Soft X-ray emission of continua from laser produced plasmas

Plasmas produced irradiating plane targets of low Z elements with moderate energy (3–10 J) lasers emit considerable amounts of free-free and free-bound continua in the soft X-ray region (10–100 Å) of the spectrum. With intensity calibrated grazing incidence spectrographs an intensity of the order of 10⁸ W sr^–1 Å^–1 cm^–2 emitted by the densest portion of the plasma inside the crater formed at the interaction was determined. This is in good agreement with theoretical predictions for a plasma of predetermined parameters. In case of high Z elements the continuum emitted has a very smooth wavelength dependence.     

Plasma diagnostic application of dielectronic satellites to the resonance line of Cr XXIII

We have measured the spectrum of plasma emission in the Frascati tokamak FT around the resonance line 1s2p → 1s² of the helium-like ion Cr XXIII. The presence of dielectronic satellites has been detected and their wavelengths determined. The intensity ratio of these satellites to the resonance line has been calculated from the corresponding lines in Fe XXV with a simple extrapolation. Good agreement with experimental points has been obtained in high electron density discharges. Line ratios systematically lower than the predicted values are obtained at low density and this has been related to the presence of a non-thermal population of electrons as indicated also by other diagnostics.     

Untersuchung derK-Strahlung beim Elektroneneinfang des Ge71 mit einem Diffraktionsspektrometer mit gebogenem Kristall

The intensity of satellites in the Gallium-x-rays emitted inK-capture of Ge⁷¹ has been measured and found to be (1,3±0,5)×10^?4 perK-capture. A curved-crystal X-ray spectrometer with a radius of curvature of 27 cm was used for the measurement. The satellites are found to be due to double ionisation ofK-shell accompanyingK-capture as described by the theory ofPrimakoff andPorter. The theoretically calculated intensity of X-ray satellites emitted due to double ionisation ofK-shell — (0,9)×10^?4 perK-capture — is in fair agreement with experiment.     

Spectroscopic diagnostics of the laser erosion plasma of an AgGaS<Subscript>2</Subscript> polycrystalline target

Results are presented from experimental studies of the radiation emitted from a plasma produced in vacuum after irradiating a polycrystalline target by 1.06-μm laser radiation with an intensity of (3–5)×10⁸ W/cm². Plasma radiation from regions located at distances of 1 and 7 mm from the target is analyzed. It is shown that the main contribution to the plasma radiation in the 220–600 nm spectral range is made by transitions from the excited states of single-charged Ag⁺ and S⁺ ions. The atomic component of plasma radiation is represented by intense spectral lines corresponding to transitions from the Rydberg states of Ag and Ga atoms, whereas no resonance lines of these atoms are observed.     

X-ray-line plasma satellites of ions in solid target plasmas produced by picosecond laser pulse

The X-ray lines of ions in a solid target interacting with picosecond laser pulses of moderate intensity (2×10¹⁷ W/cm²) were measured on the “Neodim” laser facility. X-ray Ly _α emission spectra of hydrogen-like fluorine ions were observed. Satellite lines were also observed, evidencing the presence of intense plasma oscillations. The positions and separation between the satellites allow their assignment to the intense electrostatic oscillations with an amplitude larger than 10⁸ V/cm and a frequency of about 7× 10¹⁴ s^?1 that is noticeably lower than the laser frequency ω_las～1.8×10¹⁵ s^?1. It is suggested that these oscillations may be due to strong plasma turbulence caused by the development of plasma oscillations of the Bernstein-mode type under the action of a strong magnetic field generated in plasma. The experimental results are compared with the calculated spectra of multicharged ions.     

Radiation losses of a theta pinch plasma in the wave-length range 10–200 Å

In order to measure the radiation losses of a theta pinch plasma (electron densityn _e=1?5×10¹⁶ cm^?3, electron temperatureT _e=150?350 eV), a grazing incidence spectrograph is absolutely calibrated in the range 10–200 Å. This is done in two steps: First the measured intensity ratios of lines emitted by hydrogen-like ions are compared with their calculated values thus yielding the relative sensitivity of the instrument. The result is confirmed by incorporating well known intensity ratios of lithium-like ions. Secondly absolute calibration is possible by hanging the spectrograph on an absolutely calibrated monochromator via the branching-ratios of lithium-like ions. Radiation losses from the plasma turn out to be negligible as compared with heat conduction losses and the total energy radiated is found to be small compared with the energy content of the electrons, if the impurity concentration does not exceed 0.5 percent. The radiation is found to be predominantly emitted by the resonance lines of the oxygen and carbon ions O VI, O VII, O VIII, CV, CVI whereas continuum radiation and the contribution from other ions are negligible small. However, in discharge where the oxygen concentration reaches 5 percent, radiation losses can exceed the losses by heat conduction during the early phase of the discharge. But still the final electron temperature is not significantly influenced by the impurities.     

Quasi-tunable I2-laser for absorption measurements in the near infrared

The properties and output data of an I₂-laser pumped by a pulsed dye laser have been investigated. The separation between lines to which the laser can be tuned in the region 1.0–1.3 μm is typically 0.5 cm^-1. Lines are emitted in R-P doublets with a separation of 5–15 cm^-1. The possibility of measuring low gas concentrations by recording the intensity ratio of the components in selected doublets has been tested in atmospheric water vapour.     

Spectroscopic Investigation of a Double Discharge Pulsed Electron Beam Generator

ABSTRACT

The wide range of applications of the plasma-based electron beam generator make it necessary to diagnose the device with a noninterfering method. The results of experimental and modeling studies of neutral helium and hydrogen beta spectral lines emitted from the double discharge pulsed electron beam generator are presented in this paper. Neutral helium lines emitted from the plasma in the pressure range 0.1–0.4 torr are studied and compared with results of the collisional radiative model. The duration of the electron beam is shorter than 100 ns, and the peak current intensity is of order amperes. The full width at half maximum of the H _β spectral line is used for the determination of the plasma electron density, found as 3.16 × 10²¹ m^?3 at 0.3 torr, and good agreement is obtained by comparing with the full computer simulation method.     

Bestimmung von Temperatur und Dichte eines Gleitfunkens aus der Bremsstrahlung im Infrarot

The absolute intensity of a vacuum sliding spark (length 2–10 cm, half cycle 0,8 μsec) has been measured in the spectral region between 0,4 and 3μ. From the long wavelength radiation emitted from an optically thick layer, one gets the temperature, from the short wavelength radiation emitted from an optically thin layer, one obtains the density. Using polyethylene as an insulator we reached a temperature of 4·10⁵ °K at electron densities of 8·10¹⁸ cm^?3 and current densities of 1.2·10⁶ A/cm². The temporal development of temperature and density has been determined. The maximum intensity at λ=0.43 μ was found to be 5·10⁴ (7·10¹⁰ W/cm³ ster) as large as that of the positive crater of a properly driven carbon arc. At λ=3 μ this same parameter turned out to be 300 times as large (5·10⁷ W/cm³ ster).     

Die Erzeugung von Seriengrenzkontinua mit Hilfe von Gleitfunken zur Absolutmessung im Vakuum-Ultraviolett

A lithium plasma is produced by discharging a 40 kV, 0,3 μF capacitor through a lithium-hydride-capillary (diameter 2 mm, length 20 mm) in vacuum (p～10^?4 Torr). During the first half-cycle (0,6 μs) Bremsstrahlung of Li III is observed in the visible and infrared, and the Lyman series of Li III together with the recombination continuum in the vacuum UV (100 Å). The high members of the Lyman series are broadened by Stark effect giving an electron density of about 6 · 10¹⁸ cm^?3. In the infrared the radiation is emitted from an optically thick plasma at a time when the free-free continuum in the visible is emitted from an optically thin plasma. Temporal development of electron temperatureT _e and electron density N_e has been measured from the absolute intensity in these spectral regions. Typical values ofT _e=230 000° K andN _e 5 · 10¹⁸ cm^?3 e.g. have been obtained. For these values the relaxation time for an ionisation equilibrium is short compared to the observation time. The complete ionisation of Li III has been checked by absorption measurements near 100 A. Thus the absolute intensity of the recombination continuum could be calculated. An experimental arrangement was built to measure simultaneously the time history of the intensity in the vacuum ultraviolet, in the visible, and infrared spectral regions.     

Measurements of transition probabilities for doubly ionized vanadium

Transition probabilities of 43 doubly ionized V lines have been measured in the spectral range 2280–3600 Å. These lines belong to the 3d²4s–3d²4p transition array. Emission spectroscopy was used to obtain line intensities. The spectra were emitted from a He plasma with added VOCl₃ vapour in a wall-stabilized arc.     

Total second harmonic emission from a laser produced plasma

The total and specular light emitted at 2ω by a laser produced plasma (τ = 30 ps, λ = 1 μm) have been measured versus intensity (10¹²-10¹⁴ W/cm²), polarization and angle of incidence of the laser beam. The possibility for second harmonic to arise from resonant absorption, through a rippled critical surface, or from parametric decay instability is discussed.     

Precise measurement of the KLL and KLX Auger spectra of cadmium from the EC-decay of 111In

The KLL and KLX Auger spectra of Cd from the EC-decay of ¹¹¹In have been analyzed with the 7 eV instrumental resolution using a combined electrostatic spectrometer and a source prepared by a modified Langmuir–Blodgett method. Energies and relative intensities of all the nine well resolved KLL lines have been precisely determined. While the latter quantities were found to be in very good agreement with the relativistic intermediate coupling calculations, the former ones deviate from results of the widely used semi-empirical calculations especially in the case of the absolute energies. The predicted strong influence of the relativistic effects on the KL₁L₂(³P₀) transition intensity has been proved. Most of the main KLX Auger lines have been well separated and their complex structures have been observed. Accurate energies and intensities obtained for these lines have been compared with results of calculations. The intermediate coupling splitting of the KL₂L₂ and KL₃L₃ lines have been revealed. The KLX/KLL, KLN(O)/KLM, and KXY/KLL group intensity ratios have also been determined. A conclusion is made that further finer theoretical investigation on the complex interaction mechanism for two inner-shell vacancies is still very much needed.     

Laser plasma monitored by silicon carbide detectors

The excellent physical and chemical properties and the radiation hardness of silicon carbide (SiC) render this material particularly suitable for the realization of radiation detectors. In this paper we describe the main properties of SiC and the processes needed to realize good performance detectors. To this purpose, we made SiC Schottky diodes that were electrical characterized by using different techniques. In order to test the radiation hardness, the diodes were irradiated with different ion beams and the analysis of the electrical measurements allowed to identify the defects responsible of the device degradation. These detectors have been used to monitor the multi-MeV ions of the plasma emitted by irradiation of various targets with 300-ps laser at high intensity (10¹⁶?W/cm²). These measurements highlighted that the use of SiC detectors enhances the sensitivity to ions detection due to the cutting of the visible and soft ultraviolet radiation emitted from plasma. The small rise time and the proportionality to ion energy evidence that these detectors are a powerful tool for the characterization of ion generated by high-intensity pulsed laser.     

Phonon replicas of the electron-hole liquid luminescence line in intrinsic silicon

The TO, LO and TA phonon assisted luminescence lines associated with carrier recombination inside an electron-hole drop in Si have been studied. The carrier density n and the droplet binding energy ø per electron-hole pair have been estimated from the lineshape and position of the TA-phonon assisted line. The resulting values n = (3.0±.1) × 10¹⁸cm^-3 and ø = 7.9±.1 meV are smaller than previously published values based on an analysis of the unresolved TO-LO line. The discrepancy in the fitted density arises because the TO-LO line is broader than the sum of two TA lines separated by the known TO-LO splitting at any intensity ratio. The effect of LO phonon dispersion can explain the effect, if a TO-LO intensity ratio close to unity is assumed, contrary to previously expressed theoretical expectations.     

Stark widths and transition probabilities of some multiplets of singly ionized carbon

Photoelectric measurements of lines emitted by a helium-carbon d.c. arc plasma of n_e = 1.9 × 10¹⁶cm^-3 at T = 12,800 K have been performed. Stark widths of 6 C(II) lines and transition probabilities for components of 3 C(II) multiplets were determined and compared with other experimental and theoretical data. Good agreement was generally observed except for the C(II) multiplets UV13 and UV14, where the results of Kusch deviate notably from others.     

Excitation of Doubly‐Charged Ion Emission Lines from a Grimm‐Style Glow Discharge Plasma—Comparison Between Yttrium and Zirconium

Spectra of yttrium and zirconium emitted from a Grimm‐style glow discharge plasma were investigated to elucidate the excitation mechanism of doubly‐charged ionic lines when using argon–helium mixed gas as well as argon gas alone. The energy sum for exciting doubly‐charged ion species of yttrium is slightly smaller compared to the case of zirconium, which yields an interesting correlation in the excitation energy between their ionic species and excited species of helium or argon. The Y III emission lines which were assigned to the 4p⁶5p–4p⁶5s(4p⁶4d) transitions could be observed in the argon–helium mixed gas plasma, but those were hardly excited with argon gas only. The Zr III emission lines did not appear in the spectra emitted by the argon gas plasma nor by the mixed gas plasma. A possible explanation for these phenomena is that the excitation of these ionic species is caused principally by collisional energy transfer from helium species to the analyte atoms.     

12CH3OH and 13CH3OH optically pumped by the 10P and 10HP bands of a pulsed CO2 laser: New far-infrared laser emissions and assignments

We have re-investigated the ¹²CH₃OH and the ¹³CH₃OH molecules as optically pumped far-infrared laser sources. We have used our new waveguide pulsed-high-peak-power CO₂ laser for pumping, finding 20 new far-infrared laser lines emitted by ¹²CH₃OH and seven emitted by ¹³CH₃OH. For each line we report wavelength, pump offset from the center of the exciting CO₂ line, relative polarization, optimum operating pressure and intensity. The LaseRitz program was able to assign one of the new laser systems of ¹²CH₃OH, involving two new far-infrared laser lines.PACS 42.55.Lt; 42.62.Fi     

Characterization of compact bright soft X-ray source based on picosecond laser plasma

Radiation emission of silicon and aluminum plasmas produced by 40-ps laser pulses with peak intensity above 10¹⁴ W/cm² was studied. High-resolution soft X-rayspectra of H-like and He-like ions were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the intercombination lines of He-like ions with the results of model calculations. Such comparisons gave average values of the electron number density N_e=(1-1.9)×10²¹ cm^-3 and the electron temperature T_e=460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. The plasma size is about 100 μm. According to our estimations, more than 10¹² photons were produced within the resonance line spectral width and in the solid angle 2π during the total decay period. PACS 41.50.+h; 52.25.Os; 52.50.Jm     

“碰撞-辐射”模型在Z箍缩等离子体K壳层线辐射谱分析中的应用

介绍了由K壳层谱线强度比估算等离子体状态参数的"碰撞-辐射"模型的基本原理.详细描述了自行研制的基于该模型的Z箍缩等离子体K壳层线辐射谱分析程序——ZSPEC的基本情况.给出了氖等离子体的计算结果,包括不同电离态离子的相对含量随电子温度的变化曲线和K壳层谱线强度比在"电子密度-电子温度"平面内的等高线分布图.该程序已在"阳"加速器Z箍缩实验结果分析中得到应用,将椭圆晶体谱仪测得的氖等离子体K壳层谱线强度比与ZSPEC程序计算结果相比较,得出在该发实验 关键词： 碰撞-辐射模型 K壳层线辐射谱')" href="#">K壳层线辐射谱 氖气喷气Z箍缩 阳加速器