Subimal Saha

Transient stability of NbTi Rutherford cables for energy storage magnet applications

Stability and quench behavior against transient perturbation expected during operation of a fast cycling energy storage magnet is an important issue for its design and safe operation. Understanding of thermal stability in terms of minimum quench energy (MQE) of a superconducting cable under specific operating scenario is of primary importance for its magnet application. Process of current redistribution from quench strand to adjacent strands depends on inductive coupling and has influence on quench development in the cable. The electrodynamic and thermal behavior of a ten-strand Rutherford-type cable for SMES program in the centre is studied numerically in the framework of discrete network modeling. Influence of several parameters such as uncertainties of inter-strand transverse and adjacent resistance, cooling conditions with liquid helium, etc. on MQE and quench behavior of Rutherford cable is discussed in this paper.

Design study of 4.5 MJ sector-toroidal SMES coil

In continuation of SMES technology development in our centre, design study of a 4. 5 MJ (1.25 kW h) sector-toroidal SMES coil using custom make Rutherford type NbTi cable is reported. The sector- toroid is optimized with six modular type solenoid coils connected in series. The basic module is considered to be solenoid type because of its easier winding technique though it is not the best choice from stress considerations. The coil operating current as well as maximum magnetic field at the inner layer has been determined in order to limit voltage across the coil during discharging mode of its operation and also to minimize the overall dynamic and static load in the cryostat. Due to asymmetric field distribution around the coil, each coil experiences a huge centered force that needs to be arrested with proper support structures. Therefore, extensive magneto-structural stress analysis has been carried out using commercial finite element code ANSYS. The paper describes the magnetic design, three dimensional stress analyses in coil and its support structure during cool-down and energisation, design scheme of sector- toroidal SMES cryostat, etc.

Design, Installation and Commissioning of new Vacuum chamber for Analysing Magnet of K-130 Cyclotron

In view of up-gradation of K-130 Cyclotron at VECC, Kolkata, we have designed a new Vacuum chamber to modify the existing vacuum chamber system. This new chamber is meant for C-shaped 1T dipole type 159.5° Analysing Magnet of 4710 OD × 2750 ID × 1075 mm tall in the RIB feeder beam-line. The welded type vacuum chamber is made of SS-304. The chamber with trapezoidal cross-section is of 4447 OD × 4057 ID × 61.5 mm average height. Pumping ports and modules are selected accordingly to ensure the required high vacuum for beam transport. The chamber improves the base vacuum and reduces the complicated O-ring replacement mandatory for existing chamber made of aluminium alloy. The new chamber is installed at site along with all the pumping module and beam line components. This paper presents the detailed design, installation and commissioning results.