Using an emissive probe the distribution of plasma potential V p in the bulk plasma of a dc Magnetron discharge has been determined for a range of argon pressures (0.26, 0.53 and 0.78 Pa) and cathode voltages (between −236 and −338 V). The results reveal a large axial variation in the space potential in the confined plasma, with V p ∼ 25 V over a distance of 5 cm, from plasma to sheath-edge. By combining the derived electric field with the modelled magnetic field, the distribution of single-particle drifts have been found, namely the electron E ∧ B, ∇B and curvature drift speeds. The predicted E ∧ B drift speeds (with values up to about 1.5 × 10 5 m s −1 ) are typically two to three times higher than the ∇B and curvature drifts. The Hall current channel is a broad region extending from above the 'racetrack' down to a position close to the axis, 6 cm from the cathode. The calculated total Hall current is approximately five times the discharge current. Using a simple model of the discharge, in which there is no spatial variation in electron current density J e , the gyrofrequency to collision frequency ratio averaged over the plasma bulk is found to be ω/ν ≈ 7.7 ± 4.2. In an extension to the model, a possible distribution of electron current throughout the plasma is considered, which allows the determination of ω/ν locally in the bulk. Using this method, the maximum value of ω/ν is found to be about 25, however both models indicate that cross-field electron transport occurs more rapidly than from a classical prediction.

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Organs transplanted from bacteremic donors do not transmit bacterial infection or result in poorer outcomes. Use of organs from these donors could help increase organ availability.

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The thickness x, of tungsten fuzz layers are measured for non-varying helium (He) plasma exposure conditions spanning four orders of ion fluence Φ 10 24 − 10 28 m-2 and flux Γ 10 19 − 10 23 m-2 s-1 , at 1000−1140 K under low energy He ion impact (50 − 80) eV. The data obtained are complemented by previously published data of similar growth conditions, and collectively analysed. The new analysis allows for the reconciliation of fast high flux growth with commonly observed slower growth at lower flux. It is demonstrated that the standing t 1/2 time dependence is a special case of a more general expression for determining the layer thickness, x(Φ) = (C(Φ − Φ 0)) 1 2 , that depends on Φ, an incubation fluence Φ 0 , and the growth constant C = 2.36 +1.54 −0.56 × 10-38 m 4 , which is temperature dependent. The incubation fluence, which must be exceeded before the observation on the onset of fuzz surface morphology is determined to be Φ 0 = 2.5 +1.5 −1.0 × 10 24 m −2. In fuzz growth-erosion regimes, characterized by an erosion constant fuzz , that is proportional to the sputter yield, an analytic solution for x(Φ) has been found, by solving the growth-erosion equilibria problem of prior work with the Lambert W function. Simple limit expressions follow from the solution for determining the equilibrium fluence and fuzz thickness; the predictions of such being in good agreement with previous fuzz growth-erosion equilibria results in the literature. * Values of P disch. pertain to maximum Γ. Values of Te and ne are conditions at mid-range Γ. † Calculated from ∼27 h (10 5 s) of exposure time.

The time-dependent plasma discharge ionization region model (IRM) has been under continuous development during the past seven years and used in several studies of the ionization region of high-power impulse magnetron sputtering (HiPIMS) discharges. In the present work, a complete description of the most recent version of the IRM is given, which includes improvements, such as allowing for returning of the working gas atoms from the target, a separate treatment of hot secondary electrons, addition of doubly charged metal ions, etc. To show the general applicability of the IRM, two different HiPIMS discharges are investigated. The first set concerns 400 µs long discharge pulses applied to an Al target in an Ar atmosphere at 1.8 Pa. The second set focuses on 100 µs long discharge pulses applied to a Ti target in an Ar atmosphere at 0.54 Pa, and explorers the effects when varying the magnetic field strength. The model results show that Al 2+-ions contribute negligibly to the production of secondary electrons, while Ti 2+-ions effectively contribute to the production of secondary electrons. Similarly, the model results show that for an argon discharge with Al target the contribution of Al +-ions to the discharge current is over 90 % at 800 V, while Al +-ions and Ar +-ions contribute roughly equally to the discharge current at 400 V. For high currents the discharge with Al target develops almost pure self-sputter recycling, while the discharge with Ti target exhibits close to a 50/50 combination of self-sputter recycling and working gas-recycling. For a Ti target, a self-sputter yield significantly below unity makes working gas-recycling necessary at high currents. In the discharge with Ti target the B-field was reduced in steps from the nominal value, which resulted in a corresponding stepwise increase in the discharge resistivity.

An electron-emitting probe has been used to measure the temporal evolution of the plasma potential V p along a line from target (Ti) to substrate above the racetrack in a high-power impulse magnetron sputtering discharge pulsed at 100 Hz. The 20 ns time-resolution of the probe allowed us to observe the highly dynamic nature of V p as the discharge voltage waveform develops, with large negative V p values (−210 V) and strong potential gradients existing in the magnetic trap region in the first 6 to 8 µs. After 55 to 60 µs, V p is elevated towards ground potential (0 V) and the bulk electric field collapses. Outside the magnetic trap, i.e. on the open field lines, V p reveals much smaller axial and temporal variations, similar to those observed in conventional pulsed dc magnetrons.At standard conditions (Ar pressure of 0.54 Pa and 650 W average power), the results show that for over 50% of the 100 µs plasma 'on-time' the spatial structure of V p provides a large potential barrier for the sputtered post-ionized species so impeding their transport and deposition at the substrate. This barrier is reduced markedly (by 50%) through a small reduction in the magnetic field strength (33% at the target) so increasing the deposition rate by a factor of 6 at a typical position of the substrate (z = 100 mm). The structure of V p is marginally sensitive to changes in pressure (over the range 0.54 to 1.08 Pa), but more strongly dependent on the applied power (over the range 650 to 950 W).

Using molecular beam mass spectroscopy, time-resolved measurements of the ionic species in the plasma plume of an atmospheric-pressure helium microplasma jet have been made for a range of excitation frequencies (5, 10 and 25 kHz) and source-instruments orifice distances (1, 7 and 11 mm). Ionic species can only be observed in the visible plasma plume, with the