The wiring on the top of the test stand was burned, see entry 737.
Probable cause of this is as follows:
Coil lines are connected by a wire to HV common, the 9-pin feedthrough etc to maintain same voltage on all the insulator tops. This is also directly connected to the extraction electrode spark gap. When this sparks, it momentarily changes the potential in that line (normally HV common) which then can make this path the best route for current from the coil to return to ground.
See attached diagram.
Best solution to this problem is to disconnect the high current section from the low current section, and attach each separately to HV common.
Other possible improvements to wiring:
1. Remove jumpers between positive coil lines (and neg. coil lines) since these feethroughs are physically connected by the copper pipe.
2. Add a resistor to the jumper between coil - and TBHT - since this will eliminate all possibility of current flowing between the two.
3. Add a resistor in line where the high current section is connected to HV common to avoid possibility of current going through jumpers. |