Alignment of Electron Gun for X-Ray Photoelectron Spectroscopy Using a Faraday Cup with Two Sharp Tungsten Edges

The electron gun is a critical component of the X-ray source in X-ray photoelectron spectroscopy (XPS) systems, responsible for generating and directing an electron beam to the target from which X-rays emit. Precise alignment of the electron gun is fundamental for XPS analysis because misalignment can lead to electron beam position shift and reduce signal intensity when the objective lens current (OLC) changes slightly. This work proposes a new electron beam gun alignment method utilizing a Faraday cup fitted with two sharp tungsten edges. Following mechanical alignment, the electrical alignment parameters are optimized incrementally, while the corresponding positions and shapes of beam spots at different OLCs are measured concurrently. The electron beam alignment is considered completed when all the measured beam spots maintain a consistent center position and exhibit regular circular shapes. Employing this method, precise alignment of the electron gun can be accomplished in two types of scenarios: when the beam spot is about 52 μm or 8 μm. The alignment is also verified by a series of images captured by a camera when the electron beam bombards tungsten. This is a promising alignment method for other electron or ion guns with a similar beam size.