Many Oxford Instruments X-ray tubes come equipped with beryllium X-ray windows for maximum flux transmission. Beryllium is a metal that has low density and low atomic mass, and hence very low absorption of X-rays, making beryllium the preferred choice for X-ray tube windows where low energy transmission is desired.
Oxford Instruments also produces glass window tubes, which are much more robust than their beryllium counterparts, with the trade-off of decreased low energy flux. Glass window tubes are suitable for a wide variety of applications, including imaging and some types of analysis, and should be considered in harsh, humid, or debris filled environments.
If your X-ray tube has a beryllium window, please keep the following considerations in mind:
The beryllium exit window is comprised of high purity vacuum tight beryllium metal, typically 127 microns thick.
Beryllium can be toxic if improperly handled. Avoid contact with the beryllium window.
The beryllium window is fragile and will be damaged by the slightest impact.
Beryllium is highly soluble in polar solvents. Examples of polar solvents include water (including humidity), alcohol and acids. It is essential that you do not expose the beryllium window to these agents for prolonged periods of time, as they will destroy the beryllium window and compromise the internal high vacuum of the X-ray tube, causing it to fail.
Unless absolutely necessary, all care should be taken to avoid any contact with the beryllium window, and tube installation should take into consideration keeping the window free of dust and debris. Should your beryllium exit window need to be cleaned, gently use a cotton swab and acetone (a non-polar solvent) and then immediately dry thoroughly with a cotton swab or soft dry air. Please note that damage to the beryllium window due to mishandling is not covered under your warranty.
Helium is often used in X-ray spectroscopy. Helium is a very small atom and has a high transmission rate through the beryllium window. At a minimum, only beryllium exit windows of at least 127 microns should be considered when operating an X-ray tube in the presence of a Helium environment.
If you operate an X-ray tube with a beryllium window in a vacuum environment, it is important to remember that the beryllium window is brittle and susceptible to damage caused by cycling between atmospheric pressure and vacuum environments typical for analytical analysis. Utilization of a secondary chamber is recommended to allow the X-ray tube to operate at sub-atmospheric pressures without cycling for each sample introduction.