Experimental characterization and monte carlo simulation of the dosimetric parameters of the mosfet structure in the fields of ionizing radiation.

Rezultati naučnih istraživanja pokazuju da jonizujuće zračenje može dovesti do funkcionalnog ili trajnog oštećenja poluprovodničkih naprava različitog tipa u ekstremnim radnim uslovima (u okruženju nuklearnog reaktora, akceleratorske instalacije, nuklearne eksplozije ili prilikom testiranja naprava za eksploataciju u kosmosu). Cilj ovog rada je primena specifične metodologije kojom se preciznije prati uticaj jonizujućeg zračenja na karakteristike MOSFET komponente. Specifičnost metodologije se ogleda u tome da pored toga što se određuje zavisnost promene napona praga od eksperimentalno određene apsorbovane doze u MOSFET-u koji se nalazi u polju jonizujućeg zračenja, uvode se i Monte Karlo proračuni veličina od kojih zavise dozimetrijski parametri MOSFET strukture i sagledava se njihova veza sa rezultatima eksperimenta. Jedan od predmeta istraživanja u disertaciji obuhvata eksperimentalni rad na proučavanju izabranih parametara MOSFET komponente kojima se može sprovoditi dozimetrija u poljima jonizujućih zračenja. Eksperimenti su obuhvatili određivanje zavisnosti napona praga VT i promene napona praga ΔVT od ukupne apsorbovane doze zračenja za slučajeve različitih poluprovodničkih, strukturnih i konstrukcionih karakteristika izabranih komercijalnih MOSFET komponenti, što se postiže promenama u debljini oksida gejta, u dopiranosti poluprovodničke osnove, u različitoj vrsti poluprovodničkog materijala, u prisustvu slojeva za pasivizaciju, u dužini i širini kanala između sorsa i drejna, u naponu napajanja gejta u toku zračenja...The results of scientific research show that ionizing radiation can lead to functional or permanent damage of semiconductive devices of various types in extreme operating conditions (in the environment of a nuclear reactor, accelerator installation, nuclear explosion, or when testing the devices for exploitation in the cosmos). The aim of this study is to establish a specific methodology for more accurate monitoring of the impact of ionizing radiation on the characteristics of the MOSFET component. The specificity of this methodology is reflected in the fact that besides the determination of the dependence of the change in the threshold voltage of the experimentally determined absorbed dose in the MOSFET, which is located in the field of ionizing radiation, there is also the introduction of the Monte Carlo size calculations which the dosimetric parameters of MOSFET structure depend on and the examination of their connection with the results of the experiment. One of the objects of research in the thesis includes experimental work on studying the selected parameters of the MOSFET component in the fields of ionizing radiation. The experiments included the determination of the dependence of the threshold voltage VT and the changes in the threshold voltage ΔVT on the total absorbed dose of radiation for various semiconductor, structural and constructional characteristics, of selected MOSFET components which is achieved by changing the thickness of the gate oxide, the level of doping the semiconductor base, by using a different type of semiconductor material, the presence of passivation layers, the length and width of the channel between the source and the drain, the voltage of the power supply for the gate during the radiation..

Transport and storage of heavy metals in the Sava river basin in Serbia

Selected heavy metals (Cu, Zn, Pb and Cd) in Sava River water and sediment in Serbia were investigated on three locations in the vicinity of industrial and urban settlements (Šabac, Obrenovac, Beograd) during the period spring 2007-autumn 2011. The fluxes of heavy metals from river water to sediment due to sedimentation and heavy metal re-suspension fluxes due to sediment re-suspension at a high flow were determined, by applying the model for assessment of the transport the pollutants through rivers. Those fluxes were attributed mainly to natural processes. [Projekat Ministarstva nauke Republike Srbije, br. 43009

Investigation of the mortar and concrete resistance in aggressive solutions

U radu je prikazan utjecaj dva agresivna rastvora – sulfata i nitrata na žbuku i beton. U eksperimentalnom radu ispitivane su prizme od žbuke s 5 % specijalnog dodatka. Četiri vrste betona su također izložene agresivnim rastvorima. Kemijska otpornost ispitivana je prema metodi Koch-Steinegger. Kako je uvjet za otpornost kod agresivnih rastvora da zatezna čvrstoća žbuke nije niža od 70 % u odnosu na referentne prizme njegovane u vodi, može se zaključiti da žbuka i beton izrađeni s kombinacijom cementa i dodataka, prikazani u ovom istraživanju, nisu otporni na rastvor amonijak nitrata ali jesu na sulfatnu koroziju.Testing the influence of two aggressive solutions - sulphate and nitrate on mortar and concrete was presented in this paper. Experimental work included testing of mortar prisms with 5 % special admixture. Also, four types of concrete were exposed to aggressive solutions. The chemical resistance was tested according to the Koch-Steinegger method. As a condition for resistance in aggressive solution means that flexural strength of mortar prisms is no less than 70 % of referent prisms cured in water it can be concluded that mortar and concrete made with combination of cement and admixture presented in this investigation are not resistant to ammonium nitrate solution, but are resistant to sulphate corrosion

Legislative framework of nuclear security in the Republic of Serbia

The paper presents the concept and characteristics of nuclear security, the elements of the nu- clear safety strategy, the legislative framework and the most important solutions from the Law on Radiation and Nuclear Safety and Security. At the international level, the most important entity in this field is the International Atomic Energy Agency, while at the national level, most important is the Directorate for Radiation and Nuclear Safety and Security of Serbia. An important role is played by the Vinča Institute of Nuclear Sciences as the most referential scientific institution in this field, as well as the operational bodies - Nuclear Facilities of Serbia, the Ministry of Internal Affairs, Ministry of Defence, and the Serbian Armed Forces. Engagement of these bodies is carried out in regular peacetime circumstances, emergency situations and wartime. The most important challenges, risks and threats to nuclear security of Serbia were pointed out as well as the need to harmonize norms, procedures and processes in purpose of the strengthening institutional mechanisms in the field of nuclear security

Damage Induced by Neutron Radiation on Output Characteristics of Solar Cells, Photodiodes, and Phototransistors

This study investigates the effects of neutron radiation on I-V characteristics (current dependance on voltage) of commercial optoelectronic devices (silicon photodiodes, phototransistors, and solar panels). Current-voltage characteristics of the samples were measured at room temperature before and after irradiation. The diodes were irradiated using Am-Be neutron source with neutron emission of 2.7 x 10(6) n/s. The results showed a decrease in photocurrent for all samples which could be due to the existence of neutron-induced displacement defects introduced into the semiconductor lattice. The process of annealing has also been observed. A comparative analysis of measurement results has been performed in order to determine the reliability of optoelectronic devices in radiation environments

Floating-Gate MOS Transistor with Dynamic Biasing as a Radiation Sensor

This paper describes the possibility of using an Electrically Programmable Analog Device (EPAD) as a gamma radiation sensor. Zero-biased EPAD has the lowest fading and the highest sensitivity in the 300 Gy dose range. Dynamic bias of the control gate during irradiation was presented for the first time; this method achieved higher sensitivity compared to static-biased EPADs and better linear dependence. Due to the degradation of the transfer characteristics of EPAD during irradiation, a function of the safe operation area has been found that determines the maximum voltage at the control gate for the desired dose, which will not lead to degradation of the transistor. Using an energy band diagram, it was explained why the zero-biased EPAD has higher sensitivity than the static-biased EPAD

A new approach to the analysis of the accumulation and enrichment of heavy metals in the Danube River sediment along the Iron Gate reservoir in Serbia

The concentrations of heavy metals (Cu, Zn, Pb and Cd) and long-lived radionuclides (U, Th and Cs) along the Iron Gate reservoir of the River Danube in Serbia were determined. In the years 2005-2009, water and sediments were sampled at six sites along 200 km of the River Danube from Belgrade to the Djerdap (Iron Gate) hydroelectric power plant. The concentrations of heavy metals in the sediment were found to be in the ranges of 27.9-149.3 mg kg(-1) for Cu, 55.2-228.4 mg kg(-1) for Zn, 13.5-71.6 mg kg(-1) for Pb, 0.3-25.2 mg kg(-1) for Cd and 4.0-17.5 Bq L-1 for Cs-137. These values are in correlation with the concentrations in the river water when expressed by the equilibrium coefficients (K-d) between the solid and liquid phases. The behaviors of the heavy metals were evaluated by applications models for the prediction of the behavior of pollutants in rivers. The fluxes of heavy metals from water to sediment and vice versa were also determined

Distribution and accumulation of heavy metals in the water and sediments of the River Sava

The distribution and accumulation of assorted heavy metals and a long-lived radionuclide (Cu, Zn, Pb, Cd, U, Th and Cs-137) in the water and sediment of the River Sava (in Serbia) were investigated at three locations in the vicinity of industrial and urban settlements (Sabac, Obrenovac, Belgrade). The concentrations of heavy metals in the sediment were found to be in the ranges (mg kg(-1)): 29.6-145.1 for Cu, 53.2-253.6 for Zn, 14.2-78.6 for Pb, 0.3- -24.6 for Cd, and 4.0-12.5 Bq l(-1) for Cs-137. These values correlate to the concentrations in the river water if expressed by equilibrium distribution coefficients K-d (dM(3) g(-1)) between the solid and liquid phases. The degrees of accumulation and enrichment of tracer metals were determined

Dosimetry audit in radiotherapy centers in Serbia in period from 2017 to 2019

Kontrola kvaliteta u radioterapiji je od velike vaţnosti za poboljšanje preciznosti i pouzdanosti radioterapijskih procedura. Minimizacija negativnih posledica po pacijente se postiţe smanjenjem verovatnoće pojavljivanja slučajnih i sistematskih grešaka identifikovanjem problema u postojećim standardnim procedurama u bolnicama. Značajna metoda kontrole kvaliteta rada radioterapijskih centara jeste program poštanske termoluminiscentne dozimetrije, zajednički organizovan od strane Međunarodne agencije za atomsku energiju i Svetske zdravstvene organizacije, a u kojem učestvuje oko 1700 bolnica širom sveta. Radioterapijski centri u Srbiji takođe učestvuju u ovom programu. Program poređenja apsorbovanih doza u vodi u radioterapijskim centrima u Srbiji je sproveden i tokom 2017, 2018. i 2019. godine. U tom periodu, broj obuhvaćenih centara je porastao sa šest na osam. Radiofotoluminiscentni dozimetri su ozračivani u visokoenergetskim poljima X-fotona generisanim pomoću linearnih akceleratora.Quality control in radiotherapy is of great importance in order to improve accuracy and reliability of radiotherapy procedures in hospitals. Minimization of the possible negative consequences of these procedures is achieved by reducing the probability of any random or systematic errors appearing, by determining the existing problems in the standard hospital procedures. One of the important methods for the radiotherapy facilities quality control is the postal thermoluminiscent dosimetry programme, co-organized by International Atomic Energy Agency and the World Health Organization, in which approximately 1700 hospitals throughout the world are participating. Radiotherapy centers in Serbia also participate in this programme, which has been executed during 2017, 2018 and 2019. During this period the number of participating radiotherapy centers in Serbia has increased from six to eight. Radiophotoluminiscent dosimeters have been irradiated in the high-energy X-ray fields generated by using linear accelerators.Proceedings: [http://vinar.vin.bg.ac.rs/handle/123456789/8681]XXX симпозијум ДЗЗСЦГ (Друштва за заштиту од зрачења Србије и Црне Горе), 2- 4. октобар 2019. године, Дивчибаре, Србиј

Airborne uranium assessment by epiphytic lichen species in contaminated areas

Natural uranium, consisting of 238U, 234U and 235U isotopes is present in the environment in low concentrations especially in the atmosphere where it usually exists as a constituent of particulate matter submicron conglomerates suspended in the air. In the case of contamination, uranium may be present in the aerosol, being transferred to other areas by wind and again settled on the surface soil with possible migration into deeper layers or resuspension under certain meteorological conditions. Here results on the airborne uranium assessment based on the analysis of lichen species already present or transplanted into contaminated areas will be presented. With that aim, different in situ and transplanted epiphytic lichen species have been taken at selected locations in southern Serbia in the stage of existing contamination by depleted uranium, during the clean-up activities and afterwards, in all four seasons. Collected samples underwent analysis by sensitive nuclear analytical techniques. The INAA and ICP MS results are derived from 238U mass fraction while high resolution alpha-spectrometry gave results for each isotope expressed as specific activity concentration (Bq kg-1). Based on the isotopic ratios 235U /238U and 234U /238U, depleted uranium content was possible to distinguish from natural uranium in the samples. Results have shown that the sensitivity of the examined morphologically different lichen types and their ability to accumulate metals including uranium, strongly depend on metals’ concentration in the air as well as on the age of lichens, properties of host species, chemical properties of particles, local climate conditions, exposure time etc. Epiphytic lichen species Evernia prunastri was found to be the most suitable bioindicator for the accumulation of uranium airborne particles. Concerning the uranium content, a significant difference in concentrations had been observed for different sampling phases, with maximum depleted uranium contribution during the clean-up activities. The variability in uranium concentrations was noticeable in relation to prevailing wind direction, position and distance of the sampling points. Having in mind the results obtained within the national radioactivity monitoring program 2011-2017, it may be concluded that for detailed airborne uranium assessment, a methodology such as biomonitoring with the application of sensitive nuclear techniques should be considered.VII International Conference on Radiation in Various Fields of Research : RAD 2019 : book of abstracts; June 10-14, 2019; Herceg Novi, Montenegr