Conditioning is an important process in the manufacture and use of electron tubes, such as X-ray tubes, electron guns, ion guns and other vacuum tubes. X-ray tube conditioning is a process in which the voltage is gradually increased depending on the time since the last time, to prevent destructive discharges. Conditioning is also known as seasoning, aging, warming up, and break-in time. The inside of an X-ray tube is a vacuum, but residual gas is released from the internal surfaces and accumulates during periods of non-use. If maximum voltage is applied without conditioning, high voltage arcing in the ionized gas can damage the X-ray tube and render it unusable.
Conditioning prevents destructive damage to the X-ray tube and helps stabilize and extend its life. If the X-ray equipment has not been used for a long time, it will take longer to condition and longer before it can be used.
Conditioning procedure (warm-up procedure before using the X-ray tube)
Here is an example of a general conditioning process: If the X-ray tube manufacturer provides instructions, follow those. Please note that the procedure may vary depending on the type and application of the X-ray tube.
- Set the X-ray tube voltage to the lowest rated voltage and the X-ray tube current to 0 mA, and apply voltage to the X-ray tube.
- Wait until the X-ray tube current stabilizes at 0mA. Maintain a stable state for some time. The retention time varies from 0 to several tens of minutes depending on the period of non-use.
- Adjust the X-ray tube current to 10% of the rated current. Wait until the current stabilizes and maintain this setting for a while. The retention time is approximately 1 to 5 minutes depending on the period of non-use. If the filament is broken, no thermo electrons are generated and there is no X-ray tube current.
- Increase the tube voltage to 50% of the rated voltage in 5 or 10 steps or 5 kV increments. At each step, wait until the voltage and current stabilize and maintain that state for a while. The retention time is approximately 1 to 5 minutes depending on the period of non-use.
- Set the X-ray tube current to 50% of the rated current, wait until it stabilizes, and maintain it for a while. The stable time is about 1 to 5 minutes depending on the period of non-use.
- Increase the tube voltage to the rated voltage in 5 or 10 steps or 5 kV increments. If a discharge occurs, or if the X-ray tube current is unstable or a discharge occurs, return to the previous step. After each step, the X-ray tube current is kept stable for a while. The retention time is approximately 1 to 5 minutes depending on the period of non-use.
- At maximum rated voltage, increase the X-ray tube current to the maximum rated current. Maintain this full power state for a while. The retention time is approximately 1 to 10 minutes depending on the period of non-use.
- Turn off the X-ray output and allow conditioning to complete.
The retention time and step interval are set by categorizing unused periods into days, weeks, months, or more than a few months.
| Steps | X-ray tube voltage | X-ray tube current | Within 24 hours | Within a few days | Within a few weeks | Within a few months | More than a few months |
|---|---|---|---|---|---|---|---|
| 1 | 20 | 0 | 0 | 0 | 1 | 5 | 10 |
| 2 | 20 | 10 | 0 | 1 | 1 | 2 | 5 |
| 3 | 30 | 10 | 0 | 0 | 1 | 2 | 5 |
| 4 | 40 | 10 | 0 | 0 | 1 | 2 | 5 |
| 5 | 50 | 10 | 1 | 1 | 1 | 2 | 5 |
| 6 | 50 | 50 | 0 | 0 | 1 | 2 | 5 |
| 7 | 60 | 50 | 0 | 1 | 1 | 2 | 5 |
| 8 | 70 | 50 | 0 | 0 | 1 | 3 | 5 |
| 9 | 80 | 50 | 0 | 1 | 1 | 3 | 5 |
| 10 | 90 | 50 | 0 | 0 | 1 | 3 | 5 |
| 11 | 100 | 50 | 1 | 1 | 1 | 3 | 5 |
| 12 | 100 | 100 | 1 | 1 | 2 | 5 | 5 |
| Total Time | - | - | 3 | 6 | 13 | 34 | 65 |
The appropriate conditioning method and time will vary depending on how the X-ray tube is used (continuous use/pulse use) and how it is controlled. Another method is to shorten the hold time by narrowing the voltage interval and monitoring fluctuations in the X-ray tube voltage and X-ray tube current.
In the tube manufacturing process, conditioning is sometimes called "burn-in." The manufacturing process takes hundreds of hours to stabilize the tubes and test them for performance. During manufacturing, a voltage higher than the normal accelerating voltage (high voltage) is applied, and the device is inspected and adjusted to ensure stable operation during use.
In addition, conditioning is performed when replacing the emitter of an SEM using a Schottky field emission gun (FEG).
Matsusada Precision's X-ray inspection system automates this conditioning process, maximizing equipment performance and extending the life of your X-ray tubes.