Bremsstrahlung shielding parameters in polymer concretes

Concretes are used for shielding in nuclear power plants. Beta radiation is emitted during the nuclear reactions. This beta radiation interacts with the concrete and results in secondary radiation such as bremsstrahlung. Shielding parameters of beta-induced bremsstrahlung in concretes are important in the field of radiation protection. We have evaluated the cross section, yield, intensity and dose rate of beta-induced bremsstrahlung by pure beta nuclides of end point energy ranges from 0.4 to 5?MeV in some polymer-based concretes such as sulfur polymer concrete, barium polymer concrete, calcium polymer concrete, fluorine polymer concrete, chlorine polymer concrete and germanium polymer concrete. We have compared the shielding properties among the studied polymer concretes. The efficiency, intensity and dose rate of bremsstrahlung increases with a maximum energy of beta nuclide and modified atomic number of the concrete. From the detailed study, it is clear that the barium polymer concrete is having large bremsstrahlung dose rate and specific bremsstrahlung constant values than the other studied polymer concretes. This means barium polymer concrete is a good absorber of bremsstrahlung radiation than the other studied polymer concretes.     

Dose assessment of bremsstrahlung induced by beta-emitting radioisotopes of uranium-238 series and lead in human tissues

In the natural uranium-238 decay series, pure beta isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb and ²¹⁰Bi are released. The few lead isotopes such as ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb are good beta emitters. In certain nuclear reactions of reactor these isotopes are released. These beta isotopes have maximum beta energies, which induce the bremsstrahlung radiation. The bremsstrahlung component of these beta isotopes has been traditionally ignored in dosimetry calculations. The shapes of bremsstrahlung spectra are a basic ingredient in the understanding and quantification of beta-ray dosimetry. The bremsstrahlung spectra produced by these high-energy isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb, ²¹⁰Bi, ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb in bone, muscle and teeth are studied, and the computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth–dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The evaluated beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The efficiency, intensity and dose rate of bremsstrahlung induced by beta isotopes of natural uranium-238 decay series and beta-emitting lead isotopes in human tissues such as brain, breast, heart, kidney, liver, muscle, pancreas and bone have also been studied in the present investigation. The values of bremsstrahlung dosimetric parameters are low for pancreas, but they are high for bone. For all studied tissues these parameters are high for ²³⁴Pa, but low for ²¹⁰Pb.     

Beta-induced bremsstrahlung shielding parameters in various types of steels

ABSTRACT

Present work studies the bremsstrahlung efficiency, bremsstrahlung dose rate, probability of energy loss by beta during bremsstrahlung emission and specific bremsstrahlung constant of the beta radionuclide for various steels such as XM-5, 317LM, XM-17216, AL-6XN, JS700, NIROSTA 4565S and stainless steel. We have compared the shielding properties among the studied different steels. From the detailed study, the steel type 317LM is having the highest bremsstrahlung dose rate and specific bremsstrahlung constant values than the other studied steels. This means the steel type 317LM is a good absorber of bremsstrahlung radiation than the other studied steels. Hence it is better to use the steel type 317LM in the nuclear power plants than stainless steels and other steels to avoid the secondary radiation such as bremsstrahlung.     

Measurement of K absorption edge energies of silver and tin targets using a weak beta source

K absorption edge energies of Ag and Sn elements have been determined by using a weak beta source. In this method, the beta particles from a ⁹⁰Sr? ⁹⁰Y beta source interact with an iron foil to produce the external bremsstrahlung (EB) photons. The spectrum of EB photons is passed through the elemental target and the spectrum of transmitted photons is recorded with a high resolution HPGe detector spectrometer coupled to 16K multichannel analyzer. The recorded transmitted EB spectrum shows a sharp decrease in intensity at the K shell binding energy of elemental target. Such a sharp decrease region, which is corrected for Kβ′₂ contribution, has been used to determine the K absorption edge energies of Ag and Sn elemental targets. The measured values have been compared with theoretical and experimental values. Copyright © 2010 John Wiley & Sons, Ltd.     

External bremsstrahlung spectra of the Sr source in some lead compounds measured using NaI detector

The spectral distributions of external bremsstrahlung (EB) excited by beta particles from a ⁹⁰Sr/⁹⁰Y source in thick target compounds PbCl₂, PbF₂, Pb(NO₃)₂ and CdO were measured using a 3.8 cm × 3.8 cm NaI(Tl) crystal. The spectra, unfolded using the Liden-Starfelt procedure, showed fairly good agreement with theory (Tseng and Pratt) at low energies and some deviation (less than 15%) at higher energies. The discrepancy between theory and experiment increases with modified atomic number of the target compound and photon energy. The application of the measured/theoretical spectrum to estimate the bremsstrahlung dose is also discussed.     

Exposure of bremsstrahlung from beta-emitting therapeutic radionuclides

There has been an increased interest in beta therapeutic nuclear medicine, which emits relatively high-energy (>1 MeV) β-rays and the production in vivo of Bremsstrahlung sufficient for external imaging, the produced Bremsstrahlung radiation hazard warrants evaluation. The Bremsstrahlung dose from patient administered β-ray emitted radionuclide has been calculated by extending the national council on Radiation Protection and measurement model of a point source in air to account for biologic elimination of activity. We have estimated the probability of bremsstrahlung production, specific Bremsstrahlung constant (defined by Zanzonico et al.) and activity (A_release) in bone cortical, bone compact, different regions of tooth enamel (enamel dentin junction (EDJ), enamel middle surface, enamel inner surface), different regions of dentin (outer surface, middle surface, enamel dentin junction (EDJ)), soft tissue, lungs and skeleton for different therapeutic beta-emitting radionuclide. In the present calculations we have used modified atomic number (Z_mod) defined for bremsstrahlung process.Proper localization and quantification of incorporated beta emitters in bone and tooth are possible, because Bremsstrahlung production is greater in bone and tooth than soft tissue due to their high modified atomic number (Z_mod). Radionuclide therapy with pure β-ray emitters emitted in bone, tooth, soft tissue, lungs and skeleton does not require medical confinement of patients for radiation protection.     

Quantum effects on electron-proton bremsstrahlung spectrum in a two-component plasma

The electron-proton low energy bremsstrahlung process is investigated in a two-component plasma. The corrected Kelbg potential taking into account the quantum effects is applied to describe the electron-proton interaction potential in a two-component plasma. The straight-line trajectory method is applied to the motion of the projectile electron in order to investigate the variation of the bremsstrahlung cross-section as a function of the scaled impact parameter, thermal de Broglie wavelength, projectile energy, and photon energy. The results show that the quantum-mechanical effects decrease the bremsstrahlung cross-sections when the de Broglie wavelength (λ) is greater than the Bohr radius (a₀). It is also found that the quantum effects are important only for the region of impact parameters b < 3a ₀. Received 13 March 2001     

Bremsstrahlung of hot quantum plasma

The classical Debye field is replaced by the respective quantum modification for a hot quantum plasma. The bremsstrahlung spectrum and the total bremsstrahlung intensity are investigated in detail. The results of numerical calculations are tabulatedvs. the characteristic parameter=₀ /kT, where ₀ is the plasma frequency and other symbols have their standard meaning. It is found that the deviations from the bremsstrahlung of a classical plasma become significant for the values10^–2. These modifications are to be taken into consideration in the interpretation of the bremsstrahlung measurements.     

Plasma heating by a strong laser field with statistically distributed parameters

Summary The energy absorption rate by a classical homogeneous plasma irradiated by a strong fluctuating laser field via inverse bremsstrahlung is considered. A chaotic-field model is used and comparison is made with the fundamental model of a purely coherent field. In the present analysis, the emphasis is put on the interplay between the laser field statistics and the plasma electron energy distribution. Numerical calculations are concerned with the dependence of the energy absorption rates on laser intensity and frequency. Laser intensity values up to 4.6\10¹⁵ W/cm² are considered. The multiphoton structure of the energy absorption is analysed as well. Concerning the joint influence of the radiation and particle statistics on the absorption rate, the basic result may be stated as follows. For situations where the particle thermal velocityv _T is larger than the oscillatory velocityv ₀ imparted by the field (v _T ≥v ₀, relatively weak field), the absorption rate is only weakly dependent on the field statistics. For situations, instead, whenv ₀≫v _T , which occurs for very high intensities, the reverse becomes true: now the initial particle velocity distribution plays the modest role of a velocity spread of an electron beam oscillating atv ₀. In general, for very high intensities (v ₀≫v _T ), the energy absorption via bremsstrahlung becomes less effective because the high oscillatory velocityv ₀ reduces the time available to electrons for the interaction with the ions, the third body which makes possible the exchange for energy between electrons and a radiation field. We report also, for the first time, results on the Marcuse effect for the case of a chaotic laser field, along with calculations of the absorption rate for a directed electron beam.     

哺乳动物五种离体组织光学特性的测量

光在哺乳动物组织中的传输依赖于组织体的光学特性,组织的光学特性是由吸收系数、散射系数和散射相位函数决定的。我们设计并实现了哺乳动物5种离休组织光学特性的测量。对实验方法和技术作了较大的改进,联合组织体漫反射特性和光能流率的测定,获得了满意的结果:光穿透深度δ=1.1～5.06mm,吸收系数μ_a=0.4～1.6cm^-1.有效散射系数μ_s(1-g)=2.7～17.7cm^-1.这种测量方法可用于人体组织光学特性的测量。     

Study of the K shell photoelectric parameters of Dy,Yb and W atoms using low energy bremsstrahlung radiation

Low energy external bremsstrahlung (EB) photons were used to estimate the K shell photoelectric parameters; the K shell photoelectric cross section at the K edge, the K shell binding energy, the K shell jump ratio, the K shell jump factors, the Davisson-Kirchner ratio and the K shell oscillator strength for dysprosium (Dy), ytterbium (Yb) and tungsten (W) atoms. The EB photons are produced in the nickel (Ni) target by using the beta particles from a weak beta source of ⁹⁰Sr–⁹⁰Y. These photons are made to fall on these elemental targets of our interest and the transmitted spectrum is measured using GMX 10P HPGe detector coupled to an 8K multichannel analyzer. The sharp decrease at the K edge in the measured spectrum is used to determine the K shell photoelectric parameters of these elements. The experimental results are in good agreement with the theoretical values.     

High-repetition-rate hard X-ray generation with sub-millijoule femtosecond laser pulses

Hard X-ray radiation is generated at 1-kHz repetition rate on metal targets using 30-fs sub-millijoule laser pulses. Spinning-disc targets of medium-Z (Ti, Cr, Fe, Ni, Cu, Zn and Mo) and high-Z (Ta) metals are investigated. For medium-Z targets, characteristic K-shell emission (K and K) is observed in the 4–20 keV energy range in addition to a broadband bremsstrahlung background. Whereas in former studies similar results have been obtained by applying laser pulses in the tens-to-hundreds-of-millijoules range, we observe characteristic X-ray generation even at applied pulse energies as low as 100 J. The well-defined emission wavelength, the high intensity and the high brightness of this radiation makes this source a promising tool for time-resolved experiments with high-repetition-rate (10 kHz) small-scale table-top laser systems . PACS 42.65.-k; 52.38.Ph; 52.50.Jm     

Spectroscopy of the gamma and X ray leakage radiation from the built-in sources of a Risø TL/OSL reader

In this work we evaluate the intensity and the spectral shape of the leakage radiation from the built-in beta and alpha sources of a Risø TL/OSL reader. LiF (TLD-100), fluorite-based pellets and Al₂O₃:C detectors were used in order to determine the dose rate delivered to the dosimeters when the sources are closed. The leakage spectra under both alpha and beta sources were registered with a CdTe semiconductor detector. The spectrum measured under the beta source shows the X-ray beam generated by the interaction of the beta particles with the lead used to shield the source. Besides, the 59.4 keV gamma ray from ²⁴¹Am was registered under the alpha source. Dose rates from 50 to 100 μGy/h were obtained for the dosimeter positions in the turntable under the beta and the alpha sources with the luminescent dosimeters.     

光源附近空间分辨漫反射的SP3研究

根据P₃近似对半无限生物组织的空间分辨漫反射理论,研究了强吸收条件下光源附近 光辐射分布的简化表达式SP₃函数.研究表明:组织吸收越强, SP₃函数越能准确描述光源附近空间 分辨漫反射;应用SP₃函数反演强吸收组织光学参数时,由不同起始距离的漫反射数据拟合得到的反演 结果曲线存在极值,极值附近对应的反演结果最接近实际组织光学参数.     

Thermal source of stimulated radiation

The action of a source of stimulated radiation is investigated under conditions when the energy is supplied from a thermal reservoir. For the three-level system a calculation based on thermodynamic considerations and kinetic equations is carried out. Relations expressing the dependence of the minimum temperature of the hot reservoir, which is necessary for inversion, on the parameters of the system and on the maximum intensity of exciting radiation are found.The expression for the efficiency of conversion of thermal energy into stimulated radiation is _max<(1–T ₀/T)(A ₃₂–A ₂₁)/(A ₃₂+A ₃₁).This efficiency is always lower than the Carnot efficiency and depends also on the value of the Einstein coefficients for spontaneous emission between different levels.The author heartily thanks M. Trlifaj, K. Pátek and A. Fousková for stimulating discussions.     

New method to determine effective atomic number of samples via external bremsstrahlung

In the present investigation, the variation in the external bremsstrahlung (EB) intensity produced due to the beta particles emitted by the ⁹⁰Sr–⁹⁰Y source in the elements Al, Cu, Ag, Sn, and Pb as well as some lead compounds was studied as a function of their masses per unit area. By a suitable regression analysis, two new, handy, and simple expressions for the effective atomic number of the radiator were derived in terms of the measured EB intensity. The novelty of the present method is that these expressions require either two different samples of the same mass per unit area or a single sample of two different masses per unit area for determining the effective atomic number. To check the efficacy of the method, from the measured EB intensity of the group of lead compounds, their effective atomic number was determined by making use of these expressions. The results were found to be in good agreement with the modified atomic number Z_mod, calculated by using the theoretical expression of Markowicz and Van Grieken. This establishes the fact that this new method employs simple and very handy expressions which will be convenient particularly in the case of samples which are not abundantly available in nature. Copyright © 2014 John Wiley & Sons, Ltd.     

Observation of the muon inner bremsstrahlung at?LEP1

Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2<E _γ ≤1 GeV and transverse momentum with respect to the parent muon p _T <40 MeV/c, and 1<E _γ ≤10 GeV and p _T <80 MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z ⁰ decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06±0.12±0.07 in the photon energy range 0.2<E _γ ≤1 GeV and 1.04±0.09±0.12 in the photon energy range 1<E _γ ≤10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP. Deceased.     

Charmonium suppression by gluon bremsstrahlung in p-A and A-B collisions

Prompt gluons are an additional source for charmonium suppression in nuclear collisions, in particular for nucleus-nucleus collisions. These gluons are radiated as bremsstrahlung in N-N collisions and interact inelastically with the charmonium states while the nuclei still overlap. The spectra and mean number <n _g> of the prompt gluons are calculated perturbatively and the inelastic cross section σ_abs ^Ψg is estimated. The integrated cross sections σ(A B →J/ψX) for p-A and A-B collisions and the dependence on transverse energy for S-U and Pb-Pb can be described quantitatively with some adjustment of one parameter <n _g>σ_abs ^Ψg. Received: 20 August 1999     

Nonlinear dynamics of soft boson collective excitations in hot QCD plasma III: Bremsstrahlung and energy losses

Within the framework of semiclassical approximation a general formalism for deriving an effective current generating bremsstrahlung of arbitrary number of soft gluons (longitudinal or transverse ones) in scattering of higher-energy parton off thermal parton in hot quark-gluon plasma with subsequent extension to two and more scatterers is obtained. For the case of static color centers, an expression for energy loss induced by usual bremsstrahlung of lowest-order with allowance for an effective temperature-induced gluon mass and finite mass of the projectile (heavy quark) is derived. The detailed analysis of contribution to radiation energy loss associated with existence of effective three-gluon vertex induced by hot QCD medium is performed. It is shown that in general, the bremsstrahlung associated with this vertex has no sharp direction (as in the case of usual bremsstrahlung) and therefore here, we can expect an absence of suppression effect due to multiple scattering. For the case of two-color static scattering centers it was shown that the problem of calculation of bremsstrahlung induced by four-gluon hard thermal loop (HTL) vertex correction can be reduced to the problem of the calculation of bremsstrahlung induced by three-gluon HTL correction. It was shown that for limiting value of soft gluon occupation number N_k 1/α_s all higher processes of bremsstrahlung of arbitrary number of soft gluons become of the same order in coupling, and the problem of resummation of all relevant contributions to radiation energy loss of fast parton, arises. An explicit expression for matrix element of two soft gluon bremsstrahlung in small angles approximation is obtained.