Abstract
We present a new compact electron gun based on the secondary emission through ionic bombardment principle. The driving parameters to develop such a gun are to obtain a quite small electron gun for an in-flight instrument performing Electron Beam Fluorescence measurements (EBF) on board of a reentry vehicle in the upper atmosphere. These measurements are useful to characterize the gas flow around the vehicle in terms of gas chemical composition, temperatures and velocity of the flow which usually presents thermo-chemical non-equilibrium. Such an instrument can also be employed to characterize the upper atmosphere if placed on another carrier like a balloon. In ground facilities, it appears as a more practical tool to characterize flows in wind tunnel studies or as an alternative to complex electron guns in industrial processes requiring an electron beam. We describe in this paper the gun which has been developed as well as its different features which have been characterized in the laboratory.
Highlights
The electron gun [1,2] is the primary component of many instruments employed in industrial and monitoring processes
As an example of application of the electron gun developed and described above, we present in this chapter its integration in a portable set up (Figure 5) aiming at performing electron beam fluorescence measurements in a static gas or in a flow
A new compact electron gun based on the secondary emission through ionic bombardment principle has been developed and integrated in a compact Electron Beam Fluorescence (EBF) assembly
Summary
The electron gun [1,2] is the primary component of many instruments employed in industrial and monitoring processes (welding, lithography, physical vapor deposition, irradiation/sterilization, microwave RF devices, electron microscope, etc.). Of the different types of electron guns (thermionic [6], field or cold emission [7], photocathode [8], plasma cathode [9], ionic bombardment [10,11], etc.) which exist, up to now it has been more practical to use thermionic guns In this most common gun, a heated cathode, built from massive tungsten or barium compound, emits low energy electrons which are accelerated and focused on a target. This kind of electron gun has several drawbacks for our intended in-flight application aiming at performing EBF measurements in the flow around an atmospheric reentry vehicle [12]. The system is quite sensitive to mechanical vibrations and diaphragms must be finely aligned to maintain a good beam quality
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