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| THPMA058 | Cyclotron RF Structures Leaks, Causes and Repair | vacuum, cyclotron, ion, scattering | 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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| THPMA087 | Prototype Beam Dump For 10 kW LINAC | electron, linac, radiation, beam-transport | 764 | ||
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A 10 MeV, 10 kW electron LINAC has been developed at RRCAT, Indore for developing applications in the area of radiation processing of agricultural products and medical sterilization. This paper presents the functional requirements, design and manufacturing aspects of beam dump for this LINAC. Activation, conversion of electron energy into primary bremmstralung and radiation damage are important parameters for material selection of the beam dump. Other important parameters considered are mechanical strength, thermal conductivity, corrosion in ozone environment and manufacturability. Calculations of heat deposition due to electrons & photons, thermal design, hydraulic, structural and engineering design were done. FEM based analysis was performed for calculating temperature rise, deformation and stresses. The maximum temperature is estimated to be about 320 K. A prototype beam dump has been manufactured and installed and it is being tested under actual operating conditions.
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| THPMA088 | Bremsstrahlung Converter For High Power EB Radiation Processing Facility | electron, target, photon, radiation | 767 | ||
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A radiation processing facility based on 10 kW Linac is being set up at RRCAT for irradiation of food products and sterilization of medical items. The facility is planned to operate in electron (10 MeV) and X-ray (5 & 7.5 MeV)mode. The required X-rays will be generated by bombarding an optimised target with 5 or 7.5 MeV electron beam. Monte Carlo simulation with MCNP has been performed to optimise the design of the targets for maximizing the X-ray output. The composite target is made of Ta, water & SS. Characteristics of the emerging X-ray field e.g. photon energy spectrum, angular distribution, radial dose and depth dose distribution in unit density material have been simulated & compared for 5 & 7.5 MeV. Our simulation results show that for optimised design, the fraction of the energy transmitted at 5 & 7.5 MeV is 9.3% & 14.2 % respectively, which is useful for radiation processing. The most probable energy of the photons is 0.3 MeV for both 5 and 7.5 MeV electrons and the average energy is 0.84 MeV & 1.24 MeV respectively. Large fraction of electron beam power is dissipated as heat in the targets. Necessary data has been generated to carry out thermal design.
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