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| TUPMA016 | Computation of Wakefields and Impedances for the PETRA III Longitudinal Feedback Cavity | feedback, impedance, simulation, kicker | 124 | ||
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At DESY the existing PETRA II storage ring will be converted into a 3rd generation synchrotron radiation source, called PETRA III. The total beam current is limited by coupled bunch instabilities, which are mainly driven by the parasitic modes of the RF cavities. It is planned to use longitudinal and transverse feedback systems to achieve the design current of 100 mA. Eight single cell feedback cavities will be installed into the PETRA III ring to damp the coupled bunch longitudinal phase oscillations. It is important to know the contribution of the feedback cavity to the impedance budget of PETRA III. In this article, the wake and impedance computation results, using the loss and kick parameters, will be reported. The computer codes MAFIA and Microwave Studio have been used to compute the electromagnetic fields.
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| TUPMA123 | Electron Acceleration in the Wake Field Excited by 200TW Femto Second Laser in Underdense Plasma | electron, plasma, laser, acceleration | 277 | ||
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Laser-plasama acceleration experiment has been carried out using 200TW, 30fs Ti:Sapphire laser pulses focused on helium gas-jets with F/8.75 optics. Intense mono-energetic electron beams have been produced by controlling plasma length and density precisely. Energy spectral oscillations in respect to ejection angle have been also observed. Measurements of images from Thomson scattering and fluorescence side scattering from plasma indicate highly relativistic effects such as a long self-channeling, hosing instability and filamentation. It seems that these nonlinear phenomena strongly disturb high energy gain acceleration and high quality beam generation.
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| THPMA058 | Cyclotron RF Structures Leaks, Causes and Repair | vacuum, cyclotron, ion, radioactivity | 706 | ||
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Cyclotron at VECC, Kolkata, is delivering beam since 1977. Water leaks develops inside cyclotron after 30 years operation. Major leaks appear on thin walled copper cooling tube-brazed joints with sheet of R. F. panels, D-stem structures and aluminum & copper tubes trimmer capacitator. Radioactivity enhances ozone and nitrogen oxide, which also formed due to discharge of high electric field and subsequently formation of acid on copper tube and corrodes. Another source of corrosion is free chlorine ions from irradiated halogen containing products like cables etc, residual of cleaning chemicals and trapped brazing flux. Improper selection of brazing filler containing high percentages of zinc, cadmium and phosphorous which will promote porosity due to metal vaporization under high vacuum. Joining of different electro chemical potentials metal as done in trimmer capacitor causes corrosion.μleaks have been detected by MSLD then repaired by torch / TIG brazing with appropriate filler and fluxes has been cleaned thoroughly. Quality performance test has been conducted after repair by MSLD followed by hydraulic test repeated by MSLD both individual and gross leak.
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Cycloron down time increases becaues of water leaks and became major concern for smooth operation. Referance:1. CERN Accelerator School on Vacuum Technology -'992. ASM Handbook volume-6 |
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