Along with monitoring of different species of secondary cosmic rays, ASEC detectors register several thunderstorm ground enhancements (TGEs). In 2011, a network of five thallium-doped sodium iodide (Nal(Tl)) detectors was installed on Aragats Space Environmental Center (ASEC) and was included into ASEC detectors system. It has been concluded that the regularization method Modified Truncated Singular Value Decomposition (MTSVD) is appropriate to unfold X-ray spectra in all the scintillators studied. Different unfolding methods are tested to reconstruct the actual X-ray spectrum knowing the dose curve and the response function. The effect of the mass energy-absorption coefficient of the scintillator material has been studied on the response matrix and consequently, in the reconstructed spectra. In this paper, the applicability of different flat panels for reconstructing X-ray spectra is studied. Most of the actual flat panel devices use scintillator materials that present K-edge discontinuities in the mass energy-absorption coefficient, which strongly affect the response matrix. The MCNP5 code has been used to model different flat panels (based on indirect and direct methods to produce charge carriers from absorbed X-rays) and to obtain the dose curves and system response functions. In this work, it is proposed the use of a flat panel detector together with a PMMA wedge to estimate the actual X-ray spectrum using the Monte Carlo method and unfolding techniques. The detection limits were assessed and are presented as well.Īn accurate knowledge of the photon spectra emitted by X-ray tubes in radiodiagnostic is essential to better estimate the imparted dose to patients and to improve the quality image obtained with these devices. The measurements proved the superiority of the prototypes over the scintillation detectors now commonly used regarding energy resolution and multi-nuclide identification capability. The evaluation of the two prototypes, carried out at three steel factories with standard sources of 60Co, 137Cs, 192Ir, 226Ra and 241Am in three different matrices (slag, fume dust and cast steel) and with samples provided on-site by the factories, was successful. Two prototypes based on HPGe detectors were designed and assembled to suit the needs of steel mills which had been examined previously. ![]() The final purpose of the project was the improvement and standardisation of the measurement methods and systems for the control of radioactivity of recycled metal scraps at the beginning of the working process and for the certification of the absence of any radioactive contamination above the clearance levels (IAEA-TECDOC-8S5) in final steel products, Clearance levels for radionuclides in solid materials: application of exemption principles). This new application of this type of detector is part of the Joint Research Project (JRP) MetroMETAL supported by the European Metrology Research Programme (EMRP). This paper presents the results of the tests of High Purity Germanium (HPGe) based gamma spectrometers employed for radioactivity control carried out on a daily basis in steel factories. ![]() The DECO FORTRAN code has been developed for compatible PC microcomputers. Very accurate results are obtained, which would be hard to achieve by other methods. The amplitude of each component (the area of each peak or the sum of areas of peaks characterizing an element) is fitted by the weighted least squares method, taking into account that errors in spectra are independent and follow a Poisson law. An autoregressive filter is calculated, leading to a characteristic polynomial whose complex roots represent both the location and the width of each peak, provided that the absolute value is lower than unit. The latter is multiplied by a function in order to transform original Gaussian into Lorentzian peaks. Thus, the spectrum is arranged symmetrically and transformed into the Fourier representation. The search for peaks and determination of peak areas are worked out in the Fourier representation, which enables separation of background and peaks and very efficiently discriminates peaks, or elements represented by several peaks.įirst the spectrum is transformed so that in the new representation the full width at half maximum (FWHM) is independent of energy. The principle of the method rests on the Fourier transform of the spectrum. Neutrons are provided by a low activity (5 μg) 252Cf source the detector is a BGO 3 in. ![]() Using new spectral analysis methods, it is applied to an actual case: the accurate on-line analysis of three elements (Ca, Si, Fe) in a cement plant using neutron capture gamma rays. ![]() A general deconvolution method applicable to X and gamma ray spectrometry is proposed.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |