Dust Technologies for Thermonuclear Fusion
Dust Technologies for Thermonuclear Fusion
Tech Area / Field
- FUS-MCS/Magnetic Confinement Systems/Fusion
- FUS-PLA/Plasma Physics/Fusion
8 Project completed
Senior Project Manager
Tocheny L V
Kurchatov Research Center, Russia, Moscow
- St Petersburg State Polytechnical University, Russia, St Petersburg\nState Enterprise Krasnaya Zvezda, Russia, Moscow
- European Fusion Development Agreement / EFDA Plasma Edge Technology Programme, Germany, Garching
Project summaryThe goal of the Project is to develop innovative technologies for emergency tokamak discharge quench and for the first wall maintenance by means of injection of high speed dusty jets into the tokamak plasma.
Fast quenching of tokamak discharges in case of expected major disruption or other emergencies has been performed using killer pellets and intensive gas jets. Both technologies are based on injection of cold matter (hydrogen or noble gases in gas or solid state phases) with total particle content comparable or even exceeding that one of the plasma particles. It is necessary to inject the pellet or gas into plasma in a few milliseconds after the quench precursor signal, which requires km/sec or higher velocities. For killer pellets the main technological problem is complicated injection devices and substantial time spent for pellet acceleration. The problem of gas jets technology is an absence of appropriate high-pressure (>100 bar) fast valves with large throughput (>1024 atom/shot). Another problem is low sonic speeds of heavy gases.
Since the quenching gas should be delivered into the boundary plasma and it penetrates then into the plasma core due to stimulated MHD-events the integrity of pellets providing deep pellet penetration is not very significant for the quench technology. Therefore delivery of the same amount of quenching gas in dust form will produce similar effects on plasma discharge. Meanwhile, the formation of dust jets with the desired parameters (mass, speed, injection delay time) may be possible with simpler and more efficient technology. This is the first idea that we propose to test within the Project.
A cryogenic dust injector (hydrogen, deuterium or neon) will be designed, manufactured and tested in T-10 tokamak experiments with fast discharge shutdown. In case of success the technology may be implemented on large tokamaks like JET, Tore-Supra, ASDEX Upgrade and ITER.
The advantages of the technology are as follows:
- The technique may be efficient and reliable way to produce and inject into a large tokamaks’ plasmas a sufficient amount of frozen gas (several cubic cm per shot with the speed of several km/s);
- High speed (several km/s) of dust jet and low delay time will allow to provide jet injection into plasma in a few milliseconds after the precursor signal;
- The forming gas pressure is low (~1 bar), which is very important as far as hydrogen is a highly explosive gas.
Maintenance of the first wall by evaporation of lithium limiters, laser blow-off technique and pellet injection has been already tested in several tokamaks. The lithium technology has demonstrated reduced recycling regimes for hydrogen atoms and low value of effective plasma charge.
The dust jet technology applied for injection of lithium into tokamak may be very effective in boundary and pertor plasma control and maintenance of the first wall. Ablation of lithium dust cloud the scrape-off layer or pertor region will reduce the boundary plasma temperature and will essentially change the basic mechanisms of the plasma-wall interaction reducing the amount of heavy mass impurities. Rather small dust particles with the size of several tens of microns and a low velocity about of 10 m/s will provide lithium ablation inside the SOL plasma. Then, the ablated atoms will provide a thin renewable layer over the whole first wall and pertor plates. The 10 microns width lithium jet can be injected by a piston device coupled with a sprayer.
The proposed project is aimed on a development of new technologies for the magnetic confinement plasma devices. The technologies will open the effective ways of high temperature plasma discharge control. Successful realization of the project will sufficiently reduce the cost of the laboratory scale device of self-sustained fusion reaction (DEMO reactor) because of the simplification of the first wall and pertor design and its lifetime growth.
The Project content directly corresponds to the ISTC basic goals. Project support will be a contribution into an international program of Controlled Fusion and will also support fundamental and applied research and technology of high temperature plasmas. Project will also help Russian “weapon” scientists to join the international scientific community.
The schedule of the Project includes 2 calendar years. The Project implies scientific and technical collaboration of the scientists of FSI RSC «Kurchatov Institute» (7 persons), SEI SPbSPU (6 persons) and FSUI «Krasnaya Zvezda» (3 persons). The dust jet injector design and manufacturing will be done in SEI SPbSPU, experiment will be carried out on T-10 tokamak in FSI RSC «Kurchatov Institute». Experts of FSUI «Krasnaya Zvezda» will bring their experience of lithium technologies also applied for weapon production. They will take part in design of lithium dust injector. Foreign partners will help Russian scientist, including weapon experts to get integrated into the international scientific community. Foreign collaborators will take part in analysis of obtained results and possible applications of the developed technologies to the existing fusion machines.
The Project team has an experience of experimental research of hydrogen, impurity and killer pellet injection as well as injection of gas and liquid jets into numerous modern magnetic confined plasma machines (T-10, Tuman-3M, Globus M, ASDEX Upgrade, Wendelstein-7AS, Heliotron-E, TFTR, LHD). Tokamak discharge shut down experiments and computer simulation have been done. The team includes 2 Doctors of physical and mathematical sciences, 5 Ph.D. in physics and mathematics, 2 Ph.D. in engineering.
The project include the development of 2 new devices for dust jet injection: frozen gas dust injector and liquid lithium jet injector. The diagnostics necessary for testing of the devices should include: several CCD cameras (including one fast framing camera), particle speed optical meters, thermistors and gas flow system controller. The same diagnostics will be used for testing of both injectors, which will reduce the cost of the Project. Part of the funds will be spent for T-10 diagnostics improvement to measure plasma-jet interaction effects.
The methods and approaches to be used for the Project execution:
- Optimization of the design parameters of the injector of frozen gases (hydrogen, helium, argon, xenon).
- To design and manufacture the diagnostics of dust jet interaction with high temperature tokamak plasmas.
- To find the optimal dust jets injection parameters (velocity, density, injection duration, injection direction) on the base of experimental research and simulation of dust jet interaction with high temperature tokamak plasmas.
The results expected to be obtained during the first year (12 months) of the Project:
- Simulation of dust jet injectors, development a model of dust jet interaction with high temperature tokamak plasmas will be done.
- The diagnostics of dust jet formation on a test device will be designed, manufactured and installed.
- Assembling and testing of the frozen gas dust jet injector will be fulfilled.
The results expected to be obtained during the second year of the Project:
- The diagnostics of dust jet interaction with high temperature tokamak plasmas will be developed and installed.
- First experiments on frozen gas dust jet injection into high temperature T-10 tokamak plasma will be performed. Jet penetration depth and discharge response on the injection for different jet size, velocity and duration will be measured.
- Experimental database on dust jet injection in high temperature plasma for different jet materials including the basic T-10 diagnostic data and the diagnostics of the discharge response on the injection, jet deposition and expanding to the tokamak plasma volume will be obtained.
- The plasma / jet interaction models by the comparison with the experimental results will be verified.
- Conclusions on the developed technologies potential and suggestions on its further development will be formulated.
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