Work Package 4 (WP4)

Fusion: Development of new materials for energy production via fusion

Objectives and intended results

• One of the main goals of WP 1.4 is the technical design study for the installation of an experimental set up that will allow for sample irradiations under controlled temperature conditions in the range from 4 up to about 1300 K. This setup is of fundamental importance, particularly for applications in the field of energy production via fusion, as it will facilitate research aiming at understanding the mechanisms that govern the changes of material properties under irradiation and, consequently, the development of materials that are resistant to radiation and high temperatures. The installation of such a setup has the potential to attract researchers from all over Europe, who are active in the field of materials study and design with applications in fusion and fission nuclear reactors.
• The transfer of materials in fusion reactors with magnetic plasma retention and the fuel adsorption at the walls are issues of great importance for the safe operation of these reactors. The underlying mechanisms require a deep understanding of these phenomena in order to make predictions about the lifetime of the first wall materials and estimate the amount of the adsorbed fuel mainly at the composite layers. In this frame, nuclear analytical techniques will be developed and used by utilizing ion beams in order to study plasma exposed materials at the JET tokamak. The studies will be performed on materials coming from the JET Tokamak Divertor as well as and from the main chamber. To achieve this goal, the existing experimental setups for Rutherford backscattering spectrometry (RBS) and Nuclear Reaction Analysis (NRA) used for the quantification of light elements (deuterium, beryllium, carbon, etc.) as a function of material’s depth, will be optimized.
• In the framework of Greece’s participation in the European Thermonuclear Fusion Program, the IR2 experimental setup for ion irradiations that was developed by the Fusion Technology Group and installed at the Tandem accelerator will be integrated into the CALIBRA Research Infrastructure. The IR2 setup has been successfully employed to perform studies of the recovery of radiation damage to metallic materials via in-situ electrical resistivity measurements. The IR2 setup is one of the few setups in the world with similar capabilities and with its use, innovative studies on structural materials for future fusion reactors, such as Fe-Cr ferritic steels, have been conducted. Its integration into CALIBRA will enable access to material scientists from Greece and abroad to the capabilities provided by IR2.

Tasks to implement

• Development of an appropriate infrastructure to allow for irradiation of materials under controlled temperature conditions. This is necessary as the temperature of these materials increases during irradiation increases due to the ion-beam energy deposited in the materials. Controlled temperature will be achieved by using:

1. closed cycle cryostat with temperature range from 4 up to 600K
2. furnace with temperature range from 300 up to 1300 Κ.

In addition, a high vacuum chamber with suitable ports will be installed to enable in-situ measurements with ion-beam or other complementary techniques. The irradiation chamber will connect the controlled environment devices with the ion beam. It will be able to accept the high and low temperature system and will have the capability to accept additional sample environment devices for future development (eg mechanical stress). Following instruments will also be coupled to the chamber:

1. measurement instruments for recording and temperature control
2. optical diaphragms to determine the ion beam
3. computer systems and software for data collection and analysis

• The method of analysis via nuclear reactions with deuterium beam, is one of the few ion methods that can simultaneously give the distribution of concentration of many light elements (deuterium, beryllium, carbon, oxygen, etc.) as a function of depth. This is why it is considered to be the most appropriate method for sample analysis coming from the walls of the JET Tokamak. On the other hand, the accuracy of the results of the method is significantly affected by the presence of heavy elements (Tungsten and Molybdenum) in the same sample. Improving the precision of the method involves the removal of elastic scattered deuterium from heavy elements by using appropriate filters on the detectors. For this purpose, a series of measurements will be made on samples from JET Tokamak, after an appropriate deuterium cutoff filter has been studied and installed. For this purpose a series of measurements with samples from the JET Tokamak will be carried out.
• For the integration of IR2 set-up (http://ipta.demokritos.gr/ftg/ir2.html) in the CALIBRA infrastructure, some technical modifications will be needed, related mainly to the higher levels of ion flux after the upgrade of the TANDEM accelerator. For this, a redesign of the sample / target holder is required in order to increase the capability of heat transfer and to ensure the temperature stability during ion irradiation. Also, the redesign should enable the simultaneous irradiation of multiple samples so as to maximize the utilization of the ion beam. At the same time, an appropriate user-friendly software should be developed to automate the device operation and the data collection.

Outputs (Deliverables)