Acta Physica Hungarica 69. (1991)

1991 / 3-4. szám - Nuclear Physics - S. Cierjacks - Y. Hino: Differential flux and spectrum calculations for a novel high-intensity 14-MeV cutoff neutron source based on the 1H(t,n)3He source reaction

286 S. CIERJACKS and Y. HINO should have a high 14-MeV component with the possibility of tailoring the spectra to first wall conditions. (3) High-energy tails (> 14 MeV) should be avoided, since these would require extrapolations of recoil energies, transmutation effects, etc. to lower energies; such extrapolations are expected to cause important complications similar to those experienced with fission neutrons which required tentative assump­tions in extrapolations to higher energies. (4) Flux gradients and space-dependent neutron spectra in the test cell should be kept variable to allow for conditions as close as possible to those expected in future fusion reactor components. In two preceding papers [4,5] it has been shown that the proposed novel high-energy neutron source based on the 1H(t,n)3He source reaction can, to a large extent, satisfy the specifications for a fusion materials test facility as requested by materials scientists. While in the preceding papers the main emphasis was on the technical feasibility of the source concept, the prime intention of this paper is to discuss the neutron flux profiles and spectra for this source, and the inherent possibilities for tailoring flux profiles and spectra according to fusion technology needs. In Section 2 the proposed neutron source concept is briefly outlined. The method of flux and spectrum calculations performed for this source is described in Section 3. Section 4 is devoted to the presentation and discussion of resulting flux profiles and space-dependent neutron spectra. 2. Brief summary of the proposed neutron source concept The proposed source concept, its relevant properties, and the possibility of its realization, well within the limits of present technology, have been discussed in detail elsewhere [5]. Therefore, only a brief summary is given here. The general design concept for the neutron source based on the 1H(t,n)3He reaction is similar to that recently considered for a high-performance d-lithium source [6], except for the neutron-producing reaction and the target design. In addition to the prime concept for the specific accelerator modules, also the concept of a two-target facility configuration has been adopted for the proposed source. 2.1 Neutron source reaction The neutron source is based on the 1H(t,n)3He neutron-producing reaction. This reaction has been studied in detail in the range from 3 to more than 40 MeV by several authors [7,8] (evaluated results of experimental and theoretical data on energy and angular dependences are summarized in the IAEA Handbook on Nuclear Activation Data [9]). Its practical use as a source of monoenergetic neutrons has been demonstrated [10-12], and its high potential for other applications has been described elsewhere [13]. For this reaction not only the high neutron yields, but also the special kinematic conditions are very advantageous: Neutrons are only emitted into a narrow forward cone (kinematic collimation), avoiding backward emission, Acta Physica Hungarica 69, 1991

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