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The inner shell process produced by the collision of highly charged ion with medium atoms near the Bragg peak is an important frontier area of atomic physics under extreme conditions such as celestial plasmas and controlled nuclear fusion plasmas. Because of the special complexity of the inner shell process produced by the collision of ions with atoms in the Bragg peak energy region and the relevant experimental research is less, limited by the experimental conditions, there remain some interesting and unanswered questions.We report the experimental data of X-ray spectra produced by the impact of Xe20+ with 6.0 MeV kinetic energy on V, Fe, Ni, Cu, and Zn surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou, China. The generation mechanism of X-ray with energy of 1.60 keV is analyzed. The results show that when Xe20+ without initial holes interacts with different targets, the Mα X-ray of Xe is not observed, but X-ray with energy twice as great as that of Xe Mα X-ray is observed in the experiment, which is called Xe Mαα X-ray and considered to be generated by the two-electron-one-photon process of Xe on the upper surface of the target. The existence time of the first-generation hollow atoms on the upper surface is calculated by using the classical over-barrier model when Xe20+ interacts with different targets, which is consistent with the variation of Mαα X-ray yield with the atomic number of target, therefore it is further proved that Mαα X-ray is formed by the two-electron one-photon process of Xe on the upper surface of the target. Of course, this conclusion needs further analyzing and verifying with more experimental data.

The investigations of interaction processes between ion beams and gas and between ion beams and plasma play important roles in atomic physics, astrophysics, high energy density physics, and inertial confinement fusion.The atomic density of target is one of the key experimental parameters which may determine the interaction mechanism and experimental results.How to precisely diagnose the atomic density of target in different matter states, like gas phase and plasma phase, is challenging work on the experiments in laboratory.Conventionally the vacuum gauges are used to measure the pressure inside the gas target, but the accuracy is limited for a complex target system and they can hardly work in a strong radiation surrounding, especially in plasma where the high temperature can physically damage the gauges.Therefore we propose a new method to measure the atomic densities for both gas target and plasma target based on the heavy ion beam accelerator facility at the Institute of Modern Physics, Chinese Academy of Sciences.In our experiment the protons are extracted from an electron cyclotron resonance ion source (ECRIS) and accelerated to 100 keV then transmitted to the target.A two-stage differential pumping system is constructed to keep 10-7 mbar order of magnitude in beam line when the gas is filled into the target area where the pressure could increase to higher than 1 mbar.A 45 dipole magnet is used to bend the protons which have passed through the gas.The energy is determined by the different positions of protons at the position-sensitive detector which is placed at the end of magnet.Consequently the energy losses of protons at different pressures are obtained.There have been proposed many theories for calculating the energy loss of protons in gas, and we chose the very popular code named SRIM to simulate the experimental case. Finally the effective linear atomic density of target along the ion beam trajectory in the target area is obtained.For comparison, the conventional vacuum gauges (one is the hot cathode gauge-IonIVac ITR 90 and the other is capacitance diaphragm gauge-Varian CDG-500) are simultaneously used in the experiment.The results show that the recalibrated effective pressure obtained by the energy loss is close to the pressure measured by Varian CDG-500 but much lower than the pressure from IonIVac ITR 90.Only after the detection efficiency correction, could the corrected results of IonIVac ITR 90 be coincident with the effective pressure obtained according to energy loss.Moreover we find that the effective atomic density determined by the protons energy loss shows that these advantages over the conventional gauges are not only the high accuracy and reliability but also the in-situ measurement, high temporal resolution and the ability to work in the complex radiation and hot plasma environment.These properties may play a great role in the experimental researches and relevant topics.

We report the experimental data of characteristic X-ray spectra produced by the impact of H+, Ar8+, Ar12+, Kr13+ and Eu20+ ions with different kinetic energies on Au surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou, China. The energy shifts of X-ray spectra are analyzed and the ratio of X-ray yield is calculated. The results show that H+ can excite the characteristic X-ray spectra of Mζ and Mα of Au, while Ar8+, Ar12+, Kr13+ and Eu20+ can excite the characteristic X-ray spectra of Mζ, Mα, Mγ and Mδ of Au, because the inner shells of target atom are multiply ionized by heavy ions impact, so that the relative intensity ratio of the X-rays changes when the heavy ions are incident. There are different energy shifts of Au M X-ray due to multiple ionization effect in collision. When the ion incident energy is lower, the degree of multiple ionization of the inner shells of the target atom is almost independent of the incident energy, when the ion energy is higher, the degree of multiple ionization increases with incident ion energy increasing. At the same time, the degree of multiple ionization also depends on the number of holes in the outer shell of the ion and its atomic number. That the ratio of X-ray yield increases with the increase of the atomic number of the incident ion further indicates that the degree of multiple ionization increases with atomic number of the incident ion increasing. The multiple ionization and electron configuration of the inner shells of the atom can be determined by the energy shift and spectra broadening. These measurements provide basic data for further studying the multiple ionization mechanism of the inner shells of the atom. But due to the limitation of the resolution of the detector, the spectral broadening data cannot be measured. It is necessary to use a higher-resolution detector to further study the multi-ionization effect of the inner shells of the atom.

Accurate measurement of the ionization cross section of the target atom induced by collision between ions and atoms is of great significance for studying the atomic shell process and establishing a suitable theoretical model. The experimental data and the theoretical models mostly concentrate on the cases in the low energy region at present. Only a few experimental data of high energy region are reported due to the limitation of experimental conditions. Which theory is more suitable to describe the ionization cross section of the inner shell of the target atom caused by the high energy heavy ions, is necessarily studied experimentally. The C6+ ions provided by the Heavy Ion Research Facility in Lanzhou Electron Cooling Storage Ring, are used to bombard the Ni target, in which the K-shell X-ray of Ni is measured. The incident energies of C6+ ions are 165, 300, 350 and 430 MeV/u respectively. Through analyzing the intensity ratio of K/K X-ray of Ni, it is found that the influence of incident energy on the intensity ratio of K/K X-ray is not obvious. The intensity ratios of this experiment are greater than the experimental values of incident proton and the calculated values based on the Hartree-Slater theory, which may be caused by the multiple-ionization of the L shell. The production cross sections of Ni K-shell X-ray are calculated by the binary encounter approximation (BEA) model, the plane wave Born approximation (PWBA) model and the energy-loss coulomb-repulsion perturbed-stationary-state relativistic (ECPSSR) theory respectively, which are compared with the experimental results in this paper. It is found that the experimental cross section increases with the increasing incident energy, which is consistent with the trend of BEA model estimation, but the experimental value is obviously lower than the theoretical value. We think that BEA model needs to be modified when describing the ionization process in the high energy region.

The X-ray emission spectra produced by 2.4-6.0 MeV Xe20+ ions impacting on vanadium surface were measured. The V K-shell X-ray production cross sections were extracted from the experimental yield data and compared with the theoretical predictions of the binary encounter approximation (BEA), the plane wave born approximation (PWBA), and the energy-loss coulomb-repulsion perturbed-stationary-state relativist (ECPSSR). In order to predict reasonably the inner-shell ionization induced by highly charged heavy ions during the asymmetric collisions at near the Bohr velocity, the corrections of BEA model are discussed. It is found that the X-ray production cross section induced by highly charged heavy ions moving at near the Bohr velocity is on the magnitude of 1 barn, which is almost four orders of magnitude larger than that induced by proton. The ECPSSR, which is regarded as the best model to simulate the inner-shell ionization by light ions, may underestimate the experimental data at least three orders of magnitude. The PWBA model presents a prediction to the results on an order of magnitude better than the ECPSSR simulation, but gives a worse tendency than the BEA model. The BEA calculations, corrected both by Coulomb repulsion and effective nuclear charge, present the best agreement with the experimental results. It is proposed, that in the energy region near the Bohr velocity, during the asymmetric collisions of Xe20+ ions with V atoms, the K-shell electron of V is ionized by direct ionization, and that it can be described by the binary encounter process between the xenon ions and the bound electrons. The X-ray production cross section can be simulated by BEA model, but the corrections of Coulomb repulsion and effective nuclear charge must be considered.

Sound velocities in shock-loaded solids are not only important to determine bulk moduli of solids at high pressures, but are also crucial to inform the shock melting of solids upon loading. In this letter, we first report on shock melting of porous solids at high pressures by measuring sound velocities in the porous iron of average density 6.90 g/cm3 in the pressure range of 110-180 GPa. The measured sound velocity softens at pressures from 122 to 156 Gpa, which may be attributed to shock melting of the porous iron.

The Hugoniot equation-of-state (EOS) of porous iron with an average initial density of 6.904 g/cm3 has been measured in the pressure range from 90 to 160 GPa, and a good straight fitting D = 2.997 + 1.603 u has accordingly been obtained, where D is the shock wave velocity and u the particle velocity, both in units of km/s. Combining this with the Hugoniot EOS of non-porous iron, the Gruneisen EOS and the Rankine-Hugoniot energy conservation relation, and taking the possible solid-liquid transition correction, we have calculated the Gruneisen parameter γ of iron and obtained the result γ0ρ0 = γρ = const, with γ0 = 1.945 and ρ0 = 7.856 g/cm3, ρ being the density. PACS: 62. 50. +p, 65. 90. +i, 91. 35. -x

We report the experiment data of X-ray spectra produced by the impact of Xeq+ (q=10, 15, 20, 26) with 2.4 MeV kinetic energy on Au surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou. Results show that there is different broadening of Au M X-ray owing to multiply ionized effect in the collision with heavy ions, the degree of ionization mainly depends on the distribution of the electronic states in the ions' outer shell. The yield of X-ray is calculated and compared with BEA (binary encounter approximation) model, and the effect of ion charge state on the X-ray yield is also discussed.

Energy loss of protons with energy 100 keV penetrating the partially ionized hydrogen plasma target was measured. The plasma target was created by electric discharge in the hydrogen gas, the state of the plasma target was diagnosed by using the laser interferometry method: the free electron density is up to 1016 cm-3, temperature is about 1-2 eV, and the plasma target may exist at the microsecond level. It is found that the energy loss of protons is closely related to the free electron density, and the energy loss data enable us to infer the value of the Coulomb logarithm (10.8) for the stopping power of the free electrons. This agrees well with the theoretical prediction which is 4.3 times higher than that given by the Bethe formula for neutral hydrogen, which is a little bigger than Hoffmann's result but much smaller than Jacoby's result. Comparing our result with Hoffmann's, the energy we used is only 100 keV, much lower than 1.4 MeV/u, and the low-energy regime we applied could be the cause of the increase in the enhancement factor. However, in the comparison between our result and the Jacoby's, the effective charge for protons is almost constant, unlike the Kr+ impact in wihch the enhanced ion charge state induces the giant enhancement factor. Compared to the gas target, the energy loss enhancement factor in plasma target is 2.9.

Fe K-shell ionization cross sections by 2.4-6.0 MeV Xe20+ impact were investigated. It was found that the BEA model corrected both by the Coulomb repulsion and the effective nuclear charge gives the best agreement with the experimental data.

The L-shell X-rays of iodine induced by 3MeV Iq+(q=20,22,25,26) ions impacting on Fe target were measured. The results indicated that, in addition to the ionization of L-shell, the projectile M- and N-shell were multiply ionized. The ratios of the sub-shell X-ray relative intensity were also investigated.

L X-ray emission induced by Xe20+ and Xe30+ impacting on Mo was measured. The dependences of Mo L X-ray yield on the incident energy were investigated. The results provide evidence for the 4fσ excitation in such collision system.

As the C6+ ion beam pulses, provided by the Heavy Ion Research Facility in Lanzhou-Cooling Storage Rings, impact on Au taget surface, the Lα-and Lβ-X spectra of Au atom are measured. Results show that the production cross section of Lα is larger than that of Lβ. The production cross sections increase with the kinetic energies of the projectiles. The PWBA and ECPSSR theoretical models are compared with the experimental resulms. The significant difference between experimental data and theoretical models was discussed.

We have measured secondary electron emission yields in forward and backward directions from the carbon foils with different thicknesses, which are penetrated by Ne2+ ion of an energy from 2 to 25 keV/u. In the experiment, the contributions of projectile potential energy deposition, electronic energy loss and recoil atom to the forward and backward electron emission yields have been studied systematically by changing the projectile ions energy. Results show that the ions potential energy deposition only have the impact on the backward electron emission yield, while the forward and backward electron emission yields increase approximately linearly with the increase of the electron energy loss at the exit and entrance surfaces of the thin film respectively. When the electron energy loss is low, the impact of recoil atoms on the electron emission cannot be neglected.

The characteristic X-ray spectra produced by the impact of highly charged ions of 152Eu20+ with energies from 2.0 to 6.0 MeV on Au surface are measured. It is found that highly charged ions could excite both the characteristic X-ray spectra of Mζ, Mα and Mδ of Au and the characteristic X-ray spectra of Mα of Eu. The total X-ray yield increases with the ion kinetic energy increasing. The total production cross section of Au induced by Eu20+ is measured and compared with those obtained from the binary encounter approximation, plane-wave-Born approximation, and the energy-loss Coulomb deflection perturbed stationary state relativistic theoretical models.

X-ray emission induced by 300 MeV/u C ions impacting on copper was investigated at the Heavy Ion Research Facility in Lanzhou (HIRFL). The results showed a very high yield of K hyper-satellite emission comparing to the satellite emission.

The X-ray emission due to the impact of 129Xe30+ ions of 1.07.0 MeV kinetic energies on Au surface is detected. The experimental result shows that when ion kinetic energy is larger the incident ion excits not only Au M X-ray but also Xe L X-ray. The X-ray yield and the ion kinetic energy have a strong correlation with each other. The relationship between the X-ray yield with ion kinetic energy is analyzed.

The M X-ray spectra of Ta induced by H+, He2+, Ar11+ and Xe20+ are measured in Heavy Ion Research Facility in Lanzhou. The intensities of M-gamma (M3N5) and M-alpha beta (M4,5N6,7), i.e. I-gamma and I-alpha beta, are also derived from the spectra. It is found that the intensity ratio of I-gamma/I-alpha beta increases with the increase of projectile atomic number. The results show that the M-3-subshell fluorescence yield omega(3) of Ta target is greatly enhanced, owing to multiple ionization effect in collision with heavy ions.

Using ab initio plane-wave pseudo-potential density functional theory method, the elastic constants and band structures of stishovite were calculated. The calculated elastic constants under ambient conditions agree well with previous experimental and theoretical data. C13, C33, C44, and C66 increase nearly linearly with pressure while C11 and C12 show irregularly changes with pressure over 20 GPa. The shear modulus (C11-C12)/2 was observed to decrease drastically between 40 GPa and 50 GPa, indicating acoustic mode softening in consistency with the phase transition to CaCl2-type structure around 50 GPa. The calculated band structures show no obvious difierence at 0 and 80 GPa, being consistent with the high incompressibility of stishovite. With a quasi-harmonic Debye model, thermodynamic properties of stishovite were also calculated and the results are in good agreement with available experimental data.

Plate impact experiments are conducted on high density glass (HDG) with an initial density of ～4.817g/cm3 (Brand ZF6) at a two-stage light gas gun facility. A copper flyer plate is used as a standard sample. Experimental shock pressure is between 52.1GPa and 167.8GPa. A multi-wavelength pyrometer and optical analyzer technique are used to determine the Hugoniot curve, sound velocity and shock temperature of HDG. The experiment results reveal that polymorphism phase transitions occur in HDG under compression, and the onset pressures are ～23, ～78 and ～120GPa, respectively. The measured sound velocity first increases and arrives at about 78GPa, then decreases rapidly, and increases again with pressure increasing. Beyond ～120 GPa, the longitudinal sound velocity turns in to bulk sound velocity, indicating the melting of HDG. Measured shock temperatures also show discontinuities at ～78 and ～120GPa, after which its increase rate becomes small and consistent with the calculated Lindemann melting line, confirming the above HDG phase transformation behaviors. Our Hugoniot data are consistent well with LASL shock Hugoniot data of HDG, which shows discontinuity only at about 23GPa, indicating that the phase transitions at 78 and 120GPa are not first-order ones. Our shock data and the gained knowledge of dynamic response behavior of HDG are valuable for improving the accuracies in sound velocity measurements for metals and non-metals at pressures over a megabar range.

In this paper, reverse-impact method for measuring release sound velocities was improved through special treatment of the impacted face of the window, and using time-resolved velocity interferometer system for any reflector. Our experimental technique solved the problem that bulk and longitudinal sound velocities can not be obtained simultaneously using the original method reported in the literature, due to the effect of release behaviors in the buffer. With the modified reverse-impact method, sound velocities of tin were measured with higher accuracy (measuring errors of longitudinal and bulk sound velocities being about 2% and 5%, respectively) in the range of 37—80 GPa. The experimental results are consistent with thermodynamic theoretical values.

In this paper, a comparative experimental study on optical transparency of z-cut LiF, sapphire and LiTaO3 under 1011 Pa shock compression at our two-stage light-gas gun facility is presented. In our experiments, intensity contrast variation of light emitted from a modified experimental setup of Mallory-type was monitored by a high-speed electronic camera. The results demonstrated that the LiF under the shock pressure of 102 GPa retains its initial transparency in the whole observation time interval, which is in good agreement with the common view of good sustained transparency of LiF. The LiTaO3 became basically opaque at 139 GPa. Sapphire at 131 GPa shock pressure showed a continuous transparency degradation till became completely darkened when the shock wave was arriving at the free-surface.

High-pressure phase-transition behaviors of z-cut lithium tantalate single-crystal have been studied by Hugoniot measurements at our two-stage light-gas gun and DFT-PWP calculations. A distinct discontinuity was discovered on the D-u (shock-wave velocity versus particle velocity) relation. An elastic-plastic two-wave structure was observed from the VISAR measured particle velocity profiles at low pressures (25.9 GPa and 32.6 GPa), while three-wave structure appeared in the measured particle velocity profiles at the final pressure of 42.9 GPa and 53.0 GPa. Both facts indicate a shock-induced phase transition of LiTaO3 samples occurred with an onset pressure of 37.9GPa. The theoretically calculated 0K pressure versus compression ratio (P-V/V0) curve for the rhombohedral phase (R3c space group) is in good agreement with the low-pressure experimental data, while that for orthorhombic phase (Pbnm space group) is in accord with the results by deducing thermal pressure contribution from the measured shock-compression data at high pressures. This suggests that the high-pressure phase has orthorhombic symmetry. High-pressure phase transformation behaviors including the transition pressure and structures, which are unclear in current literature, have been clarified in this paper by our new shock-wave data and ab-initio calculations. These behaviors were demonstrated to be in close similarity with that of its isomorphous crystal LiNbO3. The present work is significant for the investigations of shock-induced phase-transition of similar single-crystal materials.

This article describes a method which combines the static pressure experiment,dynamic experiment and theoretical calculation to obtain the parameters in the SCG constitutive model for tungsten alloy under high pressures. By using the constitutive model we obtained in numerical simulation that the calculated profiles of particle velocity are in accordance with the experimental results. We also conducted some other simulations by using different constitutive models and compared them with experimental results. The results show that the constitutive model we obtained was the best.

Dense plasmas with uniform and constant density and temperature are generated by passage of a planar shock wave through argon gas. Our experiments in argon have produced plasmas with a temperature of 1.4—2.2eV and a density of 0.0083—0.015gcm3. The opacity of the plasma is measured versus wavelength by recording the rise time of emitted light. Measurements in visible light are compared with the calculations using the average atom model, and the agreement is well. In data treatments, the opacity and the reflectance R(λ) at the baseplate / argon interface are simultaneously worked out. The resultant R(λ) in this work are all around 0.4, which is in agreement with that given by Erskine.