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Information about energy groups in detected neutron fluxes from various sources makes it possible to compare the qualitative characteristics of the sources. Rapid determination of neutron energy groups can be accomplished with a multimodal detector, consisting of alternating layers of a neutron moderator and absorber. Slow-neutron detectors (for example, helium counters), which are placed in the moderator in a definite order, forming neutron-absorbing layers, can play the role of the absorber. A system of equations can be formulated from the indications of each layer of the counters. Thus, the counting rate in the ith layer iswhere vii(E) is the neutron-energy dependence of the neutron detection sensitivity of the detectors in the ith layer or the response function of the detectors in the ith layer; ~p(E) is the desired dependence of the neutron flux density on the energy E in a definite energy interval.A system of equations of the form U i = AoZ i, where i enumerates the layer of detectors, j enumerates theenergy group in the spectrum, and Aij is the average neutron detection sensitivity of detectors in the ith layer to the neutron flux density with a prescribed spectral distribution ~pj(E) in thejth energy group, can be obtained on the basis of the counting rates recorded in all layers of a multimodat detector. The system obtained is a system of linear equations of the form U = AZ. The values of U and A are determined with an experimental error 8 and r I, respectively, so that it is more accurate to study the system [ 1, 2] U~ = A~Z.(1)The problem of reconstructing the number of neutrons in a chosen energy group is an improperly posed inverse problem [3]. To solve such problems, a priori information about the smoothness of the solution must be used to obtain the values closest to the true values.One method of reconstruction, well-developed both theoretically and practically and widely used by specialists, is Tikhonov's regularization method [4]. This method makes it possible to obtain a solution with satisfactory smoothness by selecting a regularization parameter that takes account of the contribution of the systematic and statistical errors in the results of the measurements [4][5][6].The experimental data were obtained using a multimodal detector with five detecting layers. Each layer contained 15 helium counters connected in parallel and surrounded by layers of a polyethylene moderator. The detector was calibrated in a van-de-Graaf linear electrostatic accelerator, and the sensitivity 6f detection of intermediate and fast monoenergetic neutrons by each layer was obtained (Fig. 1). These indications were used to construct the instrumental function consisting of an i • j matrix, where i is the number of the detecting layer in the detector and j enumerates the energy groups into which the range of the measured neutron energy is partitioned.The neutron energy range from thermal to fast is partitioned in a manner so that the sensitivity function varies very little within an energy group and the elements of the se...

Ключевые слова: активационные детекторы, нейтронное излучение, наведенная активность, математическое моделирование, Geant4, геометрический фактор.Активационные детекторы, подвергнутые облучению нейтронами, преимущественно становятся излучателями гамма квантов или бета частиц (электронов или позитронов). Наиболее хорошо изученные методики регистрации нейтронов с использованием ак