Radon activity absolute measurement device

The invention belongs to the technical field of radon activity absolute measurement, and specifically relates to a radon activity absolute measurement device. The device comprises an energy spectrum signal measurement and analysis system and an extremely low temperature measurement and control system, which are respectively connected with the top and bottom of a small solid angle measurement roomin a sealed manner. The device also comprises a diffusion-type solid radon source which is in sealed connection with one side of the small solid angle measurement room and provides radon gas for the interior of the small solid angle measurement room. The extremely low temperature measurement and control system can enable the radon gas in the small solid angle measurement room to be condensed intoa condensate radon source. The energy spectrum signal measurement and analysis system can carry out the small solid angle (alpha) measurement of the condensate radon source. The device also comprisesa vacuum measurement and co