Author: Christou, C.
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WEPMB060 Modifications to the Pump Out Box to Lower the Qext of Diamond SCRF Cavities 2251
  • S.A. Pande, C. Christou, P. Gu
    DLS, Oxfordshire, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  Diamond's CESR-B cavities are iris coupled and have fixed Qext. For reliability, the cavities are operated at lower voltages. This results in the optimum condition for beam loading being satisfied at a much lower power typically about 100 kW. For operation at 300 mA with two cavities, the RF power needed per system exceeds 200 kW. Consequently, the cavities need to be operated under-coupled. To lower the Qext and move the optimum operating point nearer to 200kW, 3 stub tuners are used in the waveguide feed line. The difference in the height of the coupling waveguide on cavity and that of the vacuum side waveguide on the window assembly results in a step transition which affects the Qext. The present window/step location results in Qext higher than that without the window. The Qext can be lowered by re-locating the RF window or by shifting the step change in the waveguide cross-section from its present location. This needs modification to the Pump Out box. The pros and cons of the proposed modification to the pump out box in terms of standing waves and multipacting characteristics studied with CST Studio are discussed in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB060  
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WEPOW047 A Hybrid Superconducting/Normal Conducting RF System for the Diamond Light Source Storage Ring 2950
  • C. Christou, A.G. Day, P. Gu, N.P. Hammond, J. Kay, M. Maddock, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink
    DLS, Oxfordshire, United Kingdom
  300 mA beam in the Diamond Light Source storage ring is presently maintained by two 500 MHz superconducting CESR-B cavities. Cavity reliability is acceptable at modest operating voltages up to 1.4 MV per cavity but falls off rapidly beyond this value. The installation of an extra cavity or cavities would reduce the voltage demand on the current superconducting cavities and also the operating power level of the high power amplifiers, with commensurate improvement in machine reliability. Furthermore, two superconducting cavity failures in recent years have resulted in machine down-time and reduced-current operation and repair has proven to be prolonged and expensive. It is therefore planned to install two normal conducting cavities into the ring to support operation of the superconducting cavities and to act as a safeguard against any future superconducting cavity failures. Details are presented in this paper of plans and progress towards the installation of the hybrid RF system.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW047  
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