Antimatter Tanks - sswelm/KSP-Interstellar-Extended GitHub Wiki
Antimatter Containment Devices are storage vessels for Antimatter. These tanks require MegaJoules to remain powered, the amount of which depends on how full the device is. The devices are empty until filled using either a Science Lab or Antimatter Collector.
If a tank contains Antimatter and becomes unpowered for long enough, it will explode.