Od: IOPP Customer Services [custserv@iop.org] Wysłano: 12 listopada 2004 04:20 Do: andrzejg@ifpilm.waw.pl Temat: Electronic Journals Alert (user AGalkowski, PlasmaPhysics) The following articles have been released since 5/11/2004, matching your alert profile "PlasmaPhysics": Selected journals Plasma Sources Science and Technology Volume 13, November 2004 http://www.iop.org/EJ/toc/-alert=15022/0963-0252/13/4 Modelling of magnetic field profile effects in a helicon source Deepak Bose, T R Govindan and M Meyyappan 2004 Plasma Sources Sci. Technol. 13 553-561 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/001 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/001/psst4_4_001.pdf The effect of altering the dc magnetic field on plasma properties and wave characteristics in a helicon source is studied. A two-dimensional, numerical model with self-consistency between wave propagation, including the Trivelpiece-Gould mode, and plasma transport is used. A parametric study is carried out to ascertain the magnetic field profile effects on wave propagation, peripheral versus bulk power absorption, plasma density, uniformity, temperature and potential. It is found that diffusion of plasma and power absorption away from the radio frequency antenna can be enhanced by adjusting the magnetic field profile. The effect on plasma uniformity qualitatively agrees with the measured data in the literature. Electron density measurements in afterglow of high power pulsed microwave discharge M Mesko, Z Bonaventura, P Vasina, A Ta'lsky', Z Frgala, V Kudrle and J Janca 2004 Plasma Sources Sci. Technol. 13 562-568 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/002 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/002/psst4_4_002.pdf In this paper, we present experimental results of diagnostics of a high power microwave pulsed discharge (100 kW at 9 GHz, 2.5 us) in nitrogen and oxygen gases. We used microwave interferometers operating at 15 and 35 GHz equipped with dielectric rod antennae. The operating pressure was between 20 and 2000 Pa. In nitrogen the large value of the recombination coefficient &agr;r = (1-2) x 10-6 cm3 s-1 suggests that {\rm N}_{2}^{ + } (&agr;r = 2 x 10-7 cm3 s-1) ions coexist with the predominant complex ions, {\rm N}_{4}^{ + } and {\rm N}_{3}^{ + } , at pressures greater than 700 Pa. In oxygen the value of the recombination coefficient increases with increasing pressure from a value typical of {\rm O}_{2}^{ + } (&agr;r = 3 x 10-7 cm3 s-1) at a pressure of 200 Pa to a value of &agr;r = (2-4) x 10-6 cm3 s-1 at pressures above 1000 Pa as a consequence of the formation of {\rm O}_{4}^{ + } at higher pressures. Effect of insulator sleeve length on soft x-ray emission from a neon-filled plasma focus device R S Rawat, T Zhang, C B L Phua, J X Y Then, K A Chandra, X Lin, A Patran and P Lee 2004 Plasma Sources Sci. Technol. 13 569-575 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/003 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/003/psst4_4_003.pdf Insulator sleeves of different lengths were used at the closed end of the coaxial electrode assembly of the 3.3 kJ United Nation University-International Centre for Theoretical Physics (UNU-ICTP) plasma focus device to investigate soft x-ray (SXR) (900-1550 eV) yield for different filling gas pressures of neon. The time and space resolved SXR emission characteristics were investigated using a multi-channel diode x-ray spectrometer and a CCD based pinhole imaging camera. At pressures below 6 mbar, the average SXR yield was also found to increase with increasing sleeve length from 19 to 22 mm. A further increase in insulator sleeve length to 25 mm, however, decreased the SXR yield. At pressures above 6 mbar, the SXR yields were almost the same for insulator sleeves of different lengths. The UNU-ICTP plasma focus device is found to be best optimized for neon SXR production with a 22 mm insulator sleeve at 4 mbar filling gas pressure, with the highest average yield of 8.2 J per shot, for which the conversion efficiency is about 0.25%. For this sleeve length, even the average yield at 2 or 6 mbar pressure was comparable with the maximum yield of a 25 mm sleeve. Analysis of excitation processes and electron temperature changes from spectral data in a dc micro plasma discharge Davide Mariotti, Paul Maguire, Charles M O Mahony and James McLaughlin 2004 Plasma Sources Sci. Technol. 13 576-581 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/004 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/004/psst4_4_004.pdf A micro scale dc plasma discharge was studied to determine the potentialities for lab-on-the-chip applications. Different working conditions for the micro plasma discharge were considered: the pressure was varied between 2.7 and 5.3 kPa and the applied dc voltage was between 400 and 540 V, generating a discharge current in the range of 0.02-0.09 mA. The electrode distance was maintained at 0.025 cm and argon was used as the gas for the formation of plasma discharges. The number densities of excited states were determined by spectral emission data (400-1000 nm) and then were calculated by introducing a few assumptions: comparison of experimental and calculated number densities allowed an analysis of a volume averaged electron energy distribution function. Also, it was possible to estimate an effective electron temperature for different conditions of pressure and applied voltage. Characterization of a dielectric barrier discharge operating in an open reactor with flowing helium G Nersisyan and W G Graham 2004 Plasma Sources Sci. Technol. 13 582-587 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/005 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/005/psst4_4_005.pdf A dielectric barrier discharge (DBD) generated by flowing helium between the parallel-plate electrodes of an open air reactor has been characterized using time resolved optical and electrical measurements. A sinusoidal voltage of up to 5 kV (peak to peak) of frequencies from 3 to 50 kHz has been applied to the discharge electrodes. The helium flow rate is varied up to 10 litre min-1. The adjustment of flow rate allows the creation of uniform DBDs with optimized input power equal to 120 ± 10 mW cm-3. At flow rates from 4 to 6 litre min-1 a uniform DBD is obtained. The maxima in the line intensities of {\rm N}_2^ + and helium at 391.4 nm and 706.5 nm, respectively, under those conditions indicate the importance of helium metastables and {\rm He}_2^ + in sustaining such a discharge. The power efficiency and discharge current show maxima when the DBD in He/air is uniform. The gas temperature during the discharge has been measured as 360 ± 20 K. High-pressure operation of a toroidal, inductively coupled discharge A Shabalin 2004 Plasma Sources Sci. Technol. 13 588-593 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/006 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/006/psst4_4_006.pdf Steady-state operation of a toroidal, inductively coupled discharge at pressures up to 640 Torr is described. Measurements of the plasma loop voltage and broadband light emission are reported for different pressures up to one atmosphere, flows up to 14 slm and power levels up to 8 kW. While most of the experiments relate to pure argon plasmas, measurements in mixed argon plasmas with up to 10% of reactive gases such as oxygen and nitrogen are also reported. High-frequency electrodeless discharges in helium N Denisova and A Skudra 2004 Plasma Sources Sci. Technol. 13 594-599 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/007 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/007/psst4_4_007.pdf Modelling of high-frequency electrodeless discharges (HFEDs) in helium is presented. The model combines calculations of electromagnetic field profiles and plasma parameters including kinetics of the excited atomic states. A method of the self-consistent numerical solution for the plasma-field system is proposed. The method takes into account a temporal hierarchy of the kinetic processes in the HFED plasma. A stationary collision-radiative model for helium plasma is developed considering the following equations: (i) the transport equations for the electrons, (ii) the electron energy balance equation, (iii) the population rate equations for balance in the excited states and (iv) the electromagnetic field equations. Discharge properties are investigated in a numerical simulation. The electron density, electron temperature and absorbed power versus gas pressure and external magnetic field amplitude are obtained. The electromagnetic field profiles demonstrate a significant role of the skin effect. The intensities of the lines 587.6 and 728.1 nm are calculated, and are found to be in good agreement with the experimental data. The developed model is used to obtain optimal operation conditions of high-frequency electrodeless helium lamps. Ionization kinetics and E-H mode transition in a noble gas, low-pressure pulsed ICP dischargeThis paper is declared a work of the US Government and is not subject to copyright protection in the United States. V I Demidov, C A DeJoseph Jr and A A Kudryavtsev 2004 Plasma Sources Sci. Technol. 13 600-603 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/008 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/008/psst4_4_008.pdf Under some conditions of power modulation, an rf ICP will exhibit a rapid transition between E and H modes following application of the rf power. It is shown that in noble gases this transition may be connected with the dynamics of the electron density and metastable density of the atoms, and competition between direct and stepwise ionization of the atoms by electron impact. A simple model allows us to demonstrate that after application of rf power the initial slow growth of electron density changes to a rapidly rising function. This rapid rise is consistent with observed E-H transitions that take place in these discharges. The model thus allows us to calculate the characteristic time for the transition beteween modes. A new small microwave plasma torch Robert Stonies, Susanne Schermer, Edgar Voges and Jose' A C Broekaert 2004 Plasma Sources Sci. Technol. 13 604-611 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/009 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/009/psst4_4_009.pdf The development of a new, very small coaxial plasma source based on the microwave plasma torch (MPT) is described. It generates a plasma jet up to 4 mm long and can be operated with a argon gas flow rate less than 70 ml per min at down to 2 W microwave power (2.45 GHz) at atmospheric pressure. It also works well with helium and does not show any wear during a test period of 30 h of operation with argon. It is, in particular, thought to be a source for the atomic spectroscopy of gaseous species. The excitation temperature is found to be ~4700 K for this device operating with helium and 17 W microwave power. A detection limit for an example application in which Cl is detected from HCCl3 is found to be below 66 ppb. For the first time, to our knowledge, microstrip circuits are used to match the small MPT to the generator's 50 &OHgr; impedance. The design considerations for the microstrip circuits are discussed and an approximated calculation for the layout is presented. With the introduced procedure it is possible to design even smaller MPTs for special applications. Optimization of plasma etch processes using evolutionary search methods with in situ diagnostics J Al-Kuzee, T Matsuura, A Goodyear, L Nolle, A A Hopgood, P D Picton and N St J Braithwaite 2004 Plasma Sources Sci. Technol. 13 612-622 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/010 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/010/psst4_4_010.pdf This paper presents several approaches that have been used to control, optimize and characterize a low pressure (10-300 mTorr) plasma processing system. Methods such as contour following and differential evolution have been used to find contours of DC bias, total ion flux, ion energy flux, quadrupole mass spectrum (QMS) intensity ratios and line intensity ratios of the optical emission spectrum (OES) in argon and nitrogen plasmas. A mapping for a 4 x 4 multi-dimensional parameter space is also presented, in which the relationship between four control parameters (power, pressure, mass flow rates of two supplied gases) and four measurement outputs (DC bias, ion flux, QMS ratios and OES line intensity ratios) is determined in a plasma etching process. The use of these methods significantly reduces the time needed to re-configure the processing system and will benefit transfer of processes between different systems. A similar approach has also been used to find quickly an optimum condition for directional etching of a silicon wafer. Analysis of two-dimensional microdischarge distribution in dielectric-barrier discharges A Chirokov, A Gutsol, A Fridman, K D Sieber, J M Grace and K S Robinson 2004 Plasma Sources Sci. Technol. 13 623-635 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/011 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/011/psst4_4_011.pdf The two-dimensional spatial distribution of microdischarges in atmospheric pressure dielectric-barrier discharges (DBDs) in air was studied. Experimental images of DBDs (Lichtenberg figures) were obtained using photostimulable phosphors. The storage phosphor imaging method takes advantage of the linear response of the phosphor for characterization of microdischarge intensity and position. A microdischarge interaction model in DBDs is proposed and a Monte Carlo simulation of microdischarge interactions in the discharge is presented. Comparison of modelled and experimental images indicates interactions and short-range structuring of microdischarge channels. Electrical measurements in dusty plasmas as a detection method for the early phase of particle formation J-C Schauer, S Hong and J Winter 2004 Plasma Sources Sci. Technol. 13 636-645 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/012 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/012/psst4_4_012.pdf The formation of dust particles in reactive plasmas affects the electrical characteristics of the plasma. We have investigated the time resolved development of the electrical characteristics due to particle formation, i.e. the voltage and current at the surface of the powered electrode in capacitively coupled Ar-C2H2 and Ar-CH4 dusty plasmas. The stray impedances of the reaction chamber were characterized in order to trace the change in plasma impedance during particle formation. Using a simple equivalent circuit model the plasma impedance is represented as a series combination of a resistor and a capacitor. It was observed that the plasma impedance becomes more resistive as the particles grow. In the case of Ar-CH4 plasmas three different characteristic steps were observed, which might be related to the nucleation, coagulation and agglomeration phase of particle formation. Compared with other dust particle detection methods this technique is easy to implement, non-intrusive and very sensitive even for the smallest particles. Experimental electron energy distribution functions in argon, nitrogen and oxygen high-density and low-pressure reflex and microwave plasma sources Emil I Toader 2004 Plasma Sources Sci. Technol. 13 646-653 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/013 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/013/psst4_4_013.pdf The Langmuir probe method and Druyvesteyn procedure coupled with suitable software are used to measure the electron energy distribution functions (EEDFs) in atomic and molecular gases. Two complementary high-density and low-temperature plasma sources are used, i.e. a low-pressure direct current reflex discharge plasma source and a low-pressure electron cyclotron resonance (ECR) microwave discharge plasma source. The electron energy is restrained within the range 0-15 eV. The electron density and electron temperature are obtained directly from the EEDF data. The experiment is run within the pressure range 1.0-10-2 Pa with a gas flow rate of 1.0-3.0 sccm. The discharge mechanism and the kinetic and dynamic processes in reflex discharge and ECR plasmas play a key role in determining the shape of the EEDFs. The EEDF is bi-Maxwellian in the reflex discharge plasma and is Maxwellian in the ECR plasma, and is independent of the gas used. The distinctive feature of all the EEPDs in nitrogen and oxygen reflex plasmas and in the nitrogen ECR plasma is the presence of a complex structure independent of the plasma source, discharge mode, and/or radial position. The complex dip/shoulder structures obtained for the EEDFs in molecular plasmas are discussed by considering different inelastic interaction channels between electrons and heavy particles. Measurement of the magnetic field change in a pulsed high current magnetron discharge Johan Bohlmark, Ulf Helmersson, Michael VanZeeland, I Axna"s, Jones Alami and Nils Brenning 2004 Plasma Sources Sci. Technol. 13 654-661 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/014 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/014/psst4_4_014.pdf In this paper we present a study of how the magnetic field of a circular planar magnetron is affected when it is exposed to a pulsed high current discharge. Spatially resolved magnetic field measurements are presented and the magnetic disturbance is quantified for different process parameters. The magnetic field is severely deformed by the discharge and we record changes of several millitesla, depending on the spatial location of the measurement. The shape of the deformation reveals the presence of azimuthally drifting electrons close to the target surface. Time resolved measurements show a transition between two types of magnetic perturbations. There is an early stage that is in phase with the axial discharge current and a late stage that is not in phase with the discharge current. The later part of the magnetic field deformation is seen as a travelling magnetic wave. We explain the magnetic perturbations by a combination of E x B drifting electrons and currents driven by plasma pressure gradients and the shape of the magnetic field. A plasma pressure wave is also recorded by a single tip Langmuir probe and the velocity (~103 m s-1) of the expanding plasma agrees well with the observed velocity of the magnetic wave. We note that the axial (discharge) current density is much too high compared to the azimuthal current density to be explained by classical collision terms, and an anomalous charge transport mechanism is required. Electron temperature control with a small mesh number grid in inductively coupled plasmas K H Bai, C K Choi and H Y Chang 2004 Plasma Sources Sci. Technol. 13 662-667 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/015 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/015/psst4_4_015.pdf The electron temperature is controlled to 0.6 eV with a small mesh number (the number of the grid wire per 2.54 cm) grid in Ar 1.3 Pa inductively coupled plasma. The key factor in determining the electron temperature is different for different mesh numbers: when the mesh number is large, the key factor is the potential difference between the plasma potential in region II and the grid bias voltage, but when the mesh number is small the plasma potential difference between regions I and II is the key factor. Furthermore, in such cases, the electron density in region II increases with discharge pressure, which is the opposite of what occurs when the mesh number is large. The measured electron energy probability functions show a bump structure for some conditions. This could be explained by the low electron-electron or electron-neutral collision frequencies due to the low electron density and operating pressure. Simultaneous measurement of N and O densities in plasma afterglow by means of NO titration P Vasina, V Kudrle, A Ta'lsky', P Botos, M Mra'zkova' and M Mesko 2004 Plasma Sources Sci. Technol. 13 668-674 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/016 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/016/psst4_4_016.pdf In this work we describe a method based on NO titration that permits us to measure at the same time the absolute concentrations of N and O atoms in the gas phase. This method is suitable for low concentrations of oxygen atoms. We also discuss the validity of the titration method, especially the influence of the reaction time. It was used to study the influence of O2 admixture on the degree of dissociation of nitrogen in the afterglow. The results of the NO titration technique were compared with those obtained by means of electron paramagnetic resonance and with the relative values determined from emission of {\rm N}_{2}(B^{3}\Pi_{g}\hbox{--}A\,^3\Sigma^{+}_{\mathrm u}) . On the time of lasing onset and the end-effect of a soft x-ray laser device using a capillary z-pinch discharge Yasushi Hayashi, Nobuhiro Sakamoto, Yongpeng Zhao, Yuanli Cheng, Priya Chalise, Masato Watanabe, Akitoshi Okino, Kazuhiko Horioka and Eiki Hotta 2004 Plasma Sources Sci. Technol. 13 675-679 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/017 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/017/psst4_4_017.pdf We have measured the time of lasing onset of a capillary z-pinch discharge used for Ne-like Ar soft x-ray laser generation. It was found that for a relatively long plasma, the relationship between the time of lasing onset and the filling pressure of the Ar gas agrees, in trend, with that predicted by simulation. An interesting result was observed: the time of lasing onset becomes delayed when the length of the capillary becomes shorter, which is considered to be caused by an end-effect of the capillary on the pinching process. This also implies that a relatively long capillary is favourable for obtaining a plasma column of uniformity, and thus for reducing the relative absorption of laser power. Similarity analysis for the high-pressure inductively coupled plasma source D Vanden-Abeele and G Degrez 2004 Plasma Sources Sci. Technol. 13 680-690 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/018 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/018/psst4_4_018.pdf It is well known that the optimal operating parameters of an inductively coupled plasma (ICP) torch strongly depend upon its dimensions. To understand this relationship better, we derive a dimensionless form of the equations governing the behaviour of high-pressure ICPs. The requirement of similarity then naturally leads to expressions for the operating parameters as a function of the plasma radius. In addition to the well-known scaling law for frequency, surprising results appear for the dependence of the mass flow rate, dissipated power and operating pressure upon the plasma radius. While the obtained laws do not appear to be in good agreement with empirical results in the literature, their correctness is supported by detailed numerical calculations of ICP sources of varying diameters. The approximations of local thermodynamic equilibrium and negligible radiative losses restrict the validity of our results and can be responsible for the disagreement with empirical data. The derived scaling laws are useful for the design of new plasma torches and may provide explanations for the unsteadiness observed in certain existing ICP sources. Determination of gas temperature and thermometric species in inductively coupled plasmas by emission and diode laser absorption Alexander A Bol'shakov, Brett A Cruden and Surendra P Sharma 2004 Plasma Sources Sci. Technol. 13 691-700 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/019 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/019/psst4_4_019.pdf A vertical cavity surface-emitting laser diode (VCSEL) was used as a spectrally tunable emission source for measurements of the radial-integrated gas temperature inside an inductively coupled plasma reactor. The data were obtained by profiling the Doppler-broadened absorption of metastable Ar atoms at 763.51 nm in argon and argon/nitrogen plasmas (3%, 45%, and 90% N2 in Ar) at pressures of 0.5-70 Pa and inductive powers of 100 and 300 W. The results were compared to the rotational temperature derived from the N2 emission at the (0,0) vibrational transition of the C 3&Pgr;u-B 3&Pgr; g system. The differences in integrated rotational and Doppler temperatures were attributed to non-uniform spatial distributions of both temperature and thermometric species (Ar* and {\rm N}_{2}^* ) that varied depending on the conditions. A two-dimensional, three-temperature fluid plasma simulation was employed to explain these differences. This work should facilitate further development of a miniature sensor for non-intrusive acquisition of data (temperature and densities of multiple plasma species) during micro- and nano-fabrication plasma processing, thus enabling diagnostic-assisted continuous optimization and advanced control over the processes. Such sensors would also enable us to track the origins and pathways of damaging contaminants, thereby providing real-time feedback for adjustment of processes. Our work serves as an example of how two line-of-sight integrated temperatures derived from different thermometric species make it possible to characterize the radial non-uniformity of the plasma. Characteristics of an inductively coupled plasma source using a parallel resonance antenna D S Lee, Y K Lee and H Y Chang 2004 Plasma Sources Sci. Technol. 13 701-706 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/020 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/020/psst4_4_020.pdf We report experimental results from a new inductively coupled plasma (ICP) source for next generation plasma processing. The new source, which we have called a parallel resonance antenna, is designed to reduce problems caused by a large antenna inductance and to improve the plasma density uniformity for large area processing. The key techniques of this new source are reduction of the inductance of the antenna system in parallel connection and induction of LC-resonance with external capacitance variation. The parallel connection of the coils reduces the antenna inductance and the low inductance decreases the antenna voltage. In addition, it allows the antenna size to be easily scaled up to a 300 mm process. An external variable capacitor is connected in series to an outer coil to obtain good plasma uniformity. Because the current distribution in each coil is adjusted by varying the external capacitance, the radial profile of the plasma density can be controlled. The LC-resonance effect is elucidated by observing the reduction in the antenna voltage and variation in the current in the outer coil. We can control the radial plasma density with 3% uniformity by only varying the external capacitance with various discharge powers and pressures. The plasma parameters measured by the rf-compensated Langmuir probe show properties similar to those of general ICPs. These results are consistent with previous modelling work. Conversion of methane to methanol in an ac dielectric barrier discharge F M Aghamir, N S Matin, A H Jalili, M H Esfarayeni, M A Khodagholi and R Ahmadi 2004 Plasma Sources Sci. Technol. 13 707-711 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/021 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/021/psst4_4_021.pdf A dielectric barrier discharge (DBD) has been used to investigate the conversion of methane to methanol and higher hydrocarbons in ac non-equilibrium plasmas. Experiments were carried out at atmospheric pressure and ambient temperature. A non-equilibrium plasma was generated in a DBD reactor by applying a high voltage to the reactor electrodes. Activation of methane molecules led to the production of C2 hydrocarbons and methanol. The effect of the applied voltage, residence time and feed mixture such as helium and oxygen on the methane conversion and product selectivity was studied. Helium appears to have no effect on the conversion and selectivity at our applied voltages. The methane conversion increases significantly on introduction of oxygen in the feed stream. Inclusion of oxygen leads to the formation of methanol. Our results show that production of methanol is initiated around an applied voltage of 12 kV and the conversion of methane increases with increasing voltage and residence time, while the product selectivity is independent of the applied voltage. Magnetoplasmadynamic (MPD) accelerator assisted synthesis of diamondThis work was performed at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. J J Blandino and D G Goodwin 2004 Plasma Sources Sci. Technol. 13 712-718 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/022 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/022/psst4_4_022.pdf The use of a magnetoplasmadynamic (MPD) accelerator for diamond synthesis is investigated. The acceleration process in an MPD device is reviewed and results presented for a test in which a low power (15 kW) MPD accelerator was used as the gas activation source for diamond deposition. A hydrogen-argon mixture was used in the discharge with externally injected methane as the carbon precursor. Results, including SEM images, Raman and x-ray diffraction spectra are presented for a 3.3 um thick film deposited over a 100 min period. The Raman spectra include a broad background and shift in the diamond peak, indicative of contamination and stresses in the deposited film. Potential scaling benefits of the MPD accelerator as well as some of the drawbacks associated with methane injection and sample contamination underscored by the experiments are identified and discussed. Comparison of kinetic calculation techniques for the analysis of electron swarm transport at low to moderate E/N values N R Pinha~o, Z Donko', D Loffhagen, M J Pinheiro and E A Richley 2004 Plasma Sources Sci. Technol. 13 719-728 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/023 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/023/psst4_4_023.pdf We present a comparison between results for the electron velocity distribution function (evdf), and transport and rate coefficients of an electron swarm obtained under different assumptions for the space and angular dependence of the evdf. Several solution techniques for the Boltzmann equation as well as Monte Carlo simulations have been tested. The comparison is made in neon at a constant and homogeneous reduced electric field in the range 10 Td ≤ E/N ≤ 500 Td taking into account the production of electrons in ionizing collisions. The results show that to obtain an accurate description of the electron swarm we need to take into account the variation in space of the electron density in the representation of the evdf. In what regards the angular dependence on velocity we discuss criteria to estimate the importance of the anisotropy of the evdf for any gas. Depending on the solution technique and on the E/N value, we find good to excellent agreement between the Boltzmann results obtained with a half-range method, a multi-term Legendre expansion, an elliptic approximation and the Monte Carlo results. The accuracy of the transport and rate coefficients obtained with each approach is evaluated and it is found that although the two-term velocity expansion is not sufficiently accurate to be used for cross section fitting, the corresponding rate and transport coefficients can generally be used in discharge modelling. Electron beam induced fluorescence measurements of the degree of hydrogen dissociation in hydrogen plasmas C Smit, G J H Brussaard, E C M de Beer, D C Schram and M C M van de Sanden 2004 Plasma Sources Sci. Technol. 13 729-738 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/024 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/024/psst4_4_024.pdf The degree of dissociation of hydrogen in a hydrogen plasma has been measured using electron beam induced fluorescence. A 20 kV, 1 mA electron beam excites both the ground state H atom and H2 molecule into atomic hydrogen in an excited state. From the resulting fluorescence the degree of dissociation of hydrogen is determined. In addition, the absolute atomic hydrogen density can be determined if the gas temperature and pressure are known without any additional calibration. To check the consistency of the method the fluorescence from the first four Balmer transitions is measured. It is demonstrated that this technique can be applied in hydrogen and argon-hydrogen plasmas with a pressure of up to 1 mbar and 0.2 mbar, respectively. Study of the x-ray emission scaling law in a low energy plasma focus M Sharif, S Hussain, M Zakaullah and A Waheed 2004 Plasma Sources Sci. Technol. 13 B7-B13 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/B01 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/B01/psst4_4_B01.pdf The performance of a low energy (0.6-1.8 kJ) Mather-type plasma focus (PF) device as a Cu-K&agr; x-ray source is examined. The Cu-K&agr; and total x-ray emissions are measured for argon and hydrogen filling. It is found that Cu-K&agr; emission varies as YK [J] ~ [E(kJ)]3.5-4.5 ~ [I(100 kA)]3.5-4.5, whereas the total x-ray emission is found to follow Ytot [J] ~ [E( kJ)]4.5-5.5 ~ [I(100 kA)]4.5-5.5. At optimum conditions, the system with discharge energy of 1.8 kJ is found to generate x-rays with 1.44 ± 0.07% efficiency. About 32% of the emission constitutes the Cu-K&agr; line radiation. With a cut at the anode tip, the x-ray flux in the side-on direction is increased three times. The modified geometry may help in using the PF as a radiation source for x-ray diffraction. Message from the Editor-in-Chief Noah Hershkowitz 2004 Plasma Sources Sci. Technol. 13 Abstract: http://www.iop.org/EJ/abstract/-alert=15022/0963-0252/13/4/E01 Full text: http://www.iop.org/EJ/article/-alert=15022/0963-0252/13/4/E01/psst4_4_e01.pdf 2004 has been a successful year for PSST---we have received an increase in the number of articles submitted to the journal, and the growing popularity of the journal is also shown by significant increases in the electronic access and download figures. We would like to thank all our authors and referees for their continued support of the journal, with a special thank-you to the referees for all their time spent reviewing articles on our behalf; their advice and help are always greatly appreciated. Our aims for 2005 include introducing new software to enable both myself and the journal's publishing team to continue to reduce processing times, continuing to work to ensure that the scope and coverage of the journal meets the needs of the community, and maintaining the high quality standards of the journal. We would also like to work towards increasing the number of review articles in the journal. If you consider that a review in your topic of specialization would be timely, please get in touch! We look forward to working with you to achieve these aims and I would like to wish you all success in 2005. Author index with titles 2004 Plasma Sources Sci. 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