82 Matching Results

Search Results

Advanced search parameters have been applied.

Functional observer and state feedback

Description: In this paper, we show the relation between state space approach and transfer function approach for functional observer and state feedback design. Two approaches can be transformed into each other, based on this result. More importantly, we find that the state space approach introduces some severe, unnecessary restrictions in solving the problem. The restrictions are, however, reduced to be a trivial condition in transfer function approach. It is believed that the result presented in this paper will be useful in developing both approaches, and motivate some new results for solving the problem.
Date: January 1, 1986
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

Comparison of the domain and frequency domain state feedbacks

Description: In this paper, we present explicitly the equivalence of the time domain and frequency domain state feedbacks, as well as the dynamic state feedback and a modified frequency domain state feedback, from the closed-loop transfer function point of view. The difference of the two approaches is also shown.
Date: January 1, 1986
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

Incoherent and coherent tune shifts

Description: The longitudinal and transverse microwave instabilities are the two important limiting factors for the performance of an accelerator. Comparing with the fairly unified approach for the longitudinal microwave instabilities, different approaches have been used to define the transverse microwave instabilities. One reason of this is related to the role played by the space charge incoherent and coherent tune shifts. In this article, the transverse microwave instabilities will be discussed by defining separately the roles of the space charge incoherent and coherent tunes, which are represented by the space charge transverse impedances. Preliminary results for the AGS as proton driver are presented by using this approach.
Date: December 31, 1995
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

Thyristor converter simulation and analysis

Description: In this paper we present a simulation on thyristor converters. The simulation features nonlinearity, non-uniform firing, and the commutations. Several applications such as a current regulation, a converter frequency characteristics analysis, and a power line disturbance analysis will be presented. 4 refs., 4 figs.
Date: January 1, 1991
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

Comments on momentum aperture of 100 GeV/n Au runs in RHIC

Description: In RHIC 2010 100 GeV/n Au run, the momentum aperture has been an issue in the re-bucketing and the beam intensity lifetime in store. Both Blue and Yellow beams with comparable storage RF voltage and peak current have suffered more beam loss than in Run 2007. In this note, some comments are made for the momentum aperture of the lattices used from the Au runs in 2007, 2008 and 2010. From the wigglings and the beam decays of each lattice, information regarding the machine momentum aperture is presented. Several directions in further improvement are discussed.
Date: November 1, 2011
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

Compare 100 GeV/n Au Run 2010 with Run 2007

Description: With the very successful commissioning of the vertical stochastic cooling in 100 GeV/n Au Run 2010, the IBS (intra-beam scattering) is no longer the dominant factor in terms of the integrated luminosity. A new luminosity model is needed, where the beam intensity lifetime is more important and the burn-off needs to be accounted for. Toward this goal, a brief review of the Run 2010, compared with Run 2007, is presented.
Date: January 1, 2011
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

A luminosity model of RHIC gold runs

Description: In this note, we present a luminosity model for RHIC gold runs. The model is applied to the physics fills in 2007 run without cooling, and with the longitudinal cooling applied to one beam only. Having good comparison, the model is used to project a fill with the longitudinal cooling applied to both beams. Further development and possible applications of the model are discussed. To maximize the integrated luminosity, usually the higher beam intensity, smaller longitudinal and transverse emittance, and smaller {beta} are the directions to work on. In past 10 years, the RHIC gold runs have demonstrated a path toward this goal. Most recently, a successful commissioning of the bunched beam stochastic cooling, both longitudinal and transverse, has offered a chance of further RHIC luminosity improvement. With so many factors involved, a luminosity model would be useful to identify and project gains in the machine development. In this article, a preliminary model is proposed. In Section 2, several secondary factors, which are not yet included in the model, are identified based on the RHIC operation condition and experience in current runs. In Section 3, the RHIC beam store parameters used in the model are listed, and validated. In Section 4, the factors included in the model are discussed, and the luminosity model is presented. In Section 5, typical RHIC gold fills without cooling, and with partial cooling are used for comparison with the model. Then a projection of fills with more coolings is shown. In Section 6, further development of the model is discussed.
Date: November 1, 2011
Creator: Zhang, S. Y.
Partner: UNT Libraries Government Documents Department

Luminosity issues in 2009 100 GeV polarized proton run

Description: Several luminosity issues are reviewed. Questions remain, which are stated for further investigation. Some suggestions are made for possible luminosity improvement. There are several factors affecting the luminosity in 2009 100 GeV polarized proton run: (1) The highest bunch intensity at RHIC early store (1.5 hour after accramp in this note) in 2009 is 1.25 x 10{sup 11} protons. In 2008 run, it was 1.42 x 10{sup 11} protons, which gives rise to 30% higher luminosity if other conditions are the same. Yellow ramp efficiency is identified as one of the main problem. Meanwhile, the beam-beam induced loss in about 1 hour into collision accounts actually no less than the ramp. (2) The typical transverse emittance at early store is 13 {pi}{micro}m for bunch intensity of 10{sup 11} protons, but it is 17 {pi}{micro} for 1.25 x 10{sup 11} protons. The increase of the emittance implies a 30% difference in luminosity if other conditions are the same. The emittance growth with electron cloud below instability threshold may be partially responsible. Meanwhile, the Booster scraping may also be relevant. (3) The luminosity lifetime in 2009 run is significantly lower than that in 2005, 2006, and 2008 runs. At the beam-beam parameter of 0.01, the typical average luminosity lifetime in early store is 10 hours in 2009, and it is 15 hours in previous runs. Given 8 hours of store time, this implies more than 20% of the difference in integrated luminosity. The 0.7 m betastar adopted in 2009 might be relevant, but the evidence is not fully convincing. On the other hand, the continuing RF voltage ramp in store may be of concern. (4) In the last month of the run, the polarization at RHIC early store is declined from 60% to 55%, a 30% reduction in p{sup 4} factor. It ...
Date: August 1, 2009
Creator: Zhang,S. Y.
Partner: UNT Libraries Government Documents Department

Transverse and longitudinal microwave instability thresholds

Description: Taking the first orthogonal polynomials in the conventional radial mode expansion in the eigenvalue type perturbation approach, the usual Keil-Schnell criteria for the microwave instabilities can be obtained. In this way, a close relationship between the two approaches is established. The existing results are reviewed, and some comments and modifications are made.
Date: December 1, 1996
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

INSTABILITY ISSUES AT THE SNS STORAGE RING

Description: The impedance and beam instability issues of the SNS storage ring is reviewed, and the effort toward solutions at the BNL is reported. Some unsettled issues are raised, indicating the direction of planned works.
Date: June 28, 1999
Creator: ZHANG,S.Y.
Partner: UNT Libraries Government Documents Department

Error analysis of acceleration control loops of a synchrotron

Description: For beam control during acceleration, it is conventional to derive the frequency from an external reference, be it a field marker or an external oscillator, to provide phase and radius feedback loops to ensure the phase stability, radial position and emittance integrity of the beam. The open and closed loop behaviors of both feedback control and their response under the possible frequency, phase and radius errors are derived from fundamental principles and equations. The stability of the loops is investigated under a wide range of variations of the gain and time delays. Actual system performance of the AGS Booster is analyzed and compared to commissioning experiences. Such analysis is useful for setting design criteria and tolerances for new proton synchrotrons. 4 refs., 13 figs.
Date: January 1, 1991
Creator: Zhang, S.Y. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

A new formulation of longitudinal coherent instabilities

Description: The quadrature response of longitudinal impedance is shown to be the effective impedance for the beam instability. The results of the application of this formulation are compared with that obtained using the Robinson-Pedersen approach and the Sacherer integral equation. The formulation is further generalized to the rigid bunch motion using signal analysis method, where a form factor shows up naturally. Finally, the formulation is applied to solve the coupled bunch instabilities. Examples of the AGS Booster and the AGS coupled bunch instabilities are used to illustrate the applications of the formulation.
Date: January 1, 1993
Creator: Zhang, S.Y. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

Analysis of periodic transient beam loading of the AGS

Description: In this note, we discuss the multi-batch bunched ;beam loading during the injection from the Booster to the AGS. The full intensity beam injection to the upgraded AGS RF system with beam phase and radial feedbacks will be studied. It is shown that a beam phase feed-back is necessary in order to guarantee a predictable beam behavior after the first batch injection, otherwise the initial phase deviation for the following batch injections cannot be controlled. However, the effectiveness of the phase feedback control of the transient beam loading is limited by the associated emittance blow-up in the process. It is shown that a fast power amplifier feedback with a moderate gain can significantly reduce the transient effect of the bunched beam injection.
Date: July 13, 1992
Creator: Zhang, S.Y. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

Spectrum analysis in beam diagnostics

Description: In this article, we discuss fundamentals of the spectrum analysis in beam diagnostics, where several important particle motions in a circular accelerator are considered. The properties of the Fourier transform are presented. Then the coasting and the bunched beam motion in both longitudinal and transverse are studied. The discussions are separated for the signal particle, multiple particle, and the Schottky noise cases. To demonstrate the interesting properties of the beam motion spectrum, time domain functions are generated, and then the associated spectra are calculated and plotted. In order to show the whole picture in a single plot, some data have been scaled, therefore they may not be realistic in an accelerator.
Date: April 23, 1993
Creator: Zhang, S.Y. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

Topics on RF beam control of a synchrotron

Description: In this paper, several typical situations of longitudinal motion in synchrotron design and operation are studied. The study is based on a unified beam dynamic model of synchrotron oscillation under phase and radial feedbacks. Cases studied include frequency error, lock-in range, bunch excursion, phase manipulation, injection and field errors.
Date: July 13, 1992
Creator: Zhang, S.Y. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

Bunched beam longitudinal instability: Coherent dipole motion

Description: In this paper, the authors present a new formulation for the longitudinal coherent dipole motion, where a quadrature response of the environmental impedance is shown to be the effective longitudinal impedance for the beam instability. The Robinson-Pedersen formulation for the longitudinal dipole motion is also presented, the difference of the two approaches is discussed in the comparison. The results by using the Sacherer integral equation for the coherent dipole motion can generate the same results as by using the other two approaches, except for a scaling difference. The formulation is further generalized to the rigid bunch motion using signal analysis method, where a form factor shows up naturally. Finally, the formulation is applied to solve the coupled bunch instabilities. Examples of the AGS Booster and the AGS coupled bunch instabilities are used to illustrate the applications of the formulation.
Date: April 23, 1993
Creator: Zhang, S.Y. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

Spectrum analysis in beam diagnostics

Description: In this article, we discuss fundamentals of the spectrum analysis in beam diagnostics, where several important particle motions in a circular accelerator are considered. The properties of the Fourier transform are presented. Then the coasting and the bunched beam motion in both longitudinal and transverse are studied. The discussions are separated for the signal particle, multiple particle, and the Schottky noise cases. To demonstrate the interesting properties of the beam motion spectrum, time domain functions are generated, and then the associated spectra are calculated and plotted. In order to show the whole picture in a single plot, some data have been scaled, therefore they may not be realistic in an accelerator.
Date: April 23, 1993
Creator: Zhang, S. Y. & Weng, W. T.
Partner: UNT Libraries Government Documents Department

Bunched beam longitudinal instability: Coherent dipole motion

Description: In this paper, the authors present a new formulation for the longitudinal coherent dipole motion, where a quadrature response of the environmental impedance is shown to be the effective longitudinal impedance for the beam instability. The Robinson-Pedersen formulation for the longitudinal dipole motion is also presented, the difference of the two approaches is discussed in the comparison. The results by using the Sacherer integral equation for the coherent dipole motion can generate the same results as by using the other two approaches, except for a scaling difference. The formulation is further generalized to the rigid bunch motion using signal analysis method, where a form factor shows up naturally. Finally, the formulation is applied to solve the coupled bunch instabilities. Examples of the AGS Booster and the AGS coupled bunch instabilities are used to illustrate the applications of the formulation.
Date: April 23, 1993
Creator: Zhang, S. Y. & Weng, W. T.
Partner: UNT Libraries Government Documents Department

On solutions of Sacherer integral equation

Description: There are basically two approaches in solving the Sacherer integral equation, one uses the orthogonal polynomial expansion for radial functions, and another uses the Hankel harmonic samplings, both have extensive application. In this article, we discuss these approaches and present the corresponding solutions. If the azimuthal modes are not coupled, the Sacherer integral equation can be treated as an eigenvalue problem. It is shown that the information provided by the eigenvalue alone are insufficient in determining the system response. The initial perturbation pattern with respect to the radial modes must be considered. Several particle distributions are used as examples to show the solutions to the equation, and the physical implication of the radial modes is illustrated by using the examples.
Date: June 17, 1994
Creator: Zhang, S. Y. & Weng, W. T.
Partner: UNT Libraries Government Documents Department

A new formulation of longitudinal coherent instabilities

Description: The quadrature response of longitudinal impedance is shown to be the effective impedance for the beam instability. The results of the application of this formulation are compared with that obtained using the Robinson-Pedersen approach and the Sacherer integral equation. The formulation is further generalized to the rigid bunch motion using signal analysis method, where a form factor shows up naturally. Finally, the formulation is applied to solve the coupled bunch instabilities. Examples of the AGS Booster and the AGS coupled bunch instabilities are used to illustrate the applications of the formulation.
Date: June 1, 1993
Creator: Zhang, S. Y. & Weng, W. T.
Partner: UNT Libraries Government Documents Department

Evaluating impedances in a Sacherer integral equation

Description: In Sacherer integral equation, the beam line density is expanded on the phase deviation {phi}, generating a Hankel spectrum, rather than on the time, which generates a Fourier spectrum. This is a natural choice to deal with the particle evolution in phase space, it however causes complications whenever the impedance corresponding to the spectrum has to be evaluated. In this article, the line density expansion on {phi} is shown to be equivalent to a beam time modulation under an acceptable condition. Therefore for a Hankel spectrum, a number of sidebands, and the corresponding impedance as well, will be involved. For wideband resonators, it is shown that the original Sacherer solution is adequate. For narrowband resonators, the solution had been compromised, therefore a modification may be needed.
Date: August 1, 1994
Creator: Zhang, S. Y. & Weng, W. T.
Partner: UNT Libraries Government Documents Department

Analysis of Periodic Transient Beam Loading of the AGS

Description: In this note, we discuss the multi-batch bunched ;beam loading during the injection from the Booster to the AGS. The full intensity beam injection to the upgraded AGS RF system with beam phase and radial feedbacks will be studied. It is shown that a beam phase feed-back is necessary in order to guarantee a predictable beam behavior after the first batch injection, otherwise the initial phase deviation for the following batch injections cannot be controlled. However, the effectiveness of the phase feedback control of the transient beam loading is limited by the associated emittance blow-up in the process. It is shown that a fast power amplifier feedback with a moderate gain can significantly reduce the transient effect of the bunched beam injection.
Date: July 13, 1992
Creator: Zhang, S. Y. & Weng, W. T.
Partner: UNT Libraries Government Documents Department