Tungsten Insert Research Articles

Sensitivity enhancement in flameless atomization systems by use of a rigid tungsten collar

Sensitivity enhancement was achieved in a flameless atomization system by the insertion of a rigid tungsten “collar” 1 cm long and 0.5 mm thick. With such a collar the electrical and thermal properties of the furnace were essentially those of the original tube, and the existing power pack could be used without modification. A significant improvement in sensitivity was found for the majority of the sixteen elements studied. The system did not appear to suffer from the deformation problems associated with other systems of atomization from metal surfaces.

Photoinduced insertion of tungsten into methanol giving a tungsten-methyl derivative

Photolysis of [(η-C5H5)2WH2] in methanol gives the compounds [(η-C5H5)2WH(OMe)] and [(η-C5H5)2W(Me)(OMe)]; tungstenocene is proposed as an intermediate.

Analysis of self-cooling with infiltrated porous tungsten composites

With the advent of solid rocket engines utilizing high-energy aluminized propellants, the need for a noneroding nozzle-throat insert material has become acute. The wall temperatures attained at the throat are above even the maximum practical operating temperature of tungsten. However, by infiltrating a porous tungsten insert with a second material, which is subject to gasification by boiling, sublimation, or decomposition, it is possible to reduce the wall temperature to a tolerable value. This paper presents an analysis of the behavior of this so-called self-cooling process with infiltrated porous tungsten composites. A one-dimensional, finite thickness, flat plate model is specified. As gasification of the infiltrant proceeds, the gaseous/liquid or solid infiltrant interface recedes from the surface. The transient partial differential equations describing the model consist of the continuity, momentum, and energy relations. The effect of transpiration is included. The equations are solved by a numerical finite-difference solution that was programed for the IBM 7094. Typical results of the computer program are presented for a number of organic and inorganic infiltrants at typical high-pressure solid rocket nozzle-throat conditions to illustrate the effects of certain variables such as porosity and permeability of the porous tungsten.

X-Ray Apparatus

X-ray apparatus comprises a linear accelerator adapted to produce a beam of electrons at one of at least two selectable energies and being controlled to change the selected energy on a periodic basis, and a target to which the beam is directed thereby to produce a beam of x-radiation, the target being non-homogenous and being driven to move periodically in synchrony with the change of the selected energy. In this way, the target can move so that a different part is exposed to the electron beam when different pulses arrive. This enables the appropriate target material to be employed depending on the selected energy. The easiest form of periodic movement for the target is likely to be a rotational movement. The target can be immersed in a coolant fluid such as water. The linear accelerator can be of the type disclosed in WO2006/097697A1. The target preferably contains at least one exposed area of tungsten and/or at least one exposed area of carbon. These can be present as inhomogeneities in the material of which the target is composed, such as Carbon inserts in a Tungsten substrate (or vice versa), alternating segments of Carbon and Tungsten, Carbon and Tungsten inserts in a substrate of a third material, or arrangements involving other materials in addition to or instead of Carbon and/or Tungsten. Alternatively, the target can be of a homogenous material but have inhomogeneities in its thickness to cater for the different electron energies. The same concept can be applied to the filter. A detector can be provided, operating in synchrony with the energy variation. Such an x-ray apparatus can form a part of a radiotherapy apparatus, in which case the first selected energy can be a diagnostic energy and a second selected energy a therapeutic energy.