| Paper | Title | Page |
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| THPMA058 | Cyclotron RF Structures Leaks, Causes and Repair | 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.
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 |