Some properties of a microwave boosted glow discharge source using neon as the operating gas

The use of neon as the operating gas for the analysis of aluminium samples with the microwave boosted glow discharge source has been studied. A new type of anode tube allowed the gas to enter the source near the sample surface so that more material was transported into the discharge. Erosion rates have been measured under conditions optimised for high line-to-background ratios and found to be lower than with argon (9 and 21 n/s, respectively). Despite the lower erosion rate the detection limits measured for a number of elements in aluminium are in the range 0.02–1 g/g and comparable to those obtained with argon as the operating gas.     

Some properties of a microwave boosted glow discharge source using neon as the operating gas

The use of neon as the operating gas for the analysis of aluminium samples with the microwave boosted glow discharge source has been studied. A new type of anode tube allowed the gas to enter the source near the sample surface so that more material was transported into the discharge. Erosion rates have been measured under conditions optimised for high line-to-background ratios and found to be lower than with argon (9 and 21 n/s, respectively). Despite the lower erosion rate the detection limits measured for a number of elements in aluminium are in the range 0.02-1 microg/g and comparable to those obtained with argon as the operating gas.     

Temperatures,electron densities and degrees of ionization in a boosted glow discharge emission lamp

The intensities of FeI and FeII spectral lines emitted by a boosted glow discharge lamp were measured over a range of typical lamp operating conditions. Several spectral lines were chosen for determinations of FeI and FeII excitation temperatures.It was found that when sufficient booster current was applied, the FeI and FeII temperatures were comparable (ca. 4000 K) and reasonably independent of discharge parameters. Determinations of electron density (5 × 10¹³ cm^?3) and degrees of ionization for calcium (81.3%), chromium (19.5%), magnesium (5.5%) and manganese (5.2%) were made in similar stable excitation conditions.An equation which allows the calculation of the degree of ionization for any element in typical discharge conditions was formulated and the expected degree of ionization was calculated for fifteen elements.     

Design and characterization of a direct current glow discharge lamp for analytical applications

This paper describes a compact, small volume direct current glow discharge lamp operating at low wattage for atomic emission spectrometric analysis and its process optimization for copper and brass solid samples. The design aspects, fundamental characteristics and analytical performance are described in detail. The discharge is observed end-on, with water-cooled cathode surface parallel to the spectroscopic entrance slit. The anode diameter is 7 mm and the minimum sample diameter required is 20 mm. The sample is located outside the lamp for easy access and interchangeability. The lamp is powered by a dc power supply capable of delivering 300 mA (max.) and 1500 V. The studies of fundamental characteristics include the current-voltage relationship and their dependence on pressure and the emission intensity of copper spectral line (324.7 nm). The studies were made in the pressure range of 2-7 mbar. Long-term stability of optical emission spectra was also recorded to be within ±0.75%. The performance of the lamp is quite linear in the pressure range 3.5-7 mbar at an applied voltage of about 450 V.     

Reduction of ground state atom concentration in a boosted output discharge lamp

Measurements of the concentration of ground state metal atoms in a boosted output discharge lamp show a ten-fold decrease in the number density when the boosting discharge is operating. Thisdecrease in the ground state population depends on the nature of the carrier gas, being most pronounced for neon, and also on the magnitude of the discharge current. Removal of atoms from the ground state is relatively slow, indicating that a heavy-body process is involved. Cataphoresis does not appear to play a significant role. The most likely process is shown to be aggregration of atoms to form clusters which are detected, for silver by measurements on an anomalous absorption band arising from Mie Scattering.     

Self-absorption and Doppler temperatures of emission lines excited in a glow discharge lamp

The shapes of the emission lines of calcium and chromium emanating from a Grimm type glow discharge lamp have been determined by use of a pressure-scanning Fabry—Perot interferometer using various excitation conditions for different concentrations of these metals in standard matrices. Assuming a certain model for the light source, theoretical line profiles were calculated.The Doppler temperature as a function of current at constant voltage was determined from a comparison of the experimental and theoretical profiles. Also determined was the degree of absorption in emitting and non-emitting layers of the model.It was found that considerable self-absorption and reversal occur in the lamp at higher currents and concentrations.     

Spectroscopic evaluation of a compact magnetically boosted radiofrequency glow discharge for time-of-flight mass spectrometry

A compact magnetically boosted radiofrequency glow discharge (GD) has been designed, constructed and its analytical potential evaluated by its coupling to a mass spectrometer (MS). Simple modifications to the original source configuration permitted the insertion of permanent magnets. Small cylindrical Nd–Fe–B magnets (∅ = 4 mm, h = 10 mm) were placed in an in-house-modified GD holder disc that allows easy and fast exchange of the magnets. The different processes taking place within the GD plasma under the influence of a magnetic field, such as sputtering, ionisation processes and ion transport into the MS, were studied using different GD operating conditions. Changes to the ionisation and ion transport efficiency caused by the magnetic field were studied using an rf-GD-TOFMS setup. A magnetic field of 60–75 gauss (G) was found not to affect the sputtering rates but to enhance the analyte ion signal intensities while decreasing the Ar species ion signals. Moreover, magnetic fields in this range were shown not to modify the crater shapes, enabling the fast and sensitive high depth resolved analysis of relatively thick coated samples (micrometre) by using the designed compact magnetically boosted rf-GD-TOFMS.

A glow discharge lamp with supplementary excitation by a radio—frequency discharge-preliminary measurements

The emission radiant output of an ordinary glow discharge plasma was increased by several factors through secondary inductively coupled RF excitation produced by an external coil and a 136.2MHz oscillator. The gain factor was determined at several glow discharge currents and voltages in copper alloys and cast iron samples. Improved linear calibration curves were obtained because the RF-boosted glow discharge source decreased the effect of self-absorption.     

Spatial and temporal studies of a glow discharge

A demountable glow discharge tube was constructed with the objective of studying the various processes taking place in the discharge and resolving these both spatially and temporally. Argon and neon were used as fill gases. Continuous wave laser excited fluorescence was used to study the spatial distribution of sodium atoms which were sputtered off the cathode; a value for the diffusion coefficient of sodium in argon was obtained from time-resolving these experiments. From the population ratios of the various excited levels which we observed, we conclude that no single excitation temperature predominates anywhere between the electrodes under our conditions; instead, several population inversions were observed. Emission intensities of lines from atoms and ions were resolved as a function of the axial position between the electrodes. A temporal region was found where the signal-to-noise ratio for the detection of small quantities of analytes may be optimized. In addition to numerous atomic lines from the fill gas, we also detected fill gas ions as well as Fe, Fe⁺ and Cr when using stainless steel as a sample.     

CCCO: Generation by dc glow discharge in carbon suboxide,and microwave spectrum

Generation of the CCCO molecule was observed through its microwave spectrum in a dc glow discharge of carbon suboxide. Thirteen rotational transitions J = 7-6 to 19-18 were measured in the frequency region 67–183 GHz with the use of a source-modulation microwave spectrometer. A least-squares analysis of 19 observed spectral lines, including the six previously reported by Brown et al., yielded the following revised molecular constants for CCCO: B_o = 4810.88624(65) MHz and D_o = 0.00077707(130) MHz, with 3σ in parentheses. The concentrations of CCO as well as CCCO produced in the glow discharge are estimated to be about 11 ppm.     

Sputtering and emission intensity of copper alloys in a grimm glow lamp

The effects of the metallurgical structure and the aluminium content of copper—aluminium alloy (1–12% Al) on the sputtering and intensities of spectral lines in the Grimm glow lamp are reported. The electrical current and sputtering yield decreased linearly with increasing aluminium content; the intensities of the Al I lines depended linearly on the amount of aluminium in the sputtering yield at a fixed voltage and argon pressure. The structure affected the intensities of the Al I and Cu I lines but not the intensity ratio (Al I/Cu I) for about 100 s after burn-off. Working curves for aluminium for samples of different structure were very similar.     

Deposition of polysiloxane films in a glow discharge

The method of polymerization in the plasma of a dc glow discharge was used to obtain thin-film polysiloxane coatings on metallic substrates. The chemical composition, structure, and deposition rate of the coatings were studied in relation to process parameters.     

Electrical characteristics of a millisecond pulsed glow discharge

A μs and ms pulsed argon glow discharge was investigated with respect to the breakdown condition (Paschen curve). Moreover, current–voltage profiles were acquired for different discharge frequencies, pulse durations, cathode–anode spacing and discharge pressures. The breakdown voltage was dependent on the cathode material (Cu, steel, Ti and Al). No severe change in the breakdown voltage was observed for a 1 ms pulse at different frequencies. However, the theoretical breakdown curve, calculated based on the Paschen equation did not fit the experimental data. The current plots for different cathode–anode spacing showed a maximum at intermediate distance (8–10 mm). These data were consistent with mass spectrometric data acquired using the same instrument in a GC-GD-TOFMS chemical speciation study.     

The electret properties of tetrafluoroethylene-hexafluoropropylene copolymer films modified in glow discharge

The electret properties of tetrafluoroethylene-hexafluoropropylene copolymer films modified in direct-current discharge were studied. It was shown that the treatment of the films mounted on the anode had an insignificant effect on the relaxation of negative homocharge despite substantial changes in the chemistry of the surface. However, the low-temperature relaxation process responsible for the instability of the electret state in the untreated film is completely suppressed in the case of decay of positive homocharge. Deep traps associated with high-temperature relaxation processes in the polymer are simultaneously eliminated from the spectrum of surface states.