جستجوی مقالات مرتبط با کلیدواژه "کد مونت کارلو" در نشریات گروه "فیزیک"

In this paper self-dose of lungs were calculated by Monte Carlo and point source kernel methods for different photon energies. Then, factors influencing on dose and in different energies were evaluated. The results showed that the dose of lungs is dependent on an attenuation coefficient setting (μ), the interaction of photons with tissue, the shape of lungs and adjacent organs of it.

The present study deals with a new method for measuring the power of a reactor. This method uses gamma and neutron radiation resulted from the entire reactor structure, without changing its structure (online). In terms of functionality, this method can measure the reactor power in real-time and report it instantly. In order to obtain the relationship between reactor power and gamma and neutron leakage radiation by simulation, the values of the F5 tally are calculated at different distances from the reactor wall, using the MCNP5 code (Monte Carlo N-Particles). Then, we plot the diagram to observe the variation trend. However, an increase in the distance from the reactor reduces both the amount of radiation and the energy of the radiation particles until the neutron leakage radiation reaches zero within five meters of the body, due to its good insulation. However, this number is only about four meters for gamma irradiation. The reactor power can be calculated by measuring the flux at the given point and any time by determining the point for a range of leakage radiation reduction to background and the linear relationship between power and leakage flux.

Performance of parallel-hole collimators may be evaluated by determining their response to a point radioactive source which for instance, the amount of collimator resolution is calculated by measuring the full width at half maximum (FWHM) of point spread function (PSF). The conventional method in calculating the response of the collimator to a point source by using Monte Carlo simulations is to map the signal values in each detector cell to the center of cell on the x or y axis. In this paper, a new computing algorithm has been proposed which optimally maps the signal values on these axes. The responses of LEUHR, LEHR, LEGP and LEHS collimators are simulated based on the conventional method and the optimized computing one by the MCNP5 code. The results have been indicated that the response based on the optimized method has a higher accuracy compared to that of the conventional one. The average relative differences between the amounts of resolution based on the optimized method and experimental data have been found to be considerably fewer than those of the conventional one. Therefore, one may obtain parallel hole collimators’ response with a higher accuracy by using the optimized computing method.

Todays, X-ray imaging system for cargo and containers inspecting of country gates are highly regarded. The dual energy imaging system due to the use of two beams with different spectrums can extracts more information about the materials in cargo than the conventional X-ray imaging system. Since the X-ray beam is an ionizing radiation, three parameters should be taken into account including justifiably, optimization and dose limits. In this study to evaluate the exposure for materials inside cargo, staffs and for around of system, we simulated a typical system using Monte Carlo code. With using 750 mCi of 137Cs and 1 Ci of 60Co, exposure rates for the water phantom in the center of cargo were 10μSv/h and 20μSv/h for 137Cs and 60Co, respectively. Also, the exposure rate at a distance of 10 meter around the system without any additional protection lies almost in the appropriate value. The results of simulations show that with using the line scan system and a good designing for source shielding, the exposure at cargo inside and environment of it can be put in suitable values.

During the radiation therapy with electron beam, due to electron interaction and scattering from structures of the head of the medical linear accelerator, unwanted photons are produced. The main contribution of the photon contamination is resulted from the various components of the medical linear accelerator on the way of the high energy electron beam, and few percent is due to the interaction of the beam with the phantom or the patient's body. Structure and material of the head of the medical linear accelerator have effective roles on production of x-rays dose from the electrons beam. Therefore, the parameters of electron beam produced by a linear accelerator manufactured by different companies were varied. This difference may be seen even among the accelerators produced by one company. Therefore, this parameter must be described separately for each machine. In order to measure photon contamination at the electron mode of the Elekta Precise linear accelerator, thermoluminescence detectors (TLD700 & GR200) at two energies (10 & 15MeV) in polyethylene phantom were applied. These data were compared with the calculations using MCNPX code. Our results show an appropriate match between theory and experimental data at both energies. It shows that the rate of produced bremsstrahlung photons dose for tallies that are close to the phantom are in mSv range. Then it will be possible to calculate bremsstrahlung photon dose for different point of radiotherapy room of the Ayat-O-lah Khansari hospital by the Monte Carlo codes.