Abstract
We report modeling results for electron cloud buildup and instability in the International Linear Collider positron damping ring. Updated optics, wiggler magnets, and vacuum chamber designs have recently been developed for the 5 GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effects of diffuse and specular photon scattering on the interior surfaces of the vacuum chamber. The results provide input to the cloud buildup simulations for the various magnetic field regions of the ring. The modeled cloud densities thus obtained are used in the instability threshold calculations. We conclude that the mitigation techniques employed in this model will suffice to allow operation of the damping ring at the design operational specifications.
Highlights
The discoveries at the Large Hadron Collider [1,2] have reintensified interest in the proposed International Linear Collider (ILC) [3]
We have updated the lattice design for the 3.2-km, 5 GeV ILC positron damping ring and calculated the distributions of synchrotron radiation around the ring, including the effects of photon scattering inside the vacuum chamber. This analysis was used to refine the choice of electroncloud-mitigating techniques in the various magnetic field environments of the arcs and straights
Groove patterns and antechambers were used as mitigation techniques in the modeled dipole magnets, along with TiN-coating in the 5-cm-diameter quadrupole and sextupole magnet vacuum chambers
Summary
The discoveries at the Large Hadron Collider [1,2] have reintensified interest in the proposed International Linear Collider (ILC) [3]. Operation of the ILC depends critically on the reliable performance of the electron and positron damping rings (DRs) which will serve as injectors. Electron cloud (EC) buildup has been shown to limit the performance of storage rings at KEK-B [4] and PEP-II [5], the operating parameters of which are comparable to those of the ILC DRs. For the past several years, we have been developing and validating modeling. Codes for the purpose of designing the ILC DRs. This paper presents the results of those efforts. We present the beam optics design, the vacuum chamber designs including recommended cloud buildup mitigation techniques, cloud buildup simulations and modeling estimates of the effects on beam dynamics, deriving conclusions on the feasibility of building and operating the positron DR to specification
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