Use of cyclotron-produced fast neutrons in activation analysis

The determination of 15 elements: Pb, Sr, Ba, ti, Ca, Sc, Cs, Zr, Rb, Cr, Se, Ni, Y, Co and Zn was investigated by fast neutron activation analysis using 80 MeV deuterons on various environmental samples. Detection limits of these elements from interference-free spectra were calculated.     

A method for bulk hydrogen analysis based on transmission and back scattering of fast neutrons

A method was proposed for bulk hydrogen analysis. It is based on simultaneous detection of transmitted fast neutrons and back scattered thermal neutrons from the investigated samples by ³He detectors. The fast neutron beams were obtained from ²⁵²Cf and Pu–Be neutron sources. The experimental set-up as well as samples preparation were described. Incident thermal neutrons beams obtained from either ²⁵²Cf or Pu–Be sources, were used to investigate the samples by neutron backscattering. The results obtained from transmission and backscattering of fast neutrons were compared and discussed. The advantage and capabilities of the proposed method were presented. The results obtained using fast neutron beams are more sensitive than those obtained using thermal neutron beams. Validation procedures were proposed to credit the results.     

Possibilities of using hafnium neutron filters for reactor NAA with fast neutrons

The possibilities of using hafnium irradiation filters for reactor fast neutron activation analysis have been evaluated. The filter characteristics of hafnium for this application are discussed and compared with some traditional filter materials. The main advantage for hafnium is its ability to remove a great portion of the slowing down neutrons, which may enhance the sensitivity of determination via threshold reactions.     

Nuclear inelastic scattering spectroscopy of iron-sulfur cubane compounds

The potential of NIS spectroscopy to study the iron-sulfur clusters in metalloproteins is illustrated using model compounds. The origin of the intense low energy transfer bands is discussed.     

An approximate simple formula for the shielding effect of the cadmium jacket designed for the use of fast neutrons among reactor neutrons

If a pneumatic tube in an experimental hole of a reactor is covered with a cadmium jacket, a sample inserted in the pneumatic tube will be exposed to not only fast and epithermal neutrons but also the few thermal neutrons that will not have been obstructed by the jacket. To obtain a simple method of estimation for the flux of these thermal neutrons, a formula has been made. The ratio of change in thermal-neutron flux due to the setting of the jacket has been expressed as a function of 5 dimensionless numbers. The formula enables one to design a well-proportioned jacket.     

The generalized Sturmian method and inelastic scattering of fast electrons

The generalized Sturmian method for solving the many-electron Schrödinger equation is reviewed. This method yields rapidly convergent solutions directly, without the use of the SCF approximation. As a simple illustrative example, differential cross sections are calculated for inelastic scattering of fast electrons by atoms and ions in the 2-electron isoelectronic series.     

Use of252Cf for elemental analysis

The neutron sources based on the²⁵²Cf isotope and having relatively long half-lives and the highest specific neutron yields compared with other ampouled sources are proved to be the most convenient for use in industrial analytical laboratories situated far from the basic nuclear centers. Research making use of californium sources is currently carried out in a number of nuclear centers of the USSR, including the Institute of Nuclear Physics of the Uzbek Academy of Sciences, where a great amount of work have been done on verification of practical use of Cf sources of various activity in different branches of industry, first of all, in geology and mining industry.     

Gamma-ray production cross section from energetic neutron inelastic scattering for methodical improvements in planetary gamma-ray spectroscopy

Planetary gamma-ray spectroscopy can be used to chemically analyze the top soil from planets in future planetary missions. The production from inelastic neutron interaction plays an effective role in the determination on the C and H at the surface. The gamma-ray production cross section from the strongest lines excited in the neutron bombardment of Fe have been measured by the use of a time analyzed quasi-mono-energetic neutron beam and a high purity germanium detector. The results from En=6.5, 32, 43, and 65 MeV are presented.     

Utilization of cyclotron produced fast neutrons in the activation analysis for oxygen

The possible application of cyclotron-produced fast neutrons to activation analysis for oxygen based on the¹⁶O(n, p)¹⁶N reaction has been investigated. Neutrons were produced by bombarding a thick beryllium target with 22 to 45 MeV deuterons. It was found that the sensitivity increases rapidly with the energy of the deuterons. Using 45 MeV deuterons and a 10 μA beam current a sensitivity of about 20 counts per 1 μg oxigen could be achieved, enabling the determination of less than 1 μg oxigen. In a direct comparison it was experimentally established that the sensitivity for cyclotron-produced neutrons assuming a deuteron beam of about 10 μA, is up to two orders of magnitude higher than that achievable for 14 MeV neutrons with a flux of about 10¹⁰ n/s. The interference of fluorine is at about the same level for both the cyclotron-produced and 14 MeV neutrons. Using cyclotron-produced fast neutrons in the investigated energy range, sodium and magnesium can also interfere, but only to a very much lower extent.     

Vibrational spectroscopy of adsorbed species on nickel by neutron inelastic scattering

In a test of the utility of neutron inelastic spectroscopy (NIS) for studying molecular vibrations in surface reactions, we have examined the adsorption, co-adsorption, and reaction of hydrogen and carbon monoxide on Raney nickel catalysts.     

Dosimetry of fast neutrons in 1W nuclear reactor with plastic nuclear-track detectors

A nuclear reactor at Kinki University is operated at the maximum of 1W. It produces fission neutrons as much as gamma-rays. To facilitate its use for neutron radiobiology, fast neutrons inside the reactor were measured with nuclear-track detectors TS 16 N and a pair of ion chambers. The angular dependence of TS 16 N response, an anisotropy of fast neutron fluxes in the reactor and misuse of the kerma factor assumed for radiation protection business are the major causes of discrepancy is measured doses by the two methods. Correction factors for the three causes are proposed. After correction, neutron doses estimated with TS 16 N and chambers agree within 5%. The dose-rate at the reactor's center is about 20 tissue-cGy/h. This is the first in situ dosimetry of fast neutrons in a reactor with track detectors attached to biologic samples. Our routine usage has demonstrated that, if used with caution, TS 16 N elements are handy, reliable monitors for fast neutron dosimetry as they are insensitive to contaminated gamma-rays and small enough to be attached to biologic samples.     

The spectrum of inelastic scattering of neutrons by ammonia adsorbed on a surface of silica gel

Theoretical and Experimental Chemistry -     

Simultaneous elemental determination of aluminum and silicon in soils by gamma-ray detection following inelastic neutron scattering

The detection of prompt γ-rays produced by the inelastic scattering of fast monoenergetic neutrons has been used to determine the elemental composition of soil samples. Multigram samples were bombarded with 2.5 MeV neutrons, and concentrations were measured by analyzing the spectrum of emitted γ-rays. Particular emphasis has been placed on the simultaneous determination of aluminum and silicon. Possible extensions of the method to light elements are suggested.     

Possibilities of the elemental analysis of dry biological material by fast neutron activation analysis

The applicability of a 400 kV neutron generator in the elemental analysis of dry biological material is considered. Data for the specific count-rates of 66 elements are given. A procedure for the determination of N, Mg, Si, P, K and Ca is described. The results for three Standard Reference Materials and some samples are given.     

Atmospheric aerosols and possibilities of their analysis for elemental content at the IBR-2 reactor

Possibilities of neutron activation analysis for studying the elemental content of atmospheric aerosols at the IBR-2 reactor are discussed on the bases of the experimental results on concentrations of nearly 40 elements in the air of two, remote and industrial Siberian regions. Methodological aspects of the use of small-pore filters, the influence of their background trace-element contents on the sensitivity of NAA, the reliability of the results, as well as preferable strategy of atmospheric aerosols sampling are discussed.     

Vibrational analysis of the inelastic neutron scattering spectrum of s-triazine and trichloro-s-triazine

The inelastics neutron scattering (INS) spectra of s-triazine and trichloro-s-triazine at 5 K provide the first observation of the IR and Raman inactive modes, v₄ and v₅. A full assingment is made by fitting a harmonic force field to the INS spectra profile. In the case of trichloro-s-triazine we demonstrate that this approach can be used successfully for a molecule without H atoms.     

Complete assignment of the vibrational modes of C60 by inelastic neutron scattering spectroscopy and periodic-DFT

In this paper we exploit the complementarity of inelastic neutron scattering (INS), infrared and Raman spectroscopies with ab initio calculations to generate an updated assignment of the vibrational modes of C(60). We have carried out periodic-DFT calculations of the high temperature face centred cubic phase modelled as the standard structure and also of the low temperature simple cubic phase, the latter for the first time. Our assignment differs from all previous work, however, it is the only one that is able to successfully reproduce the INS spectrum in terms of both transition energies and intensities. In addition to the INS spectrum we are also able to quantitatively simulate the major features of the infrared and Raman spectra in the high temperature phase and the infrared spectrum in the low temperature phase.     

Vibrational spectroscopy of aqueous solutions at high concentrations: Raman and inelastic neutron scattering

We review work performed by our group on vibrational spectroscopy of water and aqueous solutions of strong II-I electrolytes at high concentrations. Evidence shall be presented for the existence of intermediate range, solute-connected, ordered patches, whose collective vibrational modes yield a continuous vibrational density of states, as in amorphous solids. We shall review Raman and inelastic neutron scattering results, obtained for electrolytes such as ZnCl₂, NiCl₂, CuBr₂, CdCl₂. Other results, such as EXAFS, viscosity and ultrasonic attenuation will also be discussed.     

Automatic activation analysis of fertilizers and plant samples by fast neutrons

Instrumental neutron activation methods are suggested in order to carry out automatic analysis of fertilizers and plant samples for N, P, K and Si allowing for the investigation of more than 40 samples per 8 hours. The experimental errors do not exceed ±3% for N, ±6% for P, ±5% for K and ±15% for Si.