Hollow Anode Research Articles

Investigation of rotating d.c. discharge for diamond deposition

A modification of the anomalous d.c. discharge, which uses plasma rotation induced by an external magnetic field is suggested for the deposition of diamond. Application of the magnetic field results in a better stability of the discharge and in an increase in the deposition rate. Raman analysis shows that diamond can be deposited from gas mixtures containing a high volume percentage of methane. The plasma produced in the d.c. discharge between two parallel electrodes was also expanded through a hollow anode, forming a d.c. jet. This configuration yielded a higher diamond deposition rate.

Characterization of a helium discharge for hollow anode furnace atomization non-thermal excitation spectrometry

A discharge in He has been characterized for hollow anode furnace atomization non-thermal excitation spectrometry (HA-FANES). The small surface area of the cathode and high current densities make it possible to stabilize He discharges up to 1200 hPa using a d.c. power supply operating in the constant current mode. Current—voltage characteristics were determined for pressures up to 800 hPa. Characterization at higher pressures was not possible owing to limitations of the power supply. The release of thermionic electrons from the cathode surface at temperatures in excess of 1750 K caused a dramatic decrease in the discharge potential during the atomization cycle. Increased ohmic heating of the cathode with increased currents caused a time shift in the release of thermionic electrons. Excitation temperatures, obtained from Boltzmann plots of five He I lines, decreased slightly as a function of increasing pressure and increased as a function of increasing current. Dramatic decreases in the discharge potential were observed for high concentrations (250 mg ml–1) of NaCl. The potential decreases were too short-lived to permit the accurate measurement of excitation temperatures. Integrated analytical signals increased linearly with increasing pressure.

Broad beam electron sources with plasma cathodes

Plasma cathodes are used in large-cross-section electron beam sources. The cathode plasma is created by a low-pressure arc discharge with a hollow anode. The physical processes in the discharge anode region associated with electron emission from the plasma and the formation of a stable plasma boundary as well as the methods used for reaching a more uniform electron current density distribution are discussed. The electron source designs allowing one to produce electron beams with currents of 10−10 3 A, durations of 10 −5–10 −3s, current densities of 0.1−1.0 A/cm 2, and cross sections of ∼10 4cm 2 are described.

Magnetic field enhanced performance of a copper hollow anode cathode laser

The output beam power and small-signal unsaturated gain on the He-Cu 780.8 nm transition in a hollow slotted-anode cathode laser are increased significantly by the application of a longitudinal magnetic field and each shows a marked dependence on the field in the range 10 to 40 mT. The laser output power and the gain increase with the discharge current, while the optimum magnetic field (∼22 mT) results in a further significant increase both in output power and gain. These effects have their origin in the transverse deflection of the beam electrons by the magnetic field.

Industrial sputter coating of large stainless steel sheets

A complete production line was designed, and built for the industrial coating of large stainless steel sheets. On a production scale sheets can be coated in gold, bronze, blue and black colours with a productivity of 60 000 m 2 year −1. The complete processing of the steel sheets consists of precleaning, the drying process, preheating, sputter etching and sputter coating. For the sputter etching an arrangement with a hollow anode is used to realize high etching rates and uniformity under magnetron-like sputter etch conditions. The coating procedure is carried out using magnetron cathodes 1.6 m long. For gold-coloured coatings a titanium target and for all other colours a Ti-Al (50:50) target are used. The coated products show excellent colour uniformity. A high colour repeatability was achieved by using fully automatic control of the production line. The results of salt spray tests show high corrosion resistance of the coated stainless steel. The formability of the coated product is similar to that of the uncoated sheet, allowing a wide range of use for the coated products.

Gain measurements at 780.8 nm in a copper hollow anode cathode laser

The results of a parametric study of a copper hollow anode cathode laser operating on the He-Cu+ infrared lines are reported. The discharge voltage, the small-signal unsaturated gain on the 780.8-nm transition, and the ground-state copper atom concentration each exhibit a universal dependence on the ratio J/p of the discharge current density to the total pressure of the helium-argon buffer gas mixture. The laser output power dependencies (780.8 and 782.5 nm) on J/p, while not resulting in universal curves, have common threshold values of J/p. The threshold value of J/p for the 782.5-nm line is approximately twice that for the 780.8-nm line.

High power induction linac for FEL applications at CESTA

The purpose of the LELIA program developed at CESTA is to acquire the knowledge on induction accelerator technology for high peak power FEL applications. In a first step we study basic technology: (1) A high voltage pulse generator (150 kV, 60 ns, 2 ω) has been designed to drive the induction injector and the accelerating cells. It is able to work at high repetition rate (typically 1 kHz) by the use of magnetic switches. A flat top of 130 kV with ΔV V = ±0.8% has been obtained for about 50 ns. (2) An induction cell prototype has been built in order to check technological choices (vacuum, mechanics, magnetic guiding, voltage supply, etc.) for injector and accelerating modules. (3) The injector geometry is being studied using Euphrosyne (a classical intense relativistic electron beam device) which consists of a concave thermo-ionic oxide cathode, an intermediate electrode and a hollow anode with a magnetic guiding channel. This diode delivers an electron beam between 1 and 3 MV, about 1 kA and a flat top pulse during 20 ns. We will carry on the injector studies with our induction injector LELIA I (1.5 MV, 1.5 kA, 1 kHz) which will be available at the end of 1990. An accelerating module is also being designed, taking into account guiding and stability problems. All these points are described in more detail in a poster paper [J. Bardy et al., these Proceedings (12th Int. FEL Conf., Paris, France, 1990) Nucl. Instr. and Meth. A304 (1991) 311]. The main goal is to build a 10 MV, 1–3 kA, 1 kHz induction accelerator and to have it running at CESTA in 1993. On the other hand, we want to use the electron beam provided by Euphrosyne then in LELIA I to perform FEL experiments at 35 GHz using a bifilar helical wiggler [H. Bottollier-Curtet et al., these Proceedings, p. 197].

PSI-1 Direct Current Arc Facility for Studying Plasma/Wall Interaction

The PSI-1 facility for studying plasma/wall interaction is described. It uses a direct current arc as a plasma generator together with a hollow anode. The plasma expands through the anode into the target chamber and is confined by an axial magnetic field. The design values for the plasma parameters near the target are n{sub e} {le} 10{sup 20} m{sup {minus}3}, T{sub e} {le} 50 eV, {Gamma} {le} 6 {times} 10{sup 23} m{sup {minus}2} {center dot} s{sup {minus}1}, and q {le} 3.5 MW/m{sup 2}.

New glow discharge lamp with Co–axially–arranged dual hollow anodes

AbstractA glow discharge lamp consisting of two hollow anodes set co‐a‐axially has been developed to attempt to improve the resolution at interfaces in depth profiling. The structure and the operating conditions of the lamp are described. In addition, an in‐depth analysis of Fe/Zn layers on steel plates has been attempted with this glow lamp. Compared to a conventional glow lamp, the measurements can be performed with improved depth resolution.

Sources of multiply charged ions for heavy-ion fusion

We report experiments on methods to raise the proportion of multiply charged ions for high-flux-ion extraction from vacuum-arc plasma sources. Beams of doubly and triply charged ions have application to induction linacs for heavy-ion fusion. We confirmed that the arc cathode material strongly influenced the ion-charge-state proportions. We believe the electrostatic potential of the plasma streaming from the arc played a major role in the transport of multiply charged ions. Reduction of electron losses from the plasma increased the observed fluxes of doubly charged ions. We inhibited electron loss and enhanced the flux of multiply charge ions by applying a bias voltage to the plasma source and by adding an axial magnetic field. We also investigated a method to increase the proportion of multiply charged ions by time-of-flight separation following rapid switching of the expanding plasma. We developed a new arc-source geometry for the experiments. The source had a hollow anode and an axial magnetic field to anchor the position of emission spots on the cathode.

Furnace atomic non-thermal excitation spectrometry with the furnace as a hollow anode

Furnace atomic non-thermal excitation spectrometry with the furnace as the hollow anode (HA-FANES) was characterised for the determination of Cd and Cu. Operating in the abnormal glow discharge region, the current was limited by the current density at the cathode. Higher currents were attained with a larger diameter cathode and at higher pressures. The emission signals were dependent on the current density. More intense signals were observed when viewing the top and left of the discharge. This positional dependence of the signal strength was much more pronounced for Cu than for Cd. Peak areas and signal to noise ratios increased linearly with the discharge pressure to a maximum of 25.3 kPa. Emission intensities were constant as a function of the discharge current above a threshold of 20 mA for Cd and 50 mA for Cu. Both Cd and Cu gave the largest peak areas at the lowest atomisation temperature (1390 °C). The peak areas decreased roughly in proportion to the increased diffusion coefficients at higher temperatures. The detection limits for HA-FANES (0.8 and 1.5 pg for Cd and Cu, respectively) are comparable to those for conventional FANES with the furnace as a hollow cathode and graphite furnace atomic absorption spectrometry.

New generation of electron sources

A new type of an electron beam source, based on a hollow anode discharge - hollow anode electron source is presented. The main characteristics of this compact cold cathode electron source are: high efficiency with low gas flow rates (without the need for differential pumping), good power efficiency, instant beam upon switch-on (no warm-up period) and long life-time.

Hollow anode ion source

A new type of cold cathode ion source, based on a hollow anode discharge in a magnetic field, is presented. The influence of the magnetic field is very strong: It is possible to considerably change the ion current by some slight changes of the magnetic field.

Absorption and emission of copper radiation in a low and a high voltage internal anode hollow cathode discharge

The internal anode hollow cathode discharge (IAHCD) achieves positive current voltage behavior in a hollow cathode related construction by using the obstructed discharge phenomenon. A stronger current-voltage dependence is obtained by increasing the degree of obstruction or decreasing the fill gas pressure. Of the five noble gases He, Ne, Ar, Kr and Xe, Ne provides the highest intensity for the Cu I 324.7 nm emission in both a low and high voltage version of the IAHCD. The other four noble gases have increased Cu I 324.7 nm emission intensity relative to neon in the high voltage discharge. Atomic absorption measurements through the cathode bore indicate that at the pressure yielding the highest Cu I 324,7 nm emission for each gas and the same current for all investigated gases, the absorbance of the discharge increases with the atomic weight of the fill gas. The intensity of the Cu II 224.3 and 224.7 nm lines compared to the Cu I 324.7 nm line are greatest for Ar, Ne and He gases whose metastable or ion energies are greater or equal to the excitation energy of the ion lines. The ionic-atomic line intensity ratio is higher in the high voltage than the low voltage IAHCD.

High-power, high-current pseudospark switches

A low-pressure gas switch with a hollow cathode and hollow anode (pseudospark geometry) that switches an order-of-magnitude-higher current than commercially available thyratrons, over 100 kA, is reported. The switch is not a spark gap and does not form arcs at the electrodes. The cold cathode produces much higher emission than hot cathodes presently in use. The switch significantly extends the performance capabilities of switching technology. >

Hollow-anode discharge with axial-magnetic field as an electron beam source

The hollow-anode discharge, with a hollow-anode aperture 0.5-mm i.d., on which the axial-magnetic field has been applied, is studied. From the hollow anode, outside the discharge tube, an intensive, narrow, and well-focused beam of fast electrons, more than 30 cm long, is obtained.

Spot deposition by focusing in Penning discharge sputtering

In order to obtain an efficient spot-sized deposition in Penning discharge sputtering, an electrode configuration for focusing of sputtered atoms has been designed and evaluated. In the apparatus designed, a conical beam of sputtered atoms is produced by a combination of a concave cathode, a planar cathode with a ring-shaped slit, and a hollow conical frustum anode between the two cathodes. By adjusting the distance of the electrodes a sharp focus is obtained on a substrate which lies behind the planar cathode. The focusing position can be controlled easily. When a circular disk gold film is deposited on the glass substrate, its diameter became smaller in inverse proportion to the distance between the substrate and planar cathode. With an input power of 4.5 W the deposition rate of the gold film is found to be 1 nm/s. It has been shown that the technique is very suitable for spot-sized film deposition on various substrates and for other applications such as dental-caries-preventing coating on extracted teeth and the coating for fine adjustment of resonant frequency of quartz-crystal wafers.

Some characteristics of the hollow anode glow

A new type of discharge realized in a diode consisting of a cathode and a special type of hollow anode is presented. The distinctive arrangement of dark and luminous regions between the cathode and anode with a characteristic hollow anode glow has been observed in the discharge. The optical spectrum strongly depends on the discharge current, and can be practically a spark or arc spectrum without any lines of anode or cathode material.

Pulsed soft x-ray source for laser-plasma diagnostic calibrations

Improvement in laser-plasma analysis makes it necessary to perform accurate calibration in the soft x-ray range. For this purpose we have modified a plasma focus device (27 kJ, 40 kV, and 400 kA) in order to enhance its soft x-ray emission: A hollow anode is used to prevent hard x-ray bremsstrahlung emission, and a lot of filling gases are chosen for their characteristic lines in the keV and sub-keV range (Ne, Ar, O, N, and CH4). These emissions have been absolutely measured with an x-ray bolometer and can be used directly or indirectly (in the fluorescent mode: Mg Kα at 1.254 keV) for x-ray calibration of various diagnostics. Some detector calibrations in pulsed regime (10 ns) are presented [films, solid state Si doped p-intrinsic-n (PIN) diodes, and charge-coupled devices (CCD) arrays.]

Optical characteristics of the hollow anode discharge

A new type of discharge realized in a diode consisting of a concave cathode and a special type of a hollow anode is presented. The concave cathode focuses electrons toward the hollow anode increasing the density of high-energy electrons and the efficiency of excitation and ionization in the hollow anode. The distinctive arrangement of dark and luminous regions between the cathode and anode has been observed in the discharge.