摘要:

Future damping rings for linear colliders will need to have very small vertical equilibrium emittances. In the limit of low beam current, the vertical emittance is primarily determined by the vertical dispersion and the betatron coupling. In this paper, the contributions to these effects from random misalignments are calculated and tolerances are derived to limit the vertical emitance with a 95% confidence level.

ISSN:0094-243X    

DOI:10.1063/1.42314

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

With a small low‐frequency perturbation, the transverse emittance of a storage‐ring beam will grow. The growth mechanism due to betatron tune dependence on amplitude is discussed in the Hamiltonian approach. Applications are given when the perturbation is due to Jostlein’s scheme of bunch centering as well as ground wave.

ISSN:0094-243X    

DOI:10.1063/1.42315

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

This report addresses the question of the trajectory correction and simultaneous reduction of the dispersion in the linacs of future linear colliders. With high frequencies for the acceleration wave, the effects of wake fields in the presence of finite trajectory distortions can be large and the subsequent transverse emittance dilution intolerable. Therefore, the beam trajectory has to be optimised in a suitable momentum range and a ‘‘dispersion‐free’’ algorithm has been proposed at SLAC, with this object. The present work describes an application of this method, with the aim to include in the model the nonlinearity with momentum of the lattice transfer‐coefficient. In this approach, the function to be minimized contains one term related to the on‐momentum trajectory as well as a finite number of terms associated with the momentum dependence of the dispersion, to increasing orders in &Dgr;p/p. The particular case of second‐order development is treated separately and an example is given for the CLIC beam.

ISSN:0094-243X    

DOI:10.1063/1.42316

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

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. In addition, phase and radius feedback loops are also provided to ensure the phase stability, radial position and emittance integrity of the beam. The open and closed loop behaviors of both feedback controls and their responses 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 with commissioning experiences. Such analysis is useful for setting design criteria and tolerances for new proton synchrotrons.

ISSN:0094-243X    

DOI:10.1063/1.42317

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The sensitivity to errors of the new generation of synchrotron light sources is a challenging issue. The effects of individual errors on machine characteristics have been investigated for the ESRF storage ring lattice. Resulting tolerances and correction procedures have been established.

ISSN:0094-243X    

DOI:10.1063/1.42318

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new coupling correction method is proposed which is applicable to the ring where noninterlaced sextupoles dominate the horizontal‐vertical coupling sources. It is based on the beam‐based alignment technique: It measures a vertical orbit response to a horizontal orbit bump with large amplitude which encompass several sextupole pairs. The vertical‐orbit changes give information of vertical misalignment of sextupoles in the bump orbit. Simulation for the B‐Factory design of KEK shows misalignments of several tens of microns are detectable.

ISSN:0094-243X    

DOI:10.1063/1.42319

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Many existing circular accelerators have been able to adequately compensate their horizontal/vertical coupling by one or two families of skew‐quadrupole corrector magnets. For example, the HERA proton storage ring at DESY has used just two skew quadrupoles correctors, the SPS at CERN can operate with just one skew quadrupole corrector, and the Tevatron at Fermilab with two families of skew quadrupoles. At first sight just two corrector families seem unlikely to be enough, since there are four independent horizontal/vertical coupling coefficients in the 4×4 transfer matrix from one point to any other in the ring. Thus, for the general case four families of correctors would seem to be necessary. It will be shown that the adequacy of two‐family correction for storage rings is a consequence of operating near the diagonal of the tune diagram.

ISSN:0094-243X    

DOI:10.1063/1.42320

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The concept of quasilocal (F, C, D) correction of nonlinearities is reviewed. Correction by two or more orders of magnitude is obtained; in addition, separated‐function control of the horizontal, coupled and vertical motion becomes possible. Quasi‐local correction of dipole nonlinearities is planned for LHC, and will greatly increase the linear aperture. The 1990 SSC Site‐Specific Conceptual Design includes quasilocal correction in the 20 TeV Collider, but restrictions may limit correction capability. Quasilocal (F, C, D) correction may also be useful in the SSC 2‐TeV High Energy Booster (HEB). In high‐luminosity collider mode, the nonlinear effects of the interaction‐region (IR) quadrupoles may be dominant; these errors may also be compensated quasilocally. Extensions of the (F, C, D) concept for IR correction, which exploit the restricted IR symmetry, are also suggested.

ISSN:0094-243X    

DOI:10.1063/1.42299

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Questions are raised here, without providing any answers to them, regarding the standard way of specifying the tolerances on various multipole components in superconducting dipoles. They are: 1. Dependence of systematic b6(normal 14‐pole) and b8(normal 18‐pole) on the required momentum aperture, 2. Importance of resonance width (and its precise meaning) for specifying random low‐order multipoles, and 3. Understanding tracking results in terms of multipole components.

ISSN:0094-243X    

DOI:10.1063/1.42300

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this paper, we show how to restore the symmetry of a sextupole lattice which has been broken by insertion devices. The method works perfectly (on momentum) in the limit of linear devices. Rather than using quadrupoles placed around each insertion device, we rematch the ring using many if not all the existing quadrupoles. We also point out that the sextupoles can be used in the process.

ISSN:0094-243X    

DOI:10.1063/1.42301

出版商:AIP    

年代:1992

数据来源: AIP