, are individually controlled as a function of electron energy through the control unit of the electron energy analyser.

Total Electron Yield – Drain current for NEXAFS

The entry cone of the analyser's pre-lens has an aperture of 0.3mm and is isolated from ground to allow collection of TEY NEXAFS by measuring the drain current through a Stanford Research SR 570 current amplifier (image below). In total, four currents can be recorded simultaneously:

^{Current Amplifier Squemes: left, centre and right}