A Multichannel Radiation Monitor with Logarithmic Response from 0.1 to 106 Mrem/Hr

A radiation monitoring system having a very wide dynamic range and providing continuous audible information feedback to the user was built for the 55-MeV Princeton A. V. F. Cyclotron. A remote sensor in each room consists of a plastic scintillator and photomultiplier. At the control room there is a DC amplifier with output proportional to the log of the anode current and hence to the dose rate. This is examined by two independently adjustable set points with DTL outputs which establish limits for human occupancy and radiation damage to equipment respectively. For each channel discrete pulses from the photomultiplier are also amplified and operate a loudspeaker placed near the detector. When the lower set point is tripped the speaker broadcasts a sirenlike tone. A failure condition logic signal is generated if discrete pulses are not present when the low level set point is not tripped. Although this type of detector does not directly respond to slow neutrons, it does indicate the radiation hazzard by detecting the fast neutrons and capture gamma rays which accompany them in a cyclotron environment.