To apply the above general results, it is necessary to obtain an expression for the pulse generated at the amplifier uulput by the detection of a single neutron, and this can be derived from the energy spectral density of the pulse or from a knowledge of the time constants of the circuit.

For example, consider a system whose linear portion (cable plus amplifier) has a single low-frequency break at шa single high-freauency break at and a mid-frequency

transfer impedance of Z^, and whose detector is a neutron-sensitive ion chamber. The energy

spectral density of a current pulse from the detector is flat and eaual to Qe / я between the angular frequencies 2 я/Tj and я/Те, where Qg is the product of the fraction of the chamber potential through which the electrons travel and the total charge of one sign released in the cham­ber by the detection of one neutron, T is the ion collection time, and is the electron collec­tion time. So if ^>2я/Т4 and и:ц<тт/Те (see Figure 3-2), the energy spectral density of v(t) is the product of Qe2/W and the square of the absolute value of the transfer function of the linear portion of the system:

Qe2zi22 “2/wL2

E(u>, v) = , (3-50)

and the pulse itself is given by

This expression for v(t) can be used in any of the preceding equations.