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This report describes a conceptual design of a high-fluence source of 14 MeV D-T neutrons for accelerated testing of materials. The design goal of 10 MW/m2 year corresponding to 100 displacements per atom per year is taken to be sufficient for end-of-life tests of candidate materials for a fusion reactor. Such a neutron source would meet a need in the program to develop commercial fusion power that is not yet addressed. In our evaluation, a fusion-based source is preferred for this application over non-fusion, accelerator-type sources such as FMIT because, first, a relevant 14 MeV D-T neutron spectrum is obtained. Second, a fusion source will better simulate the reactor environment where materials can be subjected to high thermal loads, energetic particle irradiation, high mechanical stresses, intense magnetic fields and high magnetic field gradients as well as a 14 MeV neutron flux of several MW/m2. Although the actual reactor environment can be realized only in a reactor, a fusion-based neutron source can give valuable design information of synergistic effects in this complex environment. The proposed small volume, high-fluence source would complement the capabilities of a facility such as ITER, which addresses toroidal fusion component development. For our source, the volume of reacting plasma and the fusion power have been minimized, while maintaining an intense neutron flux. As a consequence, tritium consumption is modest, and the amount of tritium required is readily available.
This report summarizes discussions and conclusions of the workshop to 'Assess The Mission and Technology of a Gas Dynamic Trap Neutron Source for Fusion Material and Component Testing and Qualification'. The workshop was held at LBNL, Berkeley, CA on March 12, 2009. Most workshop attendees have worked on magnetic mirror systems, several have worked on similar neutron source designs, and others are knowledgeable of materials, fusion component, and neutral beams The workshop focused on the gas dynamic trap DT Neutron Source (DTNS) concept being developed at the Budker Institute of Nuclear Physics (BINP) in Novosibirsk, Russia. The DTNS may be described as a line source of neutrons, in contrast to a spallation or a D-Lithium source with neutrons beaming from a point, or a tokamak volume source. The DTNS is a neutral beam driven linear plasma system with magnetic mirrors to confine the energetic deuterium and tritium beam injected ions, which produce the 14 MeV neutrons. The hot ions are imbedded in warm-background plasma, which traps the neutral atoms and provides both MHD and micro stability to the plasma. The 14 MeV neutron flux ranges typically at the level of 1 to 4 MW/m2.
The dense Z-pinch (DZP) is one of the earliest and simplest plasma heating and confinement schemes. Recent experimental advances based on plasma initiation from hair-like (10s .mu.m in radius) solid hydrogen filaments have so far not encountered the usually devastating MHD instabilities that plagued early DZP experiments. These encouraging results along with debt of a number of proof-of principle, high-current (1--2 MA in 10--100 ns) experiments have prompted consideration of the DZP as a pulsed source of DT fusion neutrons of sufficient strength (/dot S//sub N/ greater than or equal to 1019 n/s) to provide uncollided neutron fluxes in excess of I/sub .omega./ = 5--10 MW/m2 over test volumes of 10--30 litre or greater. While this neutron source would be pulsed (100s ns pulse widths, 10--100 Hz pulse rate), giving flux time compressions in the range 105−−1°sup 6/, its simplicity, near-time feasibility, low cost, high-Q operation, and relevance to fusion systems that may provide a pulsed commercial end-product (e.g., inertial confinement or the DZP itself) together create the impetus for preliminary considerations as a neutron source for fusion nuclear technology and materials testings. The results of a preliminary parametric systems study (focusing primarily on physics issues), conceptual design, and cost versus performance analyses are presented. The DZP promises an expensive and efficient means to provide pulsed DT neutrons at an average rate in excess of 1019 n/s, with neutron currents I/sub .omega./ /approx lt/ 10 MW/m2 over volumes V/sub exp/ greater than or equal to 30 litre using single-pulse technologies that differ little from those being used in present-day experiments. 34 refs., 17 figs., 6 tabs.
Accelerator-based neutron sources for R D of materials in nuclear energy systems, including fusion reactors, can provide sufficient neutron flux, flux-volume, fluence and other attractive features for many aspects of materials research. The neutron spectrum produced from the D-Li reaction has been judged useful for many basic materials research problems, and to be a satisfactory approximation to that of the fusion process. The technology of high-intensity linear accelerators can readily be applied to provide the deuteron beam for the neutron source. Earlier applications included the Los Alamos Meson Physics Facility and the Fusion Materials Irradiation Test facility prototype. The key features of today's advanced accelerator technology are presented to illustrate the present state-of-the-art in terms of improved understanding of basic physical principles and engineering technique, and to show how these advances can be applied to present demands in a timely manner. These features include how to produce an intense beam current with the high quality required to minimize beam losses along the accelerator and transport system that could cause maintenance difficulties, by controlling the beam emittance through proper choice of the operating frequency, balancing of the forces acting on the beam, and realization in practical hardware. A most interesting aspect for materials researchers is the increased flexibility and opportunities for experimental configurations that a modern accelerator-based source could add to the set of available tools. 8 refs., 5 figs.
Several accelerator-driven neutron sources have been proposed for satisfying the requirements of a high-flux high-volume international fusion materials testing facility that could be built in the near future. This paper summarizes the features and projected performance for the three accelerator sources that are leading candidates for such a role and that are viewed by the International Energy Agency (IEA) as worthy of further evaluation. These are: (1) the d-Li source, in which 35-MeV deuteron beams are incident on flowing lithium targets, (2) the t-H2O source, in which 21-MeV triton beams strike high-speed water jets, and (3) the Spallation source in which a 600-MeV proton beam bombards a heavy-metal target.
The conceptual design of an ohmically heated, reversed-field pinch (RFP) operating at (approximately)5-MW/m2 steady-state DT fusion neutron wall loading and /approximately/124-MW total fusion power is presented. These results are useful in projecting the development of a cost effective, low input power (/approximately/206 MW) source of DT neutrons for large-volume (/approximately/10 m3), high-fluence (3.4 MW yr/m2) fusion nuclear materials and technology testing. 19 refs., 15 figs., 9 tabs.
Particle accelerators are important tools for materials research and production. Advances in high-intensity linear accelerator technology make it possible to consider enhanced neutron sources for fusion material studies or as a source of spallation neutrons. Energy variability, uniformity of target dose distribution, target bombardment from multiple directions, time-scheduled dose patterns, and other features can be provided, opening new experimental opportunities. New designs have also been used to ensure hands-on maintenance on the accelerator in these factory-type facilities. Designs suitable for proposals such as the Japanese Energy-Selective Intense Neutron Source, and the international Fusion Materials Irradiation Facility are discussed.