input: Background: Later in life, Tesla made claims concerning a "teleforce" weapon after studying the Van de Graaff generator. The press variably referred to it as a "peace ray" or death ray. Tesla described the weapon as capable of being used against ground-based infantry or for anti-aircraft purposes.
  Question: What was he studying that gave him the teleforce weapon idea?
  Answer:<extra_id_0>.
output: <extra_id_0> Van de Graaff generator<extra_id_1>