نشریه سنجش و ایمنی پرتو
سال هشتم شماره 2 (پیاپی 31، زمستان 1398)

Digital Holographic interferometry is a powerful and widely used optical technique for accurate measurement of variations in physical quantities such as density, refractive index, and etc. In this study, an experimental digital holographic interferometry setup was designed and used to measure the amount of energy changes induced by absorption of radiation from a non-ionizing infrared laser beam in a water cell. An effective theoretical method is used to measure the absorption dose, which is based on tracing of the interference pattern displacement due to changes in the energy content of the adsorbent material. It is shown that the results of the interferometric method are in good agreement with the results obtained from the measurement with a precise temperature sensor. Experimental results show the capability of this optical method for non-contact and non-intrusive monitoring of the changes in the amount of absorbed energy by non-ionizing laser radiation in material.

Control the laser beam hazards for class IIIB and IV laser is concluded: engineering and executive controls. In executive control, when laser beam enters to the free space, the controlled area must be identified to protect people and control the radiation exposure limits. Given the fact that the laser light of the laser is entering the environment, the identification of the area under control is necessary and the traffic must be controlled in accordance with certain criteria. By limiting the region where the radiation density is greater than the radiation limits, restrictions can be applied in a smaller space. Due to space constraints in such centers, determining the boundaries of the risk zone is appropriate methods. By specifying this area and observing the rules and regulations, it is possible to prevent radiation damage caused by the laser beam and its reflections.

Radiation damage depends on energy absorption, and is approximately proportional to the absorbed energy density in the tissue. In external radiation consideration with a certain energy flux, the amount of absorbed dose in each point of the tissue depends on the type of radiation, the radiation energy, the depth of the place of receipt, and the main components of the absorber environment. The absorbed energy in tissue is important in radiotherapy. This issue is well known for ionizing radiation such as X and Gamma, and is implemented in therapeutic protocols. But less attention is paid to laser therapy. Due to the actual risks of laser use, dosimeters in laser therapy are very important, in addition to observing the permissible radiation limits, in terms of radiation protection, radiation dose is required to achieve the desired effect from the requirements of this laser application in medicine.

Lasers can produce a beam of light of such intensity that permanent damage to human tissue, in particular the retina of the eye, can be caused instantaneously, even at distances of over 10 km. At lower intensities, laser beams can seriously affect visual performance without causing physical damage to the eyes; causing transient damage or causing sensation and loss of focus. Laser illumination of aircraft can cause distraction, disorientation, and discomfort for pilots resulting in a potentially hazardous situation during critical phases of flight. It should be of interest to air Traffic controllers, aerodrome operators, and to the operators of laser shows.

In this paper, portable and online monitoring systems for non-ionizing EMF measurement, as well as some measurement results in Tehran are discussed. First of all, standards and recommendations related to EMF monitoring, measurement and exposure such as ISIRI No.8567, ICNIRP guideline and ITU-K.83 are reviewed. Then, technical facts and operation of portable device and monitoring station are introduced and EMF measuring and surveillance procedure are elaborated. Finally, results of 45 portable and online measurement carried out in Tehran are provided and statistically analyzed. From portable results, it is revealed that most of the measurements are between 1 and 2V/m2 and in online results, instantaneous value for electric field does not exceed 4.5 V/m2.

The widespread use of cell phones has led to an increase in concern about the effect of radiofrequency radiation on the physiology of the human body. This study was conducted to determine the different reaction temperatures of different brain tissue in exposure to mobile radiofrequency waves.

This was an experimental study. The cow's brain tissue was examined in a chamber at three depths of 2,12 and 22 mm and at a distance of 4 mm and 4 in the cell phone from the tissue for 15 min of the radiofrequency radiation of the mobile phone during exposure and after the exposure was discontinued. . Luteron thermometer was used to measure tissue temperature.

During the exposure to the brain tissue at a distance of 4 mm from the mobile phone, the temperature increase at 22 mm depth was more than the depths of 2 and 12 mm, so that the tissue temperature at 2, 12 and 22 mm depths was 29 ° C 0 /, 0.3 / 0 and 0/37 respectively. Also, the temperature of the brain tissue at 4 cm intervals was greater than the other depths with increasing tissue depth. An increase in tissue temperature was also associated with increased brain tissue depth after exposure to mobile phones. The temperature of the depth of 22 mm of texture increased during exposure to higher temperatures.
 

Mobile radiofrequency waves not only increased the temperature of the tissue at all depths of the brain but at higher depths (22 mm), brain tissue was higher than the temperature of mobile radiofrequency waves.

Photoacoustic (PA) imaging of biological tissues using laser diodes instead of conventional Q switched pulsed systems provides an attractive alternative for biomedical applications. However, the relatively low energy of laser diodes operating in the pulsed regime, results in generation of very weak acoustic waves, and low signal-to-noise ratio (SNR) of the detected signals. This problem can be addressed if optical excitation is modulated using custom waveforms and correlation processing is employed to increase SNR through signal compression. This work investigates the effect of the parameters of the modulation waveform on the resulting correlation signal and offers a practical for optimizing PA signal detection. The advantage of coherent signal averaging is demonstrated using theoretical analysis and a numerical model of PA generation. It was shown that an additional 5–10dB of SNR can be gained through waveform engineering by adjusting the parameters and profile of optical modulation waveforms. Also Diode lasers are also more intense and have more power output Therefore, the data can be combined quickly and provide more precise control and are absorbed by the pigment cells such as hemoglobin, because of their proximity to the infrared spectrum. And due to the presence of blood flow throughout the body, it is very useful in the treatment of diseases.

In this paper, a local magnetic field was designed and simulated using a Helmholtz coil along with a ferromagnetic core with an appropriate geometric Structure to concentrate a magnetic flux. This field can be used for magnetic guiding of Boron-borne drugs in BNCT.

In radiation calorimetry by using laser beams and interferometry setups, variations induced by dose absorption in phantom can be precisely measured. Dose absorption and the induced temperature change result in refractive index variation of the material. In order to be able to measure the low amount of absorbed dose in the phantom, temperature dependence of refractive index of the material must be precisely known. Water and Plexiglas phantoms can be used as tissue-equivalent materials and a multitude of reports have been published in recent years regarding their use for radiation calorimetry.  In this study, temperature dependence of refractive index of water and Plexiglas (poly- methyl methacrylate) is measured using a laser interferometry setup. The results show that the refractive index of Plexiglas has more variations with temperature compared to water. This shows that use of Plexiglas as the absorbing material for optical calorimetry, due to its nearly zero heat defect, increases the accuracy of absorbed dose measurements.

In this paper, a one-dimensional photonic crystal filter based on the [SiO2/ZrO2] bilayer have been designed for application in safety glasses for working in 350-nm wavelength. High power lasers with low wavelength e.g. 350-nm have very high power which can cause serious damage to the operator’s eyes. In this paper using the transfer matrix method and theoretical calculation in MATLAB software a photonic crystal filter based on the [SiO2/ZrO2] bilayer have been designed. Simulations have shown that the structure of Glass/[SiO2/ZrO2]8 can filter the 350-nm laser and reduce the transmittance to 0.0038 which is very promising and brings a high level of safety to work with this class of lasers.

In this paper, the use of quantum technology in the radar system and the advantages of these radars as compared to classical radars have been analyzed. In the beginning, briefly, we present the basic structure of the theory of quantum electrodynamics, and then the role of photon in this theory and photon interactions is presented.  In the next step, the most general form of the quantum radar cross section equation is extracted. This equation is also studied through a particle-type approach and introduces single-particle and two-particle illumination. Further, this equation is written in terms of Fourier transforms, since this method will pave the way for analyzing the cross-section of a quantum radar for defense purposes with various geometries. Finally, an analysis of the radar cross-sectional equation for flat panel geometry will be plotted, and computer simulations are carried out using MATLAB software, and finally, by comparing charts drawn from MATLAB software for classical and quantum radars, to analyze and compare them.