Jun-Sik Choi

Fabrication of the KSTAR superconducting CICC

A superconducting cable-in-conduit conductor (CICC) is adopted for the Korea Superconducting Tokamak Advanced Research (KSTAR) superconducting magnet system which consists of 16 TF coils and 14 PF coils. The KSTAR Magnet system uses two different types of CICCs-Nb/sub 3/Sn cable with Incoloy 908 conduit and NbTi cable with 316LN stainless-steel conduit. A continuous CICC jacketing system is developed for the KSTAR CICC fabrication and the jacketing system uses the tube-mill process, which consists of forming, welding, sizing and squaring procedures. The design specification of CICCs and the fabrication process is described. The welding of the Incoloy 908 strip joint is also discussed. The fabrication results including the geometrical specification and the void fraction will be discussed.

Development of CICC for KSTAR TF coil system

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system consists of 16 TFs (Toroidal Field) and 14 PFs (Poloidal Field) coils. Internally-cooled cabled superconductors will be used for the magnet system. The magnet systems adopt a superconducting CICC (Cable-In-Conduit Conductor) type conductor. The KSTAR TF CICC uses Nb/sub 3/Sn superconducting cable with Incoloy 908 conduit. For the fabrication of TF 1/spl sim/3 CICC, cables have been fabricated and the cable has a length of 640 m and a diameter of 22.3 mm. A continuous CICC jacketing system is developed for the CICC jacketing and the jacketing system uses the tube-mill process, which consists of forming, welding, sizing and squaring procedures. The cabling and the jacketing process is described. The welding condition of the Incoloy 908 and design specification of CICCs are also discussed. The fabrication results including the geometrical specification and the void fraction will be discussed.

A Performance Investigation of an Internal Quad-Band Antenna With Double-Spiral Structures

This letter describes a design of an internal quad-band antenna resonating at cellular (824~894 MHz), DCS/PCS (1710~1880 MHz/1850~1990 MHz), and WiBro (wireless broadband Internet, 2300~2390 MHzs) system band by inserting the spiral slits corresponding to the resonant frequencies. In order to accomplish this goal, double-spiral structures are suggested and analyzed by using a commercially available software package based on the finite-difference time-domain (FDTD) algorithm and basic equation for fundamental resonant frequency. In addition to that, the experimental results are compared with the predicted data obtained from the software package, CST MW Studio by considering the criterion of VSWR as 3:1. The proposed antenna and substrate are so small that they can be mounted and packaged in mobile phones. The measured radiation patterns are in good agreement with simulated results

Development of the conical spring linear vibrator (CSLV) for mobile phone

In this paper, we proposed a coin shaped linear vibrator having a conical spring. The design of linear vibrator is simple rather than rotary vibrator, which leads to lower cost, easy manufacturing and long lifetime. To increase the vibration force of linear vibrator, we used conical spring. This paper details design procedure of the conical spring linear vibrator (CSLV) using electromagnetic field simulation, structural FE simulation and transient vibration analysis.