Ayşegül Kahraman

Measurements of radon concentrations in waters and soil gas of Zonguldak, Turkey

The radon concentrations in soil-gas and water samples (in the form of springs, catchment, tap, thermal) used as drinking water or thermal were measured using a professional radon monitor AlphaGUARD PQ 2000PRO. The measured radon concentrations in water samples ranged from 0.32 to 88.22 Bq l(-1). Most of radon levels in potable water samples are below the maximum contaminant level of 11 Bq l(-1) recommended by the US Environmental Protection Agency. The calculated annual effective doses due to radon intake through water consumption varied from 0.07 to 18.53 µSv y(-1). The radon concentrations in soil gas varied from 295.67 to 70 852.92 Bq m(-3). The radon level in soil gas was found to be higher in the area close to the formation boundary thrust and faults. No correlation was observed between radon concentrations in groundwater and soil gas. Also, no significant correlation was observed between soil-gas radon and temperature, pressure and humidity. The emanation of radon from groundwater and soil gas is controlled by the geological formation and by the tectonic structure of the area.

Investigation of RadFET response to X-ray and electron beams

The irradiation response of Radiation Sensing Field Effect Transistor (RadFET), also known as MOSFET/pMOS dosimeter, to high energy X-rays and electron beams was investigated. The threshold voltages before and after irradiation were measured and the trap densities in the gate oxide and oxide/silicon interface of the RadFETs are evaluated. The RadFETs were irradiated with 6MV X-rays, and 10 and 18MeV electron beams emitted from a Linear accelerator (LINAC). Linear and non-linear fits to experimental results showed that after an initial linear response up to several Gy, deviation from the linearity occurred due to electric field screening by the radiation induced oxide trapped charges. The radiation-induced fixed traps (FTs) and switching traps (STs) were analysed and the FT density was found to be higher than the ST density for all beam types and doses. The radiation response, fading characteristics, and variation of the trapped charges of the RadFETs showed similar behaviour in tests.

Variation in the radon concentrations and outdoor gamma radiation levels in relation to different geological formations in the thermal regions of Bursa, Turkey.

Spring waters used as spas and their region may contain significant amounts of natural radionuclides. The main sources of exposure are the inhalation of radon and its decay products released from the water and soil and terrestrial gamma-radiation. In order to evaluate the potential risk of thermal regions in Bursa, located in the impact area of the NAF (North Anatolian Fault), radon and thoron concentrations in soil gas, radon concentrations in thermal waters and outdoor gamma radiation levels were measured in thermal regions that have different geological formations. The radon and thoron concentrations in soil-gas were found to vary from 2272  ±  121 to 245196  ±  3455 Bq m-3 and from 999  ±  218 to 178 848  ±  17 742 Bq m-3, respectively. The radon concentrations in thermal waters ranged from 0.99  ±  0.21 to 226.74  ±  2.51 Bq l-1 in the rainy season and from 0.26  ±  0.10 to 178.03  ±  12.86 Bq l-1 in the dry season. The measured outdoor gamma radiation levels varied from 38 to 180 nGy h-1. The gamma dose rates were found to be strong positively correlating with the radon and thoron concentrations in soil-gas. The radon and outdoor gamma radiation levels were observed to be a function of the geological formations of the area.

The investigation of radionuclide distributions in soil samples collected from Bursa, Turkey.

The distributions of (226)Ra, (232)Th, (40)K and (137)Cs activity concentrations were determined using a high-purity germanium detector in uncultivated surface soil samples collected from Bursa. The range of (226)Ra, (232)Th, (40)K and (137)Cs activity concentrations varied from 10±1 to 61±3 Bq kg(-1) (mean value 25±3 Bq kg(-1)), from 12±1 to 50±2 Bq kg(-1) (mean value 26±3 Bq kg(-1)), from 257±5 to 1010±11 Bq kg(-1) (mean value 435±44 Bq kg(-1)) and from 1.01±0.07 to 48.97±0.54 Bq kg(-1) (mean value 8.52±2.59 Bq kg(-1)), respectively. In addition, the mean outdoor absorbed dose rates in air, annual effective dose equivalent, radium equivalent activity and external hazard index were found to be 45 nGy h(-1), 56 μSv y(-1), 96 Bq kg(-1) and 0.26, respectively. The gross beta activity concentrations were determined using a Tennelec LB 1000-PW detector. The range of gross beta activity concentrations varied from 46±9 to 1199±113 Bq kg(-1) with a mean value of 541±19 Bq kg(-1).

Calculation of angular distribution of 662 keV gamma rays by Monte Carlo method in copper medium.

This paper presents results on the angular distribution of Compton scattering of 662 keV gamma photons in both forward and backward hemispheres in copper medium. The number of scattered events graph has been determined for scattered gamma photons in both the forward and backward hemispheres and theoretical saturation thicknesses have been obtained using these results. Furthermore, response function of a 51 x 51 mm NaI(Tl) detector at 60 degrees angle with incoming photons scattered from a 10mm thick copper layer has been determined using Monte Carlo method.

Proposal of alternative sensitive region for MOS based radiation sensors: Yb2O3

The purpose of this study is to investigate the usability of ytterbium oxide (Yb2O3) as a sensitive region/gate oxide in metal oxide semiconductor (MOS) based dosimeters and to determine the advantages and disadvantages of this device relative to its alternatives. For this purpose, amorphous Yb2O3 films were grown on p type Si by radio-frequency magnetron sputtering and aluminum (Al) was used as front and back ohmic contacts of the capacitor. Yb2O3 MOS devices were irradiated incrementally to the total dose of 70 Gy by 60Co radioactive source. The capacitance–voltage measurements were performed at low (100 kHz) and high (1 MHz) frequencies to examine the behavior of the traps. The sensitivity of the device for 70 Gy was obtained using flat band voltage shifts as 27.5 ± 1.1 and 28.1 ± 1.3 mV/Gy for 100 kHz and 1 MHz, respectively. The changes in the oxide trap charge densities in the studied dose between 0.5 and 70 Gy are in the ranges of (1.09 ± 0.04)× 1011–(1.23 ± 0.05) × 1012 cm−2 for 100 kHz and (−3.26...

Mosses beta radioactivity in Katirli mountain‐Bursa, TURKEY

Mosses are one of the most widely used procedures to determine via plant of radioactive contamination. The high concentrating capacity of mosses may be used as bioindicator of environmental radioactive contamination. In this study, the mosses were collected in region of Katirli Mountain in northwestern Turkey, activities were determined using TENNELEC LB 1000‐PW detector. Samples of mosses growing on soil, rock, and tree bark were collected.

Correlation of radon and thoron concentrations with natural radioactivity of soil in Zonguldak, Turkey

Radon and thoron gases are produced by the decay of the radioactive elements those are radium and thorium in the soil. In this study, the correlations between soil radon and thoron concentration with their parent nuclide (226Ra and 232Th) concentrations in collected soil samples from the same locations were evaluated. The result of the measurement shows that the distribution of radon and thoron in soil showed the same tendency as 226Ra and 232Th distribution. It was found a weak correlation between the radon and the 226Ra concentration (R =0.57), and between the thoron and the 232Th concentration (R=0.64). No strong correlation was observed between soil-gas radon and thoron concentration (R = 0.29).

Evaluation of the pre-irradiation electrical characterisations of the RadFET dosimeters with diverse gate oxides by TCAD simulation program

The aim of the present study is to determine the pre-irradiation threshold voltages of the RadFET dosimeters with gate oxide composed of high-k dielectrics and compare the results with the traditional sensors, the gate oxide of which is composed of SiO2. The effects of the p regions with different concentration, depth and length on the electrical characteristic of the RadFETs were also investigated in the study. For these purposes, Al2O3, HfO2 high-k dielectrics and SiO2 with the thicknesses of 400 nm were used as the sensitive regions of the dosimeters. The sensors were designed in the Silvaco TCAD simulation program. While the lengths of the p regions changed the Id-Vg characteristics of the RADFETs, the depths and concentrations until a certain value of these regions did not play an important role in electrical characteristic. The lowest threshold voltages obtained from the SiO2, Al2O3 and HfO2-RadFETs were found to be -5.22, -3.63, and 3.10 V, respectively. These results demonstrated that RadFETs with high-k dielectrics may be promising candidate for the new generated dosimeters in terms of broader measurable dose range providing their radiation tests.