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Stability of a Landau damped system

Description: Dispersion relation serves as a base for all the Landau damping theory. In this paper we rederive the dispersion relation for general oscillator systems from a different approach which hopefully gives a little clearer view of the problem. Stability criteria are obtained by mapping technique. Two examples will be discussed to illustrate the sufficient condition for stability. 5 refs., 3 figs.
Date: December 1, 1980
Creator: Yao, C.Y.
Partner: UNT Libraries Government Documents Department

Estimate of coherent tune shifts for PEP

Description: Transverse and longitudinal instabilities for a bunched PEP beam with a Gaussian distribution are treated using the standard technique in which instability problems are solved by looking for eigenvalues of the linearized Vlasov equation. The eigen solutions are conveniently expanded in terms of the Laquerre polynomials, and the eigenvalues are given by a symmetric matrix whose elements can be expressed in infinite series. The well-known formalism is used to obtain the matrix formula, and then applied numerically to the PEP ring to estimate the transverse coherent tune shifts. The impedance used is that estimated for the PEP RF cavities. The agreement with experimental data seems reasonable.
Date: February 1, 1981
Creator: Yao, C.Y. & Chao, A.W.
Partner: UNT Libraries Government Documents Department

Transverse instability excited by rf deflecting modes for PEP

Description: We have looked at the possible transverse instability effects which are caused by the deflecting modes of the rf cavities in PEP. The results are obtained by applying the expression of the instability damping rate. We have assumed that there equal bunches equally spaced in PEP. We have worked out the equivalent for a single bunch beam. The effect of chromaticity xi is included as a frequency shift in the bunch mode spectra. We rewrite this result in terms of the transverse wake field instead of the impedance. We include an application of the Sacherer formalism to the case of resistive wall. The resulting expression of the damping rate contains two terms. The first term corresponds to the effect of the short wake fields; it agrees with the result of the head-tail instability as derived by Sands. A numerical estimate of this resistive-wall head tail case for PEP is given. It re-confirms that the resistive wall instability is not a serious problem for PEP. The second term gives the effect of long wake fields and it agrees with the result of Courant and Sessler. 10 refs., 2 figs.
Date: November 1, 1979
Creator: Chao, A.W. & Yao, C.Y.
Partner: UNT Libraries Government Documents Department

Transverse wake field effects on intense bunches with application to the SLAC linear collider

Description: The theory of transverse beam break-up is summarized and briefly discussed in this paper. It is then applied to the SLAC linear accelerator to give the various design tolerances for beam injection and alignment of accelerator components for the linear collider operation.
Date: July 1, 1980
Creator: Chao, A.W.; Richter, B. & Yao, C.Y.
Partner: UNT Libraries Government Documents Department

The feasibility of near-field ODR beam-size monitoring at 23 GeV at FACET

Description: Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam-size sensitivity at the 10- to 20-{micro}m sigma level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year.
Date: March 1, 2011
Creator: Lumpkin, A.H.; /Fermilab; Yao, C.-Y.; /Argonne; Hogan, M.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

The Feasibility of Near-field ODR Beam-size Monitoring at 23 GeV at FACET

Description: Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam-size sensitivity at the 10- to 20-{micro}m sigma level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year.
Date: June 1, 2012
Creator: Lumpkin, A.H.; /Fermilab; Yao, C.-Y.; /Argonne; Hogan, M.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Considerations on ODR beam-size monitoring for gamma = 1000 beams

Description: We discuss the feasibility of monitoring the beam size of {gamma} = 1000 beams with 3000 times more charge in a video frame time and with a more sensitive 12- to 16-bit camera than were used in the previous electron beam studies at 7 GeV at the Advanced Photon Source. Such a beam would be generated at Fermilab in a new facility in the coming years. Numerical integrations of our base model show beam size sensitivity for {+-} 20% level changes at 200- and 400-{micro}m base beam sizes. We also evaluated impact parameters of 5 {sigma}{sub y} and 12 {sigma}{sub y} for both 800-nm and 10-{micro}m observation wavelengths. The latter examples are related to a proposal to apply the technique to an {approx}0.98 TeV proton beam, and this study shows there are trades on photon intensity and beam size sensitivity to be considered at such gammas. In addition, we report on first results at {gamma} = 1800 on a superconducting rf linac.
Date: April 1, 2008
Creator: Lumpkin, A.H.; /Fermilab; Yao, C.-Y.; /Argonne; Chiadroni, E.; Castellano, M. et al.
Partner: UNT Libraries Government Documents Department