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Discuss The Life Of X-ray Tubes From A Purely Technical Point Of View

Mar 16, 2018

According to the current situation, the general handheld EDXRF is several watts, the power of the X-ray tube of the desktop EDXRF instrument is several tens of watts, the WDXRF of the fixed track is generally several hundred watts, and the WDXRF of the scanning channel is several kilowatts. In addition, the service life of the X-ray tube has a great relationship with the use state of each user. For example, the closer to the design power of the light pipe, the shorter the service life is. Therefore, the service life of the X-ray tube is more complicated. In general (not very strict), the more powerful X-ray tubes, the shorter life expectancy.

The X-ray tube can be roughly divided into side window tubes, end window tubes, and the like. The structure of the target can be divided into a rotating target, a fixed target, a reflective target, a transmission target, and the like. In addition, the target material is based on Different applications are also different. There are many commonly used tungsten targets, molybdenum targets, silver targets, germanium targets, and so on. In addition, the X-ray tube can also be classified according to the power size. In particular, it is necessary to point out that at present, X-ray tubes have been fully mass-produced in China, and the quality can be guaranteed. Many foreign X-ray tubes are produced in China, especially small- and medium-power X-ray tubes.

The life of the X-ray tube is mainly determined by the following three aspects: filament, target, and vacuum. The working process of the X-ray tube is: the free electrons generated by the heating of the filament are accelerated in a high-voltage electric field and bombarded to the target material to generate characteristic X-rays and bremsstrahlung radiation of the target material. X-ray tube life is mainly determined by:

     1. Whether the X-ray tube vacuum can be maintained for a long time

     2、Whether the filament is easy to blow

     3. Whether the target can withstand long-term high-speed electron bombardment


In addition, it should be emphasized that the X-ray tube is a power device and its heat dissipation effect is also crucial to the service life of the X-ray tube. What I want to show is that for the life of the X-ray tube, as long as we understand its structure, principle, and failure process, we can make a sensible judgment on this issue, not just listen to the instrument manufacturer. One-sided promotion.

The failure of the X-ray tube has three main aspects: filament, target, and vacuum. Because the vacuum seal of the X-ray tube is quartz glass, the vacuum can be maintained for a long time. The important issues are the quality of the sealing material (quartz glass), the blowing process, and the joint sealing between the glass and metal parts. Process, and many other factors, another important point is the heat sealing performance of the entire component (since the X-ray tube is a power component, it is very high temperature at work), especially in the case of alternating hot and cold. When the X-ray tube is assembled into the instrument, an X-ray tube cooling jacket is also added. On the one hand, a cooling medium is added inside the cooling jacket (an external circulation is also used for high power) to dissipate heat. The role of protection will generally use metal materials. So the X-ray tube we see in the instrument is not the naked tube of the X-ray tube but the cooling jacket part.

The issue of target and filament is relatively simple, and the main requirement is that the purity of the material is high and the amount of the material must be sufficient (a joke). Because both the filament and the target are being consumed while the X-ray tube is in operation.

In addition, the use of XRF instruments and the use of the environment will also affect the service life of the X-ray tube. Therefore, when using XRF instruments, we must pay special attention to the following points:

1. When opening and closing the X-ray tube system, gradually increase and gradually reduce the tube flow and tube pressure of the X-ray tube, and do not suddenly increase or suddenly shut off the X-ray tube in the state of high tube flow and tube pressure. If there is an external circulation cooling system, do not turn off the cooling system immediately after working with a large load.

2, in the use of the environment, we must ensure that the environment temperature and humidity conditions, especially in the wet weather in the South, but also pay special attention. The instrument laboratory must install air conditioning equipment.

3, the use of the instrument environment, there must be no acid mist, that is, XRF instrument and the chemical laboratory in the same room. Because both the X-ray tube and the detector have a window made of a metal crucible, the metal crucible is easily corroded by the acid.