Open Access

Sajjad Hussain Mirza

• The realization of a fast and robust closed orbit feedback (COFB) system for the on-ramp orbit correction at SIS18 synchrotron of FAIR project is reported in this thesis. SIS18 has some peculiar behaviors including on-ramp optics variation, very short lengths of the ramps (200 ms to 1 s) and a cycle-to-cycle variation of beam parameters. The realized fast COFB system being robust against above mentioned features of SIS18 is a first of its kind and the course to its realization led to some novel contributions in the field of closed orbit correction. A new method relying on the discrete Fourier transform (DFT)-based decomposition of the orbit response matrix (ORM) has been introduced, exploiting the symmetry in the arrangement of beam position monitors (BPMs) and the corrector magnets in the synchrotrons. A nearest-circulant approximation has also been introduced for synchrotrons having slight deviation from the symmetry, making the method applicable to a vast majority of synchrotrons. Moreover, the performance and the stability analysis of COFB systems in the presence of ORM mismatch between the synchrotron and the feedback controller is presented. The COFB systems are divided into slow and fast regimes and a new stability criterion consistent with measurements, is introduced. The practicality of the criterion is verified experimentally at COSY Jülich and is used for the analysis of various sources of ORM mismatch at SIS18. The commissioning of the SIS18 COFB system is also reported in detail which relies on Libera Hadron as the main hardware resource for the controller implementation. The on-ramp orbit correction is demonstrated for the horizontal plane of SIS18, for the disturbance rejection up to 600 Hz.
• Thema dieser Doktorarbeit ist die Entwicklung eines Systems zur schnellen Orbitkorrektur (Englisch: closed orbit feedback, COFB) Systems und dessen Anwendung an den GSISchwerionensynchrotrons SIS18 bzw. SIS100. Das wichtigste Ziel ist es eine Ortsstabilität (RMS-Wert) unterhalb 1 mm zu erreichen insbesondere auch während der Beschleunigungsrampe; diese Ortsstabilität entspricht ca. 10% der RMS-Strahlbreite. Das COFB-System soll desweiteren möglichst breitbandig wirken können – die natürliche obere Grenzfrequenz ist hier durch die erreichbare Bandbreite der Korrektordipolmagnete gegeben. In SynchrotronLichtquellen und Hadronen-B...