Study of Extracted Beam Characteristics of the Photoneutron Source at the Institute for Nuclear Research of the Russian
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udy of Extracted Beam Characteristics of the Photoneutron Source at the Institute for Nuclear Research of the Russian Academy of Sciences S. V. Zuyeva, E. S. Konobeevskia, *, M. V. Mordovskoya, V. N. Ponomareva, G. V. Solodukhova, and A. A. Afonina aInstitute
for Nuclear Research, Russian Academy of Sciences, Moscow, 117312 Russia *e-mail: [email protected]
Received March 4, 2019; revised March 20, 2019; accepted March 29, 2019
Abstract—The characteristics of the extracted beam of thermal neutrons at the IN-LUE photoneutron source are investigated. A collimator with a cross-section diameter of 30 mm, located at an angle of 67° relative to the electron beam direction, was used to extract neutrons from the source. The neutron flux density as a function of the distance from the source center and the distribution of flux density over the distance from the collimator axis (beam profile) are obtained. DOI: 10.1134/S1063779619050277
At the Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), a W–Be photoneutron source of neutrons has been developed [1] based on the LUE-8-5 linear electron accelerator. Over several years the source has been used intensely to irradiate various small-size samples in the inner cavity of the source with the maximum thermal neutron flux density of 107–108 s–1 cm–2. However, for a number of problems, the irradiation of large-size objects (neutronography) or the study of secondary irradiation with detectors near the irradiated sample are required. For these purposes, the extracted beam of neutrons passing through a collimator is envisaged. The goal of this work is to study the parameters of this beam.
to irradiate the small-size samples by thermal neutrons. Layers of protection 4 of borated polyethylene slow down the fast neutrons exiting from the moderator and absorb the slow and thermal neutrons.
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INTRODUCTION
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W–Be NEUTRON SOURCE AT INR RAS
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The schematic layout of the photoneutron source is shown in Fig. 1. Electrons from the LUE-8-5 accelerator with the maximum energy of 8.5–9 MeV fall on tungsten converter 1 and generate in it a flux of bremsstrahlung photons with the end-point energy of 8.5– 9 MeV. The bremsstrahlung gamma quanta falling on beryllium target 2 that consists, as shown in Fig. 1, of two (10 × 10 × 10 cm ) units produce fast neutrons in the 9 Be(γ, n) reaction. Neutrons are thermalized in the polyethylene moderator unit 3; in this case, the maximum flux density of thermal neutrons is reached in volume 5 (10 × 10 × 10 cm ) located between units of the beryllium target. This inner region usually is used 619
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Fig. 1. Schematic layout of the photoneutron source: W-bremsstrahlung target-converter (1), neutron-forming Be target (2), polyethylene moderator (3), shielding of borated polyethylene (4), cavity for internal irradiation of targets (5), collimator of extracted neutron beam (6), activation 55 Mn samples (7).
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