Performance of the closed orbit feedback systems with spatial model mismatch

Mirza, Sikander M.; Singh, Rahul; Forck, P.; Lorentz, B.

doi:10.1103/physrevaccelbeams.23.072801

Cited by 7 publications

(2 citation statements)

References 16 publications

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“…analytical Jacobian, if this mismatch is manageable then the fitting will still converge. This has similarities to how Closed Orbit Feedback (COFB) correction with model mismatch works [84].…”

Section: Fitting the Orbit Response Matrixmentioning

confidence: 67%

Efficient modeling and mitigation of quadrupole errors in synchrotrons and their beam transfer lines

Vilsmeier

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This thesis investigates the problem of estimating quadrupole errors on synchrotrons as well as how to minimize the influence of quadrupole errors for beam transfer lines (beamlines). It emphasizes the importance to treat possible error sources in all parts of an accelerator in order to provide constantly high beam quality to the experimental stations. While the presented methods have been investigated by using the example of the SIS18 synchrotron and the HEST beamlines at GSI Helmholtz Centre for Heavy Ion Research, they are equally relevant for the future synchrotrons and beamlines of the Facility for Antiproton and Ion Research in Europe (FAIR). Part 1 discusses the problem of estimating quadrupole errors via orbit response measurements at synchrotrons. An emphasis is put on investigating the influence of the availability of steerer magnets and beam position monitors (BPMs) on the solvability of the inverse problem as well as on the propagation of measurement uncertainty for the estimation of quadrupole errors. The problem is approached via analytical considerations as well as via dedicated simulation studies. By developing an analytical expression for the Jacobian matrix, the theoretical boundaries for the solvability of the inverse problem are derived. Moreover, it is shown that the analytical expressions for the Jacobian matrix can be used during the fitting procedure to achieve a significant improvement in the computational efficiency by a factor $N_{steerers} \times N_{quadrupoles}$, where $N$ denotes the number of lattice elements of the respective type. The presented results are tested via dedicated measurements at the SIS18 synchrotron. Part 2 discusses – complementary to part 1 – the influence of quadrupole errors in beam transfer lines with respect to the beam quality requirements given by the experimental stations. A preventive approach is presented which allows to minimize the influence of possible quadrupole errors on the degradation of beam quality. By identifying and selecting robust quadrupole configurations, a stable operation of the beamline can be enabled and the time needed by operators to readjust the beamline parameters can be reduced. The concept of beamline robustness is developed and is studied with the help of dedicated simulations. The simulation results are used to identify certain properties that distinguish robust from nonrobust quadrupole configurations. Also, various methods for improving the computational process of identifying robust quadrupole configurations are presented. The methods and results are tested via dedicated measurements at two different beamlines at GSI Helmholtz Centre for Heavy Ion Research and at Forschungszentrum Jülich.

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Section: Fitting the Orbit Response Matrixmentioning

confidence: 67%

Efficient modeling and mitigation of quadrupole errors in synchrotrons and their beam transfer lines

Vilsmeier

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“…The contributions of the work presented in this chapter are listed as below, out of which many are also published in [88].…”

Section: Summary and Contributionsmentioning

confidence: 99%

Closed orbit feedback system for the fast ramping hadron synchrotrons

Mirza¹

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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.

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Beam position measurement system at HIRFL-CSRm

Xiao

Mao

et al. 2023

Nuclear Engineering and Technology

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Performance of the closed orbit feedback systems with spatial model mismatch

Cited by 7 publications

References 16 publications

Efficient modeling and mitigation of quadrupole errors in synchrotrons and their beam transfer lines

Efficient modeling and mitigation of quadrupole errors in synchrotrons and their beam transfer lines

Closed orbit feedback system for the fast ramping hadron synchrotrons

Beam position measurement system at HIRFL-CSRm

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