Uttam Bhunia

Online quality factor measurement of the SRF cavity in injector cryomodule of VECC electron LINAC

The ANURIB facility being planned at VECC will use a super-conducting electron linac (e-Linac) as photo-fission driver. The e-Linac will initially be of 30 MeV, 2 mA with an optional upgrade to 50 MeV planned in the future. An identical e-Linac is being built for the ARIEL project at TRIUMF, Canada. The 30 MeV e-linac is made using three 1.3GHz nine cell niobium cavities of Cornell-type, each cavity supplying 10 MV acceleration. The first 9-cell cavity is housed in a cryomodule called Injector Cryomodule (ICM) followed by an Accelerator Cryo-Module (ACM) comprising two 9-cell cavities. In the first phase, the ICM has been developed in collaboration with TRIUMF. The cavity operates at 1.3 GHz and 2 K. The paper highlights the online quality factor measurement of the ICM using calorimetric method.

Fabrication of racetrack-type double pancake HTS coil for K500 extraction beam line steering magnet

A High Temperature Superconductor (HTS) based cryorefrigerator assisted steering magnet sunder development at VECC for the extraction beam line of K500 cyclotron. The magnet designed is specified for ± 3 degree horizontal correction and ± 1.5 degree of vertical correction of the beam of maximum rigidity of 3.3 T-m. The magnet is composed of two sets of double pancake racetrack coil-one set for vertical field (By) and other for horizontal field inside the return iron yoke. Double pancake coils are fabricated in-house using BSCCO-2223 HTS tapes by wet winding technique using cryogenic grade epoxy. The critical characteristics of the coils are tested at liquid nitrogen temperature in terms of critical current and index parameters. The paper describes the winding details of double pancake coils and test results at liquid nitrogen temperature.

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.