Type of neutron detector Fission counter Type of signal cable Coaxial

Location of pulse preamplifier Top of counter tube at reactor Location of pulse amplifier Control room Distance between pulse amplifier and preamplifier 250 ft Distance between neutron detector and preamplifier 50 ft

Method of grounding This system uses a single-point ground at the pulse amplifier The detector and preamplifier chassis are also equipped with r-f paths to building ground at the counter tube Operating problems and modifications After the system was installed, the preamplifier gain was increased to give a better signal-to-noise ratio for the signal between the preamplifier and pulse amplifier A filter was installed in the signal output lead of the preamplifier, this filter eliminated the disturbance on the system caused by the interaction of the ground system in the pulse-amplifier cabinet and the building ground at the counter tubes To protect against any ground loops, the shield on the high-voltage coaxial cable to the preamplifier was lifted from the preamplifier chassis and terminated into a high-valued bleeder resistance Low-pass filters were installed on the power leads to the nuclear instrumentation to eliminate the signal induced by having high — and low-power leads running together