[en] Ion temperature and ion density, measured on October 25, 1977 during the flight of the geophyisical rocket ''Vertical-6'' by means of a group of five retarding potential analyzers looking into different directions of space, are compared with the International Reference Ionosphere 1978. The measurements were carried out in a geomagnetically quiet period to a height of 1500 km. The results show that both the ion temperature and the ion density are lower than the values predicted by the Reference Ionosphere, the difference is decreasing with increasing altitude. (author)

[en] Franklin's criticism (Franklin R N 2005 J. Phys. D: Appl. Phys. 38 2790) of our previous paper (Lampe M et al 2004 Plasma Sources Sci. Technol. 13 15-26) is based on three arguments: (1) that the limit of weak attachment is equivalent to low pressure, where our model is inappropriate; (2) that our use of the T_n → 0 limit is inappropriate; (3) that the negative ion density n_n is never singular at the centre. We point out that the weak attachment limit also corresponds (at high pressure) to low fraction of attaching gas, give conditions for the T_n→ 0 limit and discuss its consequences, and reiterate that we never argued that n_n(0) is infinite, but rather discussed a quite different type of singularity. This correspondence is now closed. (comment)

[en] In this paper, we report on studies of ion back bombardment in high average current dc and rf photoinjectors using a particle-in-cell/Monte Carlo method. Using H₂ ion as an example, we observed that the ion density and energy deposition on the photocathode in rf guns are order of magnitude lower than that in a dc gun. A higher rf frequency helps mitigate the ion back bombardment of the cathode in rf guns

[en] Calculations are reported on the expansion of a plasma into a vacuum, using a model of cold ions and Boltzmann electrons. The initial distribution of the ions at the edge of the plasma greatly affects the subsequent expansion. An initial abrupt drop of ion density leads to an expansion in which the abrupt drop is maintained. A finite slope, however, leads to the formation of a peak of ion density at the ion front. The subsequent behaviour may lead to wave breaking and the formation of multi-valued ion velocity distributions

[en] Design criteria are established for parallel plate, cylindrical and spherical air-filled ionization chambers that are used in radiation protection and other applications at rates from 0.01 to 1000 rad/h. The saturation curves and design parameters were determined from numerical solutions of the Thomson equations. Ion recombination and space charge effects were taken into account. The calculations were carried out to low percentages of saturation values and the current densities in such cases are found to behave in a Heaviside fashion at the plates. 5 refs

[en] Complete text of publication follows. The Planar Langmuir Probe, PLP, is a simple device generally consisting of a flat plate and guard ring placed on the ram side of a spacecraft such that it can intersect an uninterrupted flow of plasma. The probe area needs to be sufficiently large as to intersect a measurable current of ions when biased to a small negative potential, thus providing a relatively unambiguous measure of the ion density. When the PLP is swept in voltage through the plasma potential to a small positive potential, the current-voltage curve contains information about the electron temperature. Unlike the ion density which can be understood with a very simple model, the electron temperature must be interpreted using a more complex probe theory. One element of this theory is the response of the spacecraft potential to the changing potential of the non-negligible probe area. Failure to account for this interaction with the spacecraft potential can lead to error, and in general a bias towards an elevated electron temperature measurement. A theory for PLP electron temperature analysis will be presented and demonstrated using data from the CHAMP and C/NOFS satellites.

No abstract available

[en] An evaluation of the resonant fluorescence lidar technique as a method of measuring ion density during ionospheric barium releases is presented. We find that it is technically feasible to measure ion densities of 10⁴ cm^-3 at an altitude of 200 km with a time resolution of 0.5 s by using a ground-based laser and telescope. One application of the lidar technique would be observation of the critical ionization velocity effect at nighttime, without the complication of solar illumination. Criteria useful for evaluating the feasibility of other experiments are presented

No abstract available

[en] We present a systematic analytical approach to the trapping of a random walk by a finite density ρ of diffusing traps in arbitrary dimension d. We confirm the phenomenologically predicted e^-c_dtρt^d/2 time decay of the survival probability, and compute the dimension-dependent constant c_d to leading order within an ε=2-d expansion. (author)