HFIR Cold Source Upgrade Options

Abstract

Several cold source configurations that provide 40% to 90% higher brightness than the reference cold source in broad ranges of wavelengths longer than ~ 2 Å were identified. These CS configurations use hydrogen volumes 2.5 to 4 times larger than the reference source, require a nearly pure para-hydrogen for operation (99% para-hydrogen was assumed in the calculations), and impose heating 1.9 to 2.7 times higher than the reference cold source. Implementation would require adding an ortho-para hydrogen converter and increasing the refrigeration capacity. The brightness increase varies considerably with energy through the cold and thermal neutron range; however, the shapes of the curves of the brightness-increase-versus-energy are very similar for all the configurations analyzed. Up to 2.3 times higher brightness is observed around 3 Å wavelength. The even higher gains of 3.1 at 35 Å are practically of lower interest. Meanwhile, around 1.5 Å a brightness decrease of up to 50% is seen for all but one configuration. The configurations with connected HB-1 and HB-4 beamtubes allow the extraction of neutron beams from both sides of the cold source, therefore effectively doubling the potential number of instruments served, while providing brightness increases in the 40 % to 90 % range. A higher intensity neutron source, which would deliver ~2 times more neutrons down the beamtube, at brightness increased up to 45 %, can be obtained by increasing the radius of the HB-4 and the cold source by ~ 1 cm; which can be realized within the restrictions imposed by the reactor vessel flanges.