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The ocean plays a major role in climate change, and its impact has an extreme effect on the process of coastal and other activities around the globe. The comprehensive analysis of long-term wave climate is carried out at selected locations in the western Bay of Bengal (BoB), by observing the distribution of significant wave height (SWH) using monthly averaged satellite and WAM model for 20 years (1996–2015). The data used in this study were compared with two in situ buoy observations obtained from the National Institute of Ocean Technology (NIOT), Chennai, India. The satellite and wave model (WAM) data show a good correlation with both in situ buoy observations. The probability distribution functions indicated a significant increase in the higher range of SWH during the recent decade. The analysis of 20-year SWH indicates a positive trend with significant annual and semiannual periodicities. The northwestern bay depicts higher energy in the annual cycle, whereas the southwestern bay exhibits equal contributions from annual and semiannual cycles. The study also reveals that the increasing trends in local SWH in the western BOB are modified due to the number of tropical cyclones as well as the migrating swells generated in the southern Indian Ocean. [ABSTRACT FROM AUTHOR]

The Indian test facility (INTF) is a negative hydrogen ion-based 100-kV, 60-A, 5-Hz modulated NBI system having 3-s ON/20-s OFF duty cycle. Prime objective of the facility is to characterize ITER diagnostic neutral beam (DNB) with full specifications, prior to shipment and installation in ITER. The automated and safe operation of the system will require a reliable and rugged instrumentation and control system which provide control, data acquisition (DAQ), safety, and interlock functions, referred as INTF-DACS. The INTF-DACS has been designed based on the ITER CODAC architecture and ITER- plant control design handbook (PCDH) guidelines with the aim of developing the technical understanding of CODAC framework to be utilized for development of plant system instrumentation and control for DNB. Presently, the development work has been initiated for both the control system and DAQ system of INTF DACS. The INTF DAQ system has to perform functions related to acquiring, monitoring, timing synchronization, and archiving of the signals. It also has to interface with the control system of INTF to ensure proper operations. The DAQ system is designed for acquiring over 700 signals for 14 plant systems. The development of this whole system is done in NI LabVIEW using NI real-time PXIe. The PXIe platform with RTOS performs acquisition of signals at sampling rate of up to 10 KS/s. One of the main challenges is to develop the DAQ system to support multichannel triggered-based acquisition and monitoring for pulse durations up to 3600 s. The host layer is a distributed processing system consisting of two hosts and database system. To ensure timing synchronization, a dedicated timing network is included based on IEEE 1588 protocol with help of PXI timing cards. This helps in providing a timing reference to other future systems. For archiving data, MySQL-based data server is integrated for storing data for each experimental shot continuously which can be utilized later for query based data retrieval. In this paper, the development strategy and test results are discussed in order to develop the DAQ system for INTF including the development of interfaces with other components of DACS and experiences obtained, which can be utilized to develop similar DAQ systems of large scale. The novel methods developed for monitoring signals and file size reduction are also discussed. [ABSTRACT FROM AUTHOR]

The Indian test facility (INTF) is a negative hydrogen ion-based 100-kV, 60-A, 5-Hz modulated neutral beam injector system having a 3 s on/20 s off duty cycle. The prime objective of the facility is to characterize the ITER diagnostic neutral beam (DNB) with full specifications prior to shipment and installation in ITER. The automated and safe operation of the system will require a reliable and rugged instrumentation and control system that provides control, data acquisition (DAQ), safety, and interlock functions, referred to as INTF-DAQ and control system (DACS). The INTF-DACS has been designed based on the ITER Control, Data Access and Communication (CODAC) architecture and ITER-plant control design handbook guidelines to develop a technical understanding of the CODAC framework to be utilized for the development of plant system instrumentation and control for DNB. The hardware has been selected from the ITER slow-and-fast controller catalog. For high-speed diagnostics, non-National Instruments (NI) high-speed digitizers have been selected. In the area of software, the CODAC core software for control application and NI-LabVIEW for the DAQ application have been finalized. There are around 300 control and 500 acquisition channels consisting of thermal, optical, current, and voltage measurements. The DACS has the mandate to operate INTF for pulselengths up to 3600 s by integrating 14 different plant systems, which includes the power supply plant system under a separate controller. The corresponding development possesses many technical challenges. The estimated file size of a single experimental pulse is in GBs for which the ITER suggested HDF5 format is selected. The timing distribution is another challenge because of the different resolutions required in fast controller, slow controller, and high-speed diagnostics in a distributed area. Long pulse DAQ and monitoring is another challenge. Data exchange across the software platforms, based on Experimental Physics and Industrial Control System (EPICS) and LabVIEW, is also required for integration. At present, the control and DAQ hardware have been integrated and the development phase has been initiated on actual hardware platforms. This paper describes the various developmental activities undertaken to solve the technical challenges in the previously mentioned areas and integration of various components of the DACS toward realizing the full-fledged functional INTF DACS. [ABSTRACT FROM AUTHOR]

A comprehensive study on the statistics, variability, and three-dimensional properties of the mesoscale eddies in the western Bay of Bengal (BOB) using satellite altimetry and Argo floats for the period 1993−2014 is presented. This is a key region characterized by ocean circulation variability at a wide range of scales, including the generation of seasonal boundary currents and mesoscale eddies. A hybrid algorithm based on the physical and geometrical properties of mesoscale eddies is applied to detect the eddies and track their propagation. The potential eddies with radius larger than 50 km and lifespan longer than 30 days are considered for the analysis. Two highly eddy−productive zones are identified: offshore of Visakhapatnam and the northern part of western BOB. It is noticed that the occurrence of anticyclonic eddies (ACEs) dominate the offshore of Visakhapatnam and cyclonic eddies (CEs) in the northern part of western BOB. In general, the ACEs move westward, but the CEs move southwestward and southward along the continental shelf of the western BOB. The ACEs are larger but the CEs have longer lifetime and are more energetic. The eddy genesis is found to be sensitive to the strength of the seasonal wind stress curl. The strong positive wind stress curl during summer favors the formation of more CEs. Investigation on three-dimensional properties of the eddies show that the CEs are generally intensified in the subsurface depths in the western BOB. Both ACEs and CEs have single-core vertical structure with the core at a depth of about 100 dbar. [ABSTRACT FROM PUBLISHER]

A three-dimensional coupled hydrodynamic biogeochemical sediment transport model is proposed to simulate the response of plankton dynamics in the Hooghly estuary to freshwater discharge under the presence and absence of tide, and in-depth understanding the significant processes involved in estuarine biogeochemistry based on Regional Ocean Modeling System (ROMS). Riverine-estuarine circulations are used to evaluate the tidal consequence on wavering of biogeochemical properties in the Hooghly estuary. Therefore, three numerical experiments are performed: 1) model run with tidal forcing, river discharge, and applied biogeochemical and sediment properties along with coastal current; 2) model run with tidal forcing along with coastal current plus applied biogeochemical and sediment properties; and 3) model run with river discharge along with coastal current plus applied biogeochemical and sediment properties to determine the chief role of this physical parameters on the transport of bloom in a well-mixed estuary using this coupled model for the first time in Hooghly estuary. The model divulges its capability in imitating observed temporal variability in tidal oscillation representing skill coefficients more than 0.80. The satellite remotely sensed Ocean Color Monitor Data is assimilated using an SOR algorithm to incorporate in the model as the initial field for chlorophyll-a concentration (chla) to retrieve the productivity of the estuary. Productivity is found maximum in the area of soaring suspended sediment implying maximum bottom stress contributed by tidal currents along with coastal currents evident from the realistic case. The RMSE calculated is less than 0.6, which implies that the model can perform reasonably well. [ABSTRACT FROM PUBLISHER]

Multidriver-based radio-frequency (RF) ion sources have emerged as the most promising option for producing the plasma in large ion sources required for fusion applications. In India, under domestic long-term fusion program, a negative ion source development program has been initiated. A 100-kW inductively coupled single RF driver-based negative ion source (ROBIN) has been installed and it is operational at the Institute for Plasma Research. The next step is to move to a multidriver source and address to several issues related to configuration and operation. A two-driver-based twin source has been configured for this purpose. The experimental plan is divided into two phases: 1) plasma operation phase and beam extraction and 2) acceleration phase. A vacuum chamber has been specially designed to accommodate these phases of operations. The data acquisition and control system (DACS) of the experimental system is designed based on International Thermonuclear Experimental Reactor—COntrol Data Access and Communication (ITER-CODAC) guidelines. Probe and spectroscopy diagnostics constitute the principal diagnostics. This paper presents the experimental system with emphasis on the aspects of mechanical, electrical, and DACS integration. [ABSTRACT FROM PUBLISHER]

Following the allocation of the procurement of the diagnostic neutral beam (DNB) to the Indian DA, a series of tasks have been undertaken to first assess the DNB configuration and arrive at an optimal beam-line configuration folding in the gas-feed and vacuum-pumping requirements. Specific emphasis is placed on the thermal, structural, and electrical designs of beam-line components, in order to ensure their compatibility with the criteria specified for ITER in vessel components, i.e., Structural Design Criteria for In-Vessel Components. The detailed assessment of manufacturing technologies and their compatibility with the ITER standards forms an integral part of the design. A common approach to manufacturing for DNB and heating-and-current-drive NB components shall be undertaken through a comprehensive prototyping phase which shall lead to built-to-print specifications. In addition to safety and remote-handling issues, the design also addresses the requirements of interfaces related to other systems such as cryo, hydraulic, pneumatic, vacuum pumping, gas feed, civil, power supplies and transmission, CODAC, etc. The successful delivery of DNB is dependent on two critical R&D aspects: 1) the production of a uniform low-divergence beam from the beam source and 2) a well-controlled transmission through lengths of ∼22 m. The first shall primarily be a subject of the Ion Source Test Facility-SPIDER [part of NB test facility (MITICA in Padova)]-where India is involved as a collaborator and the Indian test bed, where issues for DNB beam source which were not resolved in the SPIDER would be taken up. The second shall form one of the primary objectives of the Indian test bed to characterize the DNB. This paper presents the progress in DNB from the concept level to an engineered system along with the plans for system integration and an R&D intensive implementation. [ABSTRACT FROM AUTHOR]

The 100-kV negative-hydrogen-ion-source-based diagnostic neutral beam (NB) (DNB) injector, which forms a part of the Indian (IN) procurement package for ITER, targets a delivery of ∼18-20 A of neutral hydrogen-atom beam current into the ITER torus for charge exchange resonance spectroscopy diagnostics. Considering stripping losses, a ∼70-A negative ion current is required to be extracted from the ion source, which leads to a production of 60 A of accelerated ion beam. Subsequent process of neutralization, electrostatic ion separation, and transport to the duct leads to a large separation between the points of generation of the ion beam to the point of delivery of the NB into the torus (∼23 m). This forms one of the most important constraints for the transport of NBs to ITER. The requirements are not only for a stringent control over ion optics, the transport to electrostatic separator, minimum loss of beam due to intercepting elements, low reionization loss, and focusing to control interception losses but also for adequate compensation of residual magnetic fields to overcome magnetic field induced deflections also form important design issues for a reasonable transmission efficiency. Due to multiparameter dependence, it becomes necessary to assess the different scenarios using numerical codes. In the present case, the assessment has been carried out for the DNB using the beam-transport codes PDP, BTR, and the MCGF codes which are developed by the Russian Federation. An optimized configuration of the beamline has been arrived at on the basis of these code-enabled studies. These parameters are the following: listing of the vertical and horizontal focal lengths as 20.6 m, a spacing between ground grid and neutralizer of 1 m, and positioning of residual-ion dump at a distance of 0.75 m from the neutralizer exit. Further, optimizing the gas feed to the source and neutralizer leads to a final transmission of ∼35% of the extracted beam power to the torus. This paper shall present the methodology, the issues concerned, and the final configuration which forms the basis for the present engineering. [ABSTRACT FROM AUTHOR]