Experimental verification of the neutron spectrum from the NBS D/sub 2/O-moderated /sup 252/Cf source

We have experimentally verified the spectrum calculated for a /sup 252/Cf neutron source moderated by a D/sub 2/O sphere of 15 cm radius. Using NBS double fission chambers as threshold detectors, we find excellent agreement between our measurements and results derived from the calculated spectrum in the energy range below approx. 10 keV. Although the measurements suggest the existence of small, but significant, discrepancies above approx. 600 keV, the value of the fluence-to-dose equivalent conversion factor derived from our measurements agrees with that derived from the calculated spectrum (9.0 x 10/sup -6/ mrem cm/sup 2/) to within 2%, with an estimated uncertainty of +- 4%. 15 references, 10 figures, 8 tables.