Complex sentence: Electron Power Systems, Inc. of Acton, MA claims (as of 2004) to have developed a technology for maintaining small stable plasma toroids called electron spiral toroids (ESTs) which remain stable in Earth's atmosphere without the use of any special magnetic fields.
Split into simpler sentences: Electron Power Systems, Inc. of Acton, MA claims (as of 2004) to have developed a technology for maintaining small stable plasma toroids called electron spiral toroids (ESTs). They claim that ESTs remain stable in Earth's atmosphere without the use of any special magnetic fields.