Malay Kanti Dey

Development of a fast scintillator based beam phase measurement system for compact superconducting cyclotrons.

In an isochronous cyclotron, measurements of central phase of the ion beam with respect to rf and the phase width provide a way to tune the cyclotron for maximum energy gain per turn and efficient extraction. We report here the development of a phase measurement system and the measurements carried out at the Variable Energy Cyclotron Centres (VECCs) K = 500 superconducting cyclotron. The technique comprises detecting prompt γ-rays resulting from the interaction of cyclotron ion beam with an aluminium target mounted on a radial probe in coincidence with cyclotron rf. An assembly comprising a fast scintillator and a liquid light-guide inserted inside the cyclotron was used to detect the γ-rays and to transfer the light signal outside the cyclotron where a matching photo-multiplier tube was used for light to electrical signal conversion. The typical beam intensity for this measurement was a few times 10(11) pps.

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.

Design of cryo-refrigerator assisted HTS steering magnet for K500 cyclotron beam line

The steering magnet is required for the external beam line of K-500 cyclotron to provide corrective steering capabilities. A conventional copper based steering magnet for high rigidity beam (maximum up to 3.3 T-m) becomes very bulky and difficult to integrate in beam line if large steering (±3 degree horizontal (X) and ±1.5 degree vertical (Y)) is required. Recently, commercial availability of long length (more than 100 m) high temperature superconductor (HTS) tape along with availability of high power cryo-refrigerator has given opportunity to develop compact conduction-cooled HTS magnet operating at temperature of 20 K or even higher. Although many prototype magnets using HTS tape have been fabricated and evaluated, there are only few applications in the particle accelerator fields. The paper describes the physics design aspect of the X-Y steering magnet along with details of cryostat.

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.

Quench analysis of a novel compact superconducting cyclotron

Design and analysis of a compact superconducting cyclotron dedicated for medical applications in the fields of nuclear medicine and therapy is presently being pursued in our organization. The novelty of this cyclotron lies in the fact that it does not consist of any iron-pole. The cyclotron magnet will be made of a set of NbTi coils comprising of solenoid and sector coils which are housed in two halves on either sides of the median plane. The average magnetic field is 1.74 T and the maximum extraction energy is 25 MeV, which is sufficient for production of 99mTc from Mo. In this paper, quench analyses of the coils have been discussed in details considering adiabatic condition. The entire cryostat magnet along with coils, formers and support links were modelled for the quench simulation. Self and mutual inductances of all the coils were obtained from a separate magnetic analysis and used in the simulation. Parametric analyses were carried out with different quench initiation energy at various critical locations on the coil surface. The corresponding quench behaviour, i.e. maximum temperature rise, maximum voltage and current decay in each of the coils have been studied.