Real time closed orbit correction system

Yu, Li Hua; Biscardi, R.; Bittner, Jiřı́; Bozoki, E.; Galayda, J.; Krinsky, S.; Nawrocky, R.J.; Singh, Om V.; Vignola, G.

doi:10.1109/pac.1989.72926

Cited by 15 publications

(8 citation statements)

References 4 publications

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“…In the harmonic methods [1]- [3], [22]a, the harmonic content of the orbits are determined and selected harmonics are corrected. The corrector strengths are calculated, assuming that the harmonic composition of the dipole field 'errors' reflects that of the orbit.…”

Section: Algorithmsmentioning

confidence: 99%

“…Local bumps with a specified beam displacement and/or angle at a specified location can be created using three correctors [12], [18], [23]b or four correctors [5]c-d, [13], [22]e without effecting the orbit outside the correctors. This provides precise control of the beam orbit at SR sourcepoints (bending magnet or undulator) or interaction points of two beams, with a corrective bump confined to a limited section of the machine.…”

Section: Eigenvector Decompositionmentioning

confidence: 99%

“…In other words, continuous orbit correction is needed to suppress unwanted noise (of mechanical or electrical origin) in the 1 -100 Hz bandwidth. There are a number of analog [22] and digital [23] feedback systems already working or under design.…”

Section: Feedbackmentioning

confidence: 99%

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Closed orbit related problems: Correction, feedback, and analysis

Bozoki¹

1994

AIP Conference Proceedings

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Orbit correction -moving the orbit to a desired orbit, orbit stability -keeping the orbit on the desired orbit using feedback to filter out unwanted noise, and orbit analysis -to learn more about the model of the machine, are strongly interrelated. They are three facets of the same problem.The better we know the model of the machine, the better predictions we can make on the behavior of the machine (inverse modeling) and the more accurately we can control the machine. On the other hand, one of the tools to learn more about the machine (modeling) is to study and analyze the orbit response to 'kicks'. Orbit correctionWith smaller and smaller vertical beamsizes ( 5 50p) in the new generation of Synchrotron Radiation facilities and with the advent of small angle and crab crossing colliding beams in the B and C$ factories, there is a need for very accurate ( 5 lop) orbit control. ApproachesThere axe different approaches t o the orbit correction. They axe not all exclusive to each other, some methods can fall into more then one categories.The corrective step is calculated based on model predictions. It needs a very good knowledge of the model of the machine (including model-magnet calibrationsee Section 4). Since these models are almost all linear, orbit correction needs several iterative steps. All early methods and many of the. more recent ones (111-[14], [lS], [26]-[27]) fall into this category.They consist of a knowledge base (data) and a separate reasoning mechanism (inference machine). The knowledge base contains the model of the machine and rules what the most expert accelerator physicist/engineer/operator would apply. Thus an Expert System represents a model based system. Expert Systems are capable of treating large amount of information in an empirical way.There were attempts in mid and late 80's by CERN -using commercial ES packages, primarily for fault diagnosis [15]b, but in [27]h it was concluded, that a simple algorithmic process is more efficient for the analysis and correction of closed orbits.Basically, this was the approach taken by SLAC in collaboration with the Stanford Knowledge Systems Laboratory ([15]c, [27]b,c) A Fortran coded in-house 'expert', Able was incorporated into the system €or finding errors and misalignments in the machines and for controling the machines.

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Section: Algorithmsmentioning

confidence: 99%

Section: Eigenvector Decompositionmentioning

confidence: 99%

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Closed orbit related problems: Correction, feedback, and analysis

Bozoki¹

1994

AIP Conference Proceedings

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“…To take care of the lowcr frequcncy fluctuations, a feedback system was built and installed on the ring [5]. Actually two independent systems take care of the vertical and horizontal.…”

Section: Synchrotron Radiation "Noise"mentioning

confidence: 99%

The Application of Infrared Synchrotron Radiation to the Study of Interfacial Vibrational Modes

Hirschmugl

Williams

1994

Synchrotron Techniques in Interfacial Electrochemistry

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Synchrotron radiation provides an extremely bright broad-band source in the infrared which is ideally suited to the study of surface and interface vibrational modes in the range 50-3000 cm-1. Thus it covers the important range of molecule-substrate interactions, as well as overlapping with the more easily accessible near-ir region where molecular intemal modes are found. Compared to standard broadband infrared sources such as globars, not only is it 10f_ times brighter, but its emittance matches the phase-space of the electrochemical cell leading to full utilization of this brightness advantage. In addition, the source is more stable even than water-cooled globars in vacuum for both short-term and long-term fluctuations. Thus one can work at high resolution and use isotopic shifts to identify modes as well as study very weak modes. We will summarize the properties of synchrotron radiation in the infrared, in particular pointing out the distinct differences between this and the x-ray region. We will use experimental data in discussing important issues of signal to noise and will address the unique problems and advantages of the synchrotron source. Thus we will emphasize the important considerations ne_ssary for developing new facilities. This analysis will then lead to a discussion of phasespace matching to electrochemical cells, and to other surfaces in vacuum. Finally we will show several examples of the application of infrared synchrotron radiation to surface vibrational spectroscopy. The examples will ali be for metal crystal surfaces in ultrahigh vacuum and will include CO/Cu(100) and (111) and LO/K/Cu(100). The experiments will show how the stability of the synchrotron source allows subtle changes in the background to be observed in addition to the discrete vibrational modes. These changes are due to electronic states induced by the adsorbate. In some cases we have seen interferences between these and the discrete vibrational modes, leading to a breakdown of the dipole selection rules, and the observation of additional modes. These important experiments serve as sensitivity limit indicators and thus as a guide to future applications in the electrochemistry field.

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“…The stability has recently been 3. RESULTS improved by the installation of a global feedback system [13]. This, plus the wedged beam- Fig.…”

Section: -88°) Off Amentioning

confidence: 99%

Dipole forbidden vibrational modes for NO and CO on Cu observed in the far IR

Hirschmugl

Dumas

Chabal

et al. 1993

Journal of Electron Spectroscopy and Related Phenomena

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IRRAS spectra of NO/Cu(lll) and (4"Jx_)R30* coverage of CO/Cu(II1) in the range 3000-180 cm-t show both tl_ adsorbate internal modes and features assigned to the hindered rotational modes. These dipole-forbidden feamre,s are characterized by asymmetric (mostly negative) absorption lin_ and are accompanied by a change in broadband absorption. The shape and intensity of this brosdband absorption is well accounted for by a scattering model. *Work performed under the auspices of the U.S. Department of Energy, under contract DE-AC02-76CH00016. DI-RIB UTION_I '" OF THIS DocUMENT IS UNLIMITED __

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Real time closed orbit correction system

Cited by 15 publications

References 4 publications

Closed orbit related problems: Correction, feedback, and analysis

Closed orbit related problems: Correction, feedback, and analysis

The Application of Infrared Synchrotron Radiation to the Study of Interfacial Vibrational Modes

Dipole forbidden vibrational modes for NO and CO on Cu observed in the far IR

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