Spallation neutron source GNEIS
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pallation Neutron Source GNEIS1 O. A. Shcherbakov*, A. S. Vorobyev, and E. M. Ivanov Konstantinov Petersburg Nuclear Physics Institute, NRC “Kurchatov Institute”, Gatchina, Leningrad oblast, 188300 Russia *e-mail: [email protected] Abstract⎯A brief description of the spallation pulsed neutron source and neutron TOF spectrometer GNEIS based on the 1 GeV proton synchrocyclotron of PNPI in Gatchina is presented. The main parameters of the GNEIS are given in comparison with the analogous world-class facilities. The experimental capabilities of the GNEIS are demonstrated by the examples of some nuclear physics and applied research experiments carried out during four decades of its operation. DOI: 10.1134/S1063779618010355
DESCRIPTION OF NEUTRON SOURCE The 1 GeV proton synchrocyclotron at the PNPI was commissioned in 1969. A few years later (1975), spallation neutron source and TOF spectrometer GNEIS have been developed at the accelerator and put into operation [1]. Since that time GNEIS was effectively used for neutron-nucleus interaction studies utilizing the time-of-flight technique over a wide range of neutron energies from thermal up to hundreds of MeV, both for basic nuclear physics and applied research. The water-cooled lead target (40 × 20 × 5 cm3) of the GNEIS neutron source is located inside the accelerator vacuum chamber (Fig. 1) below the median plane. When the circulating proton bunch is deflected to strike the target, the short (~10 ns) pulses of fast neutrons are produced at a repetition rate of ≤50 Hz. At the average internal proton current of 3 μA and neutron yield of ~20 n/p for 1 GeV protons, the average intensity of fast neutrons is equal to ~3 × 1014 n/s. Neutron source is supplied with a polyethylene moderator (30 × 10 × 5 cm3) located above the target and median plane. The target and moderator are moved remotely in vertical and radial directions for optimum position during the accelerator and neutron source tuning. Five neutron beams are transported using evacuated flight tubes through the 6 m thick heavy concrete shielding wall of the accelerator main room into the experimental hall of the GNEIS. The beams are equipped with brass/steel collimators, steel shutters and concrete/steel beam dumps. Measurement stations for experimental installations are located in the GNEIS building (15 × 30 m2) at the flight path distances of 35–50 m. Neutron beams nos. 1–4, whose axes pass through the moderator, are characterized by a 1/Eα
(α = 0.65–0.92) neutron spectrum shape being well suited for measurements at resonance energies (1 eV– 100 KeV). Neutron beam no. 5, whose axis “looks” at the surface of bare lead target, has a typical spectrum shape with spallation and cascade components in the neutron energy range 0.1–1000 MeV. COMPARISON WITH OTHER FACILITIES At present, on the European neutron landscape 4 pulsed neutron sources located in Russia can be specified, namely: GNEIS (Gatchina), IREN and IBR-2 (Dubna), IN-06 (Troitsk). Currently, only first 2 facilities are used for neutron resonance TOF sp
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