X-ray diagnostics of hot dense plasma in low-inductance vacuum spark

X-ray spectroscopic diagnostics are used to study the hot dense plasma of a micropinch (MP) in a low inductance vacuum spark.     

Energy spectra measurements of X-ray emission from electron interaction in a dense plasma focus device

Electrons generated during a pinch implosion in a hollow anode Mather-like plasma focus device (PF) are considered as a possible X-ray source via the impinging of those particles on medium and high-Z targets. A usual PF device has been slightly modified to optimise the X-ray production and their measurements by means of a suitable and non-invasive spectrometer. This ensemble allows measurements of X-rays generated booth by electrons turning back to the anode and by target collision of the so-called relativistic electron beam. The spectrum of the emitted photons is evaluated by using a differential absorption based technique. The X-ray spectrometer consists of a stack of LiF dosimeters which act both as detectors and filters to give curves of attenuated intensities. Finally, the energy distribution is calculated from such attenuation curves using an iterative procedure based on spectral algebra formalism.     

Radiative corrections in highly ionized atoms

A review of the theory of radiative corrections in highly ionized atoms is given. Comparison of theory and experiment in these atoms provides an important test of the theory of strongly bound electrons. For one-electron atoms, energy level separations predicted by quantum electrodynamics among the n = 1 and n = 2 states of hydrogen-like atoms with nuclear charge Z in the range 10–40 have recently been tabulated on the basis of a complete nonperturbative calculation of the self energy. In highly ionized atoms with more than one electron, the hydrogenic radiative level shifts provide a first approximation to the few-electron radiative level shifts. Uncalculated corrections due to multielectron effects in the radiative corrections give the largest known uncertainty in the theory of two-electron atoms. Various approaches to this problem and the prospects for further improvements are described.     

Beam-gas study of low velocity highly ionised titanium in the EUV using microchannel plates

Position sensitive detection was used to record spectra of Ti XIII and XII emitted by a low velocity titanium beam after one and two electron capture in a gas cell. A three meter quasi-grazing-incidence spectrometer was equipped with two 25 mm microchannel plates coupled with a sensitive anode encoder. The detector was successively positioned to record EUV radiations in the wavelength range from 30 to 60 nm. Observed lines are unambiguously assigned to transition in Ne-like and Na-like titanium.     

Laser resonance measurements in highly ionized atoms

Recent experiments using the fast-beam laser technique to measure transition intervals in highly ionized atoms are briefly reviewed. These include: (1) measurements of the n = 2 Lamb shift in hydrogenic phosphorus, sulphur and chlorine, and (2) measurement of the 1s2p ³p₁?³p₂ fine structure interval in helium-like fluorine.     

A micropinch as a spectral source of highly ionized atoms

The phenomena of the so called “plasma points” in a highly-ionised metal plasma column with axial symmetry is treated in the context of the contraction of a Z-pinch due to an m = 0 instability with outflow of plasma and radiative energy loss. “Equilibrium” parameters of the micropinch (MP) can be derived from a balance between energy losses and heating of the plasma. A semiempirical formula for line-radiative losses taking into account density effects and a simple opacity approximation has been constructed. It is assumed also that the Bennet's quasi-equilibrium” between plasma pressure and magnetic field is valid. The time history of the neck is calculated on the basis of a simple model of plasma outflow. Approximate but useful Z_n^- and I-scaled formulas expressing some of the results are obtained: r ≈ 10³I^0.833/(Z_n²T_e) cm (Z_n — the nuclear charge; I — the current, MA;T_e — the electron temperature, eV). n_e ≈ 10¹⁵I^0.33Z⁴T_ecm^?3. For a given current I, “K-stage” ions can be achieved only for elements with Z_n ? 60 × I^0.30.     

Chemical states and thermal stability of hydrogen-implanted Ti and V studied by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) was applied to the chemical state studies of Ti and V metals bombarded with 8 keV hydrogen ions. The binding energies of the lines for the ion-implanted Ti and V shift from those for the metallic states by 0.3 eV, are consistent with the core-line shifts for the thermally synthesized hydrides such as TiH_1.97 and VH_0.55 The metal 3d-H1s bonding level for the hydrogen implanted Ti appears at ~ 3.5 eV below the Fermi level, which is lower by ~ 2.5 eV than the molecular-orbital energy previously calculated for TiH₂. In the case of the ion-implanted V, however, it appears at ~ 5.0 eV, which is almost equal to the molecular-orbital energy for VH₂. The photopeaks corresponding to the Ti-H and V-H bonds for the ion-implanted samples grew up on raising the annealing temperature up to 550°C and 150°C, respectively. The phenomena are interpreted by means of the thermal diffusion of the implanted hydrogen from bulk to surface.     

Surface segregation of Ti atoms during NiTi alloy sputtering

The paper addresses NiTi alloy sputtering by 9 keV He and Ar ions and discusses the experiment performed by V.S. Chernysh et al. about 10 years ago. The binary collision simulation has been applied to extract the concentrations of surface Ni and Ti atoms from the experimental data. The results of simulations favor segregation of Ti for both He and Ar ion bombardment. The effect of non-symmetric surface collisions (Ti on Ni and Ni on Ti) was found to be negligible. A pronounced effect of the interatomic (target–target) potential is noted.     

X射线吸收光谱技术中的滤光片研制

在同步辐射X射线吸收光谱(XAS)实验中,X射线滤光片用于吸收样品的康普顿散射和弹性散射,改善荧光信号的质量。我们将ZnO颗粒分散在聚氨酯溶液里,通过恰当的喷涂工艺,获得ZnO滤片。X射线衍射(XRD),X射线荧光(XRF)及X射线吸收光谱(XAS)实验结果表明：在滤片制备过程中,ZnO结构保持不变。进一步地,ZnO滤片用于测量Ga2O3的GaK边XAS谱,显示出好的信噪比。采用同样的方法还制备了其它X射线滤光片,表明这种X射线滤光片制备技术的可行性和实用性。     

Plasma atomic X-ray spectroscopy of tokamaks

Measurements of H- and He-like X-ray spectra of elements between Z = 16 and 26 (hv = 2 to 8 keV) are discussed and illustrated with recent results obtained for argon. Examples of instrumental development are presented together with the outlook for future experiments.     

Penetration of gas ions and atoms through a barrier in various temperature conditions

Conclusion The basic results may be formulated as follows:a simple three-parameter expression for the penetrating flux and a simple approximate formula for its calculation are obtained;the physical meaning of the parameters , , , which are a combination of all the initial parameters and uniquely determine the value of the penetrating flux, is analyzed. In particular, it is shown that the first parameter is a normalized (to the barrier thickness) depth, of the order of the depth of the deceleration zone of nonequilibrium bombarding particles, and the second parameter characterizes the concentration gradient at the inlet face;the dependence of the penetrating flux on the basic interaction parameters is analyzed;an original effect of diametrically opposite change in penetration with change in the same parameter in the same direction is detected; for example, it is shown that the penetrating flux may both increase and decrease with increase in diffusion coefficient;simple analytical criteria for superpenetration are obtained;it is shown that the facilitation of superpenetration conditions with decrease in the flux of nonequilibrium gas incident on the barrier is associated with quadratic boundary conditions;the laws of variation in the concentration profile with variation in irradiation conditions are analyzed.Translated from Atomnaya Énergiya, Vol. 61, No. 3, pp. 178–182, September, 1986.     

X-ray absorption spectroscopy and X-ray photoelectron spectroscopy studies of CaSO4:Dy thermoluminescent phosphors

Extended X-ray absorption fine structure (EXAFS) measurements have been carried out on CaSO₄:Dy phosphor samples at the Dy L₃ edge with synchrotron radiation. Measurements were carried out on a set of samples which were subjected to post-preparation annealing at different temperatures and for different cycles. The EXAFS data have been analysed to find the Dy-S and Dy-O bond lengths in the neighbourhood of the Dy atoms in a CaSO₄ matrix. The observations from EXAFS measurements were verified with XANES and XPS techniques. On the basis of these measurements, efforts were made to explain the loss of thermoluminescence sensitivity of CaSO₄:Dy phosphors after repeated cycles of annealing at 400 °C in air for 1 h.     

Investigation on plasma characteristics in a laser ablation pulsed plasma thruster by optical emission spectroscopy

In order to further improve the propulsion performance of pulsed plasma thrusters for space micro propulsion, a novel laser ablation pulsed plasma thruster is proposed, which separated the laser ablation and electromagnetic acceleration. Optical emission spectroscopy is utilized to investigate the plasma characteristics in the thruster. The spectral lines at different times,positions and discharge intensities are experimentally recorded, and the plasma characteristics in the discharge channel are concluded through analyzing the variation of spectral lines. With the discharge energy of 24 J, laser energy of 0.6 J and the use of aluminum propellant, the specific impulse and thrust efficiency reach 6808 s and 70.6%, respectively.     

Study on the behavior of oxygen atoms in swift heavy ion irradiated CeO2 by means of synchrotron radiation X-ray photoelectron spectroscopy

To study the effects of swift heavy ion irradiation on cerium dioxide (CeO₂), CeO₂ sintered pellets were irradiated with 200 MeV Xe ions at room temperature. For irradiated and unirradiated samples, the spectra of X-ray photoelectron spectroscopy (XPS) were measured. XPS spectra for the irradiated samples show that the valence state of Ce atoms partly changes from +4 to +3. The amount of Ce³⁺ state was quantitatively obtained as a function of ion-fluence. The relative amount of oxygen atom displacements, which are accompanied by the decrease in Ce valence state, is 3-5%. This value is too large to be explained in terms of elastic interactions between CeO₂ and 200 MeV ions. The experimental result suggests the contribution of 200 MeV Xe induced electronic excitation to the displacements of oxygen atoms.     

Interaction of dense nitrogen plasma with SS304 surface using APF plasma focus device

The nitridation of SS304 surfaces is obtained by irradiating nitrogen ions from Amirkabir plasma focus device, which use multiple focus deposition shots at optimum distance 10 cm from the anode. The Vickers Micro-Hardness values are improved more than twice for the nitrided samples comparing to the nonnitrided ones. The X-ray diffraction (XRD) analysis is carried out in order to explore the phase changes in the near surface structure of the metals. The results of Scanning Electron Microscopy (SEM) indicate changes in surface morphology which are the emergence of smooth and uniform film on the surface of the nitrided metals.     

八氧化三铀的X射线光电子能谱研究

用Ｘ射线光电子能谱分析研究了八氧化三铀的表面结构以及一氧化碳对Ｕ３Ｏ８表面结构的影响，Ｕ３Ｏ８为混合价比合物，ＸＰＳ分析表明它符合Ｕ２＾ⅥＵｎ－２＾ⅥＯ２ｎ＋２模式。同时ＵＯ３的量减少了１６％，研究结果表明一氧化碳气氛对Ｕ３Ｏ８的表面有一定的还原作用。     

X-ray spectroscopy of highly-charged heavy ions at FAIR

In the current contribution, we give an overview of the envisioned X-ray spectroscopy program within the atomic physics research collaboration SPARC (Stored Particle Atomic Research Collaboration) at FAIR (Facility for Antiproton and Ion Research). These activities comprise, among others, the investigation of relativistic collision dynamics, electron correlation in the presence of strong fields, the test of Quantum Electrodynamics in extremely strong electromagnetic fields, and ideas to test the predictions of fundamental theories besides Quantum Electrodynamics. The state of the art X-ray spectroscopy will be of key importance for realization of these challenging goals. The world-wide unique experimental conditions and opportunities offered by the future FAIR facility will be combined with advanced X-ray detection devices, i.e. large-area, segmented solid-state detectors, high-resolution crystal spectrometers, calorimetric detectors etc.     

Passage of a plasma burst through a magnetic mirror machine

A study has been made of the behavior of plasma bursts as they move along the axes of an Ogrenok magnetic mirror machine, The bnrsts were accelerated by a coaxial ptasma injector. For the parameters chosen, the main plasma current was injected in the form of two bursts with velocities of 10⁷ and 2·10⁵ cm/sec, In passing through the first magnetic mirror, both bursts were broken up into streams. This occurred to a larger extent in the burst with the lower velocity. The first burst passed through 380 cm of machine in a time of the order of 90 sec. The luminescence from the streams in the machine lasted 700 sec.Translated from Atomnaya Énergiya, Vol. 14, No. 4, pp. 354–358, April, 1963