The ionization chamber is an electron linear accelerator dose monitoring and control system[1]The monitoring device has the function of converting the pulsed radiation output from the accelerator to a pulse value of about 10－5A (10 μ A), mean value about 10－8A (0.01 μ A) of microcurrent to monitor the intensity and position of the irradiated field[2]。 He gas is chosen because the saturation voltage of He gas is the lowest and the ionization rate of He gas is higher than that of the same volume of air at the same charge pressure[3]。 The fault phenomenon seen in this paper has also appeared on C-type machines of some units, and the fault can be eliminated by replacing the ionization chamber, but it has not been reported. I hope that through the in-depth analysis of this article, it can be of benefit to fellow people.
