The primary requirements on the cable insulation are that, at detector operating voltages, the d-c current drain is not excessive, and that the noise generated by the cable with potential applied is not large enough to cause spurious counts in the counting channel.

1 10 100 1000

APPLIED POTENTIAL DIFFERENCE IN VOLTS

Figure 5-11. Irradiation Effects on the Electrical Properties of Fiber Insulated Cable

СЛ I to. to

Figure 5-12. D-C Leakage Current Versus Neutron Exposure

The data demonstrate that the former requirement is met. Regarding the latter require­ment, it has been found that there is a correspondence between the amount of d-c leakage and the a-c noise generated. With another in-reactor test unit, which included a quartz insulated cable and an in-core counter, a-c noise was not a problem (see Section IV).