Bremsstrahlung produced by an electron linac was measured over a distance of 600 m from that installation by the gated counting method. The synchronizing signal pulses with the electron beam emission period are transported to the counting system prepared at a measuring point. The gated counter of the system accepts signals from a γ-ray detector during the time to be expected that X-radiation due to the accelerater arrives at that point. Only background radiation counts are rejected by using this method.
In this experiment, X-radiation from the linac being in the order of 10-4 of background radiation intensity could be detected. The spatial dose distribution obtained by the experiment was discussed. This could be fitted with an expression of the form D (R) ∝e-μR/R in the region of R=2065g/cm2.
Experimental results show the gated counting method is very advantageous especially for the determination of extremely low level radiation dose distribution and was conveniently applied to a detailed dose evaluation at large distances from nuclear installations which might be necessary in population exposure estimates.