Improvement of high-voltage performance of acceleration tubes by cleaning the walls with a high-pressure water jet

We cleaned electrostatic accelerator tubes by applying a high-pressure water jet and examined their high-voltage performances at 1 and 3 MV. The cleaning was very effective in reducing discharge activities at their rated voltages. We did some experimental investigations with the tubes and their ceramic insulators. We found that removal of microparticles loosely bound on the vacuum-side ceramic surfaces had an important effect in eliminating the discharge activities.