What is NASA using helium for?

Could you possibly elaborate on the question, "What is NASA utilizing helium for?" I'm genuinely curious to understand the specific applications and reasons behind NASA's need for helium. Is it for spacecraft propulsion? Or perhaps for maintaining low-temperature environments in certain experiments? I'm also wondering if helium plays a role in the agency's radioisotope thermoelectric generators. Could you provide some insight into these or any other potential uses of helium within NASA's operations? Thank you for your time and consideration.