Volume 69, Issue 5, May 1998
Index of content:
69(1998); http://dx.doi.org/10.1063/1.1148920View Description Hide Description
Kapton foils can be used as a simple ion beam monitor. These foils act as a self-developing medium and quantitative information about the distribution of the striking beam can be obtained easily. The “burn” pattern on the film due to irradiation by the ion beam is analyzed to determine the beam distribution, here the beam power density distribution. Given the beam voltage this information can be translated to the ion current density distribution. The linearity of response of the Kapton foil with beam current density is shown. The threshold for response of the Kapton foil seems quite good; a clear response is observed with a foil of for beam current density of about at 88 kV.
Application of one-dimensional Wentzel–Kramers–Brillouin approximation in microwave reflectometry of plasma density profiles69(1998); http://dx.doi.org/10.1063/1.1148921View Description Hide Description
The accuracy of the one-dimensional (1D) Wentzel–Kramers–Brillouin (WKB) profile reconstruction algorithm currently used in microwavereflectometry of fusion plasmas is investigated. Two experimental conditions beyond the applicability of the 1D WKB approximation are discussed: a plasma with steep density gradients and the case of strong divergence of the microwave beam. It is demonstrated, that the 1D procedure of profile reconstruction provides a fairly accurate estimate for both cases, despite the influence of abrupt density changes and multidimensional effects.
69(1998); http://dx.doi.org/10.1063/1.1148922View Description Hide Description
A simple method is described for forming reliable spot welded cruciform hot junctions with thermocouple wires of diameter 12 μm for use in ac calorimeters. By following this method the mounting of small, thin samples onto thermocouples for measurements of thermal conductivity, diffusivity, and specific heat is facilitated, producing a low thermal contact resistance between sample and thermocouple junction.