| Paper | Title | Page |
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| WEPE095 | Impedance and Single-bunch Instabilities in the ILC Damping Ring | 3572 |
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The longitudinal wake fields have been calculated by using 3D code, CST Particle Studio, for a number of different vacuum chamber components of the 6.4 km ILC damping ring design. Based on the results, studies of bunch lengthening and single-bunch instabilities have been carried out. Bunch lengthening from a particle tracking code are compared with results from numerical solution of the Haissinski equation. The tracking code is used to predict the threshold for single-bunch instabilities. |
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| WEPE097 | Recommendation for the Feasibility of More Compact LC Damping Rings | 3578 |
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As part of the International Linear Collider (ILC) collaboration, we have compared the electron cloud effect for different Damping Ring designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. These studies were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design and would allow to considerably reduce the number of components, wiggler magnets and costs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design. |
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| WEPE092 | Mechanical and Vacuum Design of the Wiggler Section of the ILC Damping Rings | 3563 |
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A vacuum vessel design of wiggler sections should meet a few challenging specification. The SR power of about 40 kW is generated in each wiggler. Expanding fan of SR radiation reaches the beam vacuum chamber walls in the following wiggler and may cause the following problem: massive power dissipation on vacuum chamber walls inside the cryogenic vessel, radiation damage of superconducting coil, high photo-electron production rate that cause an e-cloud build-up to unacceptable level. Therefore this power should be absorbed in the places where these effects are tolerable or manageable. A few possible solutions for tackling all SR related problems as well as vacuum design are discussed in the paper in details. |
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| WEPE093 | Ion Induced Pressure Instability in the ILC Positron DR | 3566 |
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Ion induced pressure instability is a potential problem for the ILC positron damping ring (DR)if the chosen pumping scheme does not provide sufficient pumping. The ion induced pressure instability effect results from ionisation of residual gas molecules by the beam particles, their acceleration in the field of the beam towards the vacuum chamber walls, causing ion induced gas desorption from vacuum chamber walls; these gas molecules in their turn can also be ionised, accelerated and cause further gas desorption. If the pumping is insufficient, this effect may cause a pressure instability, in which the pressure in the beam chamber grows rapidly to an unacceptable level. To analyse the ion induced pressure instability in the ILC positron DR the energy gained by ions was calculated for the appropriate beam parameters; it was found that the energy gain of ions will be about 300 eV. The ion induced gas desorption was estimated, and pumping solutions to avoid the ion induced pressure instability are suggested. The cheapest and most efficient solution is to use NEG coated vacuum chamber. |
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| WEPE094 | SR Power Distribution along Wiggler Section of ILC DR | 3569 |
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A 374-m long wiggler section is a key part of ILC damping ring that should alloy reaching a low beam emittance for the ILC experiment. Synchrotron radiation generated by the beam in the wigglers should be absorbed by different components of vacuum vessel, including specially designed absorbers. The optimisation of the mechanical design, vacuum system and anti-e-cloud mitigation requires accurate calculation of the SR power distribution. The angular power distribution from a single wiggler was calculated with in-house developed software. Then the superposition of SR from all wigglers allows calculating power distribution for all components along the wiggler section and the downstream straight section. |