| Paper | Title | Page |
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| TUPMA097 | Characteristics of the Magnetic Channel in the Yoke Hole of K-500 Superconducting Cyclotron | 241 |
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| The detail magnetic field measurement of K-500 superconducting cyclotron has been carried out. The last magnetic channel of the extraction system placed in the yoke hole of the cyclotron before external beam line is active, unlike others, which are all passive. This channel comprises a coil and a special shaped iron to produce both quadrupole and dipole field for focussing and radially aligning the different ion species coming out from the cyclotron, with the external beam transport line. The magnetic field inside the channel along with the outside stray field has been measured for different channel currents as well as main magnet excitations. A 3-D model of the full magnet is constructed using magneto- static code RADIA [2] to simulate the yoke field. This paper reports the comparative study of measured and calculated field and studies the trajectories for the representative ions through the stray field calculated from the model. The later being used to locate the starting point (or matching point) for the external beam transport line | ||
| TUPMA113 | Design of High Current RF Ion Source for Micromachining Applications | 262 |
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| Liquid Metal Ion Source (LMIS) and Gas Field Emission Ion Source (GFEIS) are the major ones in micromachining applications so far. They have limitations of contaminations and low throughput respectively. Plasma based ion sources can produce heavier ions for higher throughput, lighter ions for fabrication of higher resolution structures, ions for doping, ion assisted direct writing of metallic, oxide, nitride and carbide layers and lines. Considering wide range of applications, a 13.56 MHz inductive coupled plasma (ICP) ion source for producing high brightness ion beams with very low energy spread has been developed. It is a very compact ion source with external helical antenna wound around a 30 mm quartz tube. 1 mA of Argon and 0.5 mA of proton ion beams have been extracted from 2 mm dia aperture in plasma electrode at 3.5 kV extraction potential and ~200W of RF power. Using LabView software and field point modules, an automated plasma diagnostic system has been designed and used to measure the plasma parameters. This paper describes the features of the ion source, ion beams produced, some results of the plasma diagnostics. | ||
| TUPMA116 | Periodic Ion Current Burst in 6.4 GHz ECR Source | 268 |
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| We studied the enhancement in extracted ion current in the 6.4 GHz ECR ion source at VECC, Kolkata by inserting a negatively biased disc in the main stripping stage. In addition to the expected increase in current, we observed a sudden jump in the current at some low bias voltage. The jump amplitude is larger for higher charge states. In order to understand the origin of the jump, we recently measured the time spectra of high charge state ion current for neon. The time spectra revealed the presence of a burst frequency in the kilohertz range. This frequency shows a correlated jump with the ion current described above. Another feature is that the observed burst frequency shows a good linear correlation with the extracted ion current. This may signify that current per burst is a constant factor, higher current means that there are more number of bursts. | ||
| WEZMA04 | Superconducting Cyclotron Project at VECC | 320 |
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| Construction of the K-500 superconducting cyclotron at Kolkata is now in final stages. The main magnet was operated satisfactorily for alomost one year during 2005. The coil was continuously kept cooled at 4.2K temperature during the entire period. Extensive magnetic field measuremens were done for correction of the imperfections, centering of the main coil, calculation of operational settings, calculation of extraction trajectory etc. Subsequently in April 2006 the coil has been warmed up to facilitate assembly of the other systems of the machine. All major systems have been fabricated and the assembly is currently going on. We plan to start the commissioning tests in the first half of year 2007. In this paper our experience with the operation of the main superconducting magnet and magnetic field measurements will be discussed. Developmental highlights of various systems will be briefly presented. | ||
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| WEPMA015 | Characteristics of Beam Extraction System of K500 Superconducting Cyclotron | 357 |
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| Extensive Magnetic Field measurement of the K500 Superconducting Cyclotron has been completed. In this paper we report the beam dynamical calculations along the extraction system based on the measured magnetic field data. The beam matching to the external beam transport system, for different ion species spanning the operating region is also explored. | ||
| WEPMA089 | Control and Instrumentation for the VEC Superconducting Cyclotron Cryogen Delivery System | 452 |
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| The cryogen delivery system for the superconducting cyclotron supplies liquid helium to the superconducting main magnet coil and three cryopanels. It also supplies liquid nitrogen to the thermal shield of the liquid helium chamber housing superconducting coil and the thermal shield and baffles surrounding the cryopanels. A suitable efficient piping network comprising vacuum jacketed cryogenic transfer lines, liquid nitrogen shielded transfer line and distribution manifold is used in the superconducting cyclotron for distribution of cryogens. A liquid helium pump ensures the required flow of liquid helium through the cryopanels. The cryogen delivery system is fitted with necessary field instrumentation and controllers to monitor and automatically control certain important process variables. The control system is a PLC based system which takes care of cool down, steady state, quench protection and warm up mode and generates alarm and interlock signals whenever necessary. The SCADA communicates with the PLC through dedicated control LAN and enables the operator to monitor, control and data log. This paper reports the overall control and instrumentation for the cryogen delivery system. | ||
| WEPMA104 | Drive System Instrumentation For VEC SCC Axial-Hole Magnetic Field Measurement | 467 |
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| Charged particle from the ECR ion source is injected axially into the VEC superconducting cyclotron. The ion beam passes through the vertical section of the axial injection system and the axial hole at the centre of the superconducting cyclotron before reaching the spiral inflector. An accurate knowledge of the magnetic field in the axial hole is essential to properly inject and accelerate the ion beam in the superconducting cyclotron. Three channel F. W. Bell tesla meter with both axial and transverse probes were used to measure the magnetic field. A probe drive with high resolution and repeatability was developed to map the field along this hole from median plane upto 3m above. Stepper motor drives three lead screws which move the hall probe assembly and position them correctly at regular intervals. The basic hardware includes a stepper motor, its drive control unit, PC with National Instrument PCI-6052E data acquisition card and RS232 interface for tesla meter. The GUI developed using Labview takes care of the stepper motor drive control, measurement of the field and statistical error analysis. This paper describes the set up and control system of this measurement. | ||
| THPMA022 | Design of the Proposed 250 Mev Superconducting Cyclotron Magnet | 661 |
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| VECC has proposed a project for the design and development of a 250 MeV superconducting proton cyclotron, which may be used in therapy. In this paper we describe the preliminary design calculations for the superconducting magnet. Hard-edge approximation method has been adopted for finding the poletip geometry to meet the basic focusing requirements of the beam. The uniform-magnetization method has been applied to calculate the 3D magnetic field distribution due to saturated iron poletips, to verify the beam dynamical issues and optimize the poletip geometry. GM type closed cryo-cooler technology is being considered for steady state liquifaction of evapourated He gas from magnet cryostat. | ||
| THPMA048 | Study of Vacuum Related Problems During the Energization of K500 Superconducting Cyclotron | 694 |
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| The K500 superconducting cyclotron main magnet has been commissioned successfully in VECC, Kolkata. During the process of energization, it has been observed that there was vacuum deterioration in the cryostat vacuum chamber with excitations. Detail studies have been carried out to examine the occurrence of such a situation. The electro-magnetic stress in the cryostat wall due to Lorentz force increases with current, and is more pronounced in the median plane of cryostat wherefrom various penetrations come out. This could be the possible reason for the OVC vacuum degradation. The paper reports the observations on vacuum deterioration during energization. An extensive study has been carried out to understand and explain the situation. | ||
| 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 |