Calculation of<Emphasis Type="Italic">Z</Emphasis><Subscript>eff</Subscript> from plasma resistivity in IR-T1 tokamak

The effective ion charge,Z _eff, represents the average charge of ionsZ _i of gasses inside the system, which indicates the level of the impurities in the plasma. Several techniques have been applied to estimateZ _eff, like mass spectroscopy, anomaly factor and Bremsstrahlung radiation.

We estimatedZ _eff in the IR-T1 tokamak through anomaly factor. The IR-T1 tokamak is a small air-core transformer tokamak with circular cross section and with out conducting shell and divertor. Its aspect ratio is

$$\frac{R}{a} = \frac{{45 cm}}{{12.5 cm}}.$$

For a tokamak discharge of 30 kA plasma current and 1.5 V of loop voltage and by anomaly factor we observed thatZ _eff value is about 1.5.     

Radial scanning diagnostics of bremsstrahlung and line emission in T-10 plasma

The paper describes the scanning spectroscopic diagnostics designed for measurement of line integrated plasma radiation in two visible spectral ranges. This diagnostic system is aimed at measuring the bremsstrahlung absolute values and profile with high spatial resolution. The bremsstrahlung absolute values are used to determine the value and radial distribution of effective plasma ion charge Z _eff(r) in T-10 discharges. The importance of Z _eff measurement is due to its strong influence on plasma heating, confinement, and stability. The spatial distribution of emission for one of the chosen spectral lines is measured simultaneously with bremsstrahlung. The spatial resolution of measurements is ~1 cm, and the temporal resolution is up to 10 ms. The spectral equipment and methods for its calibration are described. Examples of line integrated brightness distribution in a “continuum window” of 5236 ± 6 Å and brightness of the lines C⁵⁺ (5291 Å), He¹⁺ (4686 Å), and D_β (4861 Å) are given. Flattening of the bremsstrahlung brightness profile in the central region of the plasma column in some discharges with sawtooth oscillations in the T-10 is observed. The measured effective ion charge profiles in ohmic discharges with high plasma density and low discharge currents demonstrate accumulation of light impurities at the column axis; as a consequence, quenching of sawtooth oscillations in some discharges is observed. The developed diagnostics provides necessary data for investigation of heat, particle, and current transport in the plasma of the T-10. Successful application of the obtained data on Z _eff(r) for investigation of geodesic acoustic modes of plasma oscillations in the T-10 should be specially noted.     

Multifaceted asymmetric radiation from the edge along improved confinement mode in LHCD plasmas with graphite limiters on HT-7 tokamak

Multifaceted asymmetric radiation from the edge (MARFE) phenomena during lower hybrid current drive (LHCD) Experiments on the HT-7 superconducting tokamak are summarized in this paper. The best correlation has been found between the total input (ohmic + LHCD) power and the product of the edge line average density and Z _eff. Studies show that the critical density of MARFE onset is observed in the region of Z _eff ^1/2f_GW = 0.6-0.9, where , (here is the maximum line average electron density and n_GW is the Greenwald density). These MARFEs generally appear to have the same characteristics as high f_GW MARFEs and are positionally stable throughout the LHCD pulse. Improved confinement mode induced by a MARFE is observed, and it is maintained for about 65 ms. MARFE cools the plasma edge, and the electron density profile is observed to become more narrow and peaked.     

Soft x-ray PHA measurement of the long pulse discharge in HT-7 tokamak

By analyzing the soft x-ray energy spectrum measured by the soft x-ray pulse height analysis (PHA) system, the electron temperature (Te) and the effective charge number (Zeff) of the ultra-long pulse discharge driven by lower hybrid wave (LHW) were obtained in the HT-7 tokamak. Moreover, the information of medium-Z impurities such as Ti, Cr, Fe, and Ni intrinsic to HT-7 tokamak can also be inspected. The accuracy of the electron temperature derived from the soft x-ray energy spectrum measurements is verified by comparing with the temperature measured by the Thomson scattering system for various plasmas and electron cyclotron emission diagnostic system for ohmic plasmas. The bulk electron temperature of about 1 keV and Zeff≈2 were achieved for long pulse plasma. The appreciable Kα lines of Ti, Cr, Fe and Ni metallic impurities released from the antennas of radio frequency wave and/or the first wall and Ar injected into plasma can be observed, and they kept stable during the long duration discharges. As a result, the longest pulse discharge with relatively high temperature of Te(0)∼1 keV, and ne(0)∼0.5×¹⁰¹⁹ m−3 has been achieved with a duration of 400 s in the HT-7 experimental campaign in 2008.     

HL-2A 装置中利用可见光谱段轫致辐射测量有效离子电荷数

通过测量可见光谱段的轫致辐射(λ=535.1nm)强度,结合等离子体电子密度和电子温度,HL-2A     

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The multichannel bremsstrahlung measurement system on HL-2A tokamak has been using to observe the intensity of visible (535.1nm) bremsstrahlung radiation. Combined the intensity with plasma electron density and electron temperature, the effective ion charge measurements can be obtained on HL-2A tokamak. The 1×10¹⁹m⁻³ to4×10¹⁹m⁻³ experimental results show that when the plasma electron density increases from 1×10 m to 4×10 m , the effective ion charge number changes from 5 down to around 2. The bremsstrahlung radiation signal intensity is proportional to the quadratic plasma density. When the electron density is higher than 3×10¹⁹m⁻³, the multichannel bremsstrahlung measurement system can collect sufficient signal through the plasma, which enables the measurement of effective ion charge radial profile.     

Diagnostics for first plasma study on EAST tokamak

The first plasma was obtained in the EAST on September 26th, 2006. Single-null (SN) and double-null (DN) diverted plasmas were achieved successfully in the EAST tokamak on January 22nd, 2007. The employed plasma diagnostics for first plasma study of EAST are as follows: a vertical one-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer for measuring the line average density, a 10-channel soft X-ray array for intensity measurement, a 16-channel heterodyne Electron Cyclotron Emission (ECE) for measuring the electron temperature profile, a 8-channel XUV bolometer array to measure plasma radiation losses, a 3-channel hard X-ray array for intensity measurement, an electromagnetic measurement system, a 35-channel Hα radiation array, 20 probes for divertor plasma, a one-channel visible bremsstrahlung emission, an impurity optical spectrum measurement system and two optical spectroscopic multi-channel analyzers (OMA). The first experimental results of diagnostic systems are summarized in this Letter.     

HL-2A 装置可见光诊断方法初探

等离子体H_α 径向分布的测量是等离子体实验中的重要内容。在HL- 2A 实验中, 等离子体成像系统中的CCD 图片记录了等离子体辐射信息, 特别是H_α  线辐射信息( 在相机前加H_α 滤光片) 。因为光测量是辐射的线积分, 数据的处理和分析显得十分必要的。利用等离子体可见光成像系统, 采用Abel 变换, 得到H_α  在HL- 2A 装置中的径向分布, 提供了一项可靠的测量手段。     

Dependence of the Compton to Rayleigh intensity ratio on the scatterer atomic number in the range of 4(Be) to 31(Ga)

Compton to Rayleigh scattering intensity ratios (I_C/I_R) have been measured using X-rays with energy 17.44 keV for single-component materials with atomic number Z from 4 (Be) to 31 (Ga) and binary compounds of stoichiometric composition. The measurements have been performed using two optical schemes: an energy-dispersive X-ray fluorescence scheme with a molybdenum secondary target and wavelength-dispersive X-ray fluorescence one. The processing of the spectra was carried out by fitting with Pearson VII functions. For single-component and binary standards, the experimental dependence of the scattering intensity ratio on the atomic number was found to be the same. This confirms the additivity of the contribution of different atoms to the scattering. The dependence has a complex shape but is well described by the theoretical relationship for I_C/I_R with correction on the difference between Compton and Rayleigh radiation absorption coefficients. Two ranges of atomic number values are defined, in which the effective atomic number Z_eff can be determined by the calibration method using this dependence: for Z from 4 to 7 with low error of ΔZ_eff =±0.15 and for Z_eff from 10 to 18 with low error of ΔZ_eff =±0.69. A change in the shape of the Compton peak and an overestimated value of the of the Compton and Rayleigh peak intensity ratio when passing from a single-component scatterer (Al or Si) to their oxides Al₂O₃ or SiO₂, respectively, have been revealed.     

HL-2M 装置初始放电可见光辐射测量系统

HL-2M 装置初始放电实验期间采用了一套 8 通道可见光辐射测量系统,4 个通道用于测量 Hα辐射, 其余分别测量 HeⅡ线、CⅢ线、OⅤ线和轫致辐射。该系统采用新型的雪崩放大二极管(APD)模块和光电倍增管 (PMT)模块作为光探测器,这些新型的探测器由于集成度高、供电方式简单而使得整个系统的后端具有体积小、 操作简单及可靠性强等优点。在 HL-2M 装置初始放电期间,该系统为控制运行人员提供了基本的等离子体信息。     

Determination of effective atomic number and electron density of heavy metal oxide glasses

The effective atomic number (Z_eff) and effective electron density (N_eff) of eight heavy metal oxide (HMO) glasses have been determined using the Monte Carlo simulation code MCNP for the energy range of 10?keV–10?MeV. The interpolation method was employed to extract Z_eff and N_eff values from the simulation and that calculated with the help of XCOM program. Comparisons are also made with predictions from the Auto-Z_eff software in the same energy region. Wherever possible, the simulated values of Z_eff and N_eff are compared with experimental data. In general, a very good agreement was noticed. It was found that the Z_eff and N_eff vary with photon energy and do not have extended intermediate regions where Compton scattering is truly dominating; only dips slightly above ～1.5?MeV were recorded. Z_eff and N_eff are found to increase with PbO and Bi₂O₃ contents. It was found that the Z_eff value rather than the N_eff value is a better indicator for PbO and/or Bi₂O₃ contents.     

Systematic trends in the radiative emission rates for low- and medium-Z elements in high-temperature plasmas

The power radiated by an optically thin, low-density (N_e ≤ 10¹⁴ electrons/cm³) plasma has been calculated for the electron temperature range 1–10⁶ eV taking into account resonance line emission, direct recombination radiation, dielectronic recombination radiation, and bremsstrahlung from the ions of a given element. The ionization structure has been determined by using a corona equilibrium model in which collisional ionization and inner-shelled excitation followed by autoionization are balanced by direct radiative and dielectronic recombination. Based on the results for respresentative elements from carbon through nickel, graphs are presented of the maximum radiated power, the maximum emission temperature, and the mean charge at the maximum for each shell as functions of the atomic number Z. Assuming that the maximum emission temperature can be achieved, aluminum and iron are predicted to be the most efficient K-shell radiators for Z ≤28.     

Bremsstrahlung dosimetric parameters of beta-emitting therapeutic radionuclides

Dosimetric parameters such as efficiency of bremsstrahlung, probability of energy loss of beta during bremsstrahlung production, intensity and dose rate of high, medium and low-energy beta-emitting therapeutic radionuclides in different tissues of human organs are computed. These parameters are lower in adipose tissue than all other studied tissues. The efficiency, intensity and dose rate of bremsstrahlung increases with maximum energy of the beta nuclide (E_max) and modified atomic number (Z_mod) of the target tissue. The estimated bremsstrahlung efficiency, intensity and dose rate are useful in the calculations of photon track-length distributions. These parameters are useful to determine the quality and quantity of the bremsstrahlung radiation (known as the source term). Precise estimation of this source term is very important in planning for radiotherapy and diagnosis.     

Gamma or X-rays attenuation properties of some biochemical compounds

The probability of gamma or X-ray interactions with important 14 antioxidants have been discussed for total photon interactions in the wide energy range of 1?keV–100?GeV using the WinXCOM code. The variations of mass attenuation coefficient (μ_ρ), effective atomic number (Z_eff) and electron density (N_el) with photon energy were plotted for total photon interactions. It was found that the values of μ_ρ, Z_eff and N_el depend on the incoming photon energy and chemical compositions of antioxidant. The highest values of these parameters were found at a low-energy zone where the photoelectric effect is the dominant interaction process. When antioxidants were compared with each other, it was seen that Z_eff has the highest values for Oenin chloride and Delphinidin chloride which contain the Cl element. This investigation is thought to be useful for medical applications where radiation exposure is present.     

White and some colored marbles as alternative radiation shielding materials for applications

ABSTRACT

In this paper, the radiation shielding parameters such as linear attenuation coefficients (LAC, µ), mass attenuation coefficients (MAC, µ/ρ), effective atomic numbers (Z_eff), effective electron densities (N_eff), half value of layers (HVL), mean free paths (MFP) and buildup factors (exposure (EBF) and energy absorption (EABF)) were investigated for cream (M1), pink (M2), white (M3), maroon (M4) and green (M5) marbles. Attenuation coefficients were measured in the energy region 31.18–661.66 keV photon energies. The values of Z_eff and N_eff were then calculated using these coefficients with logarithmic interpolation method, and HVLs and MFPs were calculated using the values of LAC of marble samples at the same photon energies. The experimental results were compared with the theoretical values obtained from WinXCom program, and good agreements were observed between the experimental and theoretical results. HVLs and MFPs of all marble samples were compared with those of some concretes, glasses and commercial radiation shielding glasses (SCHOTT Co.). The studied marbles were better radiation shielding materials than standard shielding concretes due to lower HVL and MFP values lower than the ordinary concrete. Finally, EBFs and EABFs of the marbles were calculated in the energy region 0.015–1?MeV up to penetration depths of 40 mfps by Geometric Progression method (G-P), and the results were discussed in terms of photon energies and chemical compositions of the marbles.     

Intensity radial profiles of VUV line radiation near the solid target in a hot plasma

An investigation of hot plasma interaction with solid target is carried out at the CASTOR tokamak (IPP Prague) and the GOL-3 multi-mirror magnetic trap faccility (Budker Institute, Novosibirsk) [1], [5]. In both experiments, the Imaging Seya-Namioka Spectrometer based on a spherical dispersion grating has been upraded to monitor the radial profiles of the chord-integrated low-Z impurity line intensities in VUV spectral range. Such spatial resolved intensity monitoring in radial direction together with application of the radiation code simulation allows obtaining a radial distribution of ions of different ionization stages near the target immersed in edge plasma. The energy release from plasma to the target is order of 100 J/m² in the CASTOR tokamak and 30 MJ/m² int he GOL-3 magnetic open confinement system.     

Gamma ray shielding capabilities of rhenium-based superalloys

ABSTRACT

Because of the high radiation dose in applications involving nuclear reactors, medical treatments etc., it is important to reduce the exposure to radiation of areas and workers. In this study, we were examined gamma ray shielding parameters of the newly produced Re-based superalloys. Mass attenuation coefficient (µ/ρ) of the alloys were obtained experimentally at 81, 276, 302, 356, 383 keV photon energies emitted from ¹³³Ba radioactive source using Ultra Ge detector. The experimental results were compared with the values obtained by the WinXCOM program and were found to be in perfect agreement with each other. Additionally, effective atomic number (Z_eff) and electron density (N_eff) were determined for produced Rhenium (Re) based super alloys in the energy range 1 keV–100?GeV. S5 sample which has maximum Rhenium percentage own the largest µ/ρ and Z_eff values. Moreover, by using Geometric Progression (GP) approximation, EABF and EBF were computed for the superalloys depending on the energy and penetration depths. It has been deduced that the values of EABF and EBF are minimum in the medium energy region. EBF and EABF values of the alloys have changed depending on the equivalent atomic number. Among alloy samples under study, S5 superalloy is the best for gamma ray shielding. However, in general, considering the radiation energies used in many applications, all the alloys under study have satisfactory radiation absorption properties.     

Radiative energy losses from low and moderate Z elements

Radiative energy losses from twelve low and moderate Z elements are calculated for temperatures ranging from 2 eV to 20 keV. Each element is assumed to be in coronal equilibrium, so that the ionization structure is determined by balancing collisional ionization and autoionization against radiative and dielectronic recombination. The radiative losses are calculated by adding the emission due to bremsstrahlung, radiative and dielectronic recombination, 2-photon processes, and line radiation. Polynomial fits to the loss rates, suitable for use in computer programs, are given for each element.     

A comparative study of gamma-ray interaction and absorption in some building materials using Zeff-toolkit

The gamma-ray shielding behaviour of a material can be investigated by determining its various interaction and energy-absorption parameters (such as mass attenuation coefficients, mass energy absorption coefficients, and corresponding effective atomic numbers and electron densities). Literature review indicates that the effective atomic number (Z_eff) has been used as extensive parameters for evaluating the effects and defect in the chosen materials caused by ionising radiations (X-rays and gamma-rays). A computer program (Z_eff-toolkit) has been designed for obtaining the mean value of effective atomic number calculated by three different methods. A good agreement between the results obtained with Z_eff-toolkit, Auto_Z_eff software and experimentally measured values of Z_eff has been observed. Although the Z_eff-toolkit is capable of computing effective atomic numbers for both photon interaction (Z_eff,PI) and energy absorption (Z_eff,En) using three methods in each. No similar computer program is available in the literature which simultaneously computes these parameters simultaneously. The computed parameters have been compared and correlated in the wide energy range (0.001–20?MeV) for 10 commonly used building materials. The prominent variations in these parameters with gamma-ray photon energy have been observed due to the dominance of various absorption and scattering phenomena. The mean values of two effective atomic numbers (Z_eff,PI and Z_eff,En) are equivalent at energies below 0.002?MeV and above 0.3?MeV, indicating the dominance of gamma-ray absorption (photoelectric and pair production) over scattering (Compton) at these energies. Conversely in the energy range 0.002–0.3?MeV, the Compton scattering of gamma-rays dominates the absorption. From the 10 chosen samples of building materials, 2 soils showed better shielding behaviour than did other 8 materials.     

Experimental determination of the production mechanism for noncharacteristic radiation in swift heavy-ion collisions

Absolute differential cross sections of non-characteristic radiation emitted in energetic heavy-ion collisions (E _P =3.92–48 MeV,Z=11–22) can only be explained in the framework of quasimolecular radiation. All other processes, particularly bremsstrahlung mechanisms are found to be negligible. For high projectile and photon energies the one-step quasimolecular radiation is dominant in solid targets, whereas the two-step process contributes mainly at low projectile and photon energies.