[en] It has been observed at LBL and verified many times that the amount of 1/2 CV² energy associated with the accel grid that a neutral beam source can tolerate under sparkdown conditions is quite limited. If this energy exceeds 5-7 Joules, serious degradation of the voltage holding capability of the source occurs. When the LBL 10 x 40 cm source was upgraded from 20 to 40 kV, even the lowest capacitance power supplies devised were only marginally acceptable. Some voltage holding difficulty occurred at the higher voltages as expected. A solution for this problem was devised using a stack of transformer cores near the source and routing all the power supply leads through them. This core stack snubber is apparently essential to the operation of the present sources at 120 kV