فهرست مطالب حسین آفریده

Computed tomography using gamma- and X-rays has been using as one of the most reliable imaging modalities for non-destructive testing purposes in different fields of industry. These devices can provide a three-dimensional image of the sections inside the object under inspection. Based on the shape of the beam, the output beams from the beam source are placed in front of the source in the tomographic devices, detectors are placed in front of the source and rotated 360 degrees around the object to obtain projections and finally, the image is reconstructed. In this paper, a portable industrial CT system with the shape of a fan beam is simulated using the MCNPX2.7e Monte Carlo code. The number of detectors was selected as 19 due to its portability, and an industrial standard phantoms and an innovative phantom were used to acquire projections for verification of simulation operation. Cobalt-60 gamma rays are recorded on the detectors after being transported from the object under study and generate important projection data for various angles. The results include a large number of projection functions that can then be used to create a sinogram matrix.

Nowadays, nuclear instruments are being widely used in various scientific and industrial fields. Different types of nuclear radiations (alpha, beta, and gamma) can be used in the construction of these gauges. Gamma based densitometers, as non-contact and non-destructive test tools, are favorably being used for process monitoring in various industries, such as oil and petrochemical industries. Design and construction of a gamma ray density gauge and measurement of temperature dependence of water density via this gauge have been reported in this study. The results indicate that the designed device can measure the temperature dependence of water density with good accuracy.

In this study, a Compton camera imaging system containing several scatterer layers made of Si and a LYSO detector as an absorber layer were designed and simulated using Geant4 code. At first, the efficiency of the system according to the number of scatterer layers was optimized using a gamma point source with various energies. After finding the best structure of the system which contains 10 layers of scatterer, two similar setup of Compton camera were placed perpendicularly to the proton beam around the phantom to take image of the position of the prompt gamma emission resulted from the nuclear interaction of the proton beam with the phantom. In order to imaging the gammas, information such as interaction positions and deposited energies in the scatterers and absorber were recorded by Geant4 code in a root file. Then, using a Compton camera reconstruction algorithm, production position profile of gammas was reconstructed in a MATLAB software. A Comparison of the gamma photon distribution and dose distribution showes that this Compton camera structure is able to measure the proton beam range with less than 7 mm error, which proves the capability of prompt gammas detection for verification of the proton beam range during proton therapy.

Positronium (Ps) formation in a ground state and 2s state of the hydrogen atom by positron impact has been studied within the framework of Eikonal direct approximation in the intermediate and high energy range. For this process, we compute Eikonal charge- exchange scattering amplitude, the differential and total cross sections by reducing the six-dimensional integrals to one-dimensional integrals. Numerical results have been compared with some existing theoretical results and experimental findings.

Released radioactive materials from a nuclear power plant due to an accident can be transported to far regions by wind. Some models are available to predict the dispersion. This article reports some parts of the results of a research in which using one of the models, named HYSPLIT, to predict the dispersion of some isotopes of iodine and cesium released from ten nuclear power plant to the atmosphere. These power plants are located in 20-50o N & 25-75o E. The results show that a severe accident in each of the power plants potentially are able to contaminate Iran. In nuclear emergency preparedness and response plan, source of hazards should not only be limited to Bushehr Nuclear Power Plants, but also all the nuclear power plants located in the region should be considered. The results can be used to optimize site locations for early warning monitoring stations for radioactive materials.

Nowadays, PGNAA applications in industrial, medicine, military,… are well known. A PGNAA system design requires simulations to determining some parameters, like gamma spectrum originated from shield, sample and surrounding materials, to ability, for example, to foreseen minimum detectable activity. Simulation codes use cross section libraries for calculating interaction probabilities and products. In this investigation, 16 important elements was selected and MCNPX-2.6 cross section libraries in 293.6°K compared for each of them by prompt gamma spectrum simulation in a PGNAA setting. Results showed differences among libraries. Correct libraries specified by comparing simulated prompt gamma spectra with reported experimental results or valid references.

Multiphase flow metering, has been one of the most important issues in oil/gas industry, since the early 80s. Oil-water two-phase flow, shows off specially in flow meters that work based on separation of oil-water-gas three-phase flow into liquid (oil-water), and gas streams just before measurement. Here, at first, two-phase flow homogenizer loop (TPFHL) as a solid-liquid as well as liquid-liquid homogenizer loop, is introduced, and then its performance accuracy is verified by counting the transmitted gamma-rays of a 137Cs radioactive source. The acceptable results, compared to the reference data, endorse the capability of the introduced loop in conjunction with the gamma densitometer for volume fraction measurement in a wide range of two-phase mixtures. Moreover, the instrumentation usage for oil-water component fraction measurement was simulated, using an 241Am gamma source which showed a good agreement with the authentically published results.

In this study, Trastuzumab was labeled with 177Lu, and its dosimetric calculation was performed considering the assessment of the absorbed dose in the organs of human body. 177Lu chloride was prepared after 7 days irradiation of enriched Lu2O3 in the Tehran Research Reactor at the thermal neutron flux of 4×1013 cm-2 s-1, and the specific activity of 70-80 GBq/mg. 177Lu-DOTA-Trastuzumab was obtained with an overall radiochemical purity of >98% under the optimized conditions. Biodistribution studies of the radioimmunoconjugate in normal rats were carried up to 168 h. Relative organ mass extrapolation method was used for calculation of the human absorbed dose. Because of the highest accumulation activity in reticuloendothelial system, liver and spleen have received the maximum dose of 0.95 and 0.89 mSv/MBq, respectively.

<p>Bone metastasis is a major clinical concern that can cause severe pain, bone fractures, spinal cord compression, hypercalcemia and other problems for patients. Variuos β emitter radionuclides have been used for bone pain palliation, but recently α emitter radionucliedes also have shown acceptable results of treatment of bone metastasis. Radium-223 (t1/2=11.43 d) is one of the suitable α emitters that emits high energy α particles (Ēav=5.64 MeV) with high linear energy transfer (LET) that delivers a killing dose to the tumor cells. In this research, the feasibility of production of radium-223 from radium-226 was studied in Tehran Research Reactor (TRR) in thermal neutron flux of 4×1013 cm-2 s-1 using MATLAB software. Then, the data were compared with the experimental results. On average, over 80 percent agreement was observed between the calculated and experimental data, and under appropriate conditions the acceptable activity of 227Ac as a precursor of 223Ra was obtained. The results showed that with one month neutron bombardment of 2.5 mg 226Ra in TRR and cooling for 4 months, it is theoretically possible to achieve about 8.51 MBq (0.23 mCi) activity of 223Ra, that with respect to injection of about 3.7 MBq (0.1 mCi) per patient (with normally 70 kg weight), it is possible to administer the produced 223Ra to more than 2 patients in every equilibrium period.</p><p> </p>

In this study, 27 Achaemenid coins, 62 Parthian coins, 66 Sassanid coins, have been analyzed. The Achaemenid coins as well as 20 Parthian coins belong to the National Museum of Iran and the other 42 Parthian coins are kept in Tamashagah-e Pool Museum. Sasanid coins belong to private collectors. Using PIXE analysis, the element concentrations of the coins were measured. By using statistical analysis on the concentration of the elements, the samples were analyzed using factor analysis method. Statistical analysis shows that the coins belonging to the Achaemenid and Sassanid periods can be identified and separated based on the changes of Cu/Ag, Pb/Ag and Au/Ag ratios. In particular the relative change in Cu/Ag ratio in the Achaemenid period is very low, whereas it is high for the Parthian Coins.

Researchers and archaeologists have always been interested in the elemental analysis of ancient Iranian coins. However, a systematic analysis of the Achaemenid coins is still lacking. The Iranians minted coins since the time of the Medes. Darius I (552-486 B.C) is the first Achaemenid king have used the coinage system to regulate trade across his empire. The Achaemenid gold coins were called Daric, while their silver coins were called Sigloi. Daric was a thick gold coin, which had a standard weight of 8.4 grams. The gold used in the coins was of very high quality with a purity of 95.83%. The Sigloi weight about 5.6 grams and its purity was more than 96%. The face of the coins carried an image of a Persian bowman, thought it might be the King himself. The flip side of the coins bear irregular indentations. The Achaemenid coins bear no inscription, hence it is not possible to find the date of mintage with any accuracy. The Achaemenid coins were mainly minted in Sardis, Lyida, Lybia, Pamphilia, and Sidon. During the Parthian period (247 B.C – 224 A.D), commerce was carried out with silver, copper, and bronze coins. The face of the coins bore a relatively accurate image or profile of the King, and the flip side typically (for about 5 centuries), bore the image of of Arsaces sitting on a throne and holding a bow. This indicates the respect the Parthian kings held for the founder of their dynasty. The Parthian coins have markings that are abbreviations for city where the coins were minted. From these markings it is clear that coins were minted in Nisa, Dara, Hekatompylos (near present Damghan), Thymbrax (Sari), Syrinc (near Sari), Ecbatana (near modern Hamedan), Susa, Seleucia, Raga (Ray), Marv, Heart, Kangavar and Nahavand. In this work, 27 Achaemenid silver coins and 62 Parthian silver coins were analyzed. The Achaemenid coins and 20 of Parthian coins are belonging to the National Museum of Iran and the rest of Parthian coins are kept in Tamashagah-e Pool Museum. The concentrations of the chemical elements presenting in the coins have been measured using PIXE analysis. This analysis is carried out by bombarding the samples with protons accelerated through a 2MV electric potential to an energy of 2 MeV. The proton beam current that was used in this analysis was between 2 and 3 Nano-amperes. The beam was supplied by the 3MV Van de Graff accelerator belonging to the Physics and Accelerators School of the Nuclear Science and Technology Research Center. As a result of the proton bombardment, characteristic X-rays are emitted. The energy of these X-rays is specific to each element and can be used to identify the elements present in the sample. The number of X-ray photons of a specific energy can be used to determine the concentration of these same elements within the sample. With this technique, one can measure the concentration of Ag, Au, Pb, Zn, Al, S, Cu, Cl, Ca, Ti, Mn, and Fe in the coins with an accuracy of parts per million (ppm). Since the metallic composition of the coins is of most importance in deciding their value, we measured the concentration of metals in these coins. The average concentration of silver in the Achaemenid and Parthian coins, were 91% and 86% respectively. The Parthian coins also contained three times as much copper impurity as the Achaemenid coins and 5 times as much gold impurity. However, the concentration of lead and iron impurities in the Parthian coins were less than those of the Achaemenid coins. The statistical analysis of these coins indicated that the Achaemenid coins can be separated from the Parthian coins through elemental analysis. This analysis also showed that most of the Achaemenid coins in our sample were minted in the same place.

Design and construction of 10MeV cyclotron has been started at Amirkabir University of Technology since 2012. So far, the conceptual and detail engineering design phases have been finalized. The main purpose of this baby cyclotron is to generate proton beam for the production of PET radioisotopes. The cyclotron consists of magnet, cavity, ion source, RF and LLRF system, vacuum system, cooling system, power amplifiers and power supplies system. In this paper, a brief of design principles for all the parts of cyclotron and their final simulation results is presented. It should be noted that these simulations have been performed and optimized by the most accurate softwares such as TOSCA, ANSYS, HFSS, SolidWorks and CST. Also, the manufacturing feasibility of all the parts is performed and their dimensions and parameters are synchronized with manufacturing standards

The electric field in cavity accelerates charged particles and magnetic field of magnets changes the direction of these particles in cyclotrons. In order to establish the electric field inside the cavity, a noiseless radio frequency (RF) signal should be generated, amplified and sent to cavity. The resonant frequency of the cavity could be changed by temperature variation. Variation of resonant frequency will cause reflected power from the cavity. in this work the low level RF circuits with task of signal generation, phase and frequency Adjustment, cavity resonant frequency Adjustment, protection of the RF set from the reflected power and stability of RF system was designed.

Both of the LaBr3:Ce and NaI(Tl) detectors are inorganic scintillators that due to their high light output rate in comparison with organic scintillators and almost other inorganic scintillators are significant. In this research, experimental data for identical measurement of the sealed button sources with both detectors in the presence and absence of the shield were compared with the simulation data by using MCNP 4C code for the crystals of detectors. The obtained results from the radioactive sealed button sources measurements represented that for low energy gamma rays there are noticeable differences between the experimental and simulation data and that is highly due to non-negligible and effective attenuation of these low energy gamma rays in passing through the window and the shield of detectors included the crystals. The high energy gamma rays simulation data are, however, in agreement with the experimental observations. Also, all the simulation data as well as the experimental measurents showed that the efficiency of the LaBr3:Ce detector is higher than that of the NaI(Tl) detector. The simulation results for the shielded button sources are also in agreement with the experimental data in most ranges of gama energies.

The response of an NE213 scintillator to Am-Be neutrons, in which the neutron and neutron-induced charged particles transports have been undertaken, has been simulated with the use of MCNPX’ PTRAC card whilst the scintillation light transport has been performed with Monte Carlo light transport code, PHOTRACK. The scintillation light output for different neutron-induced charged particles has been calculated using the validated light output curves. The experimental data on the response of the NE213 scintillator exposed to Am-Be source has been obtained with a neutron-gamma discrimination circuitry using zero-crossing method. The simulation data represent a good agreement with the corresponding experimental results.

To benefit greatly from 103Rh(p,n)103Pd cross section curve and to avoid formation of radionuclide 101Pd impurity, the proton incident and exit energy of 18 and 5 MeV, must be considered, using ALICE code and experimental results. According to SRIM code, the Rh thickness must be 480µm for 90º beam/target angle geometry. To minimize the thickness of the rhodium layer, and hence to reduce the price of rhodium target, the angle of beam target has been adgusted to 6 degrees so as to decrease the thickness to 48µm.

In this article, different types of cyclotron solid targets and their advantages and disadvantages are discussed and a new design is introduced for solid targets of IBA-Cyclone 30 cyclotrons for the first time. In this new targetry, the number and depth of the back grooves for coolant passage were changed. The target material was placed behind an aluminum drawer for bombardment. For this reason the new targetry was named drawer backings. Thus we were able to bombard powders of the target material. These backings have unique capabilities: metallic salts can be bombarded behind the drawer holders and chemical separation may be performed with higher yields and lower costs with respect to other methods. The bombardment may be repeated many times with the same backing. The drawer avoids the presence of contaminant nuclides in the final product.

In this work the design of a target converting high energy electrons to bremsstrahlung x-ray is described. The system has been optimized for different energy of the accelerated electron beam, using the EGS4 Monte-Carlo computer code. For this purpose the thickness of the layers in the target, including the main converter, cooling and lower layer (for the energy spectrum tuning), suitable to the desired and practical conditions have been obtained. In order to evaluate the calculated results, measurements have been carried out for the same geometry using the x-ray converter target, for 2MeV, 5MeV and 10 MeV electron beam. It is shown that the calculated data are in good agreement with the experimental results.

In the experimental section of this project, the energy spectrum of fast neutrons is measured, after being passed through large blocks, approximately lm3 each, of graphite, aluminium, water and paraffin. Neutrons were produced via 7Li(p,n)7Be reaction by bombarding a Lithium target with 25 or 30 MeV protons of the cyclotron at the Nuclear Research Centre for Agriculture and Medicine in Karaj. Measurements are done using a 76 × 76mm NE-213 scintillator detector, in two points outside the blocks, one in the direction of proton beam and the other normal to it. In analyzing the results of the experiments, SCINFUL and RESPMG computer codes are used to produce the response matrix and the response function of the detector, respectively. FORIST code was, then, used to unfold the neutron spectrum from the pulse height spectrum of proton. In the theoretical section, the neutron energy spectrum is calculated, in Monte Carlo method, using MCNP-4C code. Finally the results from two sections are compared.

In this project the neutron spectra from the reaction of deutron on beryllium muclei is measured. The energies of deuterons were 7, 10, 13 and 15 MeV, and these measurements are performed at 10, 30 and 50 degrees relative to the beam of deutrons. The detector used is 76 by 76 mm right circular cylender of NE-213 liquid scintillator. The zero crossing technique is used for gamma discriminatin. For the elimination of the background radiation, a Polyethylene block, 40 cm in thickness, with inserted cadmium sheets, and a lead block, 5 cm in thickness, were used. In order to obtain the background radiation spectrum, the latter blocks were placed between the target and the detector to eliminate neutron and gamma radiations reaching the detector directly. FORIST code is used to unfold the neutron spectra from the measured pulse hight spectra and O5S and RESPMG codes are used to obtain the detector response matrix.

Introdution . Thall ous chloride (TI-201) radiopharmaceutical is routinly used for heart imaging in nuclear medicine departments. The goal of this project was to study the quality of TI-201 radioph armaceuticals produced in cyclotron department of atomic energy organization of Iran according to European and United States standards. Materials and Methods. This radiopharmaceuti cal was produc ed in 15 stages thro ugh 2°'TI (p,3n) 201 Pb ~ZOl TI nuclear reaction in which the inciden t pro ton energy is 28 Mev. Radionuclidic impurities (ZOPh, zo"TI, 2OTI) were det ermin ed by gamma-spectrometer with high pure Ge (HPGe) detector for production and pre -calibration dates and for one 20lTI half life (73.5 hr) later. The radiochemical impurity (TP+ in comparison to TI+), specific activity and activity distr ibution in vials were determined by electrophoresis, polarography and gamma spectrometry, and dose calibra tor, respectively. Results. In fifthteen production stages radionuclidic and radiochemical purity of product and it's specific activity have been higher than 97%, 95%, and 3.7 GBq/mg-TI resp ectively; But in three stages zoPb impurity has been higher than 0.3% determined in USP. Accuracy of activity distribution in vials was higher than 10% in all stages. Conclusion. The results show that the product quality is in accordance to the British and Euro pean standards (BP and EP). In accordance to the United States Pharmacopoeia (USP), although in three stages of fifthteen production stages 2°'Pb impurity has been higher than 0.3% determined in USP, radio nuclidic purity has bee n acceptable (>99%).