The PHOIBOS 150 NAP Analyzer is a true 180° hemispherical energy analyzer with 150 mm mean radius. The analyzer, the lens system, and the detector are surrounded by two layers of 2 mm thick µ-metal to screen external magnetic fields down to an uncritical level. For ultimate performance, the analyzer and lens system are constructed entirely from non-magnetic materials inside the µ-metal shielding.
Electron Spectrometer Design
The transfer optics are a crucial part of the NAP electron spectrometer design. The first aperture, or nozzle, is shaped conically with a half angle of 35 °. This aperture, with a diameter of down to 0.3 mm, maximizes the electron collection efficiency, using an full acceptance angle cone of 44°.
Differential Pumping System
The PHOIBOS 150 NAP consists of a differentially pumped electrostatic pre-lens, with a three-stage differentially pumped PHOIBOS 150 analyzer. Thus, the design concept provides four separate pressure stages separated by apertures. The first pumping stage (pre-lens) is separated from the analytic chamber by a nozzle with a customizable opening at the tip with diameters between 0.3 mm and 1 mm. By using a turbopump on the pre-lens stage, a pressure difference of four orders of magnitude (compared to the analytic chamber) is possible.
The first and second stages are separated by an aperture with a 4 mm diameter. An in-lens gate valve allows a high-vacuum seal between of the PHOIBOS 150 Analyzer and NAP pre-lens and enables venting of the analysis chamber and pre-lens without venting the energy analyzer.
This second stage represents the first part of the electrostatic lenses of the PHOIBOS. The front and rear parts of the electrostatic lenses are separated by an iris aperture. The third pumping stage is situated behind the iris. The fourth and final pumping stage contains the hemispheres and detector.
For Imaging NAP XPS the pre lens can be equipped with the SPECS NAP-XPS Imaging Lens Module that supports two different operation modes, one optimized for lateral resolution and one for transmission. In the lateral resolving mode the acceptance angle can be freely adjusted between +/- 3° to +/- 8° giving an ultimate lateral resolution of better than 10 µm with an acceptance area of 0.6 mm in diameter.