Though the spurious signals arising from gamma and alpha pulses are not rejected by

-/

amplitude discrimination, they are effectively suppressed, since the response is proportional to

the square of the pulse amplitude. However, the MSV gamma signal does exceed the electronic

noise level, and is the predominant source of spurious signal in the system at high gamma levels.

Shown in Figure 4-4 is the gamma contribution to the MSV signal level at a measured gamma flux

level of 3 x 10° R/h and the projected level at 2.5 x 10 R/h. Also shown in this figure is the

-3 -1 -1

counting channel output at a counting sensitivity of 0. 67 x 10 sec nv.

Figure 4-4. MMSVM Neutron Flux Threshold