[en] Quench Detection (QD) system consisting 204 signal channels has been successfully installed and working well during plasma experiment of SST-1 Tokamak. QD system requires testing, validation and maintenance in every SST-1 campaign for better reliability and maintainability of the system. Standalone test of each channel of the system is essential for hard-ware validation. The standard Testing Protocol follow in every campaign which validate each section of QD electronics as well as voltage tap signal cables which are routed inside the cryostat and then extended outside of the SST-1 machine up-to the magnet control room. Fiber link for Quench signal transmission to the SST-1 magnet power supply is also test and validate before every plasma campaign. Precise instrument used as a dummy source of quench signal and for manual quench generation to test the each channel and Master Quench Logic. Each signal Integrated with the magnet DAQ system, signal observed at 1Hz and 50Hz configuration to validate the logging data, compare with actual and previous test data. This paper describes the testing protocol follow in every campaign to validate functionality of QD electronics, limitation of testing, test results and overall integration of the quench detection system for SST-1 magnet. (author)

[en] Steady State Superconducting Tokamak (SST-1) magnet system consists of 16 superconducting Toroidal Field (TF) coils and nine superconducting Poloidal Field (PF) coils and a pair of resistive field coil inside the vacuum vessel. A wholistic approach is adopted in Quality assurance (QA) and Quality Control (QC) of process and components used in the preparation of these magnets for SST-1 operation. A Quality Control Plan (QCP) and Procedure Qualification Records (PQR) has been followed in the fabrication of superconducting magnet joints and manifolds. A pre-fabrication inspection comprised of visual inspection, dimensional measurements of copper blocks and jacket end caps and Destructive Tests (DT) of materials used for different component of these magnets like joints, manifolds, sleeves tubes etc. Fabrication inspection involved visual inspection, argon gas flow parameters and temperature monitoring, while the post fabrication inspection comprised of Non Destructive Tests (NDT) of the jointbox and manifold. This paper describes the individual QA and QC in detail. (author)

[en] The key role of the central solenoid (CS) magnet of a Tokamak is for gas breakdown, ramp up and maintaining of plasma current for longer duration. The magnetic flux change in CS along with other PF coils generates magnetic null and induces electric field in toroidal direction. The induced toroidal electric field accelerates the residual electrons which collide with the neutrals and an avalanche takes place which led to the net plasma in the vacuum vessel of a Tokamak. In order to maximize the CS volt-sec capability, the higher magnetic field with a greater magnetic flux linkage is necessary. In order to facilitate all these requirements of SST-1 a new superconducting CS has been designed for SST-1. The design of new central solenoid has two bases; first one is physics and second is smart engineering in limited bore diameter of ∼655 mm. The physics basis of the design includes volt-sec storage capacity of ∼0.8 volt-sec, magnetic field null around 0.2 m over major radius of 1.1 m and toroidal electric field of ∼0.3 volt/m.The engineering design of new CS consists of Nb_3Sn cable in conduit conductor (CICC) of operating current of 14 kA @ 4.5 K at 6 T, consolidated winding pack, smart quench detection system, protection system, housing cryostat and conductor terminations and joint design. The winding pack consists of 576 numbers of turns distributed in four layers with 0.75 mm FRP tape soaked with cyanide Easter based epoxy resin turn insulation and 3 mm of ground insulation. The inter-layer low resistance (∼1 nΩ) at 14 kA @ 4.5 K terminal praying hand joints has been designed for making winding pack continuous. The total height of winding pack is 2500 mm. The stored energy of this winding pack is ∼3 MJ at 14 kA of operating current. The expected heat load at cryogenic temperature is ∼10 W per layer, which requires helium mass flow rate of 1.4 g/s at 1.4 bars @ 4.5 K. The typical diameter and height of housing cryostat are 650 mm and 2563 mm with 80 K shield respectively. The protection system consists of SS310 made array of dump resistor of 20 mΩ. The detail physics and engineering design of new superconducting CS of SST-1 will be discussed in this presentation. (author)

[en] SST-1 magnet system consists of sixteen Toroidal Field (TF) coils and nine Poloidal Field (PF) superconducting coils along with a pair of vertical field coils and air core ohmic transformer. These magnets are instrumented with various cryogenic compatible sensors and voltage taps for its monitoring, operation, protection, and control during different machine operational scenarios like cryogenic cool down, current charging cycles including ramp up, flat top, plasma breakdown, dumping/ramp down and warm up. A VME hardware based data acquisition system has been developed for data monitoring, acquisition and control of magnet operation. A java platform based client and server utility has been developed for this data acquisition system. Upgradation of this java software utility has been carried out with enhance features, fast operating performance and new tools additions. Upgradation features includes larger data file sizes, highlights of critical data indicators, new file generation, online mass flow calculations etc. This poster describes basis hardware details, upgradation of previous software utility, testing and troubleshooting during software development. (author)

[en] Highlights: • We addressed how thermal anchoring in large scale coil test is different compare to small cryogenic apparatus? • We did precise estimation of thermal anchoring length at 77 K and 4.2 K heat sink in large scale superconducting coil test experiment. • We addressed, the quality of anchoring without covering entire wires using Kapton/Teflon tape. • We obtained excellent results in temperature measurement without using GE Varnish by doubling estimated anchoring length. -- Abstract: Effective and precise thermal anchoring of wires in cryogenic experiment is mandatory to measure temperature in milikelvin accuracy and to avoid unnecessary cooling power due to additional heat conduction from room temperature (RT) to operating temperature (OT) through potential, field, displacement and stress measurement instrumentation wires. Instrumentation wires used in large scale superconducting coil test experiments are different compare to cryogenic apparatus in terms of unique construction and overall diameter/area due to errorless measurement in large time-varying magnetic field compare to small cryogenic apparatus, often shielded wires are used. Hence, along with other variables, anchoring techniques and required thermal anchoring length are entirely different in this experiment compare to cryogenic apparatus. In present paper, estimation of thermal anchoring length of five different types of instrumentation wires used in coils test campaign at Institute for Plasma Research (IPR), India has been discussed and some temperature measurement results of coils test campaign have been presented

[en] Highlights: • Prototype of bridge type joints fabricated and validated successfully. • Bridge type joints fabricated and validated on one of the SST-1 PF#3T coil successfully. • Joint resistance was measured with precision nano volt meter and PXI based data acquisition system. • Leak tightness of joint box was better than 3 × 10⁻⁶ Pa m³ s⁻¹. • The measured joint resistance of bridge type joint was ∼1.6 nano ohm. - Abstract: A novel concept of bridge joint for Poloidal field (PF) magnet of SST-1 with damaged winding pack has been realized. This joint has been fabricated on 5th and 6th layers of PF#3T coil winding pack (WP) after validation at 10 kA at liquid helium temperature of 4.2 K in current lead test chamber. The joint resistance of bridge joint was measured ∼1.6 nΩ at flat top DC current of 10 kA. This type of joint could be economically useful for revival of a shorted and damaged WP superconducting PF magnets of Tokamaks. In this paper, details of bridge joint design, fabrication and validations are discussed

[en] The magnet system of the SST-1 tokamak at the Institute for Plasma Research, Gandhinagar, India, consists of sixteen Toroidal field and nine poloidal field superconducting coils together with a pair of resistive PF coils, an air core ohmic transformer and a pair of vertical field coils for its various magnetic field requirements. Various cryogenic compatible sensors and voltage taps are installed in those magnets for its monitoring, operation, protection, and control during different machine operational scenarios like cryogenic cool down, Magnet current charging cycles including ramp up, flat top, plasma breakdown, dumping/ramp down and Cryogenic warm up. This poster gives overview of the Magnet signal conditioning electronics hardware, testing of signal conditioning electronics with VME based data acquisition hardware and the measures taken to counter combined errors due to electronics and VME hardware after long time running experience in SST-1 cryogenic cool down campaigns

[en] Magnet system has initiated various activities for new development as well as maintenance and operation of existing systems. SST-1 related activities consist of thermal hydraulic study of superconducting TF and PF coils at RT, 200 K, 100 K and 80 K. Superconductivity of PF coils, Operation of TF coils at 1.5 T and error field measurements at RT and at low temperature. Technological initiative comprises of various conductor fabrication, heat treatment of Nb₃Sn strands, sub cables and development of high temperature superconducting cables for future Tokamaks. Laboratory level validation tests on Low Tc and high Tc superconductors have also been initiated. Achievements of magnet systems in last few months will be presented in this paper. (author)

[en] Technical High temperature superconducting (HTS) tapes are commercially available for various magnet applications. Its higher tensile strength gives rise to strain tolerance and hence can be used for winding of smaller diameter coils. HTS magnets usually consist of a number of spirals/pancakes to be connected in series through low resistance joints for the magnetic field generation. The most crucial component in making an inter-pancake joint is to make with minimum electrical joint resistance. The joining of two HTS tapes is crucial because of their structural design of materials, which are prone to deterioration, if exposed to a higher critical strain and temperature. In the present case, Pb-Sn (60% lead and 40% tin) solder material of melting point around 188°C is used for the fabrication of different joint configurations. Joints are prepared with and without SS sheath by mechanical etching for BSCCO tapes. Resistances of these joints were measured using four probe methods at 77 K and 10 K. The lowest joint resistance of 120 nano Ohm without SS sheath with parallel overlap length of 100 mm achieved at 77 K, and 47 nano Ohm at 10 K, Self-field. In this presentation, various types of joint configurations viz. overlap; parallel overlap, inclined bridge, perpendicular bridge & spiral with Di-BSCCO, BSCCO and YBCO, REBCO tapes and measured joint resistances have been reported. (author)

[en] SST- 1 Magnet Division, IPR is involved in the operations and maintenance activity of sensor signal conditioning of ∼150 temperature measurement channels used for low temperature measurement of CICC made super conducting magnets. Measurement of cryogenic temperature of different active and passive locations in the Steady State superconducting Tokamak (SST-1) machine is needed to be accurate and reliable. For reliable and safe operation of the magnet system, it is necessary to measure the temperature information with 0.1 K accuracy on 4 to 5 K operation temperature of the magnets. The signal conditioning, excitation current sources and VMEbus chassis Hardware with associated analog acquisition cards add offset in order of mV to final acquired voltage and hence in converted temperature. The non-linear negative temperature coefficient (NTC) temperature sensor has lower sensitivity at room temperature, therefore gives the 3K to 5K errors at the room temperature measurement. An error in the measurement makes difficult to establish relation between cryogenic condition and temperature of particular portion of the machine. Therefore a combine calibration of the temperature system with maximum error of 0.5 to 1 K between actual and measured temperature with DAQ is needed to be carried out. Prior to plasma campaigns is required to minimize the error due to thermal drift in offset voltage (mV/K) and permanent DC shift (order of 1 to 3 mV) in signal conditioning electronics, error in excitation current sources (order of 10 nA) and offset (order of 1 to 3 mV ) in data acquisition analog input modules. Systematically offset is compensated at each stage by proper calibration techniques to obtain minimum required accuracy in measured temperature. Conclusively we were able to minimize error in temperature measurement up to 0.5 to 1 K between actual and measured temperature through DAQ. This poster describes the temperature measurement system, results and its calibration procedure of the SST-1 superconductor magnet system. (author)