It is well-known that response function of organic SCINTILLATION DETECTORS does not appear with photopeaks. Instead, their dominant feature is a continuum, usually called the Compton edge that innately exposes the resolution characteristics of detection system. While, accurate characterization of Compton edge is crucial for calibration purposes, it is also in charge of elaborating the energy resolution of detector. This paper presents a simple method for accurate characterization of the Compton edge in organic SCINTILLATION DETECTORS. The method is based on the fact that differentiating the response function leads to accurate estimation of the constituting functions. The differentiation method, in addition to the location of the Compton edge, gives insights into the parameters of the folded Gaussian function which could lead to depict the energy resolution. Moreover, it is observed that the uncorrelated noise in the measurement of the response function does not impose significant uncertainties in the evaluations, so it could preserve its functionality even in lower-quality measurements. By simulation of the bounded electrons AND considering the Doppler effects, we are able to demonstrate-the first ever-estimation for intrinsic Doppler resolution of an organic plastic scintillator. Even though, this possibility is an immediate result of benefiting the presented method for analysis of the Compton continua.

Introduction: SURGEOSIGHT is a dedicated intra-operative hAND-held gamma camera designed AND manufactured by our team to be used for lymphoscintigraphy. Although conventional gamma cameras are widely used, they lack the capability of the sentinel lymph node (SLN) imaging in the operation room. Like conventional gamma cameras it is necessary to calibrate SURGEOSIGHT for linearity distortion, energy AND flood correction. Our main objective in this study is to develop AND implement three techniques for linearity, energy AND uniformity corrections.Methods: The camera is made up of a pixelated cesium iodide (sodium-activated) (CsI (Na)) SCINTILLATION crystal with 1 × 1 mm2 element size along with a Hamamatsu H8500 flat-panel multi-anode (64 channels) photomultiplier tube. All triple corrections required lookup tables (LUTs). To generate all three LUTs, one uncalibrated acquisition is necessary. Linearity distortion correction was based on localization of physical pixels of crystal AND thin plate spline interpolation to estimate the amount of distortion. Energy correction LUT was simply a photo-peak map of incoming events which was estimated using self-organizing map technique.Results: The results showed improvements qualitatively AND quantitatively. The extrinsic energy resolution was enhanced from 50% to about 20.6%. Integral uniformity AND the differential uniformity, after uniformity correction, in useful field-of-view (UFOV) was measured 9.5% AND 4.5%, respectively.Conclusion: Results substantiated that the correction techniques guarantee uniform AND accurate output of the SURGEOSIGHT which is desirable for intra-operative localization of the sentinel lymph nodes in breast cancer AND also for imaging of other superficial tumors.

Nowadays, due to the threats of radioactive materials, control of borders AND sensitive facilities is of particular importance. For this reason, every year the International Atomic Energy Agency publishes a report on the theft, loss or lack of monitoring AND control on the movement of the radioactive materials in some countries. Therefore, it will be necessary to create AND introduce new methods to deal with such threats. One of the most effective systems for detecting radioactive materials AND contaminants are radioactive portal monitors. In this study, the results of performance evaluation of large plastic SCINTILLATION DETECTORS for use in this type of monitoring systems are presented. Initially, the design AND construction of electronic circuits AND mechanical holders were done. Then, the functional tests of the device were performed using 60Co AND 137Cs sources. Finally, the minimum detectable activity using this monitoring device was determined. The results of the tests to determine the minimum detectable activity of the system showed that it can detect a 60Co source with a minimum activity of 1 μ, Ci at a maximum distance of 100 cm AND a 137Cs source with a minimum activity of 2 μ, Ci at a maximum distance of 75 cm respectively. Regard to the obtained results, it was found that the developed monitoring system has the ability to detect the radioactive sources with good accuracy.

Both of the LaBr3:Ce AND NaI (Tl) DETECTORS are inorganic scintillators that due to their high light output rate in comparison with organic scintillators AND almost other inorganic scintillators are significant. In this research, experimental data for identical measurement of the sealed button sources with both DETECTORS in the presence AND absence of the shield were compared with the simulation data by using MCNP 4C code for the crystals of DETECTORS. The obtained results from the radioactive sealed button sources measurements represented that for low energy gamma rays there are noticeable differences between the experimental AND simulation data AND that is highly due to non-negligible AND effective attenuation of these low energy gamma rays in passing through the window AND the shield of DETECTORS included the crystals. The high energy gamma rays simulation data are, however, in agreement with the experimental observations. Also, all the simulation data as well as the experimental measurents showed that the efficiency of the LaBr3:Ce detector is higher than that of the NaI (Tl) detector. The simulation results for the shielded button sources are also in agreement with the experimental data in most ranges of gama energies.

Background: Measurement of background radiation is very important from different points of view especially for human health. The aim of this survey was focused on determining the current background radiation in one of the highest altitude regions ( Zagros Mountains ), Chaharmahal AND Bakhtiari province, in the south west of Iran . Materials AND Methods: The outdoors-environmental monitoring exposure rate of radiation was measured in 200 rANDomly chosen regions using portable GEIGER-MULLER AND SCINTILLATION DETECTORS. Eight measurements were made for each region AND an average value was used to calculate the exposure rate from natural background radiation. Results: The exposure dose rate was found to be 28.4 m Rh-1 AND the annual average effective equivalent dose was found to be 0.49 mSv. An overall population weighted average outdoor dose rate was calculated to be 49 nGyh-1, which is higher than the world-wide mean value of 44 nGyh-1 AND is comparable to the annual effective equivalent dose of 0.38 mSv. Conclusion: A good correlation between the altitude AND the exposure rate was observed, as the higher altitude regions have higher natural background radiation levels

In this research, the Tm content as codopant in CsI(Tl) was optimized for reducing the afterglow. As an experimental reference, CsI(Tl) AND CsI(Tl-0. 05%Eu) single crystals were grown by Bridgman method. The grown crystals were characterized through photoluminescence analysis, AND the measurements of charge collection time, energy resolution, photon light yield as well as the amount of afterglow were performed. It was observed that the change in codopant shifted the emission curve of Tl+. For CsI(Tl) codoped with Tm in the range of 0. 02 to 0. 1 mol%, the afterglow of 0. 05 mol% Tm reduced in comparison with Tm-free CsI(Tl). The results showed that the Tm codopant resulted in a decrease of 32 to 42% in afterglow depending on the Tl concentration. The addition of various contents of Tm also decreased the light yield up to 23%, AND the resolution by about 2 to 33%. The light yield exhibited insignificant changes, whilst the measured energy resolution was about 8. 8% at 662 keV. Overall, the improvement in the afterglow, as well as the insignificant reduction in both the energy resolution AND light yield of CsI(Tl-Tm), may motivate some researchers to consider it as a good cANDidate for fast spectroscopy AND high-frequency imaging applications.

Earth’ s upper atmosphere, called the ionosphere, is a highly variable region with complex physical characteristics in which the density of free electrons are large enough to have considerable effects on signals’ propagation travelling through this dispersive medium. As GPS signals travel through the ionosphere, they may experience rapid amplitude fluctuations or unexpected phase changes. This is referred to as ionospheric SCINTILLATION. Ionospheric SCINTILLATION which caused by small scale irregularities in the electron density, is one of the dominant propagation disturbances in radio frequency signals. These irregularities severely affect the accuracy AND reliability of GPS measurements. Therefore, it is necessary to investigate ionospheric SCINTILLATION AND its effects on GPS observations. Hence, the focus of this paper is to detect ionospheric SCINTILLATIONs over Iran’ s region AND to investigate these effects on GPS observations in more details. The results will show the occurrance of this phenomenon AND its effects on GPS observations.

A new analytical approach is presented for the calculation of full-energy peak (FEP) efficiency of NaI (Tl) DETECTORS. The self-attenuation of the parallelepiped source matrix, the attenuation by the source container, AND the detector housing materials were considered in the mathematical treatment. The efficiency values calculated using the presently suggested analytical approach are compared with those measured values obtained by two different sizes of NaI (Tl) DETECTORS. The calculated AND the measured full-energy peak efficiency values were in a good agreement.

Background: Recent research on photon detection has led to the introduction of a silicone photomultiplier (SiPM) that operates at a low voltage AND is insensitive to magnetic fields. Objective: This work aims to model a SCINTILLATION camera with a SiPM sensor AND to evaluate the camera reconstructed images from gamma ray projection data. Material AND Methods: The type of study in this research is experimental work AND analytical. The SCINTILLATION camera, modelled from an SiPM sensor array SL4-30035, coupled with a SCINTILLATION material Caesium Iodide doped with Thallium (CsI(Tl)), is used in the experimental part. The performance of the camera was evaluated from reconstructed images by a back-projection technique of a radioactive source Caesium-137 (Cs-137). Results: The experiments conducted with a 1 μ, Ci Cs-137 radioactive source have revealed that the bias voltage (Vbias) of the SiPM needs to be set to 27. 8 V at an operating temperature between 43 °, C to 44 °, C. The radioactive source has to be placed within a 1 cm distance from the sensor to obtain the optimum projection data. Finally, the back-projection technique for image reconstruction with linear interpolation preprocessing has revealed that the Ram-Lak filter produces a better image contrast ratio compared to others. Conclusion: This research has successfully modelled a SCINTILLATION camera with SiPM that was able to reconstruct images with an 86. 4% contrast ratio from gamma ray projection data.