Abstract: An apparatus for irradiating a biological substance with a substantially uniform quantity of radiation energy comprises a radiation-generating device for producing radiation energy, a support structure for receiving the biological substance, and a motorized mechanism for reciprocating the radiation-generating device along a given path whereby the biological substance receives radiation energy from the radiation-generating device at each passage of the radiation-generating device. A series of sensors lie into a given plane and are subjected to radiation energy from the radiation-generating device upon each passage of that radiation-generating device for sensing and measuring the quantity of radiation energy by surface unit passing through the given plane and reaching the biological substance. Finally the radiation-generating device and the motorized mechanism are de-energized when the measured quantity of radiation energy by surface unit has reached a predetermined value.