فهرست مطالب ahmad akhound

The Persistent development of quick and accessible readout tools promises to remove one of the barriers to the adoption of gel dosimetry as an applicable method in treatment clinics. Research and development in the imaging of polymer gel dosimeters continues with a focus on imaging in three dimensions. Each technique comes with its own set of advantages and challenges. In gel dosimeter research, efforts have been made to identify and develop alternative imaging methods for polymer gel dosimeters. Gel dosimeters can obtain reliable and accurate three-dimensional dose distributions from the correlation of different polymerization stages caused by radiation. The irradiated samples are examined using magnetic resonance imaging, optical computed tomography, and X-ray computed tomography. This research describes the basic features of imaging devices and the readout of irradiated dose data. Costs, availability, portability, contrast and resolution, high-resolution image reconstruction algorithm, and image reconstruction time of radiation absorption dosimeters for imaging devices are investigated in this research. This review has been done to present the mentioned imaging features and review the research done in this field for the optimal use of different imaging methods.

Neutron detection techniques are widely studied in many articles. Most of this research requires a lot of electronic equipment. In this study, using the Thick Gas electron multiplier (THGEM) detector, a new method for neutron detection is proposed to reduce electronic equipment. In the neutron detection system, the converter material is used for converting neutrons to protons that are directed to the THGEM detector. By filling the detector space with noble gas and applying special voltage, THGEM enters to Self-Quenched Streamer (SQS) mode for protons detection. All these steps are examined by simulation, then the detection system is made and is examined in the laboratory. Finally, the simulation results and laboratory results are compared.    The results show that the 1 mm Plexiglas layer is suitable for converting neutrons to protons. The suitable distance between the converter layer and the THGEM detector is 3 cm. Also, the SQS mode happens in the most number of THGEM holes when the THGEM voltage is 980 volt. Investigating an approach to neutron detection by placing THGEM in SQS mode can be useful because, firstly, placing the THGEM detector in SQS mode simplifies electrical circuits and secondly, with this proposed detection system; it is possible to design detectors with different dimensions for neutrons.

In this research, a new method for detecting alpha particles using the function of thick electronic multipliers in natural glow mode is introduced. In this regard, thick electron multiplier cavities in the role of arrays of cold cathode electric discharge gas tubes have been considered and by creating a laboratory system, the possibility of operation of these detectors in natural glow mode has been investigated. One of the main advantages of working in this mode is that there is no need for an output reader, preamplifier and amplifier screen so that the signal generated can be seen directly by the oscilloscope. The results of experiments with the Americium-241 source confirm the ability of thick electron amplifiers to operate in the natural glow region to detect as well as two-dimensionally detect the location of alpha particles optically.

Addressed herein, a new monitoring method for alpha surface contamination based on the function of a thick gaseous electron multiplier (THGEM) in a self-quenching streamer mode (SQS) has been introduced. SQS mode detectors can detect alpha surface contamination in two dimensions. In the current study, the ability of thick gas electron multiplier detectors in SQS mode for two-dimensional monitoring of alpha surface contamination has been investigated by two Am-241 sources with activities equal to 33 and 150 kBq.m-3. It has been found that the brightness is stronger in front of stronger sources. This may be attributed to the difference in contamination levels. It was also observed that the spatial resolution of the contamination rate depends on the number of holes per unit area of ​​each THGEM. The advantage of this system is the ability to determine both the location and intensity of surface contamination with no need for an electronic multiplier or reader system.

In this study, we have obtained a parametric relationship for the entanglement measurement between each pair of qubits for graphs with more than four qubits. We have also calculated the value of entanglement in five-qubit entangled graphs. Analysis of our results shows that the total of 1024 five-qubit entangled graphs based on the maximum entanglement between each pair of qubits, categorizes into 31 groups and if we consider the number of graph edges and degrees of vertices then these states are classified in 40 classes. Also based on the numerical results obtained from multipartite entanglement measures such as generalized concurrence, global measurements, and Meyer-Wallach measurements, we show that 1024 graphs of the five-qubit system are in 24, 32 and 23 categories, respectively. As well as we conclude that the maximum amount of entanglement belongs to the cycle graph and the minimum value belongs to the one-edge graph. While the maximum amount of entanglement between each pair of qubits is in the one-edge graph and the minimum value is in the complete graph.

The nuclear disasters in Chernobyl and Fukushima have shown that such nuclear incidents are causing serious and undesirable long-term damage to the environment and the health of living beings, including humans. So that they should be taken very seriously. Considering the importance of the subject, in this paper, the simulation of the transmission and emission of cesium 137 nuclear abandoned from the contingency incident of Bushehr Power Plant in the Persian Gulf using the CROM (Código de cRiba para evaluaciÓn de iMpacto) code has been discussed. We assumed that the incident took place on July 1, 2018, and the most dangerous and an important nucleus of the abandoned is cesium 137. The simulation results show that the Cs-137 released from the incident is moved to the west and northwest of Persian Gulf and approach the head of the Persian Gulf after fifteen days. Then driven by the discharge of the Arvandrood River to the south coast and center of the Gulf moves forward and leads to the bottom. About two months later (late August) it will leave the Strait of Hormuz and will advance the Oman Sea and the Indian Ocean. Now, if this happens on January 1, after about 30 days, cesium 137 reaches the head of the Persian Gulf, and four months later (late March) will leave the Strait of Hormuz. The results of this study can be used under the same conditions in the nuclear emergency of Bushehr Power Plant.