مجله علوم و فنون هسته ای
سال چهل و چهارم شماره 1 (پیاپی 103، بهار 1402)

In the CMS detector, the branching fractions of Higgs boson to J/ψ(1S) and cc pairs have been measured equal to 1.8×10-3 and 2.89 × 10-2, respectively. Theoretically, one possible scenario for direct production J/ψ(1S) is that the Higgs boson initially decays into the pair of cc . Then, in the next step, each of the c and c directly fragments into J/ψ(1S) a meson. Based on this scenario, in this paper, the direct branching fractions of the standard model Higgs boson to J/ψ(1S) is calculated by direct fragmentation of c and c using of perturbative Quantum-Chromodynamics(pQCD) and also taking account the longitudinal and transverse polarization states J/ψ(1S). The results of our calculations for the direct branching fraction of the Higgs boson to a pair J/ψ(1S) equal to 1.562×10-3, agree well with the measured value in the CMS detector. Therefore, it can be concluded that the predominant contribution in the decay of the Higgs boson into the J/ψ(1S) meson is the direct fragment of c quark and antiquark c.

Due to the low cross-section to perform the reaction, muons are the earth's most common detectable cosmic rays. Like the other particles produced by the collision of energetic particles, muons are unstable and have a lifetime distribution spectrum. This paper measures the energy and lifetime of the muon cosmic radiation using a digital spectroscopy system. In the presented method, all the nuclear electronics modules are omitted, and the process of forming the signals is recorded in the software. To perform this measurement, radiation events were detected in coincidence mode using two NaI (Tl) detectors installed at the angle of 90° concerning the horizon line. The signals recorded in the pre-amplifier of the two detectors were sampled directly using a waveform digitizer and, after recording, stored as the list mode data. By programming on the data list, about 105 muon events were detected over two weeks. Their lifetime is extracted by measuring the time interval between events detected as muon radiation. By fitting the exponential function to the experimental data, the muon lifetime is determined to be 2.03 µs. The results show that this study's obtained lifetime for muon is consistent with the other experimental data. The transition from analog to digital nuclear electronics in muon radiation spectroscopy provides simplicity, high reliability, small size, light weight of the acquisition system, and the possibility to be installed on the research satellites.

Uranium compounds are toxic and radioactive. Its poisonous properties can be fatal. So, it is necessary to prevent its excessive entry into nature due to uranium's chemical toxicity and radioactivity. Waste from industrial-nuclear centers also has different amounts of uranium; therefore, the removal of this element from the effluent of these centers is essential. On the other hand, due to the importance and limited resources, uranium recovery from waste has economic value. In the present study, the Response Surface Method (RSM) based on the central composite design was used to evaluate and optimize different parameters affecting the bioremediation process of Shewanella RCRI7 in real waste. The proposed second-order model with a correlation coefficient R2 = 0.94 appropriately predicted the experimental data and the maximum uranium reduction efficiency by Shewanella RCRI7 under optimal conditions (pH = 5.7-6.5, Temperature 26.63 °C and Time 117 hours) was estimated to be about 98%. In the next step to interact between the variables, three-dimensional procedures with pH and temperature; temperature and time; pH and time interactions were obtained; finally, the uranium reduction in real effluent was investigated by XRD and spectrophotometric methods. Based on the results, Shewanella RCRI7 is determined as a valuable candidate for uranium bioreduction processes in the determined industrial wastewater. On the other hand, using the response surface methodology can provide a comprehensive understanding of the process, the mechanism of uranium bioremediation by Shewanella RCRI7, and the theoretical support for this process.

One of the driving factors for creating axial flow inside the gas centrifuge rotor to increase the separation performance is the scoop. Due to the exposure of the scoop to the high Mach gas flow, the flow will be shocked, and strong gradients will occur in the flow.  In this research, the gas flow around the scoop in a two-dimensional state (r-θ) is simulated by the Direct Simulation Monte Carlo method (DSMC) using the dsmcFoam solver at different distances of the scoop from the rotor wall. The results show that increasing the distance of the scoop from the rotor wall and decreasing the contact angle of the gas flow with the scoop reduces the maximum temperature and drag force. For instance, increasing the distance of the scoop from the wall by 31% (from 8 to 10.5 mm) in 3800 Pa wall pressure and 85° contact angle, causing a maximum temperature decrease of 1.3% (from 596 to 588 K) and also the drag force is reduced by 49.4% (2412 to 1221 dyn). Furthermore, reducing the angle of the gas flow with the scoop by 11.8% (from 85 ° to 75 °) in 3800 Pa wall pressure and at the distance of the scoop from the wall equal to 10.5 mm causes a maximum temperature decrease of 6.8% (from 588 To 548 K) and the drag force is reduced by 50.3% (1552 to 771 dyn).

The frequency of cavities in electron linear accelerators changes because of volume variation and manufacturing error. Adjusting the frequency of cavities is one of the most important steps in a cold test, which must be considered in the design. In constructing a standing-wave tube for dual-energy linac, an aluminum tube (including two half-acceleration cavities and one coupling cavity) was constructed. In this project, to modify the changes caused by a manufacturing error, adjustment screws were used. These screws change the frequency by somewhat changing the volume of the cavities. In this paper, the calculation and simulation of frequency changes due to dimensional variation were carried out. Based on the calculation and simulation, the design of screws for a frequency adjustment in experimental conditions is done. According to the results of this paper, using the screws on the cavities wall, the resonant frequency can be changed up to 10 MHz. Therefore, using the selected method, the frequency changes caused by the manufacturing error can be compensated to the extent mentioned. In this study, the tube's resonant frequency for the π/2 mode was set equal to 2998.5 MHz, and the mechanical accuracy of the construction was obtained at 200 μm.

The thermal quenching effect has not been considered in current research on the first-order kinetics of thermoluminescence. In contrast, thermal quenching as a reality should be contained in theoretical models. In this work, a new fitting function of the thermoluminescence glow curve in terms of peak temperature and intensity is obtained by considering the thermal quenching effect for the first-order kinetics model. The new function reduces to the known first-order fit function by removing thermal quenching parameters. The obtained function was applied to the glow curve of the CaF2:Mn (TLD-400) dosimeter. Since the new model differs from the known first-order fit function, different kinetic parameters extract as the result of the fitting procedure. As the new model involves the thermal quenching effect as a physical entity, the kinetic parameters obtained from the presented model are more accurate and realistic.

In this research work, hydroxyapatite samples doped with cerium, gadolinium, and a combination of these two dopants were synthesized through the hydrothermal method. MAUD code, a material diffraction analysis software based on the Rietveld method, was used to investigate the formed crystal phases in synthesized samples. The thermoluminescence dosimetry response of the samples was investigated, and the results showed that the thermoluminescence response of the sample doped with the compound dopants is the median level of the thermoluminescence response of the samples doped with one dopant. It was found that adding cerium dopant could improve the thermoluminescence response of the sample doped with gadolinium. Also, the results of Rietveld refinements showed that the formed phases of hydroxyapatite could affect the thermoluminescence dosimetry response.

In this paper, the fast neutron spectra at altitudes of 3 and 5 km were unfolded by the response of Superheated Drop Detectors and using an Adaptive Network-based Fuzzy Inference System (ANFIS). ANFIS is a Takagi-Sugeno Fuzzy Inference System implemented in the framework of adaptive networks. This tool works similarly to human thinking in dealing with uncertain and erroneous problems. The response matrix of five Superheated Drop Detectors under various external pressures was calculated by an application developed using the Geant4 simulation toolkit and was used to obtain inputs of ANFIS. Also, the neutron spectra of the IAEA technical reports were utilized as the targets. The reference spectra were unfolded with RMSEs of 0.005 and 0.011. The relative agreement between the unfolded and reference spectra shows that these detectors and ANFIS can be used as a new technique for unfolding neutron spectra produced by cosmic radiations in the atmosphere.

Data fusion between different sensors can improve the detection of nuclear threats by extracting more reliable and effective information. In this study, tracking a moving radioactive hotspot source using a combination of a radioactive detector (NaI) and a surveillance camera is addressed. For this purpose, three mobile robots were used, and a radioactive source was placed on one of these robots. An algorithm was developed to correlate the radioactive and camera data, so the robot with the highest correlation was selected as the moving source quickly. By increasing the acquisition time from 5 to 125 seconds, the algorithm's success rate in detecting the moving radioactive source increases from 42.7% to 98.3%. In addition, the moving source's detection speed and the detection's precision over different times were studied. The results have presented a model that can be scaled up by equipping surveillance cameras with radioactive detectors to provide a network, and this network can continuously monitor and control a vast area or even a city to detect and track suspicious items.

Creep rupture as a failure mechanism during a severe accident in a PWR is of particular importance as it can lead to releasing radioactive materials into the environment. Following a severe accident, the decay heat transferred to other parts of the reactor cooling system can result in the heat-up of RCS structures and failure of vulnerable pressure boundaries. SBO without operator actions accident (TMLB sequence) is considered one of the most likely scenarios threatening the integrity of the RCS pressure boundary. In addition to PWR plant modeling, in this sequence, the location of rupture in the RCS depends on the type of natural circulation phenomenon of the reactor's primary side. This research investigates the sensitivity analysis of steam generator tube rupture (SGTR) and RCS hot-leg to the type of natural circulation, i.e. con-current and countercurrent, using the MELCOR code. The results of two models of con-current and countercurrent natural circulation show when the countercurrent natural circulation phenomenon is predominant, the RCS hot leg creep rupture occurs earlier than SGTR. However, the SGTR occurs earlier than any other part of RCS due to the concurrent natural circulation phenomenon. Moreover, the amount of materials released to different parts of the plant and the environment has been estimated for both models. The results show that about 18 kg and 145.76 kg of radioactive aerosol and fission product vapor materials are ejected to the containment following the rupture for con-current and countercurrent natural circulation models, respectively. On the other hand, in the con-current natural circulation, about 136.33 kg of radioactive aerosol and fission product vapor materials are released into the environment through the main steam line safety valve.

The present research investigates the feasibility of producing the radionuclide Lutetium-177 (177Lu) at the Tehran research reactor, TRR. 177Lu, with suitable nuclear decay characteristics and good chemical behavior, is an ideal therapeutic radionuclide. Some 177Lu-containing radiopharmaceuticals are currently applied in the treatment of various cancers, and many are under development and being tested in clinical trials in Iran. The radionuclide 177Lu can be produced either directly by the 176Lu (n,γ)177Lu reaction or indirectly by the  reaction. The irradiation yield of 177Lu in both production routes was experimentally determined for 14 days at a thermal neutron flux of 5×1013 cm-2.s-1 and was compared with the theoretical calculations. The effects of higher neutron fluxes and a reduction in 176Yb-enrichment-percentage on the produced activity/specific activity variations were assessed theoretically using MATLAB software. It was found that higher neutron fluxes led to higher activity. However, it does not impact specific activity fall rates two weeks after the end of the bombardment. In addition, a lower enrichment percentage of the target material utilized in the indirect method leads to a faster specific activity fall two weeks after the end of the bombardment.

This study aimed to investigate the effect of deuterium-depleted water (DDW) in specific concentrations on HT-29 and SW-480 cells. HT-29 and SW-480 cell lines were cultured in RPMI medium containing different concentrations of DDW for 24, 48, and 72 hours, and then the percentage of cell survival was determined by MTT-based cytotoxicity assay. The findings proved the role of reducing deuterium and increasing time treatment in inhibiting the growth of these cell lines. The lowest cell survival rates for HT-29 and SW-480 cell lines were obtained during 72 hours of treatment with 30 ppm deuterium concentration, with 23% and 37% cell survival percentages, respectively. To investigate the side effects of deuterium-depleted water, normal C2C12 cells were also treated with deuterium-depleted water. The results showed that under the same conditions as cancer cells, deuterium-depleted water has a lower growth inhibitory effect on normal cells, so cell survival in this cell line was more than 50%. Our data show that deuterium-depleted water could open up a new strategic approach to preventing and treating colorectal cancer.

The effect of chronic exposure on Ramsar HBNRAs inhabitants' health was studied using Cytokinesis Blocked Micronucleus (CBMN) Assay. The results showed a significant difference (P <0.001) in the mean frequency of micronucleus of the study group, or resident in Ramsar HBNRAs, and the control group, which were selected from Tonekabon, a city near Ramsar. Significant differences (P <0.001) were observed between the mean micronucleus frequency after irradiation of blood samples, which means that after irradiation of blood samples, the control group showed a higher increase in micronuclei frequency than the study group that can be as a result of the existence of a radio adaptive response in Ramsar HBNRAs. The correlation was observed between the frequency of micronucleus and age in control groups but was not obtained for the study group.

The Miniature Neutron Source Reactor is a tank-in-pool research reactor that uses highly-enriched uranium as fuel, light water as coolant, and beryllium as reflector. During the operation of the reactor, the coolant temperature increases and leads to negative feedback in the reactor. Although the negative reactivity is amongst the advantages of this reactor and an inherent safety feature; it causes a decrease in both the additional available reactivity and the reactor operation time. Therefore, short operation time (about 2.5 hours) at nominal power is one of the main limitations of the MNSR reactor. The natural convection in the core, vessel and pool of the reactor was modeled through a CFD analysis and the effect of the cooling coil at the top of the reactor tank on increasing the reactor operation time was investigated. To reduce the computations the details were decreased by considering the reactor core as a porous medium and a heat source with a constant power of 30kw. The experimental values ​​and those ​​obtained from the numerical solution are in good agreement. Results show a steady upward slope in the temperature rise of the coolant in the absence of coil, and an about-2-hours rise of the temperature in its presence. After this 2-hours period, the increasing rate decreases and the temperature fluctuates in a certain range. Compared to the case without the cooling coil, the average temperature is reduced by 3 degrees and the reactor operation time is increased by 1.5 hours.

The basis of backscatter X-ray imaging systems is the scattering of backscattered rays that have many applications in industry and inspection. In these images, organic materials with low atomic numbers, such as drugs and explosives, produce many scattered photons and are seen more clearly. These images are blurred due to the multiple scattered X-ray. Image processing methods can help improve contrast and material detection in backscatter X-ray (BX) images. In this research, the total variation method has been used to improve the contrast of the BX images. Firstly, the BX images of the various phantoms have been processed for evaluating the BX system, then many BX images of motorcycles are investigated. The results show that the total variation method increases the contrast of the backscattered X-ray images and can be used as the additional filter in the BX imaging system. Evaluation of experts shows that the contrast of the processed images has been significantly improved and increased between 20 to 40%.

Using molecular dynamics simulations, short-term analysis on a time scale of several tens of picoseconds of displacement cascade in radiation-damaged materials was studied. Accordingly, this simulation obtained the equilibrium number of interstitial/vacancy defects and their positions in iron-alpha. Then, the object kinetic Monte Carlo (OKMC) simulations were performed using the obtained results to investigate the effect of annealing on the irradiated alpha-iron. The simulation results showed that in the isochronal annealing of the irradiated alpha-iron, only vacancy cluster defects were more significant than four vacancies, and defects remained stable at temperatures above room temperature.

In this work, laboratory-scale laser isotope separation of 13C by isotope-selective multi-photon dissociation of CF2HCl gas molecules has been done. To do this, the pulses of a tunable TEA CO2 laser, which have been shortened using a plasma shutter, were focused inside the irradiation cell with fluence in 50 J/cm2. The irradiation cell was filled with 10-20 mbar of CF2HCl gas with CF2HCl:He ratio of 1:5 and 1:10. It has been shown that the abundance of 13C in C2F4 product of dissociation increases with decreasing of the gas pressure and the number of the incident pulses. In these experiments, the highest abundance of 13C isotope was obtained with CF2HCl: He ratio of 1:5 and ten mbar pressure of CF2HCl gas, irradiated by 1500 pulses with 50 J/cm2 fluences.

In this study, the amplification of Ti: sapphire laser pulses in a regenerative amplifier with Z geometric arrangement has been demonstrated based on chirped pulse amplification method. Two pocket cells were used to transfer the seed pulses to the amplifier cavity and extract the amplified pulses. Build up time of the amplified pulses according to the energy of the pump laser has been studied, and the dynamic evolution of the pulses inside the amplifier cavity has been investigated.  The pulse duration of the generated pulses inside the cavity without seed pulses is about 80 ns, and the buildup time is 38 ns. The 2 mJ amplified femtosecond laser pulses at a repetition rate of 10 Hz are obtained after 17 round trips using pump energy of 15 mJ at 532 nm. The amplified laser wavelength is 800 nm with 30 nm spectral bandwidth, which is 30 nm narrower than the oscillator bandwidth. The amplification efficiency relative to the pump energy is obtained at about 13%, and the amplification coefficient in this scheme reached 106.

This paper aims to design and construct a Langmuir probe diagnostic system for plasma parameters measurement in the Iranian Inertial Electrostatic Confinement Fusion (IR-IECF) device. For this purpose, a Langmuir probe diagnostic system is designed and constructed to determine the plasma parameters such as temperature, ion and electron density, and potential. Considering the characteristic of the plasma source of IR-IECF, the electrode selected for the probe is a tungsten wire with a diameter and length of 0.3 and 1.5mm, respectively, protected by an alumina ceramic tube with an inner diameter of 0.7cm. The connections and probe holder base on the vacuum chamber are stainless steel. The electrical circuit of the probe provides voltage and current of 500v and 1mA, respectively. The obtained results demonstrate that between two electrodes and at a distance of 25mm from the external electrode, the electron temperature, the electron density, the plasma potential, and the ion density are 50.1 eV, 3.1×1015 1/m3, 198V, and 0.4×1015 1/m3, respectively.

Plasma impurities are one of the loss factors of confined energy in tokamaks, so from this regard their study in order to maintain the stability of tokamak plasma and improve the confinement quality is essential. In this research, in order to study the impurities of Damavand tokamak plasma, a monochromator along with a Line Scan CCD array in the assembly of a visible light spectrometer was used. The modified spectrometer system was calibrated by the characteristic wavelengths of a mercury-vapor lamp and was used in the normal plasma regime of Damavand tokamak to record and analyze the radiation in the wavelength range of 3000-7000A°. The finest instrumental resolution of the spectrometer was about 0.9A° at entrance slit width of 50μm, which was used for intensive hydrogen plasma radiation lines such as Hα and Hβ. To study the radiation from the impurities, due to their low intensity, the entrance slit width of 100 μm and the resolution of 1.8A° were selected. The results showed that the predominant impurities in Damavand tokamak plasma are oxygen, nitrogen and carbon, which are generally originated from air molecules trapped in the wall of the vacuum chamber and the plasma facing components, also iron impurities are produced as a result of hot plasma interaction with the limiter and other components inside the vacuum chamber.