Beam threading for the MAX IV accelerators

Abstract: Large particle accelerators are difficult to setup. One of the first problems that can be encountered, before production configuration is found, is the beam not passing through the accelerator. The process of guiding the beam through the accelerator is called beam threading. Depending on the accelerator complexity it can take days before the beam passes for the first time. Currently the beam threading at MAX IV is performed manually. In addition to the long average time spent, the procedure of manual beam threading is labor-intensive and tiresome. An automated solution offers the advantage of greatly speeding up this process saving both time, effort and resources. For this project an automated beam threader was developed for the 3 GeV and 1.5 GeV storage rings at MAX IV. The algorithm optimizes the available corrector magnets and uses beam position monitors or an oscilloscope to get an instant information on its progress. This way only minor effort by control room personnel is needed. The typically low signal to noise ratio in the used diagnostics made noise filtering necessary. A successful decrease of the noise levels was achieved with spectral filters. Robust counting of the number of completed turns by the beam during threading from the filtered signal is developed. It is used by the automated beam threader as a metric of progress. The automated beam threader successfully functions on the MAX IV storage rings and in simulation. It performs significantly faster than the manual threading procedure and in early attempt it outperformed the fastest manual threading for half of the time of the latter.