High resolution, low hν photoelectron spectroscopy with the use of a microwave excited rare gas lamp and ionic crystal filters

The need for not only bulk sensitive but also extremely high resolution photoelectron spectroscopy for studying detailed electronic structures of strongly correlated electron systems is growing rapidly. Moreover, easy access to such a capability in one's own laboratory is desirable. Demonstrated here is the performance of a microwave excited rare gas (Xe, Kr, and Ar) lamp combined with ionic crystal filters (sapphire, CaF(2), and LiF), which can supply three strong lines near the photon energy of hnyu hν=8.4, 10.0, and 11.6 eV, with the hν resolution of better than 600?μeV for photoelectron spectroscopy. Its performance is demonstrated on some materials by means of both angle-integrated and angle-resolved measurements.     

A UV lamp based on a Kr-Xe mixture with Br2 and I2 molecules

A small-size broadband ultraviolet lamp with an emission spectrum of 206–390 nm, which is excited by a dc glow discharge, is described. The discharge was ignited in a quartz discharge tube with an inner diameter of 1.4 cm and an anode-cathode spacing of 10 cm. The tube was filled with a Kr/Xe/Br₂/I₂ working mixture, the total pressure being 0.5–2.0 kPa. The lamp’s emission spectrum consisted of a 206.2-nm iodine atomic line 0.1 nm wide at half-height and a continuum in a spectral region of 210–390 nm. The continuum resulted from overlapping of wide emission bands with peaks at 221 nm for XeBr(D-X), 253 nm for XeI(B-X), 282 nm for XeBr(B-X), 289 nm for Br ₂ ^* , 342 nm for I ₂ ^* , and 386 nm for IBr*. The total power of the ultraviolet emission was no more than 8–12 W, the power injected into the discharge being 10–100 W. The lamp lifetime in the gas-static mode was 300–400 h.     

Performance of a gas electroluminescence x-ray detector filled with an argon-xenon mixture

The performance characteristics of a gas electroluminescence X-ray detector (DELG) filled with an Ar + Xe mixture in a range of Xe concentrations of 5–100% were investigated. For a mixture of 80% Ar + 20% Xe, an improvement of the energy resolution is observed with an increase in the gaseous-mixture pres-sure. The best result obtained at a pressure of 3 atm is 7.25% (MnK _α, 5.9 eV), which is higher than the data known from the literature by 0.5%. The peak/valley parameter for the same mixture amounts to a value of 650 for an energy of 5.9 keV compared to a value of 200 for pure Xe. The energy resolution of the DELG is suitable for use in X-ray diffractometry for effective suppression of K _β lines of characteristic radiation of the main anodes of X-ray tubes.     

A VUV-UV gas-discharge lamp on a low-pressure mixture of argon and xenon with bromine vapors

The characteristics of a lamp operating on a low-pressure (0.5–1.5 kPa) Ar-Xe-Br₂ mixture and excited with a longitudinal glow discharge have been studied. A cylindrical lamp has a 10-cm interelectrode distance and a 1.4-cm-diameter discharge tube. The lamp radiates in the spectrum range 150–300 nm. Its emission spectrum is represented by a wide continuum formed on the basis of the 282-nm XeBr(B-X) and 220-nm XeBr(D-X) bands and the 163.3-nm spectral line of atomic boron. The emission power of the lamp reaches 5–7 W at a power of up to 40 W injected into the discharge tube. The service life of the lamp on a single working mixture reaches 500 h.     

Minimizing matrix effects and spectral interferences produced by Fe absorption lines in the determination of cadmium by electrothermal atomic absorption spectrometry: Application to the fractionation of cadmium in moderated contaminated soils

Solutions, including the extracting solutions used in the sequential procedure recommended by the Standard, Measurements and Testing Program, with different cadmium and iron concentrations were prepared and analyzed using combined electrothermal atomic absorption spectrometry (ETAAS) and two background compensation techniques. The first was based on the deuterium background correction method in which a deuterium lamp was used in combination with a conventional Cd hollow-cathode lamp. For the second, a high-intensity boosted discharge hollow-cathode lamp (BDHCL) was used as in the Smith–Hieftje (S–H) background correction method, but this lamp was modulated with a low and a high current mode at a modulation frequency of 100 Hz. In the present study, the modulation cycle was 10 times higher than in the S–H system. Therefore, the background correction method was called high-speed self-reversal method. Pseudo-total Cd concentrations were determined using ETAAS in five reference materials and fractionation was made in two reference soils. With regard to the results, the high-speed self-reversal background correction method provided a method of choice to eliminate or decrease the spectral interference due to the close positioning of the analytical lines of Cd and Fe in solutions containing high iron concentrations during the Cd determination by electrothermal atomic absorption spectrometry. It is worth noting that using the HSSR-method, the sensitivity losses were from 32% to 39% compared to the continuum source background corrector equipped with a deuterium lamp. The HSSR-method was successfully applied to the determination of Cd in contaminated samples. The results showed that interferences caused by absorption line overlapping of Cd and Fe could be compensated accurately for Fe/Cd = 100,000 in 0.11 M acetic acid and Fe/Cd < 10,000 in 0.5 M hydroxylamine hydrochloride.     

A glow-discharge-pumped broadband short-wavelength lamp

A broadband ultraviolet-vacuum-ultraviolet lamp, which emits at wavelengths of 150–300 nm, and its output characteristics are described. The lamp is excited by a longitudinal glow discharge, which is initiated in a quartz tube with an inner diameter of 1.4 cm and an interelectrode distance of 10 cm. The tube is filled with a He/Br₂ working mixture at a total pressure of 0.2–1.0 kPa. The lamp emission spectrum consists of a 163.3-nm spectral line of bromine atoms and continuum in the spectral region 165–300 nm. A continuum is formed as a result of an overlap of broad emission bands of bromine molecules. The total emission power of the lamp reaches 4–5 W at an electric power of up to 60 W. The lamp’s efficiency is 5–10%, and its service life in the gas-static mode is 300–400 h.     

Description of a polarized source of He i radiation for surface studies

A polarized radiation source has been designed and built for use in angular-resolved photoelectron spectroscopy on surfaces of single crystals under ultrahigh vacuum. The light from a discharge in helium is polarized by a triple reflection from a series of gold mirrors, producing a plane-polarized beam of He i radiation (21.22 eV) with a polarization of 80%. The plane of polarization can be rotated through more than 180 degrees without breaking vacuum. Details of the construction of the lamps are given, together with how it is integrated into the overall operation of the electron spectrometer. As an illustration of the lamp's potential, data are shown on the photoemission studies of the (110) and (111) faces of copper as a function of both the orientation angle of the crystal and the polarization vector. A brief discussion of the future development and possible uses of the lamp is included.     

电子回旋共振离子推力器放电室等离子体静电探针诊断

电子回旋共振离子推力器是一种无阴极静电型推进装置,具有比冲高、无电极烧蚀和寿命长的优点,可用于深空探测和长寿命卫星。在其放电室内存在着复杂的、紧密耦合在一起含电子回旋共振区的静磁场、微波电磁场和等离子体流场,弄清放电室内复杂的场结构对于推力器的结构和性能优化有着重要的作用。为此认为放电室中的离子未被磁化,采用朗缪尔探针直接诊断放电室内的电子温度和离子密度,再根据等离子体的准中性原则,认为离子密度就反映了电子密度。根据诊断结果可以分析出放电室内的氩等离子体场结构。气体流量分别为3 sccm和8 sccm、微波功率分别为10 W和34 W时,实验诊断得到电子温度分布在1 eV～6.8 eV范围内、离子密度分布在2×1016/m3～2.8×1017/m3范围内。     

Combined experimental setup for spin- and angle-resolved direct and inverse photoemission

We present a combined experimental setup for spin- and angle-resolved direct and inverse photoemission in the vacuum ultraviolet energy range for measurements of the electronic structure below and above the Fermi level. Both techniques are installed in one ultrahigh-vacuum chamber and, as a consequence, allow quasisimultaneous measurements on one and the same sample preparation. The photoemission experiment consists of a gas discharge lamp and an electron energy analyzer equipped with a spin polarization detector based on spin-polarized low-energy electron diffraction. Our homemade inverse-photoemission spectrometer comprises a GaAs photocathode as spin-polarized electron source and Geiger-Muller counters for photon detection at a fixed energy of 9.9 eV. The total energy resolution of the experiment is better than 50 meV for photoemission and better than 200 meV for inverse photoemission. The performance of our combined direct and inverse-photoemission experiment with respect to angular and energy resolutions is exemplified by the Fermi-level crossing of the Cu(111) L-gap surface state. Spin-resolved measurements of Co films on Cu(001) are used to characterize the Sherman function of the spin polarization detector as well as the spin polarization of our electron source.     

Spectroscopically pure metal vapor source for highly charged ion spectroscopy and capillary discharge soft x-ray lasers

We describe a compact, pulsed metal vapor source used for the production of dense plasma columns of interest for both soft x-ray laser research and spectroscopy of highly ionized plasmas. The source generates spectroscopically pure cadmium vapor jets in a room-temperature environment by rapidly heating an electrode with a capacitive discharge. In the configuration described herein, the metal vapor jet produced by the source is axially injected into a fast (up to 15 kA/ ns), high current (up to 200 kA peak) capillary discharge to generate highly ionized cadmium plasma columns. Spectroscopic analysis of the discharge emission in the 12-25 nm spectral range evidences the dominance of Cu-like (CdXX) and Ni-like (CdXXI) lines and shows strong line emission at 13.2 nm from the 4d (1)S(0)-4p (1)P(1) laser transition of Ni-like Cd. Hydrodynamic/atomic physics simulations performed to describe the dynamics of the plasma column and compute the optimum discharge conditions for laser amplification are discussed.     

A confocal beam scanning white-light microscope

We report on a confocal beam scanning microscope utilizing a continuous Xe short-arc lamp operating in the visible spectrum with unprecedented radiance. Measurements of lateral and vertical resolution will be presented and compared with those of an equivalent scanning laser microscope. Resolution of the white-light microscope is equivalent to that of the scanning laser microscope. White-light microscope images positively stand out from those of the scanning laser microscope by their lack of artefacts caused by interference.     

New design for a microwave discharge lamp

A simple discharge lamp with a microwave cavity fitting inside provides an intense source of VUV resonance radiation for photochemical work inside a vacuum chamber. Good coupling and minimum reabsorption result in better efficiency ( greater, similar1%) and more intense output power (up to 2.5x10(16) quanta s(-1)) than have been achieved previously.     

Results of RIKEN superconducting electron cyclotron resonance ion source with 28 GHz

We measured the beam intensity of highly charged heavy ions and x-ray heat load for RIKEN superconducting electron cyclotron resonance ion source with 28 GHz microwaves under the various conditions. The beam intensity of Xe(20+) became maximum at B(min) ～ 0.65 T, which was ～65% of the magnetic field strength of electron cyclotron resonance (B(ECR)) for 28 GHz microwaves. We observed that the heat load of x-ray increased with decreasing gas pressure and field gradient at resonance zone. It seems that the beam intensity of highly charged heavy ions with 28 GHz is higher than that with 18 GHz at same RF power.     

High resolution short focal distance Bent Crystal Laue Analyzer for copper K edge x-ray absorption spectroscopy

We have developed a compact short focal distance Bent Crystal Laue Analyzer (BCLA) for Cu speciation studies of biological systems with specific applications to cancer biology. The system provides high energy resolution and high background rejection. The system is composed of an aluminum block serving as a log spiral bender for a 15 micron thick Silicon 111 crystal and a set of soller slits. The energy resolution of the BCLA-about 14 eV at the Cu Kα line- allows resolution of the Cu Kα(1) and CuKα(2) lines. The system is easily aligned by using a set of motorized XYZ linear stages. Two operation modes are available: incident energy scans (IES) and emission energy scans (EES). IES allows scanning of the incident energy while the BCLA system is maintained at a preselected fixed position--typically CuKα(1) line. EES is used when the incident energy is fixed and the analyzer is scanned to provide the peak profile of the emission lines of Cu.     

Plasma rotation measurement in small tokamaks using an optical spectrometer and a single photomultiplier as detector

The method for plasma rotation measurement in the tokamak TCABR is reported in this article. During a discharge, an optical spectrometer is used to scan sequentially spectral lines of plasma impurities and spectral lines of a calibration lamp. Knowing the scanning velocity of the diffraction grating of the spectrometer with adequate precision, the Doppler shifts of impurity lines are determined. The photomultiplier output voltage signals are recorded with adequate sampling rate. With this method the residual poloidal and toroidal plasma rotation velocities were determined, assuming that they are the same as those of the impurity ions. The results show reasonable agreement with the neoclassical theory and with results from similar tokamaks.     

Xenon ion laser-induced fluorescence using a visible tunable diode laser near 680 nm

Laser-induced fluorescence (LIF) measurements have been performed for the first time in a low temperature (Te approximately 0.6 eV) Xe plasma using a tunable diode laser in the visible range of wavelengths. The transition in Xe II involved the (3P1)5d[3]7/2 metastable state and the excitation wavelength was found to be 680.570+/-0.001 nm (air). LIF measurements of I 2 in a room temperature iodine gas cell were used to monitor the wavelength of the laser during the measurements.     

无人机航迹中电力线电晕紫外探测与定位

在无人机电力线巡检中,为了能快速发现并定位绝缘子产生电晕放电现象的位置,对无人机航迹中的电力线电晕探测与定位方法进行了研究。分析了电晕放电功率检测模型,并得到放电源辐射出紫外光功率的公式。设计了具有高灵敏度的电晕探测设备,提出在无人机航迹中发现绝缘子缺陷的定位方法,通过两次不同角度对电力线铁塔探测,比较两次探测结果分析出缺陷绝缘子的位置。最后根据定位方法设计了对电火花和紫外LED探测实验。结果表明,该探测设备能准确探测出电火花产生的紫外光功率,受到紫外光在空气中损耗的影响,测量值随距离的增加而逐渐减小,且在不同距离情况下相对误差在11.5%之内。在紫外LED探测实验中,探测角度选择0°和15°时测量值较为准确。该方法在微弱电晕放电探测中准确有效,能够满足无人机在航迹中对电力线缺陷绝缘子的定位要求。     

Improved high-intensity microwave discharge lamp for atomic resonance absorption and fluorescence spectrometry

An unusually good combination of high intensity and narrow line has been achieved in a microwave discharge lamp by placing the optical window in the center of the microwave cavity. Construction details and performance characteristics are described.     

Experimental investigations of silicon tetrafluoride decomposition in ECR discharge plasma

The results of first experiments on the investigation of plasma of electron cyclotron resonance (ECR) discharge, sustained by CW radiation of technological gyrotron with frequency 24 GHz are considered. The parameters of nitrogen plasma of ECR discharge in magnetic field up to 1 T were investigated by Langmuir probe in the pressure range 10(-4)-10(-2) mbar under different values of microwave power. Depending on gas pressure and power of microwave radiation, the typical temperature and density of electrons could attain values of 1-5 eV and 10(11)-10(12) cm(-3), respectively. The prospects for using of ECR discharge for plasma chemical decomposition of silicon tetrafluoride (SiF(4)) have been experimentally demonstrated. Plasma was created from SiF(4) and hydrogen (H(2)) gas mixture and heated by microwave radiation in ECR conditions. Using the method of mass-spectrometry analysis of the gas at the outlet from the reactor and the weighting method, the content of the resultants of SiF(4) decomposition as a function of process parameters was investigated. It was shown that SiF(4) decomposition degree strongly depends on the microwave power, gas pressure in the reactor, gas flow rates, and can attain the value of 50%. The possible applications of PECVD method based on ECR discharge for production of isotopically pure elements with high deposition rate are discussed.     

Scanning Fabry-Pérot interferometer with largely tuneable free spectral range for high resolution spectroscopy of single quantum dots

We report on the implementation of a scanning Fabry-Pérot interferometer for photoluminescence spectroscopy investigation. We choose a conveniently small reflectivity of the two planar semitransparent mirrors which, in spite of a moderate cavity finesse, ensures a good mechanical stability over a long time. We also exploit the large tuneability of the cavity length (i.e., of the free spectral range) for changing the spectral resolution over two order of magnitude (from ~300 μeV to ~4 μeV in full width at half maximum). Such a characteristic easily allows to scan both sharp and broad luminescence bands. We test our Fabry-Pérot interferometer on sharp photoluminescence lines resulting from excitonic recombination in self-assembled GaAs quantum dots. We demonstrate the ability of our system to resolve linewidth as small as 4 μeV.