[en] SST -1 Vacuum System is designed to cater the needs of various operational requirements of SST- 1 experiment. SST- 1 vacuum system is very complex in terms of its operation. Reliable operation of different equipment's of vacuum system demands monitoring of a large number of parameters, logical analysis of the data acquired and generating control commands for its various equipment's. This paper describes the design of the Data Acquisition and Control system for SST-1Vacuum System. (author)

[en] Full text: The SST-1 start-up studies and development of appropriate model has been initiated using electromagnetic field computation for active current carrying conductor and SST-1 vacuum vessel eddy characteristics. This electromagnetic model has been employed to predict individual electromagnetic field for active electromagnet such as vertical field coil (VF), poloidal field coil (PF), radial control coil (RCC), central solenoid (CS) and other active current carrying coil. This model can be also useful to determine the some other break-down parameter such as connection length, ionization length and electric field etc. (author)

[en] Steady State Superconducting Tokamak (SST-1) is a medium sized Tokamak. SST-1 Vacuum Vessel (VV) is one of the sub-systems of SST-1 Tokamak. The Vacuum Vessel provides an Ultra High Vacuum (UHV) environment for in-vessel components and plasma production. SST-1 vacuum vessel is a continuous torus structure fabricated using non-magnetic SS 304L material. For easy fabrication and assembly point of view, SST-1 vacuum vessel is divided into sixteen parts, out of which eight of them are vessel sectors (VS) while the other eight are vessel modules (VM). Vessel Sector (VS) is comprised of one number of Radial Port (RP), two numbers of vertical ports (top and bottom each) and one number of vessel sector ring. Vessel Module (VM) is made up of one number of Vessel Sector and two numbers of Inter Connecting Rings (ICR) on both sides. This paper will describe about the temperature measurements and calorimetric calculations of SST-1 Vacuum Vessel and its results

[en] One of the most important feature of Steady state Superconducting Tokamak -1 (SST-l) is the Nb-Ti superconducting magnet field coils. The coils will be kept in a high vacuum chamber (Cryostat) and liquid Helium will be flown through it to cool it down to its critical temperature of 4.5K. The coil along with its hydraulics has four types of joints (1) Stainless Steel (S.S.) to Copper (Cu) weld joints (2) S. S. to S. S. weld joints (3) Cu to Cu brazed joints and (4) G-10 to S. S. joints with Sti-cast as the binding material. The joints were leak tested with a Helium mass spectrometer leak detector in vacuum as well as in sniffer mode. However during the cool-down of the coil, these joints may develop leaks. This would deteriorate the vacuum inside the cryostat and coil cool-down would subsequently become more difficult. To study the effect of cooling on the vacuum condition of the Cryostat, a dummy Cryostat chamber was fabricated and a toroidal Field (TF) magnet was kept inside this chamber and cooled down to 4.5 K.A residual gas analyzer (RGA) was connected to the Cryostat chamber to study the behaviour of major gases inside this chamber with temperature. An analysis of the RGA data acquired during the coo-down has been presented in this chamber. (author)

[en] Tokamak SST - 1 is under commissioning at Institute for Plasma Research. It comprises of a toroidal doughnut shaped plasma chamber, surrounded by liquid helium cooled superconducting magnets, housed in a cryostat chamber. The cryostat has two cooling circuits, (1) liquid nitrogen cooling circuit operating at 80 K to minimize the radiation heat load on the magnets, and (2) liquid helium cooling circuit to cool magnets and cold mass support structure to 4.5 K. In this paper we describe (a) the leak testing of copper - SS joints, brazing joints, interconnecting joints of the superconducting magnets, and (b) the leak testing of the liquid nitrogen cooling circuit, comprising of the main supply header, the thermal shields, interconnecting pipes, main return header and electrical isolators. All these tests were carried out using both vacuum and sniffer methods. (author)

[en] The plasma density control plays an important role in Tokamak operation. The factors that influence plasma density in a Tokamak device are working gas injection, pumping, ionization rate and the recycle coefficient representing the wall conditions. Among these factors, gas injection is relatively convenient to be controlled. Hence, the most frequently adopted method to control the plasma density is to control the fast gas injection. This paper describes the design and experimental work carried out towards the development of Fast Gas Injection System for SST-1 Tokamak. Laboratory based test setup was successfully established for Fast Gas Injection System that can feed predefined quantity of gas in a controlled manner into vacuum chamber. Further, this FGIS system will be implemented in SST-1 Tokamak environment with online density feedback signal

[en] Density control feedback system for SST-1 is designed using heterodyne density signal as a feedback signal. During operation and control, the heterodyne system measures the plasma density and generates a signal in the form voltage ranging from 0 to 5 VDC. The generated one voltage each corresponds to a density value of 8.0 x 10"1"2 /cm''3. This signal is compared with the reference value using comparator devices. The feedback system will start when the plasma current reaches 80% and the plasma density reaches to 8.0 x 10"1"2 /cm"3. Once the plasma density reaches a maximum valve of 3.8 x 10"1"3 cm"3 or the plasma current start decaying, the feedback system will stop gas puffing. This density control feedback system will also be used to control the plasma density in H-mode plasma operation. The detailed design and implementation part of the control circuit is discussed in this paper. (author)

[en] The steady state super-conducting tokamak-SST1 comprises of two vacuum chambers (a) The vacuum vessel is a UHV chamber in which plasma will be formed and confined (b) The cryostat is a high vacuum chamber which houses the liquid Helium cooled superconducting coils. Leak detection plays a very important role in the achievement of desired vacuum level in any vacuum chamber. Leak detection of the cryostat chamber and vessel modules of SST - 1 involves various types of unconventional methods. It includes masking with thick polythene with Q- compound to cover polythene's border, masking with aluminium foil with adhesive tape to cover its border, formation of D-shaped gasket using industrial adhesive solution, acetone spray method for high order leak, etc. Pressure test with Nitrogen and Helium gas carried out to locate coarse leaks. This paper discusses description of the techniques for helium leak testing and its result. (author)

[en] A new experimental device was fabricated for CPP-IPR at the Mechanical Workshop of IPR to extract the H"- ions where Cesium (Cs) coated tungsten dust is used to produce H"- ions. The main parts of the fabricated system are plasma chamber, Cesium coating unit, grid assembly, support structure, extraction chamber and dust collection unit. The extraction chamber can be moved outside with the help of a rail fixed on the main stand. The dust collection unit will be used to collect the dust particles. Buffing and electro polishing of the chamber has been done for the better result of the vacuum and future experimental use. The device has been vacuum tested up to 10"-"7 mbar pressure and weld joints showed a He leak rate of the order of 10"-"9 mbar ltr/sec. The system is being pumped by a combination of turbo-rotary pumping system. The system has been tested in IPR workshop for its vacuum and mechanical test specifications and is presently installed at CPP-IPR, Guwahati. The poster will discuss various salient features of the system in detail and various aspects of its fabrication

[en] Full text: SST-1 Tokamak was successfully commissioned in 2012 and the first plasma was achieved in June 2013 with poloidal limiters having SS 304L as vessel wall material. Due to plasma wall interactions, high-Z impurities released from the vessel wall which in turn cools the plasma by radiation loss. In order to reduce this effect, in 2nd phase of SST-1 refurbishment, PFC components were installed in the system. PFCs were integrated inside SST-1 vacuum vessel which is designed to withstand an input heat load of 1.0 MW/m². Graphite was chosen as plasma facing material considering its good thermal properties and low atomic mass. Cu-Zr and Cu-Cr-Zr alloy plates embedded with SS 304L piping were used as back plate materials for proper heat conduction. Each and every component was tested at operating conditions to verify its functionality and to ensure conformity. Approximately 3800 tiles were mounted on 132 copper alloy back-plates. The total surface area of the installed PFCs exposed to plasma is about 40 m² which is nearly 50% of the total surface area of stainless steel vacuum chamber (∼75 m²). The volume of the vessel with the PFCs is ∼16 m³. Gas-togas heat exchange method was adapted to heat nitrogen gas which was pressurized using a dedicated gas blower system to bake the PFC components. All PFC components passed through a temperature of 250° C for 8 hours flat top and working pressure of 4 bar under UHV conditions in validation tests. Strict metrology and QA/QC plans were structured and executed to integrate the PFC components inside the vacuum vessel. During pump down of the SST-1 main vacuum vessel, PFCs were baked at 250° C for nearly 10 days to remove the absorbed water vapours. At this condition, this main vacuum vessel was maintained at 150° C. In addition, initially hydrogen discharge cleaning was carried out followed with subsequent helium discharge cleaning to remove other surface impurities. With all PFCs and diagnostic integrated to the system, a base pressure of 4.5 x 10^-8 mbar was achieved. This paper represents SST-1 post PFC Plasma-scenario, PFC requirement inciting factors, PFC architecture and lay-out details, PFC components experimental validations, metrology plan with QA/QC and final installation of PFC with the vacuum vessel. (author)