Motor-driven autonomous system for controlling beamline iris diaphragm apertures

At the collinear apparatus for laser spectroscopy and applied sciences (COALA) at TU Darmstadt, collinear laser spectroscopy is applied to perform high-precision measurements of atomic transition frequencies and high voltages in an ultra-high vacuum beamline. In such laser spectroscopy beamlines, iris diaphragms are used to reduce ion beam divergence, and to ensure a good laser and ion beam overlap. Since the system that controls the diameter of the apertures presents strong hysteresis, an automated adjustment is desirable to enhance reproducibility in the aperture settings, and to reduce the effort in performing measurements where different diameters are required, especially in alternating collinear and anti-collinear measurements. To achieve this, the Iris Mover system was designed and implemented. The Iris Mover system consists of motor-driven iris apertures which can be easily controlled by users through a computer, and which accounts for hysteresis effects. Here, we explain the design process of the Iris Mover and demonstrate and discuss its functionality.