Radiation monitoring at Belle

High beam currents at the KEK B factory lead to high radiation background (order of 100 krad/y, consisting mostly of spent electrons/positrons) around the interaction point where the silicon vertex detector is located. In order to monitor the background conditions close to the interaction point a radiation monitoring system has been developed and installed. It is based on 16 monitoring modules containing RadFET chip (containing 4 sensors) for measurement of total accumulated dose and PIN diodes for measurement of instantaneous dose rate.