人造太陽的週圍

If this is true, I think they are performing an experiement on nuclear fusion, which is the nuclear reaction process taking place in the sun.

Matters at this high temperature is in plasma form, which is a state of complete ionization. Plasma is commonly kept in place by magnetic confinement. That is to say, using a well designed magnetic field configuration to avoid the ionized particles in the plasma to escape.

The size of a cloud of man-made plasma usually cannot be compared with the sun. If the mass of the plasma cloud is not large (and normally this is the case), the energy radiated from the high temperature plasma will not be as large as what you think.