BEAM DECOHERENCE DUE TO COMBINATION OF WAKE FORCE AND NONLINEARITY IN SP-RING-8 STORAGE RING

Abstract To understand particle behavior from a beam injection state to equilibrium state determined by radiation effects, we have performed a simple experiment to observe the beam decoherence, i.e., temporal variation of the damping of beam coherent motion generated by a single horizontal kicker. We found that the beam decoherence much depends on chromaticities, the sign of amplitudedependent tune shift and beam current. This suggests that short-range wake force and nonlinearity of ring parameters play important roles in the observed phenomena. Simulations with transverse wake fields show good agreements with the measurements

AMPLITUDE DEPENDENT BETATRON OSCILLATION CENTER SHIFT BY NON-LINEARITY AND BEAM INSTABILITY INTERLOCK

Abstract As a result of the even symmetry of the Sextupole field, it creates the horizontal shift of the averaged position of horizontal and vertical betatron oscillation and the amount of the shift depends on its oscillation amplitude. This shift can be observed with usual slow orbit beam position monitor. At the SPring-8 storage ring, this shift is used to detect the excitation of the betatron oscillation for the interlock system for the protection of the vacuum components from strong radiation of insertion devices. AMPLITUDE DEPENDENT BETATRON OSCILLATION CENTER SHIFT The transverse beam instability drives a horizontal or vertical betatron oscillation, and if this occurs in light sources, the strong synchrotron radiation from insertion devices also oscillates as the beam and cause heat damages on beam pipe components if the radiation continuously hit them. The even symmetry of the sextupole field produces the horizontal shift of the time averaged horizontal position if the horizontal and vertical betatron oscillation exists. Here we call it an amplitude dependent betatron oscillation center shift (ADCS). The ADCS on the sextupole strength can be derived by a canonical perturbation theory as the first order effect by sextupole field [1] as where the symbols with overline are the time averaged values, J z and φ z ( z = x, y ) are the action and the phase, respectively, and related to the position and beta function β z s The sextupole strength is expressed as for the magnetic field

Isoscalar Giant Quadrupole Resonance State in the Relativistic Approach with the Momentum-Dependent Self-Energies

We study the excited energy of the isoscalar giant quadrupole resonance with the scaling method in the relativistic many-body framework. In this calculation we introduce the momentum-dependent parts of the Dirac self-energies arising from the one-pion exchange on the assumption of the pseudo-vector coupling with nucleon field. It is shown that this momentum-dependence enhances the Landau mass significantly and thus suppresses the quadrupole resonance energy even giving the small Dirac effective mass which causes a problem in the momentum-independent mean-field theory.Comment: 12pages, 2 Postscript figure

Variations of Hadron Masses and Matter Properties in Dense Nuclear Matter

Using a self-consistent quark model for nuclear matter we investigate variations of the masses of the non-strange vector mesons, the hyperons and the nucleon in dense nuclear matter (up to four times the normal nuclear density). We find that the changes in the hadron masses can be described in terms of the value of the scalar mean-field in matter. The model is then used to calculate the density dependence of the quark condensate in-medium, which turns out to be well approximated by a linear function of the nuclear density. Some relations among the hadron properties and the in-medium quark condensate are discussed.Comment: 22 pages, University of Adelaide preperint ADP-94-20/T160, submitted to Physical Review

Nucleon and hadron structure changes in the nuclear medium and impact on observables

We review the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model, which is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons. This approach leads to simple scaling relations for the changes of hadron masses in a nuclear medium. It can also be extended to describe finite nuclei, as well as the properties of hypernuclei and meson-nucleus deeply bound states. It is of great interest that the model predicts a variation of the nucleon form factors in nuclear matter. We also study the empirically observed, Bloom-Gilman (quark-hadron) duality. Other applications of the model include subthreshold kaon production in heavy ion collisions, D and D-bar meson production in antiproton-nucleus collisions, and J/Psi suppression. In particular, the modification of the D and D-bar meson properties in nuclear medium can lead to a large J/Psi absorption cross section, which explains the observed J/Psi suppression in relativistic heavy ion collisions.Comment: 143 pages, 77 figures, references added, a review article accepted in Prog. Part. Nucl. Phy

Practical method for measurement and compensation of linear coupling driving term

We demonstrated a method with practical value for the measurement and global compensation of a complex coupling driving term C of linear difference resonance, using a turn-by-turn beam position monitor (BPM) at the SPring-8 storage ring. The method is based on the perturbation theory with the single-resonance approximation. The accurate complex C was obtained from coefficients of the eigenmode expansion of the coupled betatron oscillation observed near a target linear difference resonance. The global compensation for the measured C was successfully carried out by determining optimal strengths of the two independent correcting skew quadrupoles for generating a counterterm -C without using empirical methods. Meanwhile, we then confirmed that the determined optimal strengths gave a minimum vertical beam size by scanning the strength of the correcting skew quadrupole field. To demonstrate the validity of our method, C was also measured while varying the strengths of the correcting magnets around the optimal values to generate deliberate skew quadrupole error fields. We confirmed that the measured values of C agreed with those coming from the deliberate error fields

Practical method for measurement and compensation of linear coupling driving term

We demonstrated a method with practical value for the measurement and global compensation of a complex coupling driving term C of linear difference resonance, using a turn-by-turn beam position monitor (BPM) at the SPring-8 storage ring. The method is based on the perturbation theory with the single-resonance approximation. The accurate complex C was obtained from coefficients of the eigenmode expansion of the coupled betatron oscillation observed near a target linear difference resonance. The global compensation for the measured C was successfully carried out by determining optimal strengths of the two independent correcting skew quadrupoles for generating a counterterm -C without using empirical methods. Meanwhile, we then confirmed that the determined optimal strengths gave a minimum vertical beam size by scanning the strength of the correcting skew quadrupole field. To demonstrate the validity of our method, C was also measured while varying the strengths of the correcting magnets around the optimal values to generate deliberate skew quadrupole error fields. We confirmed that the measured values of C agreed with those coming from the deliberate error fields