J. Csikai

Investigations on neutron-induced prompt gamma ray analysis of bulk samples

A systematic investigation was carried out for the improvement of the prompt gamma interrogation method used for contraband detection by the pulsed fast/thermal neutron analysis (PFTNA) technique. Optimizations of source detector shielding and geometry, role of the type and dimension of the gamma detector, attenuation of neutrons and gamma rays in bulky samples were also studied. Results obtained for both the shielding materials and elemental content of cocaine simulants have been compared with the values calculated by the MCNP-4A code.

INVESTIGATIONS ON NEUTRON FIELDS PRODUCED IN 2H(D, N)3HE AND 9BE(D, N)10B REACTIONS

Neutron spectra from the 2H(d, n)3He and 9Be(d, n)10B neutron source reactions were measured at different bombarding energies and detection angles. Use was made of the activation method and a Pulse Height Response Spectrometer. The angular dependence of the relative neutron yield and neutron energy are presented. The dependence of the zero degree neutron yield vs. the target gas pressure for the 2H(d, n)3He reaction was also measured. A comparison of our measurements with the literature data showed good agreement.

Neutron-based techniques for detection of explosives and drugs

Abstract Systematic measurements were carried out on the possible use of elastically backscattered Pu–Be neutrons combined with the thermal neutron reflection method for the identification of landmines and illicit drugs via the detection of H, C, N, and O elements as their major constituents. While our present results show that these methods are capable of indicating the anomalies in bulky materials and observation of the major elements, determination of the exact atom fractions needs further investigation.

An improved neutron reflection setup for the determination of H and (O+C)/H in oil samples

An improved experimental setup based on the thermalization and reflection of neutrons has been used for the determination of total H content and (O+C)/H atomic ratio in oil samples. The count rate response function for this setup gives a relative error of about ±1.5% and a detection limit of 0.09 H w% in the case of different hydrogeneous samples of 300–500 cm3 volumes. Results obtained for motor and household oils as well as for crude oil samples from Nigeria and Hungary are presented.

Validation of neutron data libraries by comparison of measured and calculated neutron leakage spectra

Abstract Neutron spectra from the 2H(d,n)3He and 9Be(d,n)10B neutron source reactions and a Pu–Be source were measured by a pulse height response spectrometer behind slabs of water, graphite, sand, Pb, Al and Fe up to 20xa0cm thicknesses. A comparison of the measured and the calculated data has given new results for the validation of different data libraries.

New cross-sections for production of 103Pd; review of charged particle production routes

Production cross-sections of (103)Ag obtained by irradiating (nat)Pd and (nat)Cd with 70 MeV protons are presented and compared with ALICE-IPPE model calculations. Production of (103)Ag is of interest for the generation of (103)Pd widely used in brachytherapy. The investigated energy range of the (103)Rh(d,2n)(103)Pd reaction was extended up to 40 MeV and the results were compared with the curves of ALICE-IPPE, EMPIRE-II and GNASH theoretical codes. Thick target yields were calculated. An overview and analysis of the most important charged particle induced production routes of (103)Pd is presented. An explanation of the apparent discrepancy in the activity measurements for (103)Rh based on X- or gamma-ray is given.

Detection of explosives and illicit drugs using neutrons

A procedure developed for the determination of the flux perturbation factor required for the thermal neutron activation analysis of bulky samples of unknown composition has been extended for epithermal neutrons using hydrogenous and graphite moderators. Measurements on the diffusion and backscattering of thermal neutrons in soil components were carried out for the development of novel nuclear methods in order to speed up the humanitarian demining process. Results obtained for the diffusion length were checked by MCNP-4C calculations. In addition, the effect of the weight and density of the explosives on the observation of the anomaly in the reflected thermal neutrons was examined by using different dummy landmines.

Advantages and limitations of thermal and epithermal neutron activation analysis of bulk samples

Systematic investigations have been carried out to extend the thermal neutron activation method for elemental analysis of bulk samples. A new method developed for the determination of the flux perturbation factor renders the thermal and epithermal neutron activation analyses of bulky samples of unknown compositions possible both in hydrogenous and in graphite moderators. The flux perturbation, F, depression, H, and self-absorption, G, factors are given for different samples. The limitation of the epithermal neutron activation analysis for hydrogenous bulky samples is also discussed.

Production of solid deuterium targets by ion implantation

Abstract Solid metal, semiconductor and metallic glass samples were irradiated with deuteron atomic ions between 60 and 180 keV incident energies. Accumulation rates of deuterons in different targets were recorded by the detection of protons and neutrons via the 2 H(d, p) and 2 H(d, n) reactions. A simple analytical expression is given to describe the kinetics of the accumulation. The dependence of the reaction rate on the deuteron energy gives information on the concentration profile in addition to the neutron flux density spectra. A varying distortion of the implanted deuteron profiles by a change in the beam energy were also observed for different targets.

Determination of Cu in minerals by 14-MeV neutron activation analysis and radiochemical separation

Abstract14-MeV neutron activation analysis /NAA/ and radiochemical separation technique were used for the determination of Cu in Hungarian minerals. The separation of Cu from other elements is a possibility to avoid the interferences in the 511 keV γ-line.