Francesca Bombarda

Near term perspectives for fusion research and new contributions by the Ignitor program

The main advances made within the Ignitor program, that is aimed at investigating the physics of fusion burning plasmas near ignition, are described. In particular, the operation of the machine in the H and I regimes at the 10 MA plasma current levels has been considered and analyzed. The unique properties of the plasmas that can be generated by operating the machine with reduced parameters (lower magnetic fields and plasma currents) relative to those needed to achieve ignition are identified. A key feature of this operation is the relatively fast duty cycle that can be maintained. The Ideal Ignition Conditions, under which the density barrier due to bremsstrahlung emission in high density plasmas is removed, can be attained in this case. The plasma heating cycles are identified for which the contribution of ICRH is used both to enter the H-regime and to optimize the time needed for ignition. The on going effort to set up a test ICRH facility is described. The initial results (2 km/sec) of the high speed pellet injection system developed for Ignitor and operated at Oak Ridge are reported. The combined structural analysis and integration of the entire machine core (Load Assembly) is discussed. The adopted control system for both the machine and the plasma column has been designed and is described. The design solutions of the vertical field coils made of MgB2 and operating at 10 K have been identified and the relevant R&D program is underway. The analysis of the Caorso site and of its facility for the operation of the Ignitor with approved safety standards is completed. The relevant results are being made available for the operation of Ignitor at the Triniti site within the framework of the Italy-Russia agreement on the joint construction and operation of the Ignitor facility. A development effort concerning the advanced diagnostic systems that is being carried out for fusion burning plasma regimes is described. An initial analysis of the characteristics of a neutron source based on a system of Ignitor-like machines is reported

Installation of the Ignitor Machine at the Caorso Site

The actual cost of building a new experiment can be considerably contained if infrastructures are already available on its envisioned site. The facilities of the Caorso site (near Piacenza, Italy) that, at present, houses a spent nuclear power station, have been analyzed in view of their utilization for the operation of the Ignitor machine. The main feature of the site is its robust connection to the electrical national power grid that can take the disturbance caused by Ignitor discharges with the highest magnetic fields and plasma currents, avoiding the need for rotating flywheels generators. Other assets include a vast building that can be modified to house the machine core and the associated diagnostic systems. A layout of the Ignitor plant, including the tritium laboratory and other service areas, the distribution of the components of the electrical power supply system and of the He gas cooling sytem are presented. Relevant safety issues have been analyzed, based on the in depth activation analysis of the machine components carried out by means of the FISPACT code. Waste management and environment impact issues, including risk to the population assessments, have also been addressed

Compact tokamak neutron sources as a first step towards hybrid fission-fusion reactors

Abstract An Ignitor-like tokamak that is compact, high field, and high density device, could make full use of the its intense neutron flux, without reaching ignition as a source of neutrons for materials testing in support of a fission-fusion hybrid device. The main features of this High Field Neutron Source Facility, which would have about 50% more plasma volume than Ignitor, are illustrated and the R&D required in order to achieve relevant dpa quantities in test materials are discussed. Several full-power months of operation are sufficient to obtain relevant radiation damage values in terms of dpa, and a scoping study of shielding the magnetic insulators to reduce radiation damage has been performed.

A High Field Tokamak Neutron Source Facility

Fusion creates more neutrons per energy released than fission or spallation, therefore DT fusion facilities have the potential to become the most intense sources of neutrons for material testing. An Ignitor-like device, that is a compact, high field, high density machine could be envisaged for this purpose making full use of the intense neutron flux that it can generate, without reaching ignition. The main features of this High Field Neutron Source Facility, which would have about 50% more volume than Ignitor, are illustrated and the R&D required in order to achieve relevant dpa quantities in the tested materials are discussed, in particular the adoption of superconducting magnet coils. Radiation damage evaluations have been performed by means of the ACAB code, showing the potential of high field, neutron-rich devices for fusion material testing. Few full-power months of operation are sufficient to obtain significant radiation damage values (in terms of dpa) of large size samples (~m3). The setup of a duty cycle for the device in order to obtain such operation times is discussed. The problem of radiation damage to the insulator of the Toroidal Field Coils has been explored. Two strategies for mitigating damage to the TF coil insulators have been demonstrated, and it is likely that both will need to be implemented to ensure the survival of the insulating material for the lifetime of the tokamak.