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[en] In the frame work of a development project for ITER neutral beam injection system a radio frequency (RF) driven negative hydrogen (H-/D-) ion source, (BATMAN ion source) is developed which is designed to produce several 10s of ampere of H-/D- beam current. This PhD work has been carried out to understand and optimize BATMAN ion source. The study has been done with the help of computer simulations, modeling and experiments. The complete three dimensional Monte-Carlo computer simulation codes have been developed under the scope of this PhD work. A comprehensive description about the volume production and the surface production of H- ions is presented in the thesis along with the study results obtained from the simulations, modeling and the experiments. One of the simulations is based on the volume production of H- ions, where it calculates the density profile of the vibrationally excited H2 molecules, the density profile of H- ions and the transport probability of those H- ions along the source axis towards the grid. The other simulation studies the transport of those H- ions which are produced on the surface of the plasma grid. It is expected that if there is a plasma flow in the source, the transport of plasma components (molecules and ions) would be influenced. Experimentally it is observed that there is a convective plasma flow exists in the ion source. A transverse magnetic filter field which is present near the grid inside the ion source reduces the flow velocity. Negative ions and electrons have the same sign of charge; therefore the electrons are co-extracted with the negative ions through the grid system, which is not desirable. It is observed that a magnetic field near the grid, magnetized the electrons and therefore reduce the co-extracted electron current. It is also observed experimentally that if the plasma grid is biased positively with respect to the source body, the electron density near the plasma grid is reduced and therefore the co-extracted electron current is also reduced. A double layer is formed near the positively biased plasma grid in the plasma, which would have an influence on the negative ion extraction mechanisms. In the process, two phase-sensitive diagnostic methods have been developed based on a new technique (modulation technique). One diagnostic is for measuring the H- ion density and the other one is for measuring the electron temperature. (orig.)
[en] Ultrasonic testing techniques are used for ISI of nuclear reactors, largely due to their versatility, single-surface access approach even for automated ISI system and also for components fully immersed in water or liquid etc. Ultrasonic testing systems with multiplexing unit can handle a number of transducers at a time and it can be very useful for an area needing multiple probes scanning or for a large area which needs faster coverage. Microprocessor based ultrasonic equipment can store the data for off line analysis and it can also be used with evaluation algorithm for further characterisation and reporting. Ultrasonic testing in the modem age is the most widely applicable NDT technique for ISI because of its ease of operation, inexpensiveness and faster coverage
[en] Highlights: • Development of a helicon plasma system to carry out ion–ion plasma studies in electronegative gases such as Hydrogen, Oxygen and Chlorine. • Determination of initial parameters of helicon plasma source for ion–ion plasma by using dispersion relation of bounded helicon waves. • Design and development of solenoid with magnetic field strength production capability of ∼ 600 G along the axis of the chamber. • Optimization of the chamber parameters using Helic codes and estimation of optimum attainable density. • Estimation of RF power requirements for various gases. - Abstract: A helicon plasma system is being designed and developed at CPP-IPR. The design parameters of the system are deduced from the dispersion relation of bounded helicon waves and the required magnetic fields are simulated by using Poisson Superfish code. The Helic code is used to simulate the power deposition profile for various conditions and to investigate the optimum values of chamber parameters for effective coupling of radio frequency (RF) power to plasma. The helicon source system is aimed at carrying out ion–ion plasma studies in electronegative gases such as Hydrogen, Oxygen and Chlorine. The system mainly consists of a source chamber in which helicon plasma will be produced by injecting RF power at a frequency of 13.56 MHz through a right helical antenna in presence of a DC magnetic field followed by an expansion chamber in which it is expected to produce negative ions along with the positive ions. Installation of the various parts of the system is in progress. The details of the design and development of the system is presented in this article.
[en] A conceptual design of a permanent magnet based single driver helicon plasma source module along with its design approach is described in this paper. The module unit is intended to be used in a large size ion source. The conceptual design of the helicon source module has been carried out using a computer code, HELIC. The magnetic field topology for the ring magnet is simulated with another code, BFieldM and the magnetic field values obtained from the calculation are further used as input in HELIC calculation for the conceptual design. The module is conceptualized based on a cylindrical glass vessel to produce plasma of diameter ∼50 mm, height ∼50 mm. The inner diameter of the permanent ring magnets is also of the same dimension with thickness ∼10 mm each, placed slightly above the backplate to maintain the required magnetic field. The simulated results show that for hydrogen gas, expected plasma density can be achieved as high as ∼10"1"2–10"1"3 cm"−"3 in the proposed helicon source configuration using 1 kW 13.56 MHz RF generator. An experimental setup to characterize a Helicon source module unit, consisting of a cylindrical glass (plasma) chamber along with the vacuum system, RF power supplies, probes and data acquisition system is being installed.
[en] ITER Diagnostic Neutral Beam (DNB) will inject 5Hz modulated, 100 keV energetic neutral hydrogen atom beam of equivalent neutral beam current ∼ 20 A, having duty cycle 3S ON/20S OFF into the ITER torus to measure He ash density using CXRS diagnostics during ITER’s D–T phase. DNB is negative ion based neutral beam system and possesses many technological challenges in terms of producing high extracted and accelerated negative ion beam current (60A) with minimal divergence to ensure maximum neutral current transport over a path length of 20.7 m through different beamline components, maintaining their respective optimum functionalities. Modelling calculations have been carried out to optimise the design and dispersion of the beam line components. Besides validating these calculations, new concepts related to establishing the functionality of an 8 plasma driver based RF negative ion source, the beam line components specially residual ion dump (RID) and correspondingly the beam transport need to be tested to meet the DNB needs. This is envisaged in a test facility (INTF) to be set up in the ITER-India lab of IPR. Experimental set up of such a facility requires a judicious choice of various diagnostics to characterize the beam and functionality of individual beamline components. Appropriate diagnostics based on optical spectroscopy, electrical probe, thermal imaging, water calorimetry and thermocouples along with standard electrical voltage-current measurements will ensure safe operation of individual components and also the overall system. The conceptual designs of some of these diagnostics shall be presented. (author)
[en] Negative hydrogen ion production by volume process and its transport in a negative hydrogen ion source has been simulated by a combination of three three-dimensional Monte Carlo codes: (1) neutral transport, (2) negative hydrogen ion production, and (3) negative hydrogen ion transport. Neutral transport code has been used to calculate the spatially resolved density spectrum nv of the vibrationally excited H2 molecules. With the negative hydrogen ion production code, the production and distribution of H- ion density n- in the discharge volume has been calculated. And with the negative hydrogen ion transport code, the calculation of the survival probability of H- ions up to the extraction grid has been carried out. In all cases, the experimentally observed plasma parameters, as well as background gas density and temperature profiles, are inputs during trajectory calculation. It has been found that the negative ion density is almost uniform from the ion production zone (driver) to the grid. However, H- ions, which are produced within a few centimeters from the grid, are only able to reach the extraction hole. To compare the code calculation, a zero-dimensional particle balance rate equation is also solved
[en] We have pointed out that in the race to develop negative ion source plasma physical and technical issues related to the plasma production and its transport, negative ion production and its extraction, effects of Cs and its recycling inside the source etc. have remained poorly understood. For any further improvement in the performance of the source, it is necessary to unravel different physical mechanisms leading to the formation of H- ions and its extraction and transport. For understanding these studies, we present here a conceptual design of an inductively coupled radio frequency (RF; ∼ 150 kW, 1 MHz) negative hydrogen ion source for the neutral beam injector (NBI). The source shall deliver 1.5 MW of hydrogen beam at 150 keV. A transverse magnetic filter field with ∫B.dl ∼2000 Gauss-cm, helps to separate the driver region (Te ∼ 20 eV, ne ∼ 1013 cm-3) from the extractor region (Te ∼ 1 eV, 1012 cm-3). Injection of Cs in the extractor region helps to enhance the negative ion production. During the extraction of the negative ions, the electrons are also co-extracted. Permanent magnets embedded in the extraction grid system help to filter out these electrons. (author)
[en] In boiling water reactors (BWR), austenitic stainless steels (Grades AISI 304 and 316) have been used for piping system. The welding of these pipes gives rise to sensitized microstructure and residual stress. In addition to this, presence of high temperature oxygenated water due to radiolysis provides highly corrosive environment. The conjoint action of the above three factors cause cracking along the grain boundaries which is referred to as intergranular stress corrosion cracking (IGSCC). Extensive investigations have been carried out in the last two decades to develop a technique to detect, locate and monitor the extent of IGSCC. Ultrasonic testing is found to be the most preferred NDT tool for this purpose. We have been carrying out periodic in-service inspection of BWR piping at Tarapur Atomic Power Station by ultrasonic testing to monitor the initiation and growth of IGSCC in weld heat affected zone of austenitic stainless steel piping. Of late, it has been realised that the existing technique has several limitations. Some new techniques based on ultrasonics like flaw tip diffraction method creeping longitudinal wave method, shear longitudinal inspection characteristics (SLIC) method, etc. are being developed to improve over the existing techniques. (author). 5 refs., 3 figs
[en] Surface production of negative ion is a dominating process in a high current negative ion source. In presence of surface produced negative ions, the plasma sheath near a metallic plane is modified and has been analysed in this report. The multivalued nature of electric potential at the sheath edge in electronegative plasma, determined by Bohm criterion is pursued in presence of surface produced negative ions.