S E Sytchevsky

Analysis and Optimization of the Impact of Ferromagnetic Inserts on the Toroidal Field Ripple in ITER

The discreteness of the toroidal field (TF) coils causes toroidally asymmetric perturbations of magnetic field (TF ripple). Maximum value of the TF ripple produced in the plasma by ITER TF coils is 1.16%. The ripple requirements are determined by loss of fast particles and by potential changes in H-mode characteristics. The fast particle behavior is well known and a maximum TF ripple at the plasma separatrix of <;1% is enough to avoid excessive fast particle losses in all ITER scenarios. The quantitative influence of TF ripple on plasma performance in the H-mode remains the subject of continuing R&D and at this time the prudent approach is to make ripple as small as reasonably achievable. It is shown that optimum distribution of ferromagnetic inserts (FI) allows reduction of the TF ripple to about 0.3% in regular sectors of the ITER vacuum vessel (VV) and to about 0.55% in irregular VV sectors. Error fields produced by irregularity of the FI and currents in correction coils required for their reduction were also calculated.

Some Aspects of Winding Geometry Control for ITER Superconducting Coils Using Magnetic Measurements

A feasibility has been demonstrated for numerical reconstruction of geometrical displacement or deformations of the winding occurred in the manufacture and assembly of magnet coils using magnetic measurements, that is one of the principal issues for the quality control of the magnet. For validations of the proposed approach, test results of reconstruction of possible misalignments and deviations of the ITER coil are presented.

Up-grade of the CICC stability analysis taking into account a current imbalance between strands in multistage cables

The results of the CICC stability analysis carried out with newly developed computer code STABLOS taking into account the effect of current imbalance between strands and subcables of a 40-50 kA range Nb/sub 3/Sn conductor of the type used in the ITER Model Coils and Inserts are presented. The effects of the transverse interstrand resistance, Cu: non-Cu ratio in the strands and the cabling stage which the current imbalance is referred to are considered. The approach uses a previously developed code for the multichannel CICC thermohydraulical analysis.

Modeling of magnetic field perturbations in electrophysical devices due to the steel reinforcement of buildings

We have proposed an effective method for modeling the steel reinforcement in the buildings for electrophysical devices to take into account the magnetic field perturbation caused by the magnetization of bars. The reinforcement lattice has been represented by one or several layers of a homogeneous isotropic material with preliminarily calculated equivalent (averaged) magnetic properties. Examples of calculating these magnetic properties have been considered using a simplified analytic approach, as well as by the numerical simulation of the magnetic field in a 3D cell of a periodic reinforcement lattice. The efficiency of the method has been demonstrated based on an important practical example of simulating the perturbation of a uniform magnetic field caused by the reinforced slab. The results have been compared with the simulation data based on different approaches.

Coupled electromagnetic and thermohydraulic analysis of the ITER cable joint

An analysis of the current distribution in a joint of International Tokamak ITER has been carried out using two separated models (3D static transport current model and 3D thin conducting shell model for eddy current). The calculations were made by two finite element packages KOMPOT/C and TYPHOON. The total resistance of the joint and the total Joule loss created by the transport current and induced currents due to the external magnetic field change were estimated. Different modes of ITER operation were considered. Thermohydraulic response of the cooling system on transient and steady state disturbances in the joint were modeled by the VINCENTA code, which allows to define the transient temperature behavior of the joint assembly materials and Cable-In-Conduit Conductor (CICC) cooled by supercritical helium which flows in thermally and hydraulically coupled channels.