Sprecher
Beschreibung
Thermal effects in optical elements as well as subtle changes in the experimental environment (e.g. airflow, humidity, vibrations) are well-known challenges affecting laser alignment. These effects tend to scale with the size and complexity of the laser systems. For high-power lasers comprising a multitude of amplification stages, the resulting long-term drifts (occurring over minutes to hours) affect both beam and laser parameters. For instance, a change in the beam pointing does not only shift the position of the laser focus in the experimental chamber but also translates into a variation of the laser pulse energy as the amplification dynamics change as well.
Monitoring these drifts at the Petawatt-class ATLAS laser at CALA prompted us to develop a modular solution for long-term beam stabilization. The stabilization system consists of separate diagnostic and control modules in between the individual amplification stages of the laser chain. Each module measures the laser near- and farfield and is capable of stabilizing both position and angle of the beam using motorized mirror mounts. The feedback loop activates automatically when a significant deviation is detected and comprises a variety of safety features. Since the stabilization algorithm is self-calibrating, each module adapts to the individual geometric settings resulting from the relative positioning of the diagnostic and control modules. Currently, a total of four stabilization units are installed in the ATLAS frontend, and (supervised) stabilization on the minute timescale has been successfully implemented. The modular software is integrated into our Tango Controls [1] based control system and is available open-source under [2]. In the next step, the modules will be used for a fully automated startup of the ATLAS frontend without manual alignment. Overall, the system improves the stability, precision, and reproducibility of the laser alignment and is therefore essential for high-class laser-plasma accelerators. This work was supported by the BMBF within project 01IS24028 and the Centre for Advanced Laser Applications.
[1] https://www.tango-controls.org/
[2] https://gitlab.lrz.de/cala-public/tangodeviceservers/pyds_pointingstabilization
