Pforr, Jonas (2020)
Strahldynamik und -diagnose am Energie-rückgewinnenden S-DALINAC.
Technische Universität Darmstadt
doi: 10.25534/tuprints-00011900
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

This dissertation covers beam dynamics and beam diagnostics, which are two essential parts of accelerator development at the S-DALINAC. In the scope of this work simulations of beam dynamics were conducted, a system for emittance measurements was set up and used and several other measurements were performed and analysed. This firstly includes beam dynamics simulations of the injector and of the recirculating main accelerator, which were used to investigate possible sources of error for an emittance growth. Furthermore, a simulation for the realisation of the once-recirculating ERL-mode (Energy Recovery Linac) was prepared. An improved analysis of the beam transport shall also be reached by the newly installed emittance measurement setups. By enabling an emittance determination at different positions along the beamline, changes of this central parameter can be monitored. On the one hand, this extends the operator’s options of tuning the beam, as now the emittance can be optimized. On the other hand, regular measurements improve the reproducibility of accelerator settings. For beam dynamics simulations emittance measurements are useful as well, as they can both serve the verification of calculations and provide data for starting conditions for further simulations. By using the new emittance measurement setups, a variety of measurements were conducted in the course of this work. In this process, first of all a comparison of the established screens with the newly installed transition radiation targets was conducted. Furthermore, behind the injector of the S-DALINAC a dependence of the emittance on the beam current was observed. The setups in the recirculations were commissioned and used for emittance measurements as well. Additionally, a measurement of transverse and longitudinal dispersion in thrice-recirculating operation was conducted and analysed. Unexpected non-linear contributions to the dispersion could be observed there. By using a beam dynamics simulation they can be explained at least qualitatively. The resulting understanding was also used to further develop the beam tuning procedures. Finally, the investigation of the beam break-up (BBU) threshold current shall be mentioned. An experimental search for the threshold current was conducted both before and after the installation of the third recirculation of the S-DALINAC. In the once-recirculating operation mode, we managed to increase the injected beam current to 20 µA, which is the maximum allowed value within the limits of the operation license, and to recirculate this almost loss-free without observing BBU.

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