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1

Monte-Carlo simulations of a neutron source based on a linear electron accelerator

Wasilewski Adam, Wronka Sławomir

Nukleonika

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2025

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Vol. 70, No. 1

3--10

EN

Neutron beams are employed in a multitude of applications, including neutron activation analysis, neutron radiography and tomography, nuclear waste assays, reactor start-up sources, studies of material response, geological analysis, calibration standards and cancer therapy. The global demand for access to neutron beams is increasing, necessitating the development of relatively simple, efficient and easy-to-use neutron sources to address the more complex challenges of scientific research and industrial application. One relatively readily available method is to use a linear electron accelerator to produce beams of fast neutrons. The neutron generator, comprising of an electron linear accelerator and a tungsten X-ray converter, is capable of producing a maximum neutron flux of 1.53·1010 n/s to 1.45·1013 n/s at electron energies of 10–50 MeV, with an average electron beam current of 120 miA, corresponding to an intensity of 7.5·1014 e/s. The results of the neutron generator modelling conducted with the FLUKA Monte-Carlo code are presented in this article for an equivalent incident beam power of 1.2–6.0 kW. The optimal tungsten converter thickness is proposed as a means of achieving the maximum neutron flux in all directions.

2

Effects of irradiating the beam dump with the main electron beam of the superconducting linear accelerator PolFEL

Wasilewski Adam

Nukleonika

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2025

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Vol. 70, No. 2

43--49

EN

The transport of both primary and secondary radiation in the beam dump was conducted using Monte Carlo analysis. The radiation leakage level through the shielding walls of the bunker of the superconducting, linear electron accelerator PolFEL during beam operation, as well as the radiation dose generated by radioactivity, and the activity level of the beam dump and soil after beam operation were examined. The analysis encompassed three main electron beams with energies of 72 MeV, 187 MeV, and 280 MeV, corresponding to the need to deposit in the beam dump 900.0 W, 935.1 W, and 1400.1 W of electron beam power, respectively. It was determined that 99.86%, 99.83%, and 99.81% of the primary electron beam power was deposited in the designed beam dump. It was determined that the radiation leakage level through the lateral walls of the bunker, outside which nonexposed workers may stay, should be <1.8·10-4 miSv/h, 0.008(5) miSv/h, and 0.10(2) miSv/h, respectively. It was calculated that the radiation dose rate generated by radioactivity allows staying on the shielding plates above the beam dump no earlier than about a day after the end of the 30 days exposure period of the beam dump. The maximum activity level for the soil activity level at the most exposed location should be <0.008 Bq, 3.37(15) Bq, and 29.8(9) Bq for indicated above electron beam energies, respectively.

3

Electron source model responsible for low power beam losses of 1 W/m along the entire PolFEL superconducting electron linear accelerator

Wasilewski Adam

Nukleonika

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2024

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Vol. 69, No. 4

179--184

EN

The National Centre for Nuclear Research is planning to build a facility based on a free-electron laser (FEL) photon source. It is the first center to build this kind of facility in Eastern Europe. The laser radiation source relies on a superconducting linear electron accelerator. Ultimately, electrons are to be accelerated to energies of 72 MeV, 187 MeV and 280 MeV. To safely operate such kind of accelerator, the design of a shielding bunker is required, capable of attenuating the secondary radiation generated by electrons lost from the beam. This paper proposes a model for the energy and spatial distribution of such electrons. The proposed model will be used in subsequent calculations of the distribution of secondary radiation emitted by both the beamline and some devices essential for the operation of the PolFEL accelerator, such as superconducting niobium accelerating cavities, titanium liquid helium tanks filled with liquid helium, surrounded by μ-metal steel cryomodules containing a steel tube filled with liquid nitrogen, mirrors reflecting the resulting laser beams based on copper blocks, and electron beam deflecting electromagnets made of iron and copper. It was calculated that to reproduce a complex beam loss of 1 W/m, the total lost electron flux as a source of secondary radiation should be 1.7991 × 1013 e/s for 72 MeV, 1.1537 × 1013 e/s for 187 MeV and 1.1012 × 1013 e/s for 280 MeV. Preliminary Monte Carlo calculations of the designed source were performed, obtaining the energy and spatial distributions of the lost electrons.

4

Feasibility of Monte Carlo modelling for the neutron-neutron logging tool response in specific geological models

Wiącek U., Woźnicka U.

Geology, Geophysics and Environment

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2016

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Vol. 42, no. 3

365--383

EN

Neutron well logging is one of the basic methods for the determination of the characteristic parameters of rock samples. The neutron source and neutron detectors are elements of Neutron-Neutron Thermal-Epithermal logging tool (NNTE) of significant importance. A neutron source creates the neutron field in the nearest environment. Detectors placed at specified distances from the source register neutrons from this space. A signal of a Neutron-Neutron Thermal-Epithermal tool in specific geological conditions was numerically calculated by means of the Monte Carlo (MC) codes. The main aim of this paper is to show the potential for using the Monte Carlo N-Particle Transport Code (MCNP) software in nuclear well logging prospection methods. The results of this MC modelling are presented in this paper.

5

Influence of the energy spectrum and spatial spread of proton beams used in eye tumor treatment on the depth-dose characteristics

Konefał A., Szaflik P., Zipper W.

Nukleonika

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2010

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Vol. 55, No. 3

313-316

EN

The influence of the energy spectrum and the spatial spread of a therapeutic proton beam impinging on an irradiated medium (called the entrance beam) on the depth-dose characteristics in water, in the proton energy range of 50 division sign 70 MeV was studied. It turns out that full width at half maximum (FWHM) of the Bragg peak increases almost linearly with increasing proton energy. It ranges from 1.53 mm for 50 MeV to 2.59 mm for 70 MeV, for monoenergetic protons. Moreover, the significant influence of the energy spread of the entrance proton beam on the intensity and FWHM of the Bragg peak is visible. FWHM of the Bragg peak of 60 MeV protons is equal to 2.03, 3.37 and 5.86 mm for a monoenergetic beam and beams with an energy spread of 0.5 and 1 MeV SD (standard deviation), respectively. The intensity of the Bragg peak of a 60 MeV proton beam with an energy spread of 1 MeV SD is approximately 25% less than that for a monoenergetic beam. Moreover, the Bragg peak shifts to smaller depths as the energy spread of the entrance beam increases. The shift of the peak is about 0.2÷0.3 mm for a beam with an energy spread of 0.5 MeV SD and between 0.4 division sign 0.5 mm for an energy spread of 1 MeV SD, compared with a monoenergetic beam in the energy range from 50 to 60 MeV. However, the spatial spread of the entrance proton beam does not affect significantly the depth-dose characteristic.

6

A Theoretical Study of the cis-syn Cytosine-containing Pyrimidine Dimers in the Gase Phase and a Water Cluster and a Tautomer-Bypass Mechanism for the Origin of UV-induced Mutations

Danilov V., Leś A., Alderfer J. L.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 7

1039-1049

EN

A quantum mechanical study of cis-syn cyclobutane cytosine-containing photodimers including the normal and rare tautomeric forms of bases has been performed using the ab initio method at HF/6-31G(d,p), MP2(fc)//HF/6-31G(d,p) and MP2(fc)/6-31G(d,p) levels. It is predicted that in the gas phase all photodimers containing the rare imino form of cytosine are more stable than those containing its normal form. The Monte Carlo study of the hydration for cytosine-consisting dimers showed that the dimer containing the imino form of cytosine is stabilized by water cluster more than that containing its amino forms. As a result, the imino form of cytosine in the cytosine-containing dimer directs the incorporation of adenine in the complementary strand during replicative bypass. Data obtained point to the cytosine tautomerism as a possible mechanism for the origin of UV-induced mutation.