X-ray tubes are generally designed to function properly under the most demanding conditions. Where X-ray tubes for benchtop systems would not have to be replaced during the entire system lifetime, the lifespan of an X-ray tube for floor standing systems is typically between 3 and 7 years. This is mainly determined by the way of use and maintenance. So, here is an overview of the main recommendations for optimal X-ray tube usage.
- Keep using your spectrometer and X-ray tube. X-ray tubes should not be left unused for too long, in any case not for more than 6 months. X-ray tubes like to be warm and this keeps the vacuum stable.
- Use the Iso-Watt switching feature. This forces the spectrometer to operate at a constant power during the switching between the different measuring conditions. A constant power helps the lifespan of the X-ray tube.
- Use the standby setting. In standby setting, the power -and especially the emission current- should not be too high, as this costs lifetime. A high kV setting during standby is no problem, since it helps the tube to remain stable against possible flashes.
- Keep the window of the X-ray tube clean. Make sure that no substance spills on the window, and never touch the windows under any circumstance. Not even for cleaning.
- Clean samples. When analyzing pressed powders make sure that they are prepared well and don’t crumble inside the spectrometer. Tidy sample preparation is an essential processing step for good analysis. This helps to retain your tube’s lifespan.
Tips for X-ray tube cooling maintenance
- Regularly check the condition of the chiller. Cooling water is critical (chemical and physical composition, temperature, flow), as the X-ray tube heats up, especially when operating at full power.
- The ideal water temperature. Cold water does not cool better than lukewarm water. The ideal water-in temperature for X-ray tubes is 20-25 °C. In very warm and humid conditions, 25-30 °C is recommended. It is best to always be above the dew point (dew point can be lowered by e.g. climate control in the surroundings).
- Clean and uninterrupted flow of cooling water is as important as the cooling water itself. Therefore, the tube’s cooling circuit must be checked and cleaned regularly. If you experience an unusually fast intensity degradation, it is almost certain that the X-ray tube is not properly cooled.
- Never us pure de-ionized water for cooling, as this is acid and chemically aggressive.
- Place the slit cooler in the correct way.
Tips for the X-ray tube settings
- Put the spectrometer on standby setting when the spectrometer will not be used for more than a few hours. This saves lifetime.
- Switch off the X-ray tube completely when the spectrometer will not be used for more than 24 hours.
- Switch off the water flow within 1-2 minutes when the X-ray tube is switched off completely. NEVER let the water flow for more than 2 minutes after the power is switched off. Otherwise, condensation of water inside the X-ray tube shield can occur.
- NEVER switch off the water flow first (inducing an automatic power off), as this can kill the X-ray tube instantly.
Tips to enhance the stability and lifetime of the X-ray tube
Every X-ray tube is designed to be operated at its maximum power. Applying maximum power is absolutely no problem. There is, however, no denying that every X-ray tube will undergo physical and chemical ageing. These ageing processes are driven mainly by high temperatures and high-temperature gradients inside the X-ray tube.
- Avoid maximum power if your application does not require it. At maximum power, the physical and chemical ageing processes inside the X-ray tube go faster than at lower power.
- Operating at 80-90% of the maximum power already has a significant positive effect on the stability and lifetime of the X-ray tube.
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Written by: Kimberly Oberholz, Posted by: Malvern Panalytical (www.materials-talks.com)