1. magnetic confinement - ENEA - Fusione

2. IGNITOR PROGRAM 59
2.1 Introduction
Pre-eminent among the significant events affecting the IGNITOR Project in 2001
were the conclusions of the scientific debate initiated by the US fusion community
when the U.S. withdrew from the ITER Project. These conclusions were summarised
in the final report presented by the Fusion Energy Science Advisory Committee
(FESAC) of the Department of Energy (DOE) [2.1]. The objective of the report was to
provide the basis for proposing a programme for the next burning plasma
experiment in the United States. The FESAC report clearly states that the only
magnetic configuration sufficiently developed at this time to serve as a burning
plasma experiment is the tokamak, and that all three burning plasma experimental
designs today under development worldwide (IGNITOR, ITER-FEAT and FIRE)
would deliver a large and significant advance in the understanding of burning plasma. This
is an outstanding acknowledgement, at high international level, of the relevance of
IGNITOR.
[2.1] FESAC Panel Report
on Burning Plasma Physics,
Sept. 2001
[2.2] G. Cenacchi, et al.,
Bull. Am. Phys. Soc. 46,
272 (2001)
[2.3] A. Airoldi,et al., Bull.
Am. Phys. Soc. 46, 271
(2001)
[2.4] G. Cenacchi, A.
Airoldi: Equilibrium configurations
for the
Ignitor experiment, IFP
report FP 01/1 (February
2001)
At ENEA, the design of the IGNITOR machine is sufficiently detailed to start the
procurement of systems and components, once the Italian Government assures the funds
for its construction and ENEA starts the licensing procedure. Meanwhile, the design work
on this very compact, heavily loaded machine is being constantly updated to incorporate
the latest progress in theoretical knowledge and experimental results in operating
tokamaks. Technical specifications were issued to define the activity to be carried out with
the support of industry and to update and revise the design of the main systems and
components, and the relative contract is presently under negotiation with Ansaldo. In
2001, the design activities concerned studies on the machine flexibility and advanced
scenarios, the effect of new disruption data, the development of simplified engineering
models for stress analysis of the nuclear core, plasma-wall interaction and impurity
production studies and the design of the auxiliary ion cyclotron resonance heating (ICRH)
system.
2.2.1 Advanced scenarios
2.2 Physics
The poloidal field system is formed of 13+13 coils, symmetrically located relative to
the machine equatorial plane and independently powered. The system is very
flexible and allows X-point configurations as well as the limiter configurations of the
reference scenario. Preliminary analyses, carried out with the equilibrium-transport
code JETTO, concerned the possibility of obtaining high confinement conditions (the
so-called “H-mode”) in the presence of double-null configurations around 10 MA
and with auxiliary heating. The threshold power required for the L- to H-mode
transition, evaluated according to the ITER scaling, is within the limits of the
auxiliary heating system already included in the machine design [2.2]. The flat-top
phase of the nominal IGNITOR scenario was analysed for situations in which a high
impurity content delays ignition and leads to the development of sawtooth-type
MHD instabilities [2.3].
The MHD equilibrium configurations supporting the 11-MA 13-T IGNITOR scenario
were carefully revised. The poloidal field coil currents required throughout the
plasma evolution, from start-up to ignition, were determined both for the reference
conditions and for the advanced scenario with the double null 10-MA configuration.
Equilibrium configurations were obtained for both cases [2.4].
2.3 Engineering of the Machine
2.3.1 EM analysis of vacuum vessel during plasma disruptions
The global forces induced on the IGNITOR vacuum vessel during plasma
disruptions were estimated more precisely on the basis of the JET and Alcator C-Mod