Operation of 555 Timer Circuit Under Radiation Filed

The 8-pin 555 time rs were exposed to 1,2,3,4, up to 5 Mrads gamma doses, using Co 60 as a gamma radiation source, with a total absorbed doses 5Mrads , the output of the chip, as a square wave indicate that , the electromagnetic wave (gamma radiation) affect in the operation of the timer, as : the parameter changed during radiation noise in the generated square wave, frequency (f) and duty-cycle (D) , in which the high bias (6V) with higher doses, exist a noise on the output waveform, it has been found that the effect of radiation could be handled by lowering supply voltage to 3V.this could resultant to removing noise generated due to radiation, or from the analysis in some circuits by changing the values of external resistors and capacitance, the output waveform return to initial square wave without noise, that is to say the radiation induce an energy in the chip structure.