Page 62 - Fundamentals of Magnetic Thermonuclear Reactor Design

ITER – International Thermonuclear Experimental Reactor Chapter | 3 45

TABLE 3.3 Average Characteristics of ITER Systems
Characteristics
Maximum permissible magnetic stray fields (T) ∼10 −3
Toroidal magnetic field on the plasma column axis (T) ∼5.0
Maximum magnetic field in the central solenoid (T) 13.0
Background residual pressure in vacuum chamber (Pa) ∼10 –5
Working gas pressure prior to discharge (Pa) ∼10 −3
Gas-kinetic pressure of plasma during the operation cycle (Pa) ∼3 × 10 5
Ponderomotive forces acting on vacuum chamber walls during ∼2 × 10 6
discharge current disruption (Pa)
Magnetic pressure in the central solenoid (Pa) ∼10 7
Superconductor working temperature (K) ∼4.5
Maximum working temperature of the divertor target plates (K) ∼1300
Plasma temperature during cycle plateau (K) ∼10 8

3.3 MAGNET SYSTEM
The magnet system (MS) is composed of toroidal and poloidal magnetic field
coils, sections of the central solenoid (CS) and 18 correction coils. The MS is
rigidly connected to the VV by mechanical load-bearing structures (Fig. 3.5;
Table 3.4). The coils are cooled by supercritical helium at 0.6 MPa.
The coils use uniform superconducting cables in conduits. Coils with a mag-
netic field up to 6 T are manufactured from niobium–titanium, and those with
a greater magnetic field are made of niobium–tin intermetallic compound. The
number of strands in each cable depends on the working current.
The conductors are cooled with liquid helium that travels along the cable’s
central channel and between the strands. The material and shape of the conduit
depend on a conductor’s function. The TF and correction coils use round cross-
section conductors, while the poloidal field (PF) and CS coils employ square
cross-section conductors [4].
An extensive international R&D programme and a long period of study and
testing preceded the MS live implementation. In summary, they aimed at the
following:
l Designing, fabricating and certificating Nb Sn and NbTi based supercon-
3
ducting wires;
l Developing a cable-in-conduit fabrication technology;
l Developing cable and magnet diagnostics methods and equipment;
l Studying the physical, mechanical and electrophysical properties of the
obtained superconductors, including the current-carrying capacity, energy