Investigation of spatial parity in reactions of polarized neutrons with light nuclei is an important topic in the framework of exploring the fundamental problem of understanding the manifestation of ...the weak interaction in nuclear reactions and for estimating the parameters of the weak nucleon–nucleon interaction. In this paper, the ongoing experimental program of highly sensitive and high-precision measurements of
P
‑odd asymmetries in the reactions of polarized thermal and cold neutrons with lithium and boron nuclei is reviewed. Within this program, the coefficients of
P
-odd asymmetry of reaction products in the reactions induced by cold- and thermal-neutrons on the isotopes of light nuclei
6
Li and
10
B were measured with record-high sensitivity ~10
–8
as
,
and
. For the first time ever, nonzero values were obtained for two of these asymmetries. Our data for tritium emission in the
reaction and γ emission in the
reaction agree with those of other experiments when interpreted within the cluster model, but rule out the so-called “best DDH values” of weak-interaction coupling constants. Interpreting the data on these reactions relying on “first principles” only would be highly desirable.
In this paper, we report recent results obtained in the development of digital pulse processing mathematics for prompt fission neutron (PFN) investigations using a twin ionization chamber (TIC) along ...with a fast neutron time-of-flight detector (ND). Due to some ambiguities in the literature concerning a pulse induction on TIC electrodes by fission fragment (FF) ionization, we first presented a detailed mathematical analysis of FF signal formation on the TIC anode. The analysis was done using the Shockley–Ramo theorem, which gives the relation between charged particle motion between TIC electrodes and the so-called weighting potential. The weighting potential was calculated by direct numerical solution of the Laplace equation (neglecting space charge) for the TIC geometry and ionization caused by FFs. Formulae for GI correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and used in experiments for PFN investigations of two reactions,
2
3
5
U(n
t
h
,f) and
2
5
2
Cf(sf). Results of the measurements were compared to literature data to demonstrate the feasibility of the new developed techniques. These results were necessary for the development of a new PFN investigation facility consisting of a position sensitive fission fragment detector combined with 32 liquid scintillation neutron detectors.
A new method of measuring neutron lifetimes on pulsed neutron sources based on changes in the neutron spectrum during the time of the neutron transit along a rather large path length due to their ...decay is proposed. The main advantage of this method is the use of relative measurements. Simulating the experiment made it possible to explore the influence of background and neutron losses caused by both the interaction with residual gas and the different level of detector efficiency on the systematic errors. All parameters can be measured experimentally.
The temporal characteristics of a time-of-flight spectrometer installed on the first channel of the IBR-2 reactor are investigated. A change in the flash time of the reactor relative to the start ...depending on the measurement time from the beginning of the reactor operation cycle is discovered. The neutron deceleration time is measured as a function of the neutron wavelength. A dependence of the half-width of the reflections on the neutron wavelength is established. The measurements are carried out in a wide range of Bragg angles from 0.0567232 to 0.34180977 rad (from ~3° to ~19°). An estimate is made for the mosaic pattern of a single crystal.
26 March 2016 marked since the Joint Institute for Nuclear Research was founded in 1956 and within which the Laboratory of Neutron Physics was established. Already four years later, in 1960, the ...world's first pulsed fast reactor (known by its Russian acronym as IBR) operating in the periodic mode was put into operation, followed in 1984 by IBR-2. The research achievements over the last decade are summarized, the state-of-the-art laboratory hardware is discussed, and the prospects for the future are reviewed.
—Neutron Resonance Capture Analysis (NRCA) is currently being developed in the Frank Laboratory of Neutron Physics (FLNP) for the purpose of determining the element composition of samples. This ...method is based on registering neutron resonances in radiative capture and measuring the yield of reaction products in these resonances. To test the capabilities of this method, such investigations have been carried out in collaboration with the Institute of Archaeology of the Russian Academy of Sciences at the IREN pulsed neutron source, FLNP, for ancient coins from Phanagorian treasure. A cylindrical multisectional liquid scintillator detector is used to detect γ-quanta.
Neutron Resonance Capture Analysis (NRCA) is presently being developed at the Frank Laboratory of Neutron Physics (FLNP) to determine the elemental composition of samples. The NRCA is a ...nondestructive method that allows measuring objects’ bulk composition. The procedure is based on detecting neutron resonances in radiative capture and the measurement of the yield of reaction products in these resonances. The experiments are carried out at the Intense REsonance Neutron source (IREN). In this study, we applied the NRCA to investigate an archaeological object provided by the Museum and Exhibition Complex (MVK) "Volokolamsk Kremlin". The object was a women’s Old Believer cross (second half of the 17th century) found in the Moscow region, Volokolamsk district, the village of Chubarovo.
At the JINR Laboratory of Nuclear Physics, neutron–nucleus interactions are investigated for fundamental and applied purposes using the IREN pulsed neutron source. The applied research includes an ...elemental analysis of constituent materials of various devices. This paper describes the elemental-analysis techniques employed and reports the measurement of palladium abundances in the engine components of the Proton rocket carrier. The elemental-analysis technique involving resonance neutrons, currently implemented with the Romashka apparatus, is shown to be sensitive to palladium abundances at a level of 2 mg/g for samples with masses on the order of 60 g. Further developing the method will boost its sensitivity and allow for elemental analyses of larger samples and their assemblies.
The full-scale scientific research complex IREN will comprise a 200-MeV linear accelerator LUE-200 with a beam power about 10 kW, a subcritical multiplying target, and beam infrastructure with ...experimental pavilions, as well as technological, control, safety and service systems. The characteristics of the full-scale complex IREN (integral neutron yield 1015n/s and pulse width 0.6 μs) will allow it to rank among the best neutron sources of such class GELINA (Belgium) and ORELA (USA). The realization of the project is conducted in several stages. The first stage includes the construction of the LUE-200 linear accelerator and nonmultiplying target. This will make possible to carry out experiments which require precision neutron spectroscopy in the energy range from fractions of eV to hundreds of eV already at the first stage of IREN. The results of the physical start-up of the first stage of IREN facility at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research are presented. General scheme and current status of the electron linac are described. Achieved parameters are: pulsed electron beam current – 2.0 A; electron energy – 30 MeV; pulse width – 100 ns; repetition rate – 25 Hz; integral neutron yield (3÷5)•1010 n/s.
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