Radiation Physics and Engineering

Abstract Treatment of cancer patients requires high-sensitivity diagnostic techniques. Recently, the Society of Positron Annihilation Spectroscopy (PAS) has been working on hypoxia detection using positron lifetime and hopes to diagnose cancer at its initial phases. The accepted hypothesis for the use of positron as a biomarker of tumor hypoxia is that due to the distance between the blood vessels and the cancerous tissues, the oxygen concentration strongly decreases in cancerous tissues. The point that can put the PAS technique in the category of cancer diagnosis tools is its potential capability for oxygen-sensing in tissues. So, the partial pressure of oxygen in the patient’s tissues can be measured from the Positron Annihilation Lifetime Spectroscopy (PALS). However, before the positron lifetime imaging technique can be established, it is essential to verify the oxygen-sensing capability of the PALS in various chemical environments. In this paper, the mechanisms of positron annihilation in the deionized water and air-bubbled water samples were investigated via systematic experiments by our homemade Doppler Broadening Spectroscopy (DBS) and PALS spectrometer. Three mechanisms for positron annihilation in the investigated liquid samples including oxidation, Positronium conversion, and Positronium inhibition were described. The outcome of this investigation could advance the development of the PALS method for detecting tumors before metastasis, using the J-PET machine, which is still under development at Jagiellonian University.

Abstract One of the challenges of individual dosimetry in Iran is the absence of standard radiation fields with different energies for calibration. For dosimetry in the photon fields, only the standard fields of Co-60 and Cs-137 sources, located in the (SSDL) can be utilized. This study aims to determine energy response of a personal thermoluminescence dosimeter (TLD) designed for determining the personal dose-equivalent, H_p(10), in order to investigate whether the calibration curve in the Co-60 gamma field can be utilized for assessing the dose-equivalent in the photon fields with different energies. To do this, first, the TLD dosimeters (an appropriate plastic badge including a TLD-100 chip) are irradiated with a few H_p(10) values using the Co-60 source in the Karaj SSDL. The badges are placed on a water phantom (slab), one meter distant from the source. Then, MCNP4C code is used to calculate the energy response at 662 keV and 1.25 MeV energies. Next, these responses are validated with the experimental data. Finally, the calculation is carried out for several other energies in the range of 20 keV to 1.25 MeV. Obtained results show that for the energies more than 400 keV, The response of the dosimeter is independent of the photon energy, within 10% uncertainty. On the other hand, for the energies smaller than 400 keV, a significant dependence on the energy is observed; such that in 40 keV the response is about 2 times larger than that at 1.25 MeV. Consequently, a method to reduce this uncertainty is needed.

Abstract The recent emphasis on nanocomposites composed of polymers and metal oxides is largely due to their significant promise as effective radiation sensors, detectors, and dosimeters for gamma rays, X-rays, and charged particles. The sensitivity of a system may be affected by various factors, including the volume of the sensitive material, the concentration of heavy metal oxide nanoparticles, the bias voltage applied, and the degree of crystallinity within the polymer matrix. Studies have shown that a pronounced degree of crystallinity in polymers can restrict the homogeneous spread of nanoparticles. This research utilized two distinct polymer matrices, namely HDPE and PC, to create a nanocomposite that incorporated bismuth oxide nanoparticles at concentrations reaching 60 wt%. FESEM images revealed that PC exhibited better dispersion up to 60 wt%, while HDPE showed agglomeration at 40 wt%. Under a defined dose rate of 42.67 mGy.min^-1, and with a fixed amount of Bi₂O₃ nano-fillers, the dosimetry response (measured as a change in electrical current) of PC was twice as pronounced compared to HDPE. Therefore, PC, as an amorphous polymer containing 50 wt% Bi₂O₃, may be considered a suitable candidate for dosimetry applications.

Abstract The space radiation environment includes trapped protons and electrons, solar protons, galactic cosmic radiation, and neutrons, which can lead to electronic satellite malfunctions. Radiation damage has destructive effects on the electronic components of satellites. As a result of economic reasons and the presence of various limitations, the utilization of commercial components has become common in short-term and low-altitude missions. The most efficient method of protection against radiation is the use of shields. The purpose of this study is to investigate the optimal shielding in a 3-year mission in LEO orbit by considering the radiation resistance of commercial parts using SPENVIS software, SHIELDOSE code, and MULASSIS software. The result of SHIELDOSE, MULASSIS calculations is that the amount of thickness of different materials for the radiation tolerance of commercial parts does not vary significantly in condensation thickness. Furthermore, there is no need for complex protection and you can utilize the usual protections. A comparison of the calculations obtained from MULASSIS and SHILEDOSE to deliver the dose into the silicon target indicates that the values are very similar and if there is a limitation in each of the capabilities of either MULASSIS and SHILEDOSE, another can be utilized as a substitute software.

Abstract In this study, few number of pages from an ancient manuscript that have undergone significant damage, were analyzed using micro-ion beam techniques, including micro-PIXE, micro-RBS, and micro-STIM to identify the factors responsible for the deterioration of these manuscripts. The micro-PIXE results indicate that the yellow decoration ink that has suffered severe corrosion is composed of a combination of Cu and Zn pigments. Moreover, the micro-PIXE analysis reveals that copper is the main element that forms the decoration of this manuscript. The studying the various copper pigments, it was discovered that one of the copper pigment types, which is made up of copper mineral elements, is verdigris or copper acetate (II) with the chemical formula Cu (CH₃COO)₂. This pigment is highly susceptible to environmental moisture. As a result, favorable environmental conditions such as optimal humidity and elemental composition like copper can cause local oxidation of paper to destroys the paper substrate. Furthermore, the results demonstrate that the black ink used to write the text in this manuscript is carbon-based and does not contribute to the corrosion of the paper. However, the micro-RBS analysis indicates that the ink has fully permeated and diffused in the bulk of paper and it increased the corrosion effect.

Abstract The body absorbs trace elements from food, which can have positive and negative effects depending on their type and amount. The study aimed to determine the amount of trace elements found in different varieties of Iranian rice and imported varieties. The concentration of trace elements in rice samples was measured by neutron activation analysis and inductively coupled plasma (ICP-AES). Elements concentrations (mg.kg^-1) were determined for aluminum (2.92-9.16), arsenic (0.064-0.156), bromine (0.24-5.20), calcium (102-981), chlorine (132-323 ), chromium (ND -20.4), lead (ND-0.232), cadmium (0.010-0.115), scandium (0.001-0.007), magnesium (262-519), manganese (2.97-18.50), sodium (3.99-14.30), mercury (ND- 0.002), zinc (2.62-23.60). This study found that Indian rice contains higher levels of bromine, calcium, and sodium, while Pakistani rice contains higher amounts of aluminum, chlorine, lead, and mercury. Shirodi rice is known to have higher levels of arsenic and magnesium, Tarem Hashemi rice has been found to contain higher amounts of chromium, manganese, and zinc, and cadmium is found in Sadri rice. However, the amount of toxic elements in all types of rice does not pose a significant threat to human health.

Abstract Saffron (Crocus sativus L.) is cultivated in environments with very different climatic conditions and with very different corm rates from place to place, and it is appreciated for its red dried stigmas used as cooking spice and flavoring agent. To enhance the flower morphological and colorimetric traits under environmental stresses, the applications of non-thermal plasma based techniques are increasingly being investigated in the field of agricultural science as an alternative to conventional pre-germination treatments. Therefore, a field study was conducted to compare four levels P₁ (no treatment), P₂ (5 minute treatment), P₃ (10 minute treatment), P₄ (20 minute) and the salinity stress factors in three levels were 2, 4 and 6 dS.m^-1 according a factorial design with 3 replications. Flowering beginning in saffron seems to be influenced by the combination of plasma and salinity stress. High concentration of salinity (6 dS.m^-1) resulted in a lower flower and stigma production. The highest number of leaf per plant was found when corms treated to P₄ and 2 dS.m^-1 6 salinity stress condition. Exposure of saffron corn to plasma treatments of 20 minutes showed the most stimulating effect regarding the flower phenology and stigmas yield in saffron under salinity stress.

Abstract In this study a super absorbent polymer (SAP) based on acrylic acid (AAc) and carboxymethyl cellulose (CMC), as an environmentally friendly material, was prepared using gamma irradiation. Gamma radiation was applied to synthesize CMC/AAc SAPs in the range of 5 to 20 kGy absorbed doses. Fourier Transform Infrared (FT-IR) spectroscopy was used to determine the polymerization and grafting monomer to CMC in SAP formation. The effect of radiation dose, CMC concentration on the gel content, swelling behavior and absorption under load (AUL) in water and saline solution were investigated. Based on the results with increasing irradiation dose from 10 to 20 kGy the water and saline solution absorption of the SAP decrease in SAPs containing 1 and 2% CMC, but increases in SAP containing 0.5% CMC. Also, by raise in the irradiation dose from 10 to 20 kGy AUL decreases. The results suggest that 0.5% CMC/AAc SAPs synthesized using the irradiation method may be suitable for medical applications.