The basic requirements for subsystem sensitivity are derived from the system requirements on measurable neutron flux, detector locations possible, and types of detectors being used. The system requirements are covered in other sections, along with the detector locations possible.

6. 3. 1 In-Core System

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In the in-core system, the counting chamber is a fission chamber in which the U is diffused into a base metal. The differential and integral spectra for neutrons from a Pu-Be source for this chamber are shown in Figures 6-2 and 6-3, respectively. [7] Note that the dis­tribution of pulse heights of the chamber shows a peak at small relative energies. The equivalent input charge is defined as that amount of charge which, when introduced into the input of the subsystem or device, will produce a given output level. The charge is introduced by applying a negative step voltage of V volts to the input of the device through a General Radio 10 pf standard air capacitor. The value of the charge is equal to the value of the step multiplied by 10-1*, the value of the capacitance.

0.001 0.01 fj 0.1 1.0 f2 10 100 FREQUENCY IN MEGACYCLES PER SECOND

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DISCRIMINATOR SETTING: 1.7 BASELINE: 0.00 GAIN: 1.00
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 EQUIVALENT INPUT CHARGE IN COULOMBS x 10"14	36 38 40 42
Figure 6-2, Differential Bias Curve — Chamber No. 17

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The integral pulse height curve for the sample chamber shows that with a system sensi — -14

tivity of 2 x 10 coulombs equivalent charge, the total number of counts per unit time is 28 counts/sec in a neutron flux of 1. 45 x 10^ nv.