Electron Beam Scanner and Tungsten Target

The electron beam gun is a triode system operated with a small-size tungsten bolt cathode that is indirectly heated by electron bombardment. The Wehnelt electrode and the anode are shaped as a Rogowski transducer with a bell-shaped through-hole anode. This configuration has been chosen since it greatly reduces the dependence of focal spot size on electron beam current. The electron beam gun is operated at about 10−6 mbar gas pressure which is provided by a vacuum pump system, consisting of a scroll pre-pump and a turbo molecular main pump operated in series. The gas pressure in the beam column and the scanner head is somewhat higher in the range of 10−5 mbar.

How tungsten alloy CT target work with radiation

There are a few other notable approaches to fast tomography using x-rays or gamma rays. Since all of the above-mentioned approaches have numerous drawbacks and limitations regarding multiphase flow tomography, it was decided to design and build up a dedicated electron beam x-ray CT scanner for this application. The decision for an electron beam type CT and against a CT with stationary gated sources was due to several reasons. First, electron beam technology provides excellent versatility since the electron beam can be almost arbitrarily steered and shaped as needed. In the simplest case the electron beam will be swept along a semicircular target as in medical electron beam CT to generate projection data from a single plane. Moreover, subsequent sweeping on different circular paths on the target enables multi-slice CT as well as velocity measurement for two-phase flows. Additional beam optics can be provided to shape the focal spot as required and to adjust the beam focus when scanning at different axial positions (planes). Only one beam power supply is required. Another strong argument is the straightforward upgrade capability towards higher x-ray energy by introduction of high-energy electron beam generators or superconducting accelerators. Therefore, tungsten alloy material will have advantage in this case. 

Hamilton Vial Heating Shield

Made from Tungsten, this Hamilton Vial Heating Shield holds vials the size of 2.65cm in width. Fits within standard aluminum heat blocks. Easy button top and vial cut to lift vials 

Tungsten Alloy Medical CT Radiation

Scanned electron beam x-ray tomography is therefore a promising technology. Instead of mechanical rotation of scanner components, an electron beam is rapidly swept across an x-ray target using deflection coils. This technology was introduced in medicine more than two decades ago where it is mainly being used for cardiovascular diagnostics. Tungsten Alloy material is a good choice for medical CT and X-ray radiation protection.

Tungsten Alloy CT Target

Tungsten alloy X-ray CT target as an imaging modality is highly advantage due to its non-intrusiveness and its ability to penetrate opaque wall materials. One essential disadvantage of existing CT system is the requirement for rotating components. To measure multiphase flows in a velocity range of one meter per second or more, frame rates of at least 1000 frames per second are required to produce sharp phase distribution images with a spatial resolution of about one millimeter. To achieve this, mechanically rotating parts are to be avoided. 

Why Use Tungsten Alloy Shielding?

Similar to lead (Pb), tungsten possesses a high density (19.25g/cc) and plizbility in its metal state. Where tungsten gains the advantage is in the ease of blending into plastic for extrusion or molding into custom shapes and sizes. Tungsten also differd from lead in that it is virtually non-reactive and is non-toxic. This eases handling requirements and minimizes issues associated with lead use such as long-term disposal and the potential characterization as a mixed hazardous waste.
Tungsten alloy also exists in sufficient, available quantities as to be a viable shielding material and, while more expensive than lead or steel, the cost differences are not prohibitive.

Tungsten Alloy Shielding Better than Lead Protection?-1

The most effective utilization of tungsten, in one of its many forms, will be achieved after evaluation of several key factors (space/environmental sonsiferations, long-term storage/disposal, and potential for multiple applications) on the prospective application. Though not cost-beneficial for "ordinary" shielding applications, when properly selected as the shielding material, dose avoidance exceeding that of lead will be achieved.